ATMEGA162-16MI [ATMEL]
8-Bit AVR Microcontroller with 16K Bytes In-System ProgrammableFlash; 8位AVR微控制器具有16K字节的系统ProgrammableFlash
| 型号： | ATMEGA162-16MI |
| 厂家： | 
ATMEL |
| 描述： | 8-Bit AVR Microcontroller with 16K Bytes In-System ProgrammableFlash |
| 文件： | 总323页 (文件大小：3863K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Features
• High-performance, Low-power AVR® 8-bit Microcontroller
• Advanced RISC Architecture
– 131 Powerful Instructions – Most Single-clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 16 MIPS Throughput at 16 MHz
– On-chip 2-cycle Multiplier
• Non-volatile Program and Data Memories
– 16K Bytes of In-System Self-programmable Flash
Endurance: 10,000 Write/Erase Cycles
8-bit
– Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
Microcontroller
with 16K Bytes
In-System
Programmable
Flash
– 512 Bytes EEPROM
Endurance: 100,000 Write/Erase Cycles
– 1K Bytes Internal SRAM
– Up to 64K Bytes Optional External Memory Space
– Programming Lock for Software Security
• JTAG (IEEE std. 1149.1 Compliant) Interface
– Boundary-scan Capabilities According to the JTAG Standard
– Extensive On-chip Debug Support
– Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface
• Peripheral Features
– Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes
– Two 16-bit Timer/Counters with Separate Prescalers, Compare Modes, and
Capture Modes
ATmega162
– Real Time Counter with Separate Oscillator
– Six PWM Channels
– Dual Programmable Serial USARTs
ATmega162V
– Master/Slave SPI Serial Interface
– Programmable Watchdog Timer with Separate On-chip Oscillator
– On-chip Analog Comparator
• Special Microcontroller Features
– Power-on Reset and Programmable Brown-out Detection
– Internal Calibrated RC Oscillator
– External and Internal Interrupt Sources
– Five Sleep Modes: Idle, Power-save, Power-down, Standby, and Extended Standby
• I/O and Packages
– 35 Programmable I/O Lines
– 40-pin PDIP, 44-lead TQFP, and 44-pad MLF
• Operating Voltages
– 1.8 - 5.5V for ATmega162V
– 2.7 - 5.5V for ATmega162
• Speed Grades
– 0 - 8 MHz for ATmega162V (see Figure 113 on page 265)
– 0 - 16 MHz for ATmega162 (see Figure 114 on page 265)
2513F–AVR–12/03
Pin Configurations
Figure 1. Pinout ATmega162
PDIP
(OC0/T0) PB0
(OC2/T1) PB1
(RXD1/AIN0) PB2
(TXD1/AIN1) PB3
(SS/OC3B) PB4
(MOSI) PB5
VCC
1
2
3
4
5
6
7
8
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
PA0 (AD0/PCINT0)
PA1 (AD1/PCINT1)
PA2 (AD2/PCINT2)
PA3 (AD3/PCINT3)
PA4 (AD4/PCINT4)
PA5 (AD5/PCINT5)
PA6 (AD6/PCINT6)
PA7 (AD7/PCINT7)
PE0 (ICP1/INT2)
(MISO) PB6
(SCK) PB7
RESET
(RXD0) PD0
(TXD0) PD1
9
10
11
12
13
14
15
16
17
18
19
20
PE1 (ALE)
PE2 (OC1B)
(INT0/XCK1) PD2
(INT1/ICP3) PD3
(TOSC1/XCK0/OC3A) PD4
(OC1A/TOSC2) PD5
(WR) PD6
PC7 (A15/TDI/PCINT15)
PC6 (A14/TDO/PCINT14)
PC5 (A13/TMS/PCINT13)
PC4 (A12/TCK/PCINT12)
PC3 (A11/PCINT11)
PC2 (A10/PCINT10)
PC1 (A9/PCINT9)
PC0 (A8/PCINT8)
(RD) PD7
XTAL2
XTAL1
GND
TQFP/MLF
44 42 40 38 36 34
43 41 39 37 35
(MOSI) PB5
(MISO) PB6
(SCK) PB7
RESET
(RXD0) PD0
PA4 (AD4/PCINT4)
PA5 (AD5/PCINT5)
PA6 (AD6/PCINT6)
PA7 (AD7/PCINT7)
PE0 (ICP1/INT2)
GND
PE1 (ALE)
PE2 (OC1B)
PC7 (A15/TDI/PCINT15)
PC6 (A14/TDO/PCINT14)
PC5 (A13/TMS/PCINT13)
1
2
3
4
5
6
7
8
33
32
31
30
29
28
27
26
25
24
23
VCC
(TXD0) PD1
(INT0/XCK1) PD2
(INT1/ICP3) PD3
(TOSC1/XCK0/OC3A) PD4
(OC1A/TOSC2) PD5
9
10
11
13 15 17 19 21
12 14 16 18 20 22
NOTE:
MLF bottom pad should
be soldered to ground.
Disclaimer
Typical values contained in this datasheet are based on simulations and characteriza-
tion of other AVR microcontrollers manufactured on the same process technology. Min
and Max values will be available after the device is characterized.
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ATmega162/V
2513F–AVR–12/03
ATmega162/V
Overview
The ATmega162 is a low-power CMOS 8-bit microcontroller based on the AVR
enhanced RISC architecture. By executing powerful instructions in a single clock cycle,
the ATmega162 achieves throughputs approaching 1 MIPS per MHz allowing the sys-
tem designer to optimize power consumption versus processing speed.
Block Diagram
Figure 2. Block Diagram
PE0 - PE2
PA0 - PA7
PC0 - PC7
VCC
PORTE
PORTA DRIVERS/BUFFERS
PORTA DIGITAL INTERFACE
DRIVERS/
BUFFERS
PORTC DRIVERS/BUFFERS
PORTC DIGITAL INTERFACE
PORTE
DIGITAL
INTERFACE
GND
INTERNAL
PROGRAM
STACK
OSCILLATOR
COUNTER
POINTER
XTAL1
WATCHDOG
TIMER
PROGRAM
FLASH
OSCILLATOR
SRAM
XTAL2
MCU CTRL.
& TIMING
INSTRUCTION
REGISTER
GENERAL
PURPOSE
REGISTERS
RESET
X
Y
Z
INTERNAL
CALIBRATED
OSCILLATOR
INTERRUPT
UNIT
INSTRUCTION
DECODER
CONTROL
LINES
TIMERS/
COUNTERS
OSCILLATOR
ALU
STATUS
REGISTER
AVR CPU
EEPROM
USART0
PROGRAMMING
LOGIC
SPI
+
-
COMP.
INTERFACE
USART1
PORTB DIGITAL INTERFACE
PORTD DIGITAL INTERFACE
PORTD DRIVERS/BUFFERS
PORTB DRIVERS/BUFFERS
PB0 - PB7
PD0 - PD7
3
2513F–AVR–12/03
The AVR core combines a rich instruction set with 32 general purpose working registers.
All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing
two independent registers to be accessed in one single instruction executed in one clock
cycle. The resulting architecture is more code efficient while achieving throughputs up to
ten times faster than conventional CISC microcontrollers.
The ATmega162 provides the following features: 16K bytes of In-System Programmable
Flash with Read-While-Write capabilities, 512 bytes EEPROM, 1K bytes SRAM, an
external memory interface, 35 general purpose I/O lines, 32 general purpose working
registers, a JTAG interface for Boundary-scan, On-chip Debugging support and pro-
gramming, four flexible Timer/Counters with compare modes, internal and external
interrupts, two serial programmable USARTs, a programmable Watchdog Timer with
Internal Oscillator, an SPI serial port, and five software selectable power saving modes.
The Idle mode stops the CPU while allowing the SRAM, Timer/Counters, SPI port, and
interrupt system to continue functioning. The Power-down mode saves the register con-
tents but freezes the Oscillator, disabling all other chip functions until the next interrupt
or Hardware Reset. In Power-save mode, the Asynchronous Timer continues to run,
allowing the user to maintain a timer base while the rest of the device is sleeping. In
Standby mode, the crystal/resonator Oscillator is running while the rest of the device is
sleeping. This allows very fast start-up combined with low-power consumption. In
Extended Standby mode, both the main Oscillator and the Asynchronous Timer con-
tinue to run.
The device is manufactured using Atmel’s high density non-volatile memory technology.
The On-chip ISP Flash allows the program memory to be reprogrammed In-System
through an SPI serial interface, by a conventional non-volatile memory programmer, or
by an On-chip Boot Program running on the AVR core. The Boot Program can use any
interface to download the Application Program in the Application Flash memory. Soft-
ware in the Boot Flash section will continue to run while the Application Flash section is
updated, providing true Read-While-Write operation. By combining an 8-bit RISC CPU
with In-System Self-Programmable Flash on a monolithic chip, the Atmel ATmega162 is
a powerful microcontroller that provides a highly flexible and cost effective solution to
many embedded control applications.
The ATmega162 AVR is supported with a full suite of program and system development
tools including: C compilers, macro assemblers, program debugger/simulators, In-Cir-
cuit Emulators, and evaluation kits.
ATmega161 and
ATmega162
Compatibility
The ATmega162 is a highly complex microcontroller where the number of I/O locations
supersedes the 64 I/O locations reserved in the AVR instruction set. To ensure back-
ward compatibility with the ATmega161, all I/O locations present in ATmega161 have
the same locations in ATmega162. Some additional I/O locations are added in an
Extended I/O space starting from 0x60 to 0xFF, (i.e., in the ATmega162 internal RAM
space). These locations can be reached by using LD/LDS/LDD and ST/STS/STD
instructions only, not by using IN and OUT instructions. The relocation of the internal
RAM space may still be a problem for ATmega161 users. Also, the increased number of
Interrupt Vectors might be a problem if the code uses absolute addresses. To solve
these problems, an ATmega161 compatibility mode can be selected by programming
the fuse M161C. In this mode, none of the functions in the Extended I/O space are in
use, so the internal RAM is located as in ATmega161. Also, the Extended Interrupt Vec-
tors are removed. The ATmega162 is 100% pin compatible with ATmega161, and can
replace the ATmega161 on current Printed Circuit Boards. However, the location of
Fuse bits and the electrical characteristics differs between the two devices.
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ATmega162/V
2513F–AVR–12/03
ATmega162/V
ATmega161 Compatibility
Mode
Programming the M161C will change the following functionality:
•
The extended I/O map will be configured as internal RAM once the M161C Fuse is
programmed.
•
The timed sequence for changing the Watchdog Time-out period is disabled. See
“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page
55 for details.
•
•
•
The double buffering of the USART Receive Registers is disabled. See “AVR
USART vs. AVR UART – Compatibility” on page 167 for details.
Pin change interrupts are not supported (Control Registers are located in Extended
I/O).
One 16 bits Timer/Counter (Timer/Counter1) only. Timer/Counter3 is not accessible.
Note that the shared UBRRHI Register in ATmega161 is split into two separate registers
in ATmega162, UBRR0H and UBRR1H. The location of these registers will not be
affected by the ATmega161 compatibility fuse.
Pin Descriptions
VCC
Digital supply voltage
Ground
GND
Port A (PA7..PA0)
Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port A output buffers have symmetrical drive characteristics with both high sink
and source capability. When pins PA0 to PA7 are used as inputs and are externally
pulled low, they will source current if the internal pull-up resistors are activated. The Port
A pins are tri-stated when a reset condition becomes active, even if the clock is not
running.
Port A also serves the functions of various special features of the ATmega162 as listed
on page 71.
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port B output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port B also serves the functions of various special features of the ATmega162 as listed
on page 71.
Port C (PC7..PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port C output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port C pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset
condition becomes active, even if the clock is not running. If the JTAG interface is
enabled, the pull-up resistors on pins PC7(TDI), PC5(TMS) and PC4(TCK) will be acti-
vated even if a Reset occurs.
Port C also serves the functions of the JTAG interface and other special features of the
ATmega162 as listed on page 74.
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2513F–AVR–12/03
Port D (PD7..PD0)
Port E(PE2..PE0)
RESET
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port D output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port D pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port D also serves the functions of various special features of the ATmega162 as listed
on page 77.
Port E is an 3-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port E output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port E pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port E pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port E also serves the functions of various special features of the ATmega162 as listed
on page 80.
Reset input. A low level on this pin for longer than the minimum pulse length will gener-
ate a Reset, even if the clock is not running. The minimum pulse length is given in Table
18 on page 47. Shorter pulses are not guaranteed to generate a reset.
XTAL1
XTAL2
Input to the Inverting Oscillator amplifier and input to the internal clock operating circuit.
Output from the Inverting Oscillator amplifier.
About Code Examples
This documentation contains simple code examples that briefly show how to use various
parts of the device. These code examples assume that the part specific header file is
included before compilation. Be aware that not all C compiler vendors include bit defini-
tions in the header files and interrupt handling in C is compiler dependent. Please
confirm with the C compiler documentation for more details.
6
ATmega162/V
2513F–AVR–12/03
ATmega162/V
AVR CPU Core
Introduction
This section discusses the AVR core architecture in general. The main function of the
CPU core is to ensure correct program execution. The CPU must therefore be able to
access memories, perform calculations, control peripherals, and handle interrupts.
Architectural Overview
Figure 3. Block Diagram of the AVR Architecture
Data Bus 8-bit
Program
Counter
Status
and Control
Flash
Program
Memory
Interrupt
Unit
32 x 8
General
Purpose
Registrers
Instruction
Register
SPI
Unit
Instruction
Decoder
Watchdog
Timer
ALU
Analog
Comparator
Control Lines
I/O Module1
I/O Module 2
I/O Module n
Data
SRAM
EEPROM
I/O Lines
In order to maximize performance and parallelism, the AVR uses a Harvard architecture
– with separate memories and buses for program and data. Instructions in the program
memory are executed with a single level pipelining. While one instruction is being exe-
cuted, the next instruction is pre-fetched from the program memory. This concept
enables instructions to be executed in every clock cycle. The program memory is In-
System Reprogrammable Flash memory.
The fast-access Register File contains 32 x 8-bit general purpose working registers with
a single clock cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU)
operation. In a typical ALU operation, two operands are output from the Register File,
the operation is executed, and the result is stored back in the Register File – in one
clock cycle.
7
2513F–AVR–12/03
Six of the 32 registers can be used as three 16-bit indirect address register pointers for
Data Space addressing – enabling efficient address calculations. One of the these
address pointers can also be used as an address pointer for look up tables in Flash Pro-
gram memory. These added function registers are the 16-bit X-, Y-, and Z-register,
described later in this section.
The ALU supports arithmetic and logic operations between registers or between a con-
stant and a register. Single register operations can also be executed in the ALU. After
an arithmetic operation, the Status Register is updated to reflect information about the
result of the operation.
Program flow is provided by conditional and unconditional jump and call instructions,
able to directly address the whole address space. Most AVR instructions have a single
16-bit word format. Every program memory address contains a 16- or 32-bit instruction.
Program Flash memory space is divided in two sections, the Boot Program section and
the Application Program section. Both sections have dedicated Lock bits for write and
read/write protection. The SPM instruction that writes into the Application Flash memory
section must reside in the Boot Program section.
During interrupts and subroutine calls, the return address Program Counter (PC) is
stored on the Stack. The Stack is effectively allocated in the general data SRAM, and
consequently the Stack size is only limited by the total SRAM size and the usage of the
SRAM. All user programs must initialize the SP in the reset routine (before subroutines
or interrupts are executed). The Stack Pointer SP is read/write accessible in the I/O
space. The data SRAM can easily be accessed through the five different addressing
modes supported in the AVR architecture.
The memory spaces in the AVR architecture are all linear and regular memory maps.
A flexible interrupt module has its control registers in the I/O space with an additional
Global Interrupt Enable bit in the Status Register. All interrupts have a separate Interrupt
Vector in the Interrupt Vector table. The interrupts have priority in accordance with their
Interrupt Vector position. The lower the Interrupt Vector address, the higher the priority.
The I/O memory space contains 64 addresses for CPU peripheral functions as Control
Registers, SPI, and other I/O functions. The I/O memory can be accessed directly, or as
the Data Space locations following those of the Register File, 0x20 - 0x5F.
ALU – Arithmetic Logic
Unit
The high-performance AVR ALU operates in direct connection with all the 32 general
purpose working registers. Within a single clock cycle, arithmetic operations between
general purpose registers or between a register and an immediate are executed. The
ALU operations are divided into three main categories – arithmetic, logical, and bit-func-
tions. Some implementations of the architecture also provide a powerful multiplier
supporting both signed/unsigned multiplication and fractional format. See the “Instruc-
tion Set” section for a detailed description.
Status Register
The Status Register contains information about the result of the most recently executed
arithmetic instruction. This information can be used for altering program flow in order to
perform conditional operations. Note that the Status Register is updated after all ALU
operations, as specified in the Instruction Set Reference. This will in many cases
remove the need for using the dedicated compare instructions, resulting in faster and
more compact code.
The Status Register is not automatically stored when entering an interrupt routine and
restored when returning from an interrupt. This must be handled by software.
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ATmega162/V
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ATmega162/V
The AVR Status Register – SREG – is defined as:
Bit
7
I
6
T
5
H
4
S
3
V
2
N
1
Z
0
C
SREG
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
• Bit 7 – I: Global Interrupt Enable
The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individ-
ual interrupt enable control is then performed in separate control registers. If the Global
Interrupt Enable Register is cleared, none of the interrupts are enabled independent of
the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt
has occurred, and is set by the RETI instruction to enable subsequent interrupts. The I-
bit can also be set and cleared by the application with the SEI and CLI instructions, as
described in the instruction set reference.
• Bit 6 – T: Bit Copy Storage
The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T bit as source or
destination for the operated bit. A bit from a register in the Register File can be copied
into T by the BST instruction, and a bit in T can be copied into a bit in a register in the
Register File by the BLD instruction.
• Bit 5 – H: Half Carry Flag
The Half Carry Flag H indicates a half carry in some arithmetic operations. Half Carry is
useful in BCD arithmetic. See the “Instruction Set Description” for detailed information.
• Bit 4 – S: Sign Bit, S = N
V
The S-bit is always an exclusive or between the Negative Flag N and the Two’s Comple-
ment Overflow Flag V. See the “Instruction Set Description” for detailed information.
• Bit 3 – V: Two’s Complement Overflow Flag
The Two’s Complement Overflow Flag V supports two’s complement arithmetics. See
the “Instruction Set Description” for detailed information.
• Bit 2 – N: Negative Flag
The Negative Flag N indicates a negative result in an arithmetic or logic operation. See
the “Instruction Set Description” for detailed information.
• Bit 1 – Z: Zero Flag
The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See the
“Instruction Set Description” for detailed information.
• Bit 0 – C: Carry Flag
The Carry Flag C indicates a carry in an arithmetic or logic operation. See the “Instruc-
tion Set Description” for detailed information.
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2513F–AVR–12/03
General Purpose
Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to
achieve the required performance and flexibility, the following input/output schemes are
supported by the Register File:
•
•
•
•
One 8-bit output operand and one 8-bit result input
Two 8-bit output operands and one 8-bit result input
Two 8-bit output operands and one 16-bit result input
One 16-bit output operand and one 16-bit result input
Figure 4 shows the structure of the 32 general purpose working registers in the CPU.
Figure 4. AVR CPU General Purpose Working Registers
7
0
Addr.
0x00
0x01
0x02
R0
R1
R2
…
R13
R14
R15
R16
R17
…
0x0D
0x0E
0x0F
0x10
0x11
General
Purpose
Working
Registers
R26
R27
R28
R29
R30
R31
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
X-register Low Byte
X-register High Byte
Y-register Low Byte
Y-register High Byte
Z-register Low Byte
Z-register High Byte
Most of the instructions operating on the Register File have direct access to all registers,
and most of them are single cycle instructions.
As shown in Figure 4, each register is also assigned a data memory address, mapping
them directly into the first 32 locations of the user Data Space. Although not being phys-
ically implemented as SRAM locations, this memory organization provides great
flexibility in access of the registers, as the X-, Y-, and Z-pointer registers can be set to
index any register in the file.
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ATmega162/V
2513F–AVR–12/03
ATmega162/V
The X-register, Y-register, and The registers R26..R31 have some added functions to their general purpose usage.
Z-register
These registers are 16-bit address pointers for indirect addressing of the Data Space.
The three indirect address registers X, Y, and Z are defined as described in Figure 5.
Figure 5. The X-, Y-, and Z-registers
15
XH
XL
0
0
X - register
7
0
0
7
R27 (0x1B)
R26 (0x1A)
15
YH
YL
ZL
0
0
Y - register
Z - register
7
7
R29 (0x1D)
R28 (0x1C)
15
ZH
0
0
7
7
0
R31 (0x1F)
R30 (0x1E)
In the different addressing modes these address registers have functions as fixed dis-
placement, automatic increment, and automatic decrement (see the instruction set
reference for details).
Stack Pointer
The Stack is mainly used for storing temporary data, for storing local variables and for
storing return addresses after interrupts and subroutine calls. The Stack Pointer Regis-
ter always points to the top of the Stack. Note that the Stack is implemented as growing
from higher memory locations to lower memory locations. This implies that a Stack
PUSH command decreases the Stack Pointer.
The Stack Pointer points to the data SRAM Stack area where the Subroutine and Inter-
rupt Stacks are located. This Stack space in the data SRAM must be defined by the
program before any subroutine calls are executed or interrupts are enabled. The Stack
Pointer must be set to point above 0x60. The Stack Pointer is decremented by one
when data is pushed onto the Stack with the PUSH instruction, and it is decremented by
two when the return address is pushed onto the Stack with subroutine call or interrupt.
The Stack Pointer is incremented by one when data is popped from the Stack with the
POP instruction, and it is incremented by two when data is popped from the Stack with
return from subroutine RET or return from interrupt RETI.
The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The num-
ber of bits actually used is implementation dependent. Note that the data space in some
implementations of the AVR architecture is so small that only SPL is needed. In this
case, the SPH Register will not be present.
Bit
15
SP15
SP7
7
14
SP14
SP6
6
13
SP13
SP5
5
12
SP12
SP4
4
11
SP11
SP3
3
10
SP10
SP2
2
9
SP9
SP1
1
8
SP8
SP0
0
SPH
SPL
Read/Write
Initial Value
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
R/W
R/W
0
0
0
0
0
0
0
0
0
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2513F–AVR–12/03
Instruction Execution
Timing
This section describes the general access timing concepts for instruction execution. The
AVR CPU is driven by the CPU clock clkCPU, directly generated from the selected clock
source for the chip. No internal clock division is used.
Figure 6 shows the parallel instruction fetches and instruction executions enabled by the
Harvard architecture and the fast-access Register File concept. This is the basic pipelin-
ing concept to obtain up to 1 MIPS per MHz with the corresponding unique results for
functions per cost, functions per clocks, and functions per power-unit.
Figure 6. The Parallel Instruction Fetches and Instruction Executions
T1
T2
T3
T4
clkCPU
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
Figure 7 shows the internal timing concept for the Register File. In a single clock cycle
an ALU operation using two register operands is executed, and the result is stored back
to the destination register.
Figure 7. Single Cycle ALU Operation
T1
T2
T3
T4
clkCPU
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
Reset and Interrupt
Handling
The AVR provides several different interrupt sources. These interrupts and the separate
Reset Vector each have a separate program vector in the program memory space. All
interrupts are assigned individual enable bits which must be written logic one together
with the Global Interrupt Enable bit in the Status Register in order to enable the interrupt.
Depending on the Program Counter value, interrupts may be automatically disabled
when Boot Lock bits BLB02 or BLB12 are programmed. This feature improves software
security. See the section “Memory Programming” on page 230 for details.
The lowest addresses in the program memory space are by default defined as the Reset
and Interrupt Vectors. The complete list of vectors is shown in “Interrupts” on page 56.
The list also determines the priority levels of the different interrupts. The lower the
address the higher is the priority level. RESET has the highest priority, and next is INT0
– the External Interrupt Request 0. The Interrupt Vectors can be moved to the start of
the Boot Flash section by setting the IVSEL bit in the General Interrupt Control Register
(GICR). Refer to “Interrupts” on page 56 for more information. The Reset Vector can
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also be moved to the start of the Boot Flash section by programming the BOOTRST
Fuse, see “Boot Loader Support – Read-While-Write Self-programming” on page 216.
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts
are disabled. The user software can write logic one to the I-bit to enable nested inter-
rupts. All enabled interrupts can then interrupt the current interrupt routine. The I-bit is
automatically set when a Return from Interrupt instruction – RETI – is executed.
There are basically two types of interrupts. The first type is triggered by an event that
sets the Interrupt Flag. For these interrupts, the Program Counter is vectored to the
actual Interrupt Vector in order to execute the interrupt handling routine, and hardware
clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing a
logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the
corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remem-
bered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or
more interrupt conditions occur while the global interrupt enable bit is cleared, the corre-
sponding Interrupt Flag(s) will be set and remembered until the Global Interrupt Enable
bit is set, and will then be executed by order of priority.
The second type of interrupts will trigger as long as the interrupt condition is present.
These interrupts do not necessarily have Interrupt Flags. If the interrupt condition disap-
pears before the interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and exe-
cute one more instruction before any pending interrupt is served.
Note that the Status Register is not automatically stored when entering an interrupt rou-
tine, nor restored when returning from an interrupt routine. This must be handled by
software.
When using the CLI instruction to disable interrupts, the interrupts will be immediately
disabled. No interrupt will be executed after the CLI instruction, even if it occurs simulta-
neously with the CLI instruction. The following example shows how this can be used to
avoid interrupts during the timed EEPROM write sequence.
Assembly Code Example
in r16, SREG
; store SREG value
cli ; disable interrupts during timed sequence
sbi EECR, EEMWE
sbi EECR, EEWE
out SREG, r16
; start EEPROM write
; restore SREG value (I-bit)
C Code Example
char cSREG;
cSREG = SREG; /* store SREG value */
/* disable interrupts during timed sequence */
_CLI();
EECR |= (1<<EEMWE); /* start EEPROM write */
EECR |= (1<<EEWE);
SREG = cSREG; /* restore SREG value (I-bit) */
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When using the SEI instruction to enable interrupts, the instruction following SEI will be
executed before any pending interrupts, as shown in this example.
Assembly Code Example
sei
; set global interrupt enable
sleep ; enter sleep, waiting for interrupt
; note: will enter sleep before any pending
; interrupt(s)
C Code Example
_SEI(); /* set global interrupt enable */
_SLEEP(); /* enter sleep, waiting for interrupt */
/* note: will enter sleep before any pending interrupt(s) */
Interrupt Response Time
The interrupt execution response for all the enabled AVR interrupts is four clock cycles
minimum. After four clock cycles the program vector address for the actual interrupt
handling routine is executed. During this four clock cycle period, the Program Counter is
pushed onto the Stack. The vector is normally a jump to the interrupt routine, and this
jump takes three clock cycles. If an interrupt occurs during execution of a multi-cycle
instruction, this instruction is completed before the interrupt is served. If an interrupt
occurs when the MCU is in sleep mode, the interrupt execution response time is
increased by four clock cycles. This increase comes in addition to the start-up time from
the selected sleep mode.
A return from an interrupt handling routine takes four clock cycles. During these four
clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack
Pointer is incremented by two, and the I-bit in SREG is set.
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AVR ATmega162
Memories
This section describes the different memories in the ATmega162. The AVR architecture
has two main memory spaces, the Data Memory and the Program Memory space. In
addition, the ATmega162 features an EEPROM Memory for data storage. All three
memory spaces are linear and regular.
In-System
Reprogrammable Flash
Program Memory
The ATmega162 contains 16K bytes On-chip In-System Reprogrammable Flash mem-
ory for program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is
organized as 8K x 16. For software security, the Flash Program memory space is
divided into two sections, Boot Program section and Application Program section.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The
ATmega162 Program Counter (PC) is 13 bits wide, thus addressing the 8K program
memory locations. The operation of Boot Program section and associated Boot Lock
bits for software protection are described in detail in “Boot Loader Support – Read-
While-Write Self-programming” on page 216. “Memory Programming” on page 230 con-
tains a detailed description on Flash data serial downloading using the SPI pins or the
JTAG interface.
Constant tables can be allocated within the entire program memory address space (see
the LPM – Load Program Memory instruction description).
Timing diagrams for instruction fetch and execution are presented in “Instruction Execu-
tion Timing” on page 12.
Figure 8. Program Memory Map(1)
Program Memory
0x0000
Application Flash Section
Boot Flash Section
0x1FFF
Note:
1. The address reflects word addresses.
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SRAM Data Memory
Figure 9 shows how the ATmega162 SRAM Memory is organized. Memory configura-
tion B refers to the ATmega161 compatibility mode, configuration A to the non-
compatible mode.
The ATmega162 is a complex microcontroller with more peripheral units than can be
supported within the 64 location reserved in the Opcode for the IN and OUT instructions.
For the Extended I/O space from 0x60 - 0xFF in SRAM, only the ST/STS/STD and
LD/LDS/LDD instructions can be used. The Extended I/O space does not exist when the
ATmega162 is in the ATmega161 compatibility mode.
In Normal mode, the first 1280 Data Memory locations address both the Register File,
the I/O Memory, Extended I/O Memory, and the internal data SRAM. The first 32 loca-
tions address the Register File, the next 64 location the standard I/O memory, then 160
locations of Extended I/O memory, and the next 1024 locations address the internal
data SRAM.
In ATmega161 compatibility mode, the lower 1120 Data Memory locations address the
Register File, the I/O Memory, and the internal data SRAM. The first 96 locations
address the Register File and I/O Memory, and the next 1024 locations address the
internal data SRAM.
An optional external data SRAM can be used with the ATmega162. This SRAM will
occupy an area in the remaining address locations in the 64K address space. This area
starts at the address following the internal SRAM. The Register File, I/O, Extended I/O
and Internal SRAM uses the occupies the lowest 1280 bytes in Normal mode, and the
lowest 1120 bytes in the ATmega161 compatibility mode (Extended I/O not present), so
when using 64KB (65,536 bytes) of External Memory, 64,256 Bytes of External Memory
are available in Normal mode, and 64,416 Bytes in ATmega161 compatibility mode. See
“External Memory Interface” on page 24 for details on how to take advantage of the
external memory map.
When the addresses accessing the SRAM memory space exceeds the internal data
memory locations, the external data SRAM is accessed using the same instructions as
for the internal data memory access. When the internal data memories are accessed,
the read and write strobe pins (PD7 and PD6) are inactive during the whole access
cycle. External SRAM operation is enabled by setting the SRE bit in the MCUCR
Register.
Accessing external SRAM takes one additional clock cycle per byte compared to access
of the internal SRAM. This means that the commands LD, ST, LDS, STS, LDD, STD,
PUSH, and POP take one additional clock cycle. If the Stack is placed in external
SRAM, interrupts, subroutine calls and returns take three clock cycles extra because the
2-byte Program Counter is pushed and popped, and external memory access does not
take advantage of the internal pipeline memory access. When external SRAM interface
is used with wait-state, one-byte external access takes two, three, or four additional
clock cycles for one, two, and three wait-states respectively. Interrupt, subroutine calls
and returns will need five, seven, or nine clock cycles more than specified in the instruc-
tion set manual for one, two, and three wait-states.
The five different addressing modes for the data memory cover: Direct, Indirect with Dis-
placement, Indirect, Indirect with Pre-decrement, and Indirect with Post-increment. In
the Register File, registers R26 to R31 feature the indirect addressing pointer registers.
The direct addressing reaches the entire data space.
The Indirect with Displacement mode reaches 63 address locations from the base
address given by the Y- or Z-register.
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When using register indirect addressing modes with automatic pre-decrement and post-
increment, the address registers X, Y, and Z are decremented or incremented.
The 32 general purpose working registers, 64 (+160) I/O Registers, and the 1024 bytes
of internal data SRAM in the ATmega162 are all accessible through all these addressing
modes. The Register File is described in “General Purpose Register File” on page 10.
Figure 9. Data Memory Map
Memory configuration A
Memory configuration B
Data Memory
Data Memory
0x0000 - 0x001F
0x0020 - 0x005F
0x0060 - 0x00FF
32 Registers
64 I/O Registers 0x0020 - 0x005F
0x0060
0x0000 - 0x001F
32 Registers
64 I/O Registers
160 Ext I/O Reg.
0x0100
Internal SRAM
(1024 x 8)
Internal SRAM
(1024 x 8)
0x045F
0x0460
0x04FF
0x0500
External SRAM
(0 - 64K x 8)
External SRAM
(0 - 64K x 8)
0xFFFF
0xFFFF
Data Memory Access Times
This section describes the general access timing concepts for internal memory access.
The internal data SRAM access is performed in two clkCPU cycles as described in Figure
10.
Figure 10. On-chip Data SRAM Access Cycles
T1
T2
T3
clkCPU
Address valid
Compute Address
Address
Data
WR
Data
RD
Memory Access Instruction
Next Instruction
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EEPROM Data Memory
The ATmega162 contains 512 bytes of data EEPROM memory. It is organized as a sep-
arate data space, in which single bytes can be read and written. The EEPROM has an
endurance of at least 100,000 write/erase cycles. The access between the EEPROM
and the CPU is described in the following, specifying the EEPROM Address Registers,
the EEPROM Data Register, and the EEPROM Control Register.
“Memory Programming” on page 230 contains a detailed description on EEPROM Pro-
gramming in SPI, JTAG, or Parallel Programming mode.
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space.
The write access time for the EEPROM is given in Table 1. A selftiming function, how-
ever, lets the user software detect when the next byte can be written. If the user code
contains instructions that write the EEPROM, some precautions must be taken. In
heavily filtered power supplies, VCC is likely to rise or fall slowly on Power-up/down. This
causes the device for some period of time to run at a voltage lower than specified as
minimum for the clock frequency used. See “Preventing EEPROM Corruption” on page
22 for details on how to avoid problems in these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be fol-
lowed. Refer to the description of the EEPROM Control Register for details on this.
When the EEPROM is read, the CPU is halted for four clock cycles before the next
instruction is executed. When the EEPROM is written, the CPU is halted for two clock
cycles before the next instruction is executed.
The EEPROM Address
Register – EEARH and EEARL
Bit
15
14
13
12
11
10
9
8
EEAR8
EEAR0
0
–
–
–
–
–
–
–
EEARH
EEARL
EEAR7
EEAR6
EEAR5
EEAR4
EEAR3
EEAR2
EEAR1
7
R
6
R
5
R
4
R
3
R
2
R
1
R
Read/Write
Initial Value
R/W
R/W
X
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
X
X
X
X
X
X
X
X
• Bits 15..9 – Res: Reserved Bits
These bits are reserved bits in the ATmega162 and will always read as zero.
• Bits 8..0 – EEAR8..0: EEPROM Address
The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address
in the 512 bytes EEPROM space. The EEPROM data bytes are addressed linearly
between 0 and 511. The initial value of EEAR is undefined. A proper value must be writ-
ten before the EEPROM may be accessed.
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The EEPROM Data Register –
EEDR
Bit
7
6
5
4
3
2
1
0
MSB
R/W
0
LSB
R/W
0
EEDR
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
• Bits 7..0 – EEDR7.0: EEPROM Data
For the EEPROM write operation, the EEDR Register contains the data to be written to
the EEPROM in the address given by the EEAR Register. For the EEPROM read oper-
ation, the EEDR contains the data read out from the EEPROM at the address given by
EEAR.
The EEPROM Control Register
– EECR
Bit
7
–
6
–
5
–
4
–
3
EERIE
R/W
0
2
EEMWE
R/W
1
EEWE
R/W
X
0
EERE
R/W
0
EECR
Read/Write
Initial Value
R
0
R
0
R
0
R
0
0
• Bits 7..4 – Res: Reserved Bits
These bits are reserved bits in the ATmega162 and will always read as zero.
• Bit 3 – EERIE: EEPROM Ready Interrupt Enable
Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set.
Writing EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a
constant interrupt when EEWE is cleared.
• Bit 2 – EEMWE: EEPROM Master Write Enable
The EEMWE bit determines whether setting EEWE to one causes the EEPROM to be
written. When EEMWE is set, setting EEWE within four clock cycles will write data to the
EEPROM at the selected address. If EEMWE is zero, setting EEWE will have no effect.
When EEMWE has been written to one by software, hardware clears the bit to zero after
four clock cycles. See the description of the EEWE bit for an EEPROM write procedure.
• Bit 1 – EEWE: EEPROM Write Enable
The EEPROM Write Enable signal EEWE is the write strobe to the EEPROM. When
address and data are correctly set up, the EEWE bit must be written to one to write the
value into the EEPROM. The EEMWE bit must be written to one before a logical one is
written to EEWE, otherwise no EEPROM write takes place. The following procedure
should be followed when writing the EEPROM (the order of steps 3 and 4 is not
essential):
1. Wait until EEWE becomes zero.
2. Wait until SPMEN in SPMCR becomes zero.
3. Write new EEPROM address to EEAR (optional).
4. Write new EEPROM data to EEDR (optional).
5. Write a logical one to the EEMWE bit while writing a zero to EEWE in EECR.
6. Within four clock cycles after setting EEMWE, write a logical one to EEWE.
The EEPROM can not be programmed during a CPU write to the Flash memory. The
software must check that the Flash programming is completed before initiating a new
EEPROM write. Step 2 is only relevant if the software contains a Boot Loader allowing
the CPU to program the Flash. If the Flash is never being updated by the CPU, step 2
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can be omitted. See “Boot Loader Support – Read-While-Write Self-programming” on
page 216 for details about boot programming.
Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the
EEPROM Master Write Enable will time-out. If an interrupt routine accessing the
EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be
modified, causing the interrupted EEPROM access to fail. It is recommended to have
the Global Interrupt Flag cleared during all the steps to avoid these problems.
When the write access time has elapsed, the EEWE bit is cleared by hardware. The
user software can poll this bit and wait for a zero before writing the next byte. When
EEWE has been set, the CPU is halted for two cycles before the next instruction is
executed.
• Bit 0 – EERE: EEPROM Read Enable
The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the
correct address is set up in the EEAR Register, the EERE bit must be written to a logic
one to trigger the EEPROM read. The EEPROM read access takes one instruction, and
the requested data is available immediately. When the EEPROM is read, the CPU is
halted for four cycles before the next instruction is executed.
The user should poll the EEWE bit before starting the read operation. If a write operation
is in progress, it is neither possible to read the EEPROM, nor to change the EEAR
Register.
The calibrated Oscillator is used to time the EEPROM accesses. Table 1 lists the typical
programming time for EEPROM access from the CPU.
Table 1. EEPROM Programming Time
Number of Calibrated RC
Symbol
Oscillator Cycles(1)
Typ Programming Time
EEPROM write (from CPU)
8448
8.5 ms
Note:
1. Uses 1 MHz clock, independent of CKSEL Fuse settings
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The following code examples show one assembly and one C function for writing to the
EEPROM. The examples assume that interrupts are controlled (e.g., by disabling inter-
rupts globally) so that no interrupts will occur during execution of these functions. The
examples also assume that no Flash Boot Loader is present in the software. If such
code is present, the EEPROM write function must also wait for any ongoing SPM com-
mand to finish.
Assembly Code Example
EEPROM_write:
; Wait for completion of previous write
sbic EECR,EEWE
rjmp EEPROM_write
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Write data (r16) to data register
out EEDR,r16
; Write logical one to EEMWE
sbi EECR,EEMWE
; Start eeprom write by setting EEWE
sbi EECR,EEWE
ret
C Code Example
void EEPROM_write(unsigned int uiAddress, unsigned char ucData)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEWE))
;
/* Set up address and data registers */
EEAR = uiAddress;
EEDR = ucData;
/* Write logical one to EEMWE */
EECR |= (1<<EEMWE);
/* Start eeprom write by setting EEWE */
EECR |= (1<<EEWE);
}
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The next code examples show assembly and C functions for reading the EEPROM. The
examples assume that interrupts are controlled so that no interrupts will occur during
execution of these functions.
Assembly Code Example
EEPROM_read:
; Wait for completion of previous write
sbic EECR,EEWE
rjmp EEPROM_read
; Set up address (r18:r17) in address register
out EEARH, r18
out EEARL, r17
; Start eeprom read by writing EERE
sbi EECR,EERE
; Read data from data register
in
r16,EEDR
ret
C Code Example
unsigned char EEPROM_read(unsigned int uiAddress)
{
/* Wait for completion of previous write */
while(EECR & (1<<EEWE))
;
/* Set up address register */
EEAR = uiAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from data register */
return EEDR;
}
EEPROM Write During Power- When entering Power-down sleep mode while an EEPROM write operation is active, the
down Sleep Mode
EEPROM write operation will continue, and will complete before the write access time
has passed. However, when the write operation is complete, the Oscillator continues
running, and as a consequence, the device does not enter Power-down entirely. It is
therefore recommended to verify that the EEPROM write operation is completed before
entering Power-down.
Preventing EEPROM
Corruption
During periods of low VCC, the EEPROM data can be corrupted because the supply volt-
age is too low for the CPU and the EEPROM to operate properly. These issues are the
same as for board level systems using EEPROM, and the same design solutions should
be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too
low. First, a regular write sequence to the EEPROM requires a minimum voltage to
operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the
supply voltage is too low.
EEPROM data corruption can easily be avoided by following this design
recommendation:
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Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
This can be done by enabling the internal Brown-out Detector (BOD). If the detection
level of the internal BOD does not match the needed detection level, an external low
VCC Reset Protection circuit can be used. If a Reset occurs while a write operation is in
progress, the write operation will be completed provided that the power supply voltage is
sufficient.
I/O Memory
The I/O space definition of the ATmega162 is shown in “Register Summary” on page
303.
All ATmega162 I/Os and peripherals are placed in the I/O space. All I/O locations may
be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data
between the 32 general purpose working registers and the I/O space. I/O Registers
within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI
instructions. In these registers, the value of single bits can be checked by using the
SBIS and SBIC instructions. Refer to the instruction set section for more details. When
using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be
used. When addressing I/O Registers as data space using LD and ST instructions, 0x20
must be added to these addresses. The ATmega162 is a complex microcontroller with
more peripheral units than can be supported within the 64 location reserved in Opcode
for the IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in SRAM,
only the ST/STS/STD and LD/LDS/LDD instructions can be used. The Extended I/O
space is replaced with SRAM locations when the ATmega162 is in the ATmega161
compatibility mode.
For compatibility with future devices, reserved bits should be written to zero if accessed.
Reserved I/O memory addresses should never be written.
Some of the Status Flags are cleared by writing a logical one to them. Note that the CBI
and SBI instructions will operate on all bits in the I/O Register, writing a one back into
any flag read as set, thus clearing the flag. The CBI and SBI instructions work with reg-
isters 0x00 to 0x1F only.
The I/O and peripherals control registers are explained in later sections.
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External Memory
Interface
With all the features the External Memory Interface provides, it is well suited to operate
as an interface to memory devices such as external SRAM and FLASH, and peripherals
such as LCD-display, A/D, and D/A. The main features are:
• Four Different Wait-state Settings (Including No Wait-state)
• Independent Wait-state Setting for Different External Memory Sectors (Configurable
Sector Size)
• The Number of Bits Dedicated to Address High Byte is Selectable
• Bus Keepers on Data Lines to Minimize Current Consumption (Optional)
Overview
When the eXternal MEMory (XMEM) is enabled, address space outside the internal
SRAM becomes available using the dedicated external memory pins (see Figure 1 on
page 2, Table 29 on page 69, Table 35 on page 74, and Table 41 on page 80). The
memory configuration is shown in Figure 11.
Figure 11. External Memory with Sector Select
0x0000
Internal Memory
0x04FF/0x045F(1)
0x0500/0x0460(1)
Lower Sector
SRW01
SRW00
SRL[2..0]
External Memory
Upper Sector
(0-64K x 8)
SRW11
SRW10
0xFFFF
Note:
1. Address depends on the ATmega161 compatibility Fuse. See “SRAM Data Memory”
on page 16 and Figure 9 on page 17 for details.
Using the External Memory
Interface
The interface consists of:
•
•
•
•
•
AD7:0: Multiplexed low-order address bus and data bus
A15:8: High-order address bus (configurable number of bits)
ALE: Address latch enable
RD: Read strobe.
WR: Write strobe.
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ATmega162/V
The control bits for the External Memory Interface are located in three registers, the
MCU Control Register – MCUCR, the Extended MCU Control Register – EMCUCR, and
the Special Function IO Register – SFIOR.
When the XMEM interface is enabled, it will override the settings in the Data Direction
registers corresponding to the ports dedicated to the interface. For details about this port
override, see the alternate functions in section “I/O-Ports” on page 62. The XMEM inter-
face will autodetect whether an access is internal or external. If the access is external,
the XMEM interface will output address, data, and the control signals on the ports
according to Figure 13 (this figure shows the wave forms without wait-states). When
ALE goes from high to low, there is a valid address on AD7:0. ALE is low during a data
transfer. When the XMEM interface is enabled, also an internal access will cause activ-
ity on address-, data- and ALE ports, but the RD and WR strobes will not toggle during
internal access. When the External Memory Interface is disabled, the normal pin and
data direction settings are used. Note that when the XMEM interface is disabled, the
address space above the internal SRAM boundary is not mapped into the internal
SRAM. Figure 12 illustrates how to connect an external SRAM to the AVR using an octal
latch (typically “74x573” or equivalent) which is transparent when G is high.
Address Latch Requirements Due to the high-speed operation of the XRAM interface, the address latch must be
selected with care for system frequencies above 8 MHz @ 4V and 4 MHz @ 2.7V.
When operating at conditions above these frequencies, the typical old style 74HC series
latch becomes inadequate. The external memory interface is designed in compliance to
the 74AHC series latch. However, most latches can be used as long they comply with
the main timing parameters. The main parameters for the address latch are:
•
•
•
D to Q propagation delay (tpd).
Data setup time before G low (tsu).
Data (address) hold time after G low (th).
The external memory interface is designed to guaranty minimum address hold time after
G is asserted low of th = 5 ns (refer to tLAXX_LD/tLLAXX_ST in Table 115 to Table 122 on
page 271). The D to Q propagation delay (tpd) must be taken into consideration when
calculating the access time requirement of the external component. The data setup time
before G low (tsu) must not exceed address valid to ALE low (tAVLLC) minus PCB wiring
delay (dependent on the capacitive load).
Figure 12. External SRAM Connected to the AVR
D[7:0]
AD7:0
ALE
D
G
Q
A[7:0]
SRAM
A[15:8]
AVR
A15:8
RD
RD
WR
WR
25
2513F–AVR–12/03
Pull-up and Bus Keeper
The pull-up resistors on the AD7:0 ports may be activated if the corresponding Port reg-
ister is written to one. To reduce power consumption in sleep mode, it is recommended
to disable the pull-ups by writing the Port register to zero before entering sleep.
The XMEM interface also provides a bus keeper on the AD7:0 lines. The Bus Keeper
can be disabled and enabled in software as described in “Special Function IO Register –
SFIOR” on page 30. When enabled, the Bus Keeper will keep the previous value on the
AD7:0 bus while these lines are tri-stated by the XMEM interface.
Timing
External memory devices have various timing requirements. To meet these require-
ments, the ATmega162 XMEM interface provides four different wait-states as shown in
Table 3. It is important to consider the timing specification of the external memory
device before selecting the wait-state. The most important parameters are the access
time for the external memory in conjunction with the set-up requirement of the
ATmega162. The access time for the external memory is defined to be the time from
receiving the chip select/address until the data of this address actually is driven on the
bus. The access time cannot exceed the time from the ALE pulse is asserted low until
data must be stable during a read sequence (tLLRL+ tRLRH - tDVRH in Table 115 to Table
122 on page 271). The different wait-states are set up in software. As an additional fea-
ture, it is possible to divide the external memory space in two sectors with individual
wait-state settings. This makes it possible to connect two different memory devices with
different timing requirements to the same XMEM interface. For XMEM interface timing
details, please refer to Figure 118 to Figure 121, and Table 115 to Table 122.
Note that the XMEM interface is asynchronous and that the waveforms in the figures
below are related to the internal system clock. The skew between the internal and exter-
nal clock (XTAL1) is not guaranteed (it varies between devices, temperature, and supply
voltage). Consequently, the XMEM interface is not suited for synchronous operation.
Figure 13. External Data Memory Cycles without Wait-state
(SRWn1 = 0 and SRWn0 =0)(1)
T1
T2
T3
T4
System Clock (CLKCPU
)
ALE
A15:8 Prev. addr.
DA7:0 Prev. data
WR
Address
Data
Address
Address
XX
DA7:0 (XMBK = 0)
Data
Data
DA7:0 (XMBK = 1) Prev. data
RD
Address
Note:
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
sector) or SRW00 (lower sector).
The ALE pulse in period T4 is only present if the next instruction accesses the RAM
(internal or external).
26
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 14. External Data Memory Cycles with SRWn1 = 0 and SRWn0 = 1(1)
T1
T2
T3
T4
T5
System Clock (CLKCPU
)
ALE
A15:8 Prev. addr.
DA7:0 Prev. data
WR
Address
Data
Address
Address
XX
DA7:0 (XMBK = 0)
Data
Data
DA7:0 (XMBK = 1) Prev. data
RD
Address
Note:
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
sector) or SRW00 (lower sector)
The ALE pulse in period T5 is only present if the next instruction accesses the RAM
(internal or external).
Figure 15. External Data Memory Cycles with SRWn1 = 1 and SRWn0 = 0(1)
T1
T2
T3
T4
T5
T6
System Clock (CLKCPU
)
ALE
A15:8 Prev. addr.
DA7:0 Prev. data
WR
Address
Data
Address
Address
XX
DA7:0 (XMBK = 0)
Data
Data
DA7:0 (XMBK = 1) Prev. data
RD
Address
Note:
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
sector) or SRW00 (lower sector).
The ALE pulse in period T6 is only present if the next instruction accesses the RAM
(internal or external).
27
2513F–AVR–12/03
Figure 16. External Data Memory Cycles with SRWn1 = 1 and SRWn0 = 1(1)
T1
T2
T3
T4
T5
T6
T7
System Clock (CLKCPU
)
ALE
A15:8 Prev. addr.
DA7:0 Prev. data
WR
Address
Data
Address
Address
XX
DA7:0 (XMBK = 0)
Data
Data
DA7:0 (XMBK = 1) Prev. data
RD
Address
Note:
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
sector) or SRW00 (lower sector).
The ALE pulse in period T7 is only present if the next instruction accesses the RAM
(internal or external).
XMEM Register
Description
MCU Control Register –
MCUCR
Bit
7
6
SRW10
R/W
0
5
SE
R/W
0
4
3
ISC11
R/W
0
2
ISC10
R/W
0
1
ISC01
R/W
0
0
ISC00
R/W
0
SRE
R/W
0
SM1
R/W
0
MCUCR
Read/Write
Initial Value
• Bit 7 – SRE: External SRAM/XMEM Enable
Writing SRE to one enables the External Memory Interface.The pin functions AD7:0,
A15:8, ALE, WR, and RD are activated as the alternate pin functions. The SRE bit over-
rides any pin direction settings in the respective Data Direction Registers. Writing SRE
to zero, disables the External Memory Interface and the normal pin and data direction
settings are used.
• Bit 6 – SRW10: Wait State Select Bit
For a detailed description, see common description for the SRWn bits below (EMCUCR
description).
Extended MCU Control
Register – EMCUCR
Bit
7
6
SRL2
R/W
0
5
SRL1
R/W
0
4
SRL0
R/W
0
3
SRW01
R/W
0
2
SRW00
R/W
0
1
SRW11
R/W
0
0
SM0
R/W
0
ISC2
R/W
0
EMCUCR
Read/Write
Initial Value
• Bit 6..4 – SRL2, SRL1, SRL0: Wait State Sector Limit
It is possible to configure different wait-states for different external memory addresses.
The external memory address space can be divided in two sectors that have separate
wait-state bits. The SRL2, SRL1, and SRL0 bits select the splitting of these sectors, see
Table 2 and Figure 11. By default, the SRL2, SRL1, and SRL0 bits are set to zero and
the entire external memory address space is treated as one sector. When the entire
28
ATmega162/V
2513F–AVR–12/03
ATmega162/V
SRAM address space is configured as one sector, the wait-states are configured by the
SRW11 and SRW10 bits.
Table 2. Sector Limits with Different Settings of SRL2..0
SRL2
SRL1
SRL0
Sector Limits
Lower sector = N/A
0
0
0
Upper sector = 0x1100 - 0xFFFF
Lower sector = 0x1100 - 0x1FFF
Upper sector = 0x2000 - 0xFFFF
0
0
0
1
1
1
1
0
1
1
0
0
1
1
1
0
1
0
1
0
1
Lower sector = 0x1100 - 0x3FFF
Upper sector = 0x4000 - 0xFFFF
Lower sector = 0x1100 - 0x5FFF
Upper sector = 0x6000 - 0xFFFF
Lower sector = 0x1100 - 0x7FFF
Upper sector = 0x8000 - 0xFFFF
Lower sector = 0x1100 - 0x9FFF
Upper sector = 0xA000 - 0xFFFF
Lower sector = 0x1100 - 0xBFFF
Upper sector = 0xC000 - 0xFFFF
Lower sector = 0x1100 - 0xDFFF
Upper sector = 0xE000 - 0xFFFF
• Bit 1 and Bit 6 MCUCR – SRW11, SRW10: Wait-state Select Bits for Upper
Sector
The SRW11 and SRW10 bits control the number of wait-states for the upper sector of
the external memory address space, see Table 3.
• Bit 3..2 – SRW01, SRW00: Wait-state Select Bits for Lower Sector
The SRW01 and SRW00 bits control the number of wait-states for the lower sector of
the external memory address space, see Table 3.
Table 3. Wait-states(1)
SRWn1 SRWn0
Wait-states
0
0
1
0
1
0
No wait-states
Wait one cycle during read/write strobe
Wait two cycles during read/write strobe
Wait two cycles during read/write and wait one cycle before driving out
new address
1
1
Note:
1. n = 0 or 1 (lower/upper sector).
For further details of the timing and wait-states of the External Memory Interface, see
Figure 13 to Figure 16 how the setting of the SRW bits affects the timing.
29
2513F–AVR–12/03
Special Function IO Register –
SFIOR
Bit
7
6
XMBK
R/W
0
5
XMM2
R/W
0
4
XMM1
R/W
0
3
XMM0
R/W
0
2
1
PSR2
R/W
0
0
PSR310
R/W
0
TSM
R/W
0
PUD
R/W
0
SFIOR
Read/Write
Initial Value
• Bit 6 – XMBK: External Memory Bus Keeper Enable
Writing XMBK to one enables the Bus Keeper on the AD7:0 lines. When the Bus Keeper
is enabled, AD7:0 will keep the last driven value on the lines even if the XMEM interface
has tri-stated the lines. Writing XMBK to zero disables the Bus Keeper. XMBK is not
qualified with SRE, so even if the XMEM interface is disabled, the bus keepers are still
activated as long as XMBK is one.
• Bit 6..3 – XMM2, XMM1, XMM0: External Memory High Mask
When the External Memory is enabled, all Port C pins are used for the high address
byte by default. If the full 60KB address space is not required to access the external
memory, some, or all, Port C pins can be released for normal Port Pin function as
described in Table 4. As described in “Using all 64KB Locations of External Memory” on
page 32, it is possible to use the XMMn bits to access all 64KB locations of the external
memory.
Table 4. Port C Pins Released as Normal Port Pins when the External Memory is
Enabled
XMM2 XMM1 XMM0 # Bits for External Memory Address
Released Port Pins
None
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
8 (Full 60 KB space)
7
PC7
6
PC7 - PC6
PC7 - PC5
PC7 - PC4
PC7 - PC3
PC7 - PC2
Full Port C
5
4
3
2
No Address high bits
Using all Locations of
Since the external memory is mapped after the internal memory as shown in Figure 11,
External Memory Smaller than the external memory is not addressed when addressing the first 1,280 bytes of data
64 KB
space. It may appear that the first 1,280 bytes of the external memory are inaccessible
(external memory addresses 0x0000 to 0x04FF). However, when connecting an exter-
nal memory smaller than 64 KB, for example 32 KB, these locations are easily accessed
simply by addressing from address 0x8000 to 0x84FF. Since the External Memory
Address bit A15 is not connected to the external memory, addresses 0x8000 to 0x84FF
will appear as addresses 0x0000 to 0x04FF for the external memory. Addressing above
address 0x84FF is not recommended, since this will address an external memory loca-
tion that is already accessed by another (lower) address. To the Application software,
the external 32 KB memory will appear as one linear 32 KB address space from 0x0500
to 0x84FF. This is illustrated in Figure 17. Memory configuration B refers to the
ATmega161 compatibility mode, configuration A to the non-compatible mode.
30
ATmega162/V
2513F–AVR–12/03
ATmega162/V
When the device is set in ATmega161 compatibility mode, the internal address space is
1,120 bytes. This implies that the first 1,120 bytes of the external memory can be
accessed at addresses 0x8000 to 0x845F. To the Application software, the external 32
KB memory will appear as one linear 32 KB address space from 0x0460 to 0x845F.
Figure 17. Address Map with 32 KB External Memory
Memory Configuration B
Memory Configuration A
AVR Memory Map
External 32K SRAM
AVR Memory Map
External 32K SRAM
0x0000
0x0000
0x0000
0x0000
Internal Memory
Internal Memory
0x045F
0x0460
0x045F
0x0460
0x04FF
0x0500
0x04FF
0x0500
External
Memory
External
Memory
0x7FFF
0x8000
0x7FFF
0x8000
0x7FFF
0x7FFF
0x84FF
0x8500
0x845F
0x8460
(Unused)
(Unused)
0xFFFF
0xFFFF
31
2513F–AVR–12/03
Using all 64KB Locations of
External Memory
Since the external memory is mapped after the internal memory as shown in Figure 11,
only 64,256 Bytes of external memory are available by default (address space 0x0000
to 0x05FF is reserved for internal memory). However, it is possible to take advantage of
the entire external memory by masking the higher address bits to zero. This can be
done by using the XMMn bits and control by software the most significant bits of the
address. By setting Port C to output 0x00, and releasing the most significant bits for nor-
mal Port Pin operation, the Memory Interface will address 0x0000 - 0x1FFF. See code
example below.
Assembly Code Example(1)
; OFFSET is defined to 0x2000 to ensure
; external memory access
; Configure Port C (address high byte) to
; output 0x00 when the pins are released
; for normal Port Pin operation
ldi
out
ldi
out
r16, 0xFF
DDRC, r16
r16, 0x00
PORTC, r16
; release PC7:5
ldi
out
r16, (1<<XMM1)|(1<<XMM0)
SFIOR, r16
; write 0xAA to address 0x0001 of external
; memory
ldi
sts
r16, 0xaa
0x0001+OFFSET, r16
; re-enable PC7:5 for external memory
ldi
out
r16, (0<<XMM1)|(0<<XMM0)
SFIOR, r16
; store 0x55 to address (OFFSET + 1) of
; external memory
ldi
sts
r16, 0x55
0x0001+OFFSET, r16
C Code Example(1)
#define OFFSET 0x2000
void XRAM_example(void)
{
unsigned char *p = (unsigned char *) (OFFSET + 1);
DDRC = 0xFF;
PORTC = 0x00;
SFIOR = (1<<XMM1) | (1<<XMM0);
*p = 0xaa;
SFIOR = 0x00;
*p = 0x55;
}
Note:
1. The example code assumes that the part specific header file is included.
Care must be exercised using this option as most of the memory is masked away.
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ATmega162/V
2513F–AVR–12/03
ATmega162/V
System Clock and
Clock Options
Clock Systems and their Figure 18 presents the principal clock systems in the AVR and their distribution. All of
the clocks need not be active at a given time. In order to reduce power consumption, the
Distribution
clocks to modules not being used can be halted by using different sleep modes, as
described in “Power Management and Sleep Modes” on page 41. The clock systems
are detailed below.
Figure 18. Clock Distribution
Asynchronous
Timer/Counter
General I/O
Modules
Flash and
EEPROM
CPU Core
RAM
clkI/O
clkCPU
AVR Clock
Control Unit
clkASY
clkFLASH
Reset Logic
Watchdog Timer
Source clock
Watchdog clock
Clock
Multiplexer
Watchdog
Oscillator
Timer/Counter
Oscillator
Crystal
Oscillator
Low-frequency
Crystal Oscillator
Calibrated RC
Oscillator
External Clock
CPU clock – clkCPU
I/O clock – clkI/O
The CPU clock is routed to parts of the system concerned with operation of the AVR
core. Examples of such modules are the General Purpose Register File, the Status Reg-
ister and the data memory holding the Stack Pointer. Halting the CPU clock inhibits the
core from performing general operations and calculations.
The I/O clock is used by the majority of the I/O modules, like Timer/Counters, SPI, and
USART. The I/O clock is also used by the External Interrupt module, but note that some
external interrupts are detected by asynchronous logic, allowing such interrupts to be
detected even if the I/O clock is halted.
Flash clock – clkFLASH
The Flash clock controls operation of the Flash interface. The Flash clock is usually
active simultaneously with the CPU clock.
Asynchronous Timer clock –
clkASY
The Asynchronous Timer clock allows the Asynchronous Timer/Counter to be clocked
directly from an external 32 kHz clock crystal. The dedicated clock domain allows using
this Timer/Counter as a realtime counter even when the device is in sleep mode.
33
2513F–AVR–12/03
Clock Sources
The device has the following clock source options, selectable by Flash Fuse bits as
shown below. The clock from the selected source is input to the AVR clock generator,
and routed to the appropriate modules.
Table 5. Device Clocking Options Select
Device Clocking Option
External Crystal/Ceramic Resonator
External Low-frequency Crystal
Calibrated Internal RC Oscillator
External Clock
CKSEL3..0
1111 - 1000
0111 - 0100
0010
0000
Reserved
0011, 0001
Note:
For all fuses “1” means unprogrammed while “0” means programmed.
The various choices for each clocking option is given in the following sections. When the
CPU wakes up from Power-down or Power-save, the selected clock source is used to
time the start-up, ensuring stable Oscillator operation before instruction execution starts.
When the CPU starts from Reset, there is an additional delay allowing the power to
reach a stable level before commencing normal operation. The Watchdog Oscillator is
used for timing this realtime part of the start-up time. The number of WDT Oscillator
cycles used for each Time-out is shown in Table 6. The frequency of the Watchdog
Oscillator is voltage dependent as shown in “ATmega162 Typical Characteristics” on
page 274.
Table 6. Number of Watchdog Oscillator Cycles
Typ Time-out (VCC = 5.0V)
Typ Time-out (VCC = 3.0V)
Number of Cycles
4K (4,096)
4.1 ms
65 ms
4.3 ms
69 ms
64K (65,536)
Default Clock Source
Crystal Oscillator
The device is shipped with CKSEL = “0010”, SUT = “10” and CKDIV8 programmed. The
default clock source setting is therefore the Internal RC Oscillator with longest startup
time and an initial system clock prescaling of 8. This default setting ensures that all
users can make their desired clock source setting using an In-System or Parallel
programmer.
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can
be configured for use as an On-chip Oscillator, as shown in Figure 19. Either a quartz
crystal or a ceramic resonator may be used.
C1 and C2 should always be equal for both crystals and resonators. The optimal value
of the capacitors depends on the crystal or resonator in use, the amount of stray capac-
itance, and the electromagnetic noise of the environment. Some initial guidelines for
choosing capacitors for use with crystals are given in Table 7. For ceramic resonators,
the capacitor values given by the manufacturer should be used.
34
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 19. Crystal Oscillator Connections
C2
XTAL2
XTAL1
GND
C1
The Oscillator can operate in four different modes, each optimized for a specific fre-
quency range. The operating mode is selected by the fuses CKSEL3:1 as shown in
Table 7.
Table 7. Crystal Oscillator Operating Modes
Frequency Range
(MHz)
Recommended Range for Capacitors C1 and
C2 for Use with Crystals (pF)
CKSEL3:1
100(1)
101
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
8.0 -
–
12 - 22
12 - 22
12 - 22
110
111
Note:
1. This option should not be used with crystals, only with ceramic resonators.
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown
in Table 8.
Table 8. Start-up Times for the Crystal Oscillator Clock Selection
Start-up Time from
Power-down and
Power-save
Additional Delay from
Reset (VCC = 5.0V)
Recommended
Usage
CKSEL0 SUT1:0
0
0
0
0
1
1
1
1
00
01
10
11
00
01
10
11
258 CK(1)
258 CK(1)
1K CK(2)
1K CK(2)
1K CK(2)
16K CK
16K CK
16K CK
4.1 ms
65 ms
–
Ceramic resonator,
fast rising power
Ceramic resonator,
slowly rising power
Ceramic resonator,
BOD enabled
4.1 ms
65 ms
–
Ceramic resonator,
fast rising power
Ceramic resonator,
slowly rising power
Crystal Oscillator,
BOD enabled
4.1 ms
65 ms
Crystal Oscillator,
fast rising power
Crystal Oscillator,
slowly rising power
35
2513F–AVR–12/03
Notes: 1. These options should only be used when not operating close to the maximum fre-
quency of the device, and only if frequency stability at start-up is not important for the
application. These options are not suitable for crystals.
2. These options are intended for use with ceramic resonators and will ensure fre-
quency stability at start-up. They can also be used with crystals when not operating
close to the maximum frequency of the device, and if frequency stability at start-up is
not important for the application.
Low-frequency Crystal
Oscillator
To use a 32.768 kHz watch crystal as the clock source for the device, the Low-fre-
quency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0100”,
“0101”, “0110” or “0111”. The crystal should be connected as shown in Figure 19. If
CKSEL equals “0110” or “0111”, the internal capacitors on XTAL1 and XTAL2 are
enabled, thereby removing the need for external capacitors. The internal capacitors
have a nominal value of 10 pF.
When this Oscillator is selected, start-up times are determined by the SUT Fuses (real
time-out from Reset) and CKSEL0 (number of clock cycles) as shown in Table 9 and
Table 10.
Table 9. Start-up Delay from Reset when Low-frequency Crystal Oscillator is Selected
SUT1:0
00
Additional Delay from Reset (VCC = 5.0V)
Recommended Usage
0 ms
Fast rising power or BOD enabled
Fast rising power or BOD enabled
Slowly rising power
01
4.1 ms
65 ms
10
11
Reserved
Table 10. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Start-up Time from
Internal Capacitors
Enabled?
Power-down and
Power-save
CKSEL1:0
00(1)
Recommended Usage
No
No
1K CK
32K CK
1K CK
01
Stable Frequency at start-up
10(1)
Yes
Yes
11
32K CK
Stable Frequency at start-up
Note:
1. These options should only be used if frequency stability at start-up is not important
for the application.
Calibrated Internal RC
Oscillator
The calibrated internal RC Oscillator provides a fixed 8.0 MHz clock. The frequency is
nominal value at 3V and 25°C. If 8.0 MHz frequency exceed the specification of the
device (depends on VCC), the CKDIV8 Fuse must be programmed in order to divide the
internal frequency by 8 during start-up. See “System Clock Prescaler” on page 39 for
more details. This clock may be selected as the system clock by programming the
CKSEL Fuses as shown in Table 11. If selected, it will operate with no external compo-
nents. During Reset, hardware loads the calibration byte into the OSCCAL Register and
thereby automatically calibrates the RC Oscillator. At 3V and 25°C, this calibration gives
a frequency within ± 10% of the nominal frequency. Using run-time calibration methods
as described in application notes available at www.atmel.com/avr it is possible to
achieve ± 2% accuracy at any given VCC and Temperature. When this Oscillator is used
as the chip clock, the Watchdog Oscillator will still be used for the Watchdog Timer and
36
ATmega162/V
2513F–AVR–12/03
ATmega162/V
for the Reset Time-out. For more information on the pre-programmed calibration value,
see the section “Calibration Byte” on page 233.
Table 11. Internal Calibrated RC Oscillator Operating Modes
CKSEL3:0
Nominal Frequency
0010(1)
8.0 MHz
Note:
1. The device is shipped with this option selected.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as
shown in Table 12. XTAL1 and XTAL2 should be left unconnected (NC).
Table 12. Start-up Times for the Internal Calibrated RC Oscillator Clock Selection
Start-up Time from Power-
down and Power-save
Additional Delay from
Reset (VCC = 5.0V)
SUT1:0
00
Recommended Usage
BOD enabled
6 CK
6 CK
6 CK
–
4.1 ms
01
Fast rising power
Slowly rising power
10(1)
65 ms
11
Reserved
Note:
1. The device is shipped with this option selected.
Oscillator Calibration Register
– OSCCAL
Bit
7
–
6
5
4
3
2
1
0
CAL6
R/W
CAL5
R/W
CAL4
R/W
CAL3
R/W
CAL2
R/W
CAL1
R/W
CAL0
R/W
OSCCAL
Read/Write
Initial Value
R
0
Device Specific Calibration Value
• Bit 7 – Res: Reserved Bit
This bit is reserved bit in the ATmega162, and will always read as zero.
• Bits 6..0 – CAL6..0: Oscillator Calibration Value
Writing the calibration byte to this address will trim the Internal Oscillator to remove pro-
cess variations from the Oscillator frequency. This is done automatically during Chip
Reset. When OSCCAL is zero, the lowest available frequency is chosen. Writing non-
zero values to this register will increase the frequency of the Internal Oscillator. Writing
0x7F to the register gives the highest available frequency. The calibrated Oscillator is
used to time EEPROM and Flash access. If EEPROM or Flash is written, do not cali-
brate to more than 10% above the nominal frequency. Otherwise, the EEPROM or Flash
write may fail.
37
2513F–AVR–12/03
Table 13. Internal RC Oscillator Frequency Range.
Min Frequency in Percentage of
Max Frequency in Percentage of
Nominal Frequency
OSCCAL Value
0x00
Nominal Frequency
50%
75%
100%
150%
200%
0x3F
0x7F
100%
External Clock
To drive the device from an external clock source, XTAL1 should be driven as shown in
Figure 20. To run the device on an external clock, the CKSEL Fuses must be pro-
grammed to “0000”.
Figure 20. External Clock Drive Configuration
EXTERNAL
CLOCK
SIGNAL
When this clock source is selected, start-up times are determined by the SUT Fuses as
shown in Table 14.
Table 14. Start-up Times for the External Clock Selection
Start-up Time from
Power-down and
Power-save
Additional Delay from
Reset (VCC = 5.0V)
SUT1..0
00
Recommended Usage
BOD enabled
6 CK
6 CK
6 CK
–
4.1 ms
01
Fast rising power
Slowly rising power
10
65 ms
11
Reserved
When applying an external clock, it is required to avoid sudden changes in the applied
clock frequency to ensure stable operation of the MCU. A variation in frequency of more
than 2% from one clock cycle to the next can lead to unpredictable behavior. It is
required to ensure that the MCU is kept in reset during such changes in the clock
frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of
the internal clock frequency while still ensuring stable operation. Refer to “System Clock
Prescaler” on page 39 for details.
Clock output buffer
When the CKOUT Fuse is programmed, the system clock will be output on PortB 0. This
mode is suitable when chip clock is used to drive other circuits on the system. The clock
38
ATmega162/V
2513F–AVR–12/03
ATmega162/V
will be output also during Reset and the normal operation of PortB will be overridden
when the fuse is programmed. Any clock sources, including Internal RC Oscillator, can
be selected when PortB 0 serves as clock output.
If the system clock prescaler is used, it is the divided system clock that is output when
the CKOUT Fuse is programmed. See “System Clock Prescaler” on page 39. for a
description of the system clock prescaler.
Timer/Counter Oscillator For AVR microcontrollers with Timer/Counter Oscillator pins (TOSC1 and TOSC2), the
crystal is connected directly between the pins. The Oscillator provides internal capaci-
tors on TOSC1 and TOSC2, thereby removing the need for external capacitors. The
internal capacitors have a nominal value of 10 pF. The Oscillator is optimized for use
with a 32.768 kHz watch crystal. Applying an external clock source to TOSC1 is not
recommended.
System Clock Prescaler
The ATmega162 system clock can be divided by setting the Clock Prescale Register –
CLKPR. This feature can be used to decrease power consumption when the require-
ment for processing power is low. This can be used with all clock source options, and it
will affect the clock frequency of the CPU and all synchronous peripherals. clkI/O, clkCPU
,
and clkFLASH are divided by a factor as shown in Table 15. Note that the clock frequency
of clkASY (asynchronously Timer/Counter) only will be scaled if the Timer/Counter is
clocked synchronously.
Clock Prescale Register –
CLKPR
Bit
7
CLKPCE
R/W
6
–
5
–
4
–
3
2
1
0
CLKPS3
R/W
CLKPS2
R/W
CLKPS1
R/W
CLKPS0
R/W
CLKPR
Read/Write
Initial Value
R
0
R
0
R
0
0
See Bit Description
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. CLK-
PCE is cleared by hardware four cycles after it is written or when CLKPS is written.
Setting the CLKPCE bit will disable interrupts, as explained in the CLKPS description
below.
• Bits 3..0 – CLKPS3..0: Clock Prescaler Select Bits 3 - 0
These bits define the division factor between the selected clock source and the internal
system clock. These bits can be written run-time to vary the clock frequency to suit the
application requirements. As the divider divides the master clock input to the MCU, the
speed of all synchronous peripherals is reduced when a division factor is used. The divi-
sion factors are given in Table 15.
To avoid unintentional changes of clock frequency, a special write procedure must be
followed to change the CLKPS bits:
1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits
in CLKPR to zero.
2. Within four cycles, write the desired value to CLKPS while writing a zero to
CLKPCE.
Caution: An interrupt between step 1 and step 2 will make the timed sequence fail. It is
recommended to have the Global Interrupt Flag cleared during these steps to avoid this
problem.
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2513F–AVR–12/03
The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unpro-
grammed, the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits
are reset to “0011”, giving a division factor of 8 at start up. This feature should be used if
the selected clock source has a higher frequency than the maximum frequency of the
device at the present operating conditions. Note that any value can be written to the
CLKPS bits regardless of the CKDIV8 Fuse setting. The Application software must
ensure that a sufficient division factor is chosen if the selected clock source has a higher
frequency than the maximum frequency of the device at the present operating condi-
tions. The device is shipped with the CKDIV8 Fuse programmed.
Table 15. Clock Prescaler Select
CLKPS3
CLKPS2
CLKPS1
CLKPS0
Clock Division Factor
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
2
4
8
16
32
64
128
256
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
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ATmega162/V
Power Management
and Sleep Modes
Sleep modes enable the application to shut down unused modules in the MCU, thereby
saving power. The AVR provides various sleep modes allowing the user to tailor the
power consumption to the application’s requirements.
To enter any of the five sleep modes, the SE bit in MCUCR must be written to logic one
and a SLEEP instruction must be executed. The SM2 bit in MCUCSR, the SM1 bit in
MCUCR, and the SM0 bit in the EMCUCR Register select which sleep mode (Idle,
Power-down, Power-save, Standby, or Extended Standby) will be activated by the
SLEEP instruction. See Table 16 for a summary. If an enabled interrupt occurs while the
MCU is in a sleep mode, the MCU wakes up. The MCU is then halted for four cycles in
addition to the start-up time, executes the interrupt routine, and resumes execution from
the instruction following SLEEP. The contents of the Register File and SRAM are unal-
tered when the device wakes up from sleep. If a Reset occurs during sleep mode, the
MCU wakes up and executes from the Reset Vector.
Figure 18 on page 33 presents the different clock systems in the ATmega162, and their
distribution. The figure is helpful in selecting an appropriate sleep mode.
MCU Control Register –
MCUCR
Bit
7
6
SRW10
R/W
0
5
SE
R/W
0
4
3
ISC11
R/W
0
2
ISC10
R/W
0
1
ISC01
R/W
0
0
ISC00
R/W
0
SRE
R/W
0
SM1
R/W
0
MCUCR
Read/Write
Initial Value
• Bit 5 – SE: Sleep Enable
The SE bit must be written to logic one to make the MCU enter the sleep mode when the
SLEEP instruction is executed. To avoid the MCU entering the sleep mode unless it is
the programmer’s purpose, it is recommended to write the Sleep Enable (SE) bit to one
just before the execution of the SLEEP instruction and to clear it immediately after wak-
ing up.
• Bit 4 – SM1: Sleep Mode Select Bit 1
The Sleep Mode Select bits select between the five available sleep modes as shown in
Table 16.
MCU Control and Status
Register – MCUCSR
Bit
7
6
–
5
4
JTRF
R/W
0
3
WDRF
R/W
0
2
BORF
R/W
0
1
EXTRF
R/W
0
0
PORF
R/W
0
JTD
R/W
0
SM2
R/W
0
MCUCSR
Read/Write
Initial Value
R/W
0
• Bit 5 – SM2: Sleep Mode Select Bit 2
The Sleep Mode Select bits select between the five available sleep modes as shown in
Table 16.
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2513F–AVR–12/03
Extended MCU Control
Register – EMCUCR
Bit
7
6
SRL2
R/W
0
5
SRL1
R/W
0
4
SRL0
R/W
0
3
SRW01
R/W
0
2
SRW00
R/W
0
1
SRW11
R/W
0
0
SM0
R/W
0
ISC2
R/W
0
EMCUCR
Read/Write
Initial Value
• Bit 7 – SM0: Sleep Mode Select Bit 0
The Sleep Mode Select bits select between the five available sleep modes as shown in
Table 16.
Table 16. Sleep Mode Select
SM2
SM1
SM0
0
Sleep Mode
Idle
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
1
Reserved
0
Power-down
Power-save
Reserved
1
0
1
Reserved
0
Standby(1)
Extended Standby(1)
1
Note:
1. Standby mode and Extended Standby mode are only available with external crystals
or resonators.
Idle Mode
When the SM2..0 bits are written to 000, the SLEEP instruction makes the MCU enter
Idle mode, stopping the CPU but allowing the SPI, USART, Analog Comparator,
Timer/Counters, Watchdog, and the interrupt system to continue operating. This sleep
mode basically halts clkCPU and clkFLASH, while allowing the other clocks to run.
Idle mode enables the MCU to wake up from external triggered interrupts as well as
internal ones like the Timer Overflow and USART Transmit Complete interrupts. If
wake-up from the Analog Comparator interrupt is not required, the Analog Comparator
can be powered down by setting the ACD bit in the Analog Comparator Control and Sta-
tus Register – ACSR. This will reduce power consumption in Idle mode.
Power-down Mode
When the SM2..0 bits are written to 010, the SLEEP instruction makes the MCU enter
Power-down mode. In this mode, the external Oscillator is stopped, while the external
interrupts and the Watchdog continue operating (if enabled). Only an External Reset, a
Watchdog Reset, a Brown-out Reset, an External Level Interrupt on INT0 or INT1, an
external interrupt on INT2, or a pin change interrupt can wake up the MCU. This sleep
mode basically halts all generated clocks, allowing operation of asynchronous modules
only.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the
changed level must be held for some time to wake up the MCU. Refer to “External Inter-
rupts” on page 83 for details.
When waking up from Power-down mode, there is a delay from the wake-up condition
occurs until the wake-up becomes effective. This allows the clock to restart and become
stable after having been stopped. The wake-up period is defined by the same CKSEL
Fuses that define the Reset Time-out period, as described in “Clock Sources” on page
34.
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ATmega162/V
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ATmega162/V
Power-save Mode
When the SM2..0 bits are written to 011, the SLEEP instruction makes the MCU enter
Power-save mode. This mode is identical to Power-down, with one exception:
If Timer/Counter2 is clocked asynchronously, i.e., the AS2 bit in ASSR is set,
Timer/Counter2 will run during sleep. The device can wake up from either Timer Over-
flow or Output Compare event from Timer/Counter2 if the corresponding
Timer/Counter2 interrupt enable bits are set in TIMSK, and the Global Interrupt Enable
bit in SREG is set.
If the Asynchronous Timer is NOT clocked asynchronously, Power-down mode is rec-
ommended instead of Power-save mode because the contents of the registers in the
Asynchronous Timer should be considered undefined after wake-up in Power-save
mode if AS2 is 0.
This sleep mode basically halts all clocks except clkASY, allowing operation only of asyn-
chronous modules, including Timer/Counter 2 if clocked asynchronously.
Standby Mode
When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Standby mode. This mode is identical to
Power-down with the exception that the main Oscillator is kept running. From Standby
mode, the device wakes up in six clock cycles.
Extended Standby Mode When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Extended Standby mode. This mode is
identical to Power-save mode with the exception that the main Oscillator is kept running.
From Extended Standby mode, the device wakes up in six clock cycles.
Table 17. Active Clock domains and Wake up sources in the different sleep modes
Active Clock domains
Oscillators
Wake-up Sources
INT2
INT1
INT0
SPM/
EEPROM Other
Main Clock
clkCPU clkFLASH clkIO clkASY Source Enabled
Timer Osc
Enabled
Sleep Mode
Idle
and Pin Change Timer2
Ready
I/O
X
X
X
X(2)
X(2)
X(2)
X
X
X
X
Power-down
Power-save
Standby(1)
X(3)
X(3)
X(3)
X(3)
X(2)
X(2)
X
X
Extended Standby(1)
X(2)
X(2)
Notes: 1. External Crystal or resonator selected as clock source
2. If AS2 bit in ASSR is set
3. For INT1 and INT0, only level interrupt
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2513F–AVR–12/03
Minimizing Power
Consumption
There are several issues to consider when trying to minimize the power consumption in
an AVR controlled system. In general, sleep modes should be used as much as possi-
ble, and the sleep mode should be selected so that as few as possible of the device’s
functions are operating. All functions not needed should be disabled. In particular, the
following modules may need special consideration when trying to achieve the lowest
possible power consumption.
Analog Comparator
When entering Idle mode, the Analog Comparator should be disabled if not needed. In
the other sleep modes, the Analog Comparator is automatically disabled. However, if
the Analog Comparator is set up to use the Internal Voltage Reference as input, the
Analog Comparator should be disabled in all sleep modes. Otherwise, the Internal Volt-
age Reference will be enabled, independent of sleep mode. Refer to “Analog
Comparator” on page 194 for details on how to configure the Analog Comparator.
Brown-out Detector
If the Brown-out Detector is not needed in the application, this module should be turned
off. If the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in
all sleep modes, and hence, always consume power. In the deeper sleep modes, this
will contribute significantly to the total current consumption. Refer to “Brown-out Detec-
tion” on page 49 for details on how to configure the Brown-out Detector.
Internal Voltage Reference
The Internal Voltage Reference will be enabled when needed by the Brown-out Detector
or the Analog Comparator. If these modules are disabled as described in the sections
above, the internal voltage reference will be disabled and it will not be consuming
power. When turned on again, the user must allow the reference to start up before the
output is used. If the reference is kept on in sleep mode, the output can be used imme-
diately. Refer to “Internal Voltage Reference” on page 51 for details on the start-up time.
Watchdog Timer
If the Watchdog Timer is not needed in the application, this module should be turned off.
If the Watchdog Timer is enabled, it will be enabled in all sleep modes, and hence,
always consume power. In the deeper sleep modes, this will contribute significantly to
the total current consumption. Refer to “Watchdog Timer” on page 51 for details on how
to configure the Watchdog Timer.
Port Pins
When entering a sleep mode, all port pins should be configured to use minimum power.
The most important thing is to ensure that no pins drive resistive loads. In sleep modes
where the I/O clock (clkI/O) is stopped, the input buffers of the device will be disabled.
This ensures that no power is consumed by the input logic when not needed. In some
cases, the input logic is needed for detecting wake-up conditions, and it will then be
enabled. Refer to the section “Digital Input Enable and Sleep Modes” on page 66 for
details on which pins are enabled. If the input buffer is enabled and the input signal is
left floating or have an analog signal level close to VCC/2, the input buffer will use exces-
sive power.
JTAG Interface and
On-chip Debug System
If the On-chip debug system is enabled by the OCDEN Fuse and the chip enter Power
down or Power save sleep mode, the main clock source remains enabled. In these
sleep modes, this will contribute significantly to the total current consumption. There are
three alternative ways to avoid this:
•
•
•
Disable OCDEN Fuse.
Disable JTAGEN Fuse.
Write one to the JTD bit in MCUCSR.
The TDO pin is left floating when the JTAG interface is enabled while the JTAG TAP
controller is not shifting data. If the hardware connected to the TDO pin does not pull up
44
ATmega162/V
2513F–AVR–12/03
ATmega162/V
the logic level, power consumption will increase. Note that the TDI pin for the next
device in the scan chain contains a pull-up that avoids this problem. Writing the JTD bit
in the MCUCSR register to one or leaving the JTAG fuse unprogrammed disables the
JTAG interface.
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2513F–AVR–12/03
System Control and
Reset
Resetting the AVR
During Reset, all I/O Registers are set to their initial values, and the program starts exe-
cution from the Reset Vector. The instruction placed at the Reset Vector must be a JMP
– Absolute Jump – instruction to the reset handling routine. If the program never
enables an interrupt source, the Interrupt Vectors are not used, and regular program
code can be placed at these locations. This is also the case if the Reset Vector is in the
Application section while the Interrupt Vectors are in the Boot section or vice versa. The
circuit diagram in Figure 21 shows the Reset Logic. Table 18 defines the electrical
parameters of the reset circuitry.
The I/O ports of the AVR are immediately reset to their initial state when a reset source
goes active. This does not require any clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the
Internal Reset. This allows the power to reach a stable level before normal operation
starts. The Time-out period of the delay counter is defined by the user through the
CKSEL Fuses. The different selections for the delay period are presented in “Clock
Sources” on page 34.
Reset Sources
The ATmega162 has five sources of reset:
•
•
•
•
Power-on Reset. The MCU is reset when the supply voltage is below the Power-on
Reset threshold (VPOT).
External Reset. The MCU is reset when a low level is present on the RESET pin for
longer than the minimum pulse length.
Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and
the Watchdog is enabled.
Brown-out Reset. The MCU is reset when the supply voltage VCC is below the
Brown-out Reset threshold (VBOT) and the Brown-out Detector is enabled. The
device is guaranteed to operate at maximum frequency for the VCC voltage down to
VBOT. VBOT must be set to the corresponding minimum voltage of the device (i.e.,
minimum VBOT for ATmega162V is 1.8V).
•
JTAG AVR Reset. The MCU is reset as long as there is a logic one in the Reset
Register, one of the scan chains of the JTAG system. Refer to the section “IEEE
1149.1 (JTAG) Boundary-scan” on page 203 for details.
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ATmega162/V
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ATmega162/V
Figure 21. Reset Logic
DATA BUS
MCU Control and Status
Register (MCUCSR)
Power-on
Reset Circuit
VCC
Brown-out
Reset Circuit
BODLEVEL [ 2..0]
Pull-up Resistor
SPIKE
FILTER
Reset Circuit
RESET
JTAG Reset
Register
Watchdog
Timer
Watchdog
Oscillator
Delay Counters
Clock
CK
Generator
TIMEOUT
CKSEL[3:0]
SUT[1:0]
Table 18. Reset Characteristics
Symbol Parameter
Condition
Min.
Typ.
Max.
Units
Power-on Reset
Threshold Voltage (rising)
TA = -40 - 85°C
TA = -40 - 85°C
0.7
1.0
1.4
V
VPOT
Power-on Reset
Threshold Voltage
0.6
0.9
1.3
V
(falling)(1)
RESET Pin Threshold
Voltage
VRST
VCC = 3V
VCC = 3V
0.1 VCC
0.9 VCC
2.5
V
Minimum pulse width on
RESET Pin
tRST
µs
Note:
1. The Power-on Reset will not work unless the supply voltage has been below VPOT
(falling)
Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detec-
tion level is defined in Table 18. The POR is activated whenever VCC is below the
detection level. The POR circuit can be used to trigger the Start-up Reset, as well as to
detect a failure in supply voltage.
A Power-on Reset (POR) circuit ensures that the device is Reset from Power-on.
Reaching the Power-on Reset threshold voltage invokes the delay counter, which deter-
mines how long the device is kept in RESET after VCC rise. The RESET signal is
activated again, without any delay, when VCC decreases below the detection level.
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2513F–AVR–12/03
Figure 22. MCU Start-up, RESET Tied to VCC
.
VPOT
VCC
VRST
RESET
tTOUT
TIME-OUT
INTERNAL
RESET
Figure 23. MCU Start-up, RESET Extended Externally
VPOT
VCC
VRST
RESET
tTOUT
TIME-OUT
INTERNAL
RESET
External Reset
An External Reset is generated by a low level on the RESET pin. Reset pulses longer
than the minimum pulse width (see Table 18) will generate a Reset, even if the clock is
not running. Shorter pulses are not guaranteed to generate a Reset. When the applied
signal reaches the Reset Threshold Voltage – VRST on its positive edge, the delay
counter starts the MCU after the Time-out period tTOUT has expired.
Figure 24. External Reset During Operation
CC
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ATmega162/V
Brown-out Detection
ATmega162 has an On-chip Brown-out Detection (BOD) circuit for monitoring the VCC
level during operation by comparing it to a fixed trigger level. The trigger level for the
BOD can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to
ensure spike free Brown-out Detection. The hysteresis on the detection level should be
interpreted as VBOT+ = VBOT + VHYST/2 and VBOT- = VBOT - VHYST/2.
Table 19. BODLEVEL Fuse Coding
(1)
BODLEVEL Fuses [2:0]
Min. VBOT
Typ. VBOT
BOD Disabled
Max. VBOT
Units
111
110(2)
1.7
2.5
4.1
2.1
1.8
2.7
4.3
2.3
2.0
2.9
4.5
2.5
101
V
100
011(2)
010
001
Reserved
000
Notes: 1. VBOT may be below nominal minimum operating voltage for some devices. For
devices where this is the case, the device is tested down to VCC = VBOT during the
production test. This guarantees that a Brown-out Reset will occur before VCC drops
to a voltage where correct operation of the microcontroller is no longer guaranteed.
This test is performed using BODLEVEL = 110 for ATmega162V, BODLEVEL = 101
for ATmega162L, and BODLEVEL = 100 for ATmega162.
2. For ATmega162V. Otherwise reserved.
Table 20. Brown-out Hysteresis
Symbol
VHYST
tBOD
Parameter
Min.
Typ.
50
2
Max.
Units
mV
Brown-out Detector hysteresis
Min Pulse Width on Brown-out Reset
µs
When the BOD is enabled and VCC decreases to a value below the trigger level (VBOT- in
Figure 25), the Brown-out Reset is immediately activated. When VCC increases above
the trigger level (VBOT+ in Figure 25), the delay counter starts the MCU after the Time-
out period tTOUT has expired.
The BOD circuit will only detect a drop in VCC if the voltage stays below the trigger level
for longer than tBOD given in Table 18.
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2513F–AVR–12/03
Figure 25. Brown-out Reset During Operation
VBOT+
VCC
VBOT-
RESET
t
TOUT
TIME-OUT
INTERNAL
RESET
Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle dura-
tion. On the falling edge of this pulse, the delay timer starts counting the Time-out period
tTOUT. Refer to page 51 for details on operation of the Watchdog Timer.
Figure 26. Watchdog Reset During Operation
CC
CK
MCU Control and Status
Register – MCUCSR
The MCU Control and Status Register provides information on which reset source
caused an MCU Reset.
Bit
7
6
–
5
SM2
R
4
3
2
1
0
JTD
R/W
0
JTRF
R/W
WDRF
R/W
BORF
R/W
EXTRF
R/W
PORF
R/W
MCUCSR
Read/Write
Initial Value
R/W
0
0
See Bit Description
• Bit 4 – JTRF: JTAG Reset Flag
This bit is set if a reset is being caused by a logic one in the JTAG Reset Register
selected by the JTAG instruction AVR_RESET. This bit is reset by a Power-on Reset, or
by writing a logic zero to the flag.
• Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
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ATmega162/V
• Bit 2 – BORF: Brown-out Reset Flag
This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
• Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
• Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to
the flag.
To make use of the Reset Flags to identify a reset condition, the user should read and
then Reset the MCUCSR as early as possible in the program. If the register is cleared
before another reset occurs, the source of the Reset can be found by examining the
Reset Flags.
Internal Voltage
Reference
ATmega162 features an internal bandgap reference. This reference is used for Brown-
out Detection, and it can be used as an input to the Analog Comparator.
Voltage Reference Enable
Signals and Start-up Time
The voltage reference has a start-up time that may influence the way it should be used.
The start-up time is given in Table 21. To save power, the reference is not always turned
on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODLEVEL Fuses).
2. When the bandgap reference is connected to the Analog Comparator (by setting
the ACBG bit in ACSR).
Thus, when the BOD is not enabled, after setting the ACBG bit, the user must always
allow the reference to start up before the output from the Analog Comparator is used. To
reduce power consumption in Power-down mode, the user can avoid the two conditions
above to ensure that the reference is turned off before entering Power-down mode.
Table 21. Internal Voltage Reference Characteristics
Symbol Parameter
VBG Bandgap reference voltage
tBG
Min.
Typ.
1.10
40
Max.
1.15
70
Units
V
1.05
Bandgap reference start-up time
µs
Bandgap reference current
consumption
IBG
10
µA
Watchdog Timer
The Watchdog Timer is clocked from a separate On-chip Oscillator which runs at
1 MHz. This is the typical frequency at VCC = 5V. See characterization data for typical
values at other VCC levels. By controlling the Watchdog Timer prescaler, the Watchdog
Reset interval can be adjusted as shown in Table 23 on page 53. The WDR – Watchdog
Reset – instruction resets the Watchdog Timer. The Watchdog Timer is also reset when
it is disabled and when a Chip Reset occurs. Eight different clock cycle periods can be
selected to determine the reset period. If the reset period expires without another
Watchdog Reset, the ATmega162 resets and executes from the Reset Vector. For tim-
ing details on the Watchdog Reset, refer to page 53.
To prevent unintentional disabling of the Watchdog or unintentional change of time-out
period, 3 different safety levels are selected by the Fuses M161C and WDTON as
51
2513F–AVR–12/03
shown in Table 22. Safety level 0 corresponds to the setting in ATmega161. There is no
restriction on enabling the WDT in any of the safety levels. Refer to “Timed Sequences
for Changing the Configuration of the Watchdog Timer” on page 55 for details.
Table 22. WDT Configuration as a Function of the Fuse Settings of M161C and
WDTON.
WDT
How to
Safety Initial
How to Disable
the WDT
Change Time-
out
M161C
WDTON
Level
State
Timed
sequence
Unprogrammed Unprogrammed
Unprogrammed Programmed
1
Disabled Timed sequence
Enabled Always enabled
Timed
sequence
2
0
2
Programmed
Programmed
Unprogrammed
Programmed
Disabled Timed sequence No restriction
Timed
sequence
Enabled
Always enabled
Figure 27. Watchdog Timer
WATCHDOG
OSCILLATOR
Watchdog Timer Control
Register – WDTCR
Bit
7
–
6
–
5
–
4
3
WDE
R/W
0
2
WDP2
R/W
0
1
WDP1
R/W
0
0
WDCE
R/W
0
WDP0
R/W
0
WDTCR
Read/Write
Initial Value
R
0
R
0
R
0
• Bits 7..5 – Res: Reserved Bits
These bits are reserved bits in the ATmega162 and will always read as zero.
• Bit 4 – WDCE: Watchdog Change Enable
This bit must be set when the WDE bit is written to logic zero. Otherwise, the Watchdog
will not be disabled. Once written to one, hardware will clear this bit after four clock
cycles. Refer to the description of the WDE bit for a Watchdog disable procedure. In
Safety Levels 1 and 2, this bit must also be set when changing the prescaler bits. See
“Timed Sequences for Changing the Configuration of the Watchdog Timer” on page 55.
• Bit 3 – WDE: Watchdog Enable
When the WDE is written to logic one, the Watchdog Timer is enabled, and if the WDE is
written to logic zero, the Watchdog Timer function is disabled. WDE can only be cleared
52
ATmega162/V
2513F–AVR–12/03
ATmega162/V
if the WDCE bit has logic level one. To disable an enabled Watchdog Timer, the follow-
ing procedure must be followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be
written to WDE even though it is set to one before the disable operation starts.
2. Within the next four clock cycles, write a logic 0 to WDE. This disables the
Watchdog.
In safety level 2, it is not possible to disable the Watchdog Timer, even with the algo-
rithm described above. See “Timed Sequences for Changing the Configuration of the
Watchdog Timer” on page 55.
• Bits 2..0 – WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1, and 0
The WDP2, WDP1, and WDP0 bits determine the Watchdog Timer prescaling when the
Watchdog Timer is enabled. The different prescaling values and their corresponding
Timeout Periods are shown in Table 23.
Table 23. Watchdog Timer Prescale Select
Number of WDT
Oscillator Cycles
Typical Time-out
at VCC = 3.0V
Typical Time-out
at VCC = 5.0V
WDP2 WDP1 WDP0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
16K (16,384)
32K (32,768)
17 ms
34 ms
69 ms
0.14 s
0.27 s
0.55 s
1.1 s
16 ms
33 ms
65 ms
0.13 s
0.26 s
0.52 s
1.0 s
65K (65,536)
128K (131,072)
256K (262,144)
512K (524,288)
1,024K (1,048,576)
2,048K (2,097,152)
2.2 s
2.1 s
53
2513F–AVR–12/03
The following code example shows one assembly and one C function for turning off the
WDT. The example assumes that interrupts are controlled (e.g., by disabling interrupts
globally) so that no interrupts will occur during execution of these functions.
Assembly Code Example
WDT_off:
; Reset WDT
WDR
; Write logical one to WDCE and WDE
in
r16, WDTCR
ori r16, (1<<WDCE)|(1<<WDE)
out WDTCR, r16
; Turn off WDT
ldi r16, (0<<WDE)
out WDTCR, r16
ret
C Code Example
void WDT_off(void)
{
/* Reset WDT*/
_WDR()
/* Write logical one to WDCE and WDE */
WDTCR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCR = 0x00;
}
54
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Timed Sequences for
Changing the
The sequence for changing configuration differs slightly between the three safety levels.
Separate procedures are described for each level.
Configuration of the
Watchdog Timer
Safety Level 0
This mode is compatible with the Watchdog operation found in ATmega161. The Watch-
dog Timer is initially disabled, but can be enabled by writing the WDE bit to one without
any restriction. The Time-out period can be changed at any time without restriction. To
disable an enabled Watchdog Timer, the procedure described on page 52 (WDE bit
description) must be followed.
Safety Level 1
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the
WDE bit to one without any restriction. A timed sequence is needed when changing the
Watchdog Time-out period or disabling an enabled Watchdog Timer. To disable an
enabled Watchdog Timer, and/or changing the Watchdog Time-out, the following proce-
dure must be followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be
written to WDE regardless of the previous value of the WDE bit.
2. Within the next four clock cycles, in the same operation, write the WDE and WDP
bits as desired, but with the WDCE bit cleared.
Safety Level 2
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read
as one. A timed sequence is needed when changing the Watchdog Time-out period. To
change the Watchdog Time-out, the following procedure must be followed:
1. In the same operation, write a logical one to WDCE and WDE. Even though the
WDE always is set, the WDE must be written to one to start the timed sequence.
2. Within the next four clock cycles, in the same operation, write the WDP bits as
desired, but with the WDCE bit cleared. The value written to the WDE bit is
irrelevant.
55
2513F–AVR–12/03
Interrupts
This section describes the specifics of the interrupt handling as performed in
ATmega162. For a general explanation of the AVR interrupt handling, refer to “Reset
and Interrupt Handling” on page 12. Table 24 shows the interrupt table when the com-
patibility fuse (M161C) is unprogrammed, while Table 25 shows the interrupt table when
M161C Fuse is programmed. All assembly code examples in this sections are using the
interrupt table when the M161C Fuse is unprogrammed.
Interrupt Vectors in
ATmega162
Table 24. Reset and Interrupt Vectors if M161C is unprogrammed
Program
Vector No. Address(2) Source
Interrupt Definition
1
0x000(1)
RESET
External Pin, Power-on Reset, Brown-out
Reset, Watchdog Reset, and JTAG AVR
Reset
2
0x002
0x004
0x006
0x008
0x00A
0x00C
0x00E
0x010
0x012
0x014
0x016
0x018
0x01A
0x01C
0x01E
0x020
0x022
0x024
0x026
0x028
0x02A
0x02C
0x02E
0x030
0x032
0x034
0x036
INT0
External Interrupt Request 0
External Interrupt Request 1
External Interrupt Request 2
Pin Change Interrupt Request 0
Pin Change Interrupt Request 1
Timer/Counter3 Capture Event
Timer/Counter3 Compare Match A
3
INT1
4
INT2
5
PCINT0
6
PCINT1
7
TIMER3 CAPT
TIMER3 COMPA
8
9
TIMER3 COMPB Timer/Counter3 Compare Match B
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
TIMER3 OVF
Timer/Counter3 Overflow
TIMER2 COMP
TIMER2 OVF
Timer/Counter2 Compare Match
Timer/Counter2 Overflow
TIMER1 CAPT
TIMER1 COMPA
Timer/Counter1 Capture Event
Timer/Counter1 Compare Match A
TIMER1 COMPB Timer/Counter1 Compare Match B
TIMER1 OVF
TIMER0 COMP
TIMER0 OVF
SPI, STC
Timer/Counter1 Overflow
Timer/Counter0 Compare Match
Timer/Counter0 Overflow
Serial Transfer Complete
USART0, Rx Complete
USART1, Rx Complete
USART0 Data Register Empty
USART1 Data Register Empty
USART0, Tx Complete
USART1, Tx Complete
EEPROM Ready
USART0, RXC
USART1, RXC
USART0, UDRE
USART1, UDRE
USART0, TXC
USART1, TXC
EE_RDY
ANA_COMP
SPM_RDY
Analog Comparator
Store Program Memory Ready
56
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Notes: 1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader
address at reset, see “Boot Loader Support – Read-While-Write Self-programming”
on page 216.
2. When the IVSEL bit in GICR is set, Interrupt Vectors will be moved to the start of the
Boot Flash section. The address of each Interrupt Vector will then be the address in
this table added to the start address of the Boot Flash section.
Table 25. Reset and Interrupt Vectors if M161C is programmed
Program
Vector No. Address(2) Source
Interrupt Definition
1
0x000(1)
RESET
External Pin, Power-on Reset, Brown-out
Reset, Watchdog Reset, and JTAG AVR
Reset
2
0x002
0x004
0x006
0x008
0x00A
0x00C
0x00E
0x010
0x012
0x014
0x016
0x018
0x01A
0x01C
0x01E
0x020
0x022
0x024
0x026
0x028
0x02A
INT0
External Interrupt Request 0
External Interrupt Request 1
External Interrupt Request 2
Timer/Counter2 Compare Match
Timer/Counter2 Overflow
3
INT1
4
INT2
5
TIMER2 COMP
TIMER2 OVF
TIMER1 CAPT
TIMER1 COMPA
6
7
Timer/Counter1 Capture Event
Timer/Counter1 Compare Match A
8
9
TIMER1 COMPB Timer/Counter1 Compare Match B
10
11
12
13
14
15
16
17
18
19
20
21
22
TIMER1 OVF
TIMER0 COMP
TIMER0 OVF
SPI, STC
Timer/Counter1 Overflow
Timer/Counter0 Compare Match
Timer/Counter0 Overflow
Serial Transfer Complete
USART0, Rx Complete
USART1, Rx Complete
USART0 Data Register Empty
USART1 Data Register Empty
USART0, Tx Complete
USART1, Tx Complete
EEPROM Ready
USART0, RXC
USART1, RXC
USART0, UDRE
USART1, UDRE
USART0, TXC
USART1, TXC
EE_RDY
ANA_COMP
SPM_RDY
Analog Comparator
Store Program Memory Ready
Notes: 1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader
address at reset, see “Boot Loader Support – Read-While-Write Self-programming”
on page 216.
2. When the IVSEL bit in GICR is set, Interrupt Vectors will be moved to the start of the
Boot Flash section. The address of each Interrupt Vector will then be the address in
this table added to the start address of the Boot Flash section.
57
2513F–AVR–12/03
Table 26 shows Reset and Interrupt Vectors placement for the various combinations of
BOOTRST and IVSEL settings. If the program never enables an interrupt source, the
Interrupt Vectors are not used, and regular program code can be placed at these loca-
tions. This is also the case if the Reset Vector is in the Application section while the
Interrupt Vectors are in the Boot section or vice versa.
Table 26. Reset and Interrupt Vectors Placement(1)
BOOTRST
IVSEL
Reset address
0x0000
Interrupt Vectors Start Address
0x0002
1
1
0
0
0
1
0
1
0x0000
Boot Reset Address + 0x0002
0x0002
Boot Reset Address
Boot Reset Address
Boot Reset Address + 0x0002
Note:
1. The Boot Reset Address is shown in Table 94 on page 228. For the BOOTRST Fuse
“1” means unprogrammed while “0” means programmed.
The most typical and general program setup for the Reset and Interrupt Vector
Addresses in ATmega162 is:
Address Labels
0x000
0x002
0x004
0x006
0x008
0x00A
0x00C
0x00E
0x010
0x012
0x014
0x016
0x018
0x01A
0x01C
0x01E
0x020
0x022
0x024
0x026
0x028
0x02A
0x02C
0x02E
0x030
0x032
0x034
0x036
;
Code
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
jmp
Comments
RESET
; Reset Handler
EXT_INT0
EXT_INT1
EXT_INT2
PCINT0
; IRQ0 Handler
; IRQ1 Handler
; IRQ2 Handler
; PCINT0 Handler
PCINT1
; PCINT1 Handler
TIM3_CAPT
TIM3_COMPA
TIM3_COMPB
TIM3_OVF
TIM2_COMP
TIM2_OVF
TIM1_CAPT
TIM1_COMPA
TIM1_COMPB
TIM1_OVF
TIM0_COMP
TIM0_OVF
SPI_STC
; Timer3 Capture Handler
; Timer3 CompareA Handler
; Timer3 CompareB Handler
; Timer3 Overflow Handler
; Timer2 Compare Handler
; Timer2 Overflow Handler
; Timer1 Capture Handler
; Timer1 CompareA Handler
; Timer1 CompareB Handler
; Timer1 Overflow Handler
; Timer0 Compare Handler
; Timer0 Overflow Handler
; SPI Transfer Complete Handler
; USART0 RX Complete Handler
; USART1 RX Complete Handler
; UDR0 Empty Handler
USART0_RXC
USART1_RXC
USART0_UDRE
USART1_UDRE
USART0_TXC
USART1_TXC
EE_RDY
; UDR1 Empty Handler
; USART0 TX Complete Handler
; USART1 TX Complete Handler
; EEPROM Ready Handler
; Analog Comparator Handler
; Store Program Memory Ready Handler
ANA_COMP
SPM_RDY
0x038RESET:
0x039
ldi
out
r16,high(RAMEND) ; Main program start
SPH,r16 ; Set Stack Pointer to top of RAM
58
ATmega162/V
2513F–AVR–12/03
ATmega162/V
0x03A
0x03B
0x03C
0x03D
...
ldi
out
sei
r16,low(RAMEND)
SPL,r16
; Enable interrupts
<instr> xxx
...
...
When the BOOTRST Fuse is unprogrammed, the boot section size set to 2K bytes and
the IVSEL bit in the GICR Register is set before any interrupts are enabled, the most
typical and general program setup for the Reset and Interrupt Vector Addresses is:
Address Labels
Code
ldi
out
ldi
out
sei
Comments
0x000
0x001
0x002
0x003
0x004
0x005
;
RESET:
r16,high(RAMEND) ; Main program start
SPH,r16
; Set Stack Pointer to top of RAM
r16,low(RAMEND)
SPL,r16
; Enable interrupts
<instr> xxx
.org 0x1C02
0x1C02
jmp
jmp
..
EXT_INT0
EXT_INT1
; IRQ0 Handler
0x1C04
; IRQ1 Handler
...
....
;
0x1C36
jmp
SPM_RDY
; Store Program Memory Ready Handler
When the BOOTRST Fuse is programmed and the boot section size set to 2K bytes, the
most typical and general program setup for the Reset and Interrupt Vector Addresses is:
Address Labels
.org 0x002
0x002
Code
Comments
jmp
EXT_INT0
EXT_INT1
; IRQ0 Handler
0x004
jmp
..
; IRQ1 Handler
...
0x036
;
....
;
jmp
SPM_RDY
; Store Program Memory Ready Handler
.org 0x1C00
0x1C00
0x1C01
0x1C02
0x1C03
0x1C04
0x1C05
RESET:
ldi
out
ldi
out
sei
r16,high(RAMEND) ; Main program start
SPH,r16
; Set Stack Pointer to top of RAM
r16,low(RAMEND)
SPL,r16
; Enable interrupts
<instr> xxx
59
2513F–AVR–12/03
When the BOOTRST Fuse is programmed, the boot section size set to 2K bytes and the
IVSEL bit in the GICR Register is set before any interrupts are enabled, the most typical
and general program setup for the Reset and Interrupt Vector Addresses is:
Address Labels
Code
Comments
.org 0x1C00
0x1C00
0x1C02
jmp
jmp
RESET
EXT_INT0
; Reset handler
; IRQ0 Handler
0x1C04
jmp
..
EXT_INT1
SPM_RDY
; IRQ1 Handler
...
....
;
0x1C36
;
jmp
; Store Program Memory Ready Handler
0x1C38
0x1C39
0x1C3A
0x1C3B
0x1C3C
0x1C3D
RESET:
ldi
out
ldi
out
sei
r16,high(RAMEND) ; Main program start
SPH,r16
; Set Stack Pointer to top of RAM
r16,low(RAMEND)
SPL,r16
; Enable interrupts
<instr> xxx
Moving Interrupts Between
Application and Boot Space
The General Interrupt Control Register controls the placement of the Interrupt Vector
table.
General Interrupt Control
Register – GICR
Bit
7
INT1
R/W
0
6
5
4
PCIE1
R/W
0
3
PCIE0
R/W
0
2
–
1
IVSEL
R/W
0
0
IVCE
R/W
0
INT0
R/W
0
INT2
R/W
0
GICR
Read/Write
Initial Value
R
0
• Bit 1 – IVSEL: Interrupt Vector Select
When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the
Flash memory. When this bit is set (one), the Interrupt Vectors are moved to the begin-
ning of the Boot Loader section of the Flash. The actual address of the start of the Boot
Flash section is determined by the BOOTSZ Fuses. Refer to the section “Boot Loader
Support – Read-While-Write Self-programming” on page 216 for details. To avoid unin-
tentional changes of Interrupt Vector tables, a special write procedure must be followed
to change the IVSEL bit:
1. Write the Interrupt Vector Change Enable (IVCE) bit to one.
2. Within four cycles, write the desired value to IVSEL while writing a zero to IVCE.
Interrupts will automatically be disabled while this sequence is executed. Interrupts are
disabled in the cycle IVCE is set, and they remain disabled until after the instruction fol-
lowing the write to IVSEL. If IVSEL is not written, interrupts remain disabled for four
cycles. The I-bit in the Status Register is unaffected by the automatic disabling.
Note:
If Interrupt Vectors are placed in the Boot Loader section and Boot Lock bit BLB02 is pro-
grammed, interrupts are disabled while executing from the Application section. If
Interrupt Vectors are placed in the Application section and Boot Lock bit BLB12 is pro-
gramed, interrupts are disabled while executing from the Boot Loader section. Refer to
the section “Boot Loader Support – Read-While-Write Self-programming” on page 216
for details on Boot Lock bits.
• Bit 0 – IVCE: Interrupt Vector Change Enable
The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is
cleared by hardware four cycles after it is written or when IVSEL is written. Setting the
60
ATmega162/V
2513F–AVR–12/03
ATmega162/V
IVCE bit will disable interrupts, as explained in the IVSEL description above. See Code
Example below.
Assembly Code Example
Move_interrupts:
; Enable change of Interrupt Vectors
ldi r16, (1<<IVCE)
out GICR, r16
; Move interrupts to Boot Flash section
ldi r16, (1<<IVSEL)
out GICR, r16
ret
C Code Example
void Move_interrupts(void)
{
/* Enable change of Interrupt Vectors */
GICR = (1<<IVCE);
/* Move interrupts to Boot Flash section */
GICR = (1<<IVSEL);
}
61
2513F–AVR–12/03
I/O-Ports
Introduction
All AVR ports have true Read-Modify-Write functionality when used as general digital
I/O ports. This means that the direction of one port pin can be changed without uninten-
tionally changing the direction of any other pin with the SBI and CBI instructions. The
same applies when changing drive value (if configured as output) or enabling/disabling
of pull-up resistors (if configured as input). Each output buffer has symmetrical drive
characteristics with both high sink and source capability. The pin driver is strong enough
to drive LED displays directly. All port pins have individually selectable pull-up resistors
with a supply-voltage invariant resistance. All I/O pins have protection diodes to both
VCC and Ground as indicated in Figure 28. Refer to “Electrical Characteristics” on page
263 for a complete list of parameters.
Figure 28. I/O Pin Equivalent Schematic
Rpu
Pxn
Logic
Cpin
See figure
"General Digital I/O" for
details
All registers and bit references in this section are written in general form. A lower case
“x” represents the numbering letter for the port, and a lower case “n” represents the bit
number. However, when using the register or bit defines in a program, the precise form
must be used. For example, PORTB3 for bit no. 3 in Port B, here documented generally
as PORTxn. The physical I/O Registers and bit locations are listed in “Register Descrip-
tion for I/O-Ports” on page 81.
Three I/O memory address locations are allocated for each port, one each for the Data
Register – PORTx, Data Direction Register – DDRx, and the Port Input Pins – PINx. The
Port Input Pins I/O location is read only, while the Data Register and the Data Direction
Register are read/write. In addition, the Pull-up Disable – PUD bit in SFIOR disables the
pull-up function for all pins in all ports when set.
Using the I/O port as General Digital I/O is described in “Ports as General Digital I/O” on
page 63. Most port pins are multiplexed with alternate functions for the peripheral fea-
tures on the device. How each alternate function interferes with the port pin is described
in “Alternate Port Functions” on page 67. Refer to the individual module sections for a
full description of the alternate functions.
Note that enabling the alternate function of some of the port pins does not affect the use
of the other pins in the port as general digital I/O.
62
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Ports as General Digital
I/O
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 29 shows a
functional description of one I/O-port pin, here generically called Pxn.
Figure 29. General Digital I/O(1)
PUD
Q
D
DDxn
Q CLR
WDx
RDx
RESET
Q
D
Pxn
PORTxn
Q CLR
WRx
RRx
RESET
SLEEP
SYNCHRONIZER
RPx
D
Q
D
L
Q
Q
PINxn
Q
clk I/O
WDx:
RDx:
WRx:
RRx:
RPx:
WRITE DDRx
PUD:
PULLUP DISABLE
SLEEP CONTROL
I/O CLOCK
READ DDRx
SLEEP:
WRITE PORTx
READ PORTx REGISTER
READ PORTx PIN
clkI/O
:
Note:
1. WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clkI/O
,
SLEEP, and PUD are common to all ports.
Configuring the Pin
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
“Register Description for I/O-Ports” on page 81, the DDxn bits are accessed at the
DDRx I/O address, the PORTxn bits at the PORTx I/O address, and the PINxn bits at
the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written
logic one, Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is config-
ured as an input pin.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up
resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic
zero or the pin has to be configured as an output pin. The port pins are tri-stated when a
reset condition becomes active, even if no clocks are running.
If PORTxn is written logic one when the pin is configured as an output pin, the port pin is
driven high (one). If PORTxn is written logic zero when the pin is configured as an out-
put pin, the port pin is driven low (zero).
When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn,
PORTxn} = 0b11), an intermediate state with either pull-up enabled ({DDxn, PORTxn} =
0b01) or output low ({DDxn, PORTxn} = 0b10) must occur. Normally, the pull-up
63
2513F–AVR–12/03
enabled state is fully acceptable, as a high-impedant environment will not notice the dif-
ference between a strong high driver and a pull-up. If this is not the case, the PUD bit in
the SFIOR Register can be set to disable all pull-ups in all ports.
Switching between input with pull-up and output low generates the same problem. The
user must use either the tri-state ({DDxn, PORTxn} = 0b00) or the output high state
({DDxn, PORTxn} = 0b11) as an intermediate step.
Table 27 summarizes the control signals for the pin value.
Table 27. Port Pin Configurations
PUD
DDxn PORTxn (in SFIOR)
I/O
Pull-up Comment
0
0
X
Input
No
Tri-state (Hi-Z)
Pxn will source current if ext. pulled
low.
0
0
1
1
1
1
0
1
0
1
Input
Input
Yes
No
No
No
Tri-state (Hi-Z)
X
X
Output
Output
Output Low (Sink)
Output High (Source)
Reading the Pin Value
Independent of the setting of Data Direction bit DDxn, the port pin can be read through
the PINxn Register bit. As shown in Figure 29, the PINxn Register bit and the preceding
latch constitute a synchronizer. This is needed to avoid metastability if the physical pin
changes value near the edge of the internal clock, but it also introduces a delay. Figure
30 shows a timing diagram of the synchronization when reading an externally applied
pin value. The maximum and minimum propagation delays are denoted tpd,max and tpd,min
respectively.
Figure 30. Synchronization when Reading an Externally Applied Pin Value
SYSTEM CLK
XXX
XXX
in r17, PINx
INSTRUCTIONS
SYNC LATCH
PINxn
0x00
tpd, max
0xFF
r17
tpd, min
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ATmega162/V
Consider the clock period starting shortly after the first falling edge of the system clock.
The latch is closed when the clock is low, and goes transparent when the clock is high,
as indicated by the shaded region of the “SYNC LATCH” signal. The signal value is
latched when the system clock goes low. It is clocked into the PINxn Register at the suc-
ceeding positive clock edge. As indicated by the two arrows tpd,max and tpd,min, a single
signal transition on the pin will be delayed between ½ and 1½ system clock period
depending upon the time of assertion.
When reading back a software assigned pin value, a nop instruction must be inserted as
indicated in Figure 31. The out instruction sets the “SYNC LATCH” signal at the positive
edge of the clock. In this case, the delay tpd through the synchronizer is one system
clock period.
Figure 31. Synchronization when Reading a Software Assigned Pin Value
SYSTEM CLK
0xFF
r16
out PORTx, r16
nop
in r17, PINx
INSTRUCTIONS
SYNC LATCH
PINxn
0x00
tpd
0xFF
r17
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2513F–AVR–12/03
The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and
define the port pins from 4 to 7 as input with pull-ups assigned to port pins 6 and 7. The
resulting pin values are read back again, but as previously discussed, a nop instruction
is included to be able to read back the value recently assigned to some of the pins.
Assembly Code Example(1)
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi
ldi
out
out
r16,(1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0)
r17,(1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)
PORTB,r16
DDRB,r17
; Insert nop for synchronization
nop
; Read port pins
in
r16,PINB
...
C Code Example(1)
unsigned char i;
...
/* Define pull-ups and set outputs high */
/* Define directions for port pins */
PORTB = (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0);
DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);
/* Insert nop for synchronization*/
_NOP();
/* Read port pins */
i = PINB;
...
Note:
1. For the assembly program, two temporary registers are used to minimize the time
from pull-ups are set on pins 0, 1, 6, and 7, until the direction bits are correctly set,
defining bit 2 and 3 as low and redefining bits 0 and 1 as strong high drivers.
Digital Input Enable and Sleep As shown in Figure 29, the digital input signal can be clamped to ground at the input of
Modes
the Schmitt Trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep
Controller in Power-down mode, Power-save mode, Standby mode, and Extended
Standby mode to avoid high power consumption if some input signals are left floating, or
have an analog signal level close to VCC/2.
SLEEP is overridden for port pins enabled as External Interrupt pins. If the External
Interrupt Request is not enabled, SLEEP is active also for these pins. SLEEP is also
overridden by various other alternate functions as described in “Alternate Port Func-
tions” on page 67.
If a logic high level (“one”) is present on an Asynchronous External Interrupt pin config-
ured as “Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin” while the
external interrupt is not enabled, the corresponding External Interrupt Flag will be set
when resuming from the above mentioned sleep modes, as the clamping in these sleep
modes produces the requested logic change.
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Unconnected pins
If some pins are unused, it is recommended to ensure that these pins have a defined
level. Even though most of the digital inputs are disabled in the deep sleep modes as
described above, floating inputs should be avoided to reduce current consumption in all
other modes where the digital inputs are enabled (Reset, Active mode and Idle mode).
The simplest method to ensure a defined level of an unused pin, is to enable the internal
pull-up. In this case, the pull-up will be disabled during reset. If low power consumption
during reset is important, it is recommended to use an external pull-up or pull-down.
Connecting unused pins directly to VCC or GND is not recommended, since this may
cause excessive currents if the pin is accidentally configured as an output.
Alternate Port Functions Most port pins have alternate functions in addition to being general digital I/Os. Figure
32 shows how the port pin control signals from the simplified Figure 29 can be overrid-
den by alternate functions. The overriding signals may not be present in all port pins, but
the figure serves as a generic description applicable to all port pins in the AVR micro-
controller family.
Figure 32. Alternate Port Functions(1)
PUOExn
PUOVxn
1
PUD
0
DDOExn
DDOVxn
1
Q
D
0
DDxn
Q CLR
WDx
RDx
PVOExn
PVOVxn
RESET
1
0
Pxn
Q
D
PORTxn
Q CLR
DIEOExn
DIEOVxn
SLEEP
WRx
RRx
RESET
1
0
SYNCHRONIZER
RPx
SET
D
Q
D
L
Q
Q
PINxn
CLR Q
CLR
clk I/O
DIxn
AIOxn
PUOExn: Pxn PULL-UP OVERRIDE ENABLE
PUOVxn: Pxn PULL-UP OVERRIDE VALUE
DDOExn: Pxn DATA DIRECTION OVERRIDE ENABLE
DDOVxn: Pxn DATA DIRECTION OVERRIDE VALUE
PVOExn: Pxn PORT VALUE OVERRIDE ENABLE
PVOVxn: Pxn PORT VALUE OVERRIDE VALUE
PUD:
WDx:
RDx:
RRx:
WRx:
RPx:
PULLUP DISABLE
WRITE DDRx
READ DDRx
READ PORTx REGISTER
WRITE PORTx
READ PORTx PIN
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
clkI/O
DIxn:
AIOxn:
:
I/O CLOCK
DIGITAL INPUT PIN n ON PORTx
ANALOG INPUT/OUTPUT PIN n ON PORTx
SLEEP:
SLEEP CONTROL
Note:
1. WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clkI/O
,
SLEEP, and PUD are common to all ports. All other signals are unique for each pin.
67
2513F–AVR–12/03
Table 28 summarizes the function of the overriding signals. The pin and port indexes
from Figure 32 are not shown in the succeeding tables. The overriding signals are gen-
erated internally in the modules having the alternate function.
Table 28. Generic Description of Overriding Signals for Alternate Functions.
Signal Name Full Name
Description
PUOE
PUOV
DDOE
DDOV
PVOE
Pull-up Override
Enable
If this signal is set, the pull-up enable is controlled by the
PUOV signal. If this signal is cleared, the pull-up is
enabled when {DDxn, PORTxn, PUD} = 0b010.
Pull-up Override
Value
If PUOE is set, the pull-up is enabled/disabled when
PUOV is set/cleared, regardless of the setting of the
DDxn, PORTxn, and PUD Register bits.
Data Direction
If this signal is set, the Output Driver Enable is controlled
Override Enable by the DDOV signal. If this signal is cleared, the Output
driver is enabled by the DDxn Register bit.
Data Direction
Override Value
If DDOE is set, the Output Driver is enabled/disabled
when DDOV is set/cleared, regardless of the setting of the
DDxn Register bit.
Port Value
If this signal is set and the Output Driver is enabled, the
Override Enable port value is controlled by the PVOV signal. If PVOE is
cleared, and the Output Driver is enabled, the port Value is
controlled by the PORTxn Register bit.
PVOV
Port Value
Override Value
If PVOE is set, the port value is set to PVOV, regardless of
the setting of the PORTxn Register bit.
DIEOE
Digital Input
Enable Override
Enable
If this bit is set, the Digital Input Enable is controlled by the
DIEOV signal. If this signal is cleared, the Digital Input
Enable is determined by MCU state (Normal Mode, Sleep
Modes).
DIEOV
DI
Digital Input
Enable Override
Value
If DIEOE is set, the Digital Input is enabled/disabled when
DIEOV is set/cleared, regardless of the MCU state
(Normal Mode, Sleep Modes).
Digital Input
This is the Digital Input to alternate functions. In the figure,
the signal is connected to the output of the schmitt trigger
but before the synchronizer. Unless the Digital Input is
used as a clock source, the module with the alternate
function will use its own synchronizer.
AIO
Analog
Input/output
This is the Analog Input/output to/from alternate functions.
The signal is connected directly to the pad, and can be
used bi-directionally.
The following subsections shortly describe the alternate functions for each port, and
relate the overriding signals to the alternate function. Refer to the alternate function
description for further details.
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ATmega162/V
Special Function IO Register –
SFIOR
Bit
7
6
XMBK
R/W
0
5
XMM2
R/W
0
4
XMM1
R/W
0
3
XMM0
R/W
0
2
1
PSR2
R/W
0
0
PSR310
R/W
0
TSM
R/W
0
PUD
R/W
0
SFIOR
Read/Write
Initial Value
• Bit 2 – PUD: Pull-up Disable
When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn
and PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01).
See “Configuring the Pin” on page 63 for more details about this feature.
Alternate Functions of Port A Port A has an alternate function as the address low byte and data lines for the External
Memory Interface and as Pin Change Interrupt.
Table 29. Port A Pins Alternate Functions
Port Pin
Alternate Function
AD7 (External memory interface address and data bit 7)
PCINT7 (Pin Change INTerrupt 7)
PA7
AD6 (External memory interface address and data bit 6)
PCINT6 (Pin Change INTerrupt 6)
PA6
PA5
PA4
PA3
PA2
PA1
PA0
AD5 (External memory interface address and data bit 5)
PCINT5 (Pin Change INTerrupt 5)
AD4 (External memory interface address and data bit 4)
PCINT4 (Pin Change INTerrupt 4)
AD3 (External memory interface address and data bit 3)
PCINT3 (Pin Change INTerrupt 3)
AD2 (External memory interface address and data bit 2)
PCINT2 (Pin Change INTerrupt 2)
AD1 (External memory interface address and data bit 1)
PCINT1 (Pin Change INTerrupt 1)
AD0 (External memory interface address and data bit 0)
PCINT0 (Pin Change INTerrupt 0)
Table 30 and Table 31 relate the alternate functions of Port A to the overriding signals
shown in Figure 32 on page 67.
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2513F–AVR–12/03
Table 30. Overriding Signals for Alternate Functions in PA7..PA4
Signal
Name
PA7/AD7/
PCINT7
PA6/AD6/PCINT6
PA5/AD5/PCINT5
PA4/AD4/PCINT4
PUOE
PUOV
SRE
SRE
SRE
SRE
~(WR + ADA(1)) •
PORTA7
~(WR + ADA) •
PORTA6
~(WR + ADA) •
PORTA5
~(WR + ADA) •
PORTA4
DDOE
DDOV
PVOE
PVOV
SRE
SRE
SRE
SRE
WR + ADA
SRE
WR + ADA
SRE
WR + ADA
SRE
WR + ADA
SRE
if (ADA) then
A7
if (ADA) then
A6
if (ADA) then
A5
if (ADA) then
A4
else
else
else
else
D7 OUTPUT
• WR
D6 OUTPUT
• WR
D5 OUTPUT
• WR
D4 OUTPUT
• WR
DIEOE(2 PCIE0 • PCINT7
PCIE0 • PCINT6
PCIE0 • PCINT5
PCIE0 • PCINT4
)
DIEOV
DI(3)
1
1
1
1
D7 INPUT/
PCINT7
D6 INPUT/
PCINT6
D5 INPUT/
PCINT5
D4 INPUT/
PCINT4
AIO
–
–
–
–
Notes: 1. ADA is short for ADdress Active and represents the time when address is output. See
“External Memory Interface” on page 24.
2. PCINTn is Pin Change Interrupt Enable bit n.
3. PCINTn is Pin Change Interrupt input n.
Table 31. Overriding Signals for Alternate Functions in PA3..PA0
Signal
Name
PA3/AD3/
PCINT3
PA2/AD2/
PCINT2
PA1/AD1/
PCINT1
PA0/AD0/
PCINT0
PUOE
PUOV
SRE
SRE
SRE
SRE
~(WR + ADA) •
PORTA3
~(WR + ADA) •
PORTA2
~(WR + ADA) •
PORTA1
~(WR + ADA) •
PORTA0
DDOE
DDOV
PVOE
PVOV
SRE
SRE
SRE
SRE
WR + ADA
SRE
WR + ADA
SRE
WR + ADA
SRE
WR + ADA
SRE
if (ADA) then
A3
if (ADA) then
A2
if (ADA) then
A1
if (ADA) then
A0
else
else
else
else
D3 OUTPUT
• WR
D2 OUTPUT
• WR
D1 OUTPUT
• WR
D0 OUTPUT
• WR
DIEOE(1)
DIEOV
DI(2)
PCIE0 • PCINT3
1
PCIE0 • PCINT2
1
PCIE0 • PCINT1
1
PCIE0 • PCINT0
1
D3 INPUT
/PCINT3
D2 INPUT
/PCINT2
D1 INPUT
/PCINT1
D0 INPUT
/PCINT0
AIO
–
–
–
–
Notes: 1. PCINT is Pin Change Interrupt Enable bit n.
2. PCINT is Pin Change Interrupt input n.
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Alternate Functions Of Port B The Port B pins with alternate functions are shown in Table 32.
Table 32. Port B Pins Alternate Functions
Port Pin
PB7
Alternate Functions
SCK (SPI Bus Serial Clock)
PB6
MISO (SPI Bus Master Input/Slave Output)
MOSI (SPI Bus Master Output/Slave Input)
PB5
SS (SPI Slave Select Input)
PB4
PB3
PB2
PB1
OC3B (Timer/Counter3 Output Compare Match Output)
AIN1 (Analog Comparator Negative Input)
TXD1 (USART1 Output Pin)
AIN0 (Analog Comparator Positive Input)
RXD1 (USART1 Input Pin)
T1 (Timer/Counter1 External Counter Input)
OC2 (Timer/Counter2 Output Compare Match Output)
T0 (Timer/Counter0 External Counter Input)
OC0 (Timer/Counter0 Output Compare Match Output)
clkI/O (Divided System Clock)
PB0
The alternate pin configuration is as follows:
• SCK – Port B, Bit 7
SCK: Master Clock output, Slave Clock input pin for SPI channel. When the SPI is
enabled as a Slave, this pin is configured as an input regardless of the setting of DDB7.
When the SPI is enabled as a Master, the data direction of this pin is controlled by
DDB7. When the pin is forced by the SPI to be an input, the pull-up can still be con-
trolled by the PORTB7 bit.
• MISO – Port B, Bit 6
MISO: Master Data input, Slave Data output pin for SPI channel. When the SPI is
enabled as a Master, this pin is configured as an input regardless of the setting of
DDB6. When the SPI is enabled as a Slave, the data direction of this pin is controlled by
DDB6. When the pin is forced by the SPI to be an input, the pull-up can still be con-
trolled by the PORTB6 bit.
• MOSI – Port B, Bit 5
MOSI: SPI Master Data output, Slave Data input for SPI channel. When the SPI is
enabled as a Slave, this pin is configured as an input regardless of the setting of DDB5.
When the SPI is enabled as a Master, the data direction of this pin is controlled by
DDB5. When the pin is forced by the SPI to be an input, the pull-up can still be con-
trolled by the PORTB5 bit.
• SS/OC3B – Port B, Bit 4
SS: Slave Select input. When the SPI is enabled as a slave, this pin is configured as an
input regardless of the setting of DDB4. As a Slave, the SPI is activated when this pin is
driven low. When the SPI is enabled as a Master, the data direction of this pin is con-
trolled by DDB4. When the pin is forced by the SPI to be an input, the pull-up can still be
controlled by the PORTB4 bit.
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2513F–AVR–12/03
OC3B, Output Compare Match B output: The PB4 pin can serve as an external output
for the Timer/Counter3 Output Compare B. The pin has to be configured as an output
(DDB4 set (one)) to serve this function. The OC3B pin is also the output pin for the PWM
mode timer function.
• AIN1/TXD1 – Port B, Bit 3
AIN1, Analog Comparator Negative input. Configure the port pin as input with the inter-
nal pull-up switched off to avoid the digital port function from interfering with the function
of the Analog Comparator.
TXD1, Transmit Data (Data output pin for USART1). When the USART1 Transmitter is
enabled, this pin is configured as an output regardless of the value of DDB3.
• AIN0/RXD1 – Port B, Bit 2
AIN0, Analog Comparator Positive Input. Configure the port pin as input with the internal
pull-up switched off to avoid the digital port function from interfering with the function of
the Analog Comparator.
RXD1, Receive Data (Data input pin for USART1). When the USART1 Receiver is
enabled this pin is configured as an input regardless of the value of DDB2. When the
USART1 forces this pin to be an input, the pull-up can still be controlled by the PORTB2
bit.
• T1/OC2 – Port B, Bit 1
T1, Timer/Counter1 Counter Source.
OC2, Output Compare Match output: The PB1 pin can serve as an external output for
the Timer/Counter2 Compare Match. The PB1 pin has to be configured as an output
(DDB1 set (one)) to serve this function. The OC2 pin is also the output pin for the PWM
mode timer function.
• T0/OC0 – Port B, Bit 0
T0, Timer/Counter0 counter source.
OC0, Output Compare Match output: The PB0 pin can serve as an external output for
the Timer/Counter0 Compare Match. The PB0 pin has to be configured as an output
(DDB0 set (one)) to serve this function. The OC0 pin is also the output pin for the PWM
mode timer function.
clkI/O, Divided System Clock: The divided system clock can be output on the PB0 pin.
The divided system clock will be output if the CKOUT Fuse is programmed, regardless
of the PORTB0 and DDB0 settings. It will also be output during reset.
Table 33 and Table 34 relate the alternate functions of Port B to the overriding signals
shown in Figure 32 on page 67. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute
the MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE
INPUT.
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ATmega162/V
Table 33. Overriding Signals for Alternate Functions in PB7..PB4
Signal
Name
PB7/SCK
PB6/MISO
PB5/MOSI
PB4/SS/OC3B
PUOE
PUOV
SPE • MSTR
SPE • MSTR
PORTB6 • PUD
SPE • MSTR
PORTB5 • PUD
SPE • MSTR
PORTB7 •
PUD
PORTB4 •
PUD
DDOE
DDOV
PVOE
SPE • MSTR
0
SPE • MSTR
0
SPE • MSTR
0
SPE • MSTR
0
SPE • MSTR
SPE • MSTR
SPE • MSTR
OC3B
ENABLE
PVOV
SCK OUTPUT
SPI SLAVE
OUTPUT
SPI MSTR
OUTPUT
OC3B
DIEOE
DIEOV
DI
0
0
0
0
0
0
0
0
SCK INPUT
–
SPI MSTR INPUT
–
SPI SLAVE INPUT
–
SPI SS
–
AIO
Table 34. Overriding Signals for Alternate Functions in PB3..PB0
Signal Name
PUOE
PB3/AIN1/TXD1
PB2/AIN0/RXD1
PB1/T1/OC2
PB0/T0/OC0
TXEN1
0
RXEN1
0
0
PUOV
PORTB2• PUD
0
0
DDOE
TXEN1
1
RXEN1
0
CKOUT(1)
DDOV
0
0
0
1
PVOE
TXEN1
OC2 ENABLE
CKOUT + OC0
ENABLE
PVOV
TXD1
0
OC2
if (CKOUT) then
(2)
clkI/O
else
OC0
DIEOE
DIEOV
DI
0
0
0
0
0
0
0
0
–
RXD1
T1 INPUT
–
T0 INPUT
–
AIO
AIN1 INPUT
AIN0 INPUT
Notes: 1. CKOUT is one if the CKOUT Fuse is programmed.
2. clkI/O is the divided system clock.
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Alternate Functions of Port C The Port C pins with alternate functions are shown in Table 35. If the JTAG interface is
enabled, the pull-up resistors on pins PC7(TDI), PC5(TMS) and PC4(TCK) will be acti-
vated even if a reset occurs.
Table 35. Port C Pins Alternate Functions
Port Pin
Alternate Function
A15 (External memory interface address bit 15)
TDI (JTAG Test Data Input)
PC7
PCINT15 (Pin Change INTerrupt 15)
A14 (External memory interface address bit 14)
TDO (JTAG Test Data Output)
PC6
PC5
PC4
PCINT14 (Pin Change INTerrupt 14)
A13 (External memory interface address bit 13)
TMS (JTAG Test Mode Select)
PCINT13 (Pin Change INTerrupt 13)
A12 (External memory interface address bit 12)
TCK (JTAG Test Clock)
PCINT12 (Pin Change INTerrupt 12)
A11 (External memory interface address bit 11)
PCINT11 (Pin Change INTerrupt 11)
PC3
PC2
PC1
PC0
A10 (External memory interface address bit 10)
PCINT10 (Pin Change INTerrupt 10)
A9 (External memory interface address bit 9)
PCINT9 (Pin Change INTerrupt 9)
A8 (External memory interface address bit 8)
PCINT8 (Pin Change INTerrupt 8)
• A15/TDI/PCINT15 – Port C, Bit 7
A15, External memory interface address bit 15.
TDI, JTAG Test Data In: Serial input data to be shifted into the Instruction Register or
Data Register (scan chains). When the JTAG interface is enabled, this pin can not be
used as an I/O pin.
PCINT15: The pin can also serve as a pin change interrupt.
• A14/TDO/PCINT14 – Port C, Bit 6
A14, External memory interface address bit 14.
TDO, JTAG Test Data Out: Serial output data from Instruction Register or Data Regis-
ter. When the JTAG interface is enabled, this pin can not be used as an I/O pin. In TAP
states that shift out data, the TD0 pin drives actively. In other states the pin is pulled
high.
PCINT14: The pin can also serve as a pin change interrupt.
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• A13/TMS/PCINT13 – Port C, Bit 5
A13, External memory interface address bit 13.
TMS, JTAG Test Mode Select: This pin is used for navigating through the TAP-controller
state machine. When the JTAG interface is enabled, this pin can not be used as an I/O
pin.
PCINT13: The pin can also serve as a pin change interrupt.
• A12/TCK/PCINT12 – Port C, Bit 4
A12, External memory interface address bit 12.
TCK, JTAG Test Clock: JTAG operation is synchronous to TCK. When the JTAG inter-
face is enabled, this pin can not be used as an I/O pin.
PCINT12: The pin can also serve as a pin change interrupt.
• A11/PCINT11 – Port C, Bit 3
A11, External memory interface address bit 11.
PCINT11: The pin can also serve as a pin change interrupt.
• A10/PCINT10 – Port C, Bit 2
A10, External memory interface address bit 10.
PCINT11: The pin can also serve as a pin change interrupt.
• A9/PCINT9 – Port C, Bit 1
A9, External memory interface address bit 9.
PCINT9: The pin can also serve as a pin change interrupt.
• A8/PCINT8 – Port C, Bit 0
A8, External memory interface address bit 8.
PCINT8: The pin can also serve as a pin change interrupt.
Table 36 and Table 37 relate the alternate functions of Port C to the overriding signals
shown in Figure 32 on page 67.
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Table 36. Overriding Signals for Alternate Functions in PC7..PC4
PC7/A15/TDI
/PCINT15
PC6/A14/TDO
/PCINT14
PC5/A13/TMS
/PCINT13
PC4/A12/TCK
/PCINT12
Signal Name
PUOE
(XMM < 1) •
(XMM < 2) •
(XMM < 3) •
(XMM < 4) •
SRE + JTAGEN
SRE +JTAGEN
SRE + JTAGEN
SRE + JTAGEN
PUOV
DDOE
JTAGEN
JTAGEN
JTAGEN
JTAGEN
SRE • (XMM<1)
+ JTAGEN
SRE • (XMM<2)
+ JTAGEN
SRE • (XMM<3)
+ JTAGEN
SRE • (XMM<4)
+ JTAGEN
DDOV
JTAGEN
JTAGEN +
JTAGEN •
JTAGEN
JTAGEN
(SHIFT_IR |
SHIFT_DR)
PVOE
PVOV
SRE • (XMM<1)
A15
SRE • (XMM<2)
+ JTAGEN
SRE • (XMM<3)
SRE • (XMM<4)
A12
if (JTAGEN) then A13
TDO
else
A14
DIEOE(1)
JTAGEN |
PCIE1 •
JTAGEN | PCIE1 JTAGEN |
JTAGEN |
PCIE1 •
• PCINT14
PCIE1 •
PCINT15
PCINT13
PCINT12
DIEOV
DI(2)
JTAGEN
PCINT15
TDI
JTAGEN
PCINT14
–
JTAGEN
PCINT13
TMS
JTAGEN
PCINT12
TCK
AIO
Notes: 1. PCINTn is Pin Change Interrupt Enable bit n.
2. PCINTn is Pin Change Interrupt input n.
Table 37. Overriding Signals for Alternate Functions in PC3..PC0
PC3/A11/
PCINT11
PC2/A10/
PCINT10
Signal Name
PUOE
PC1/A9/PCINT9 PC0/A8/PCINT8
SRE • (XMM<5)
SRE • (XMM<6)
SRE • (XMM<7)
SRE • (XMM<7)
PUOV
0
0
0
0
DDOE
SRE • (XMM<5)
SRE • (XMM<6)
SRE • (XMM<7)
SRE • (XMM<7)
DDOV
1
1
1
1
PVOE
SRE • (XMM<5)
A11
SRE • (XMM<6)
A10
SRE • (XMM<7)
A9
SRE • (XMM<7)
A8
PVOV
DIEOE(1)
PCIE1 •
PCIE1 •
PCIE1 • PCINT9 PCIE1 • PCINT8
PCINT11
PCINT10
DIEOV
DI(2)
1
1
1
1
PCINT11
–
PCINT10
–
PCINT9
–
PCINT8
–
AIO
Notes: 1. PCINTn is Pin Change Interrupt Enable bit n.
2. PCINTn is Pin Change Interrupt input n.
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ATmega162/V
Alternate Functions of Port D The Port D pins with alternate functions are shown in Table 38.
Table 38. Port D Pins Alternate Functions
Port Pin
PD7
Alternate Function
RD (Read strobe to external memory)
WR (Write strobe to external memory)
PD6
TOSC2 (Timer Oscillator Pin 2)
PD5
PD4
OC1A (Timer/Counter1 Output Compare A Match Output)
TOSC1 (Timer Oscillator Pin 1)
XCK0 (USART0 External Clock Input/Output)
OC3A (Timer/Counter3 Output Compare A Match Output)
INT1 (External Interrupt 1 Input)
PD3
PD2
ICP3 (Timer/Counter3 Input Capture Pin)
INT0 (External Interrupt 0 Input)
XCK1 (USART1 External Clock Input/Output)
PD1
PD0
TXD0 (USART0 Output Pin)
RXD0 (USART0 Input Pin)
The alternate pin configuration is as follows:
• RD – Port D, Bit 7
RD is the external data memory read control strobe.
• WR – Port D, Bit 6
WR is the external data memory write control strobe.
• TOSC2/OC1A – Port D, Bit 5
TOSC2, Timer Oscillator pin 2: When the AS2 bit in ASSR is set (one) to enable asyn-
chronous clocking of Timer/Counter2, pin PD5 is disconnected from the port, and
becomes the inverting output of the Oscillator amplifier. In this mode, a crystal Oscillator
is connected to this pin, and the pin can not be used as an I/O pin.
OC1A, Output Compare Match A output: The PD5 pin can serve as an external output
for the Timer/Counter1 Output Compare A. The pin has to be configured as an output
(DDD5 set (one)) to serve this function. The OC1A pin is also the output pin for the
PWM mode timer function.
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• TOSC1/XCK0/OC3A – Port D, Bit 4
TOSC1, Timer Oscillator pin 1: When the AS2 bit in ASSR is set (one) to enable asyn-
chronous clocking of Timer/Counter2, pin PD4 is disconnected from the port, and
becomes the input of the inverting Oscillator Amplifier. In this mode, a crystal Oscillator
is connected to this pin, and the pin can not be used as an I/O pin.
XCK0, USART0 External Clock: The Data Direction Register (DDD4) controls whether
the clock is output (DDD4 set (one)) or input (DDD4 cleared (zero)). The XCK0 pin is
active only when USART0 operates in Synchronous mode.
OC3A, Output Compare Match A output: The PD4 pin can serve as an external output
for the Timer/Counter1 Output Compare A. The pin has to be configured as an output
(DDD4 set (one)) to serve this function. The OC4A pin is also the output pin for the
PWM mode timer function.
• INT1/ICP3 – Port D, Bit 3
INT1, External Interrupt Source 1: The PD3 pin can serve as an external interrupt
source.
ICP3, Input Capture Pin: The PD3 pin can act as an Input Capture pin for
Timer/Counter3.
• INT0/XCK1 – Port D, Bit 2
INT0, External Interrupt Source 0: The PD2 pin can serve as an external interrupt
source.
XCK1, USART1 External Clock: The Data Direction Register (DDD2) controls whether
the clock is output (DDD2 set (one)) or input (DDD2 cleared (zero)). The XCK1 pin is
active only when USART1 operates in Synchronous mode.
• TXD0 – Port D, Bit 1
TXD0, Transmit Data (Data output pin for USART0). When the USART0 Transmitter is
enabled, this pin is configured as an output regardless of the value of DDD1.
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• RXD0 – Port D, Bit 0
RXD0, Receive Data (Data input pin for USART0). When the USART0 Receiver is
enabled this pin is configured as an input regardless of the value of DDD0. When
USART0 forces this pin to be an input, the pull-up can still be controlled by the PORTD0
bit.
Table 39 and Table 40 relate the alternate functions of Port D to the overriding signals
shown in Figure 32 on page 67.
Table 39. Overriding Signals for Alternate Functions PD7..PD4
Signal Name
PUOE
PD7/RD
SRE
0
PD6/WR
SRE
0
PD5/TOSC2/OC1A
PD4/TOSC1/XCK0/OC3A
AS2
AS2
0
PUOV
0
DDOE
SRE
1
SRE
1
AS2
AS2
0
DDOV
0
PVOE
SRE
SRE
OC1A ENABLE
XCK0 OUTPUT ENABLE |
OC3A ENABLE
PVOV
RD
WR
OC1A
if (XCK0 OUTPUT
ENABLE)then
XCK0 OUTPUT
else
OC3A
DIEOE
DIEOV
DI
0
0
–
–
0
0
–
–
AS2
AS2
0
0
–
XCK0 INPUT
T/C2 OSC INPUT
AIO
T/C2 OSC OUTPUT
Table 40. Overriding Signals for Alternate Functions in PD3..PD0
Signal Name PD3/INT1
PD2/INT0/XCK1
PD1/TXD0 PD0/RXD0
PUOE
PUOV
DDOE
DDOV
PVOE
PVOV
DIEOE
DIEOV
DI
0
0
0
0
0
0
0
TXEN0
RXEN0
0
0
PORTD0 • PUD
0
TXEN0
RXEN0
0
1
0
XCK1 OUTPUT ENABLE
XCK1
TXEN0
0
TXD0
0
INT1 ENABLE INT0 ENABLE
0
0
–
0
1
1
0
INT1 INPUT/
ICP1 INPUT
INT0 INPUT/XCK1 INPUT
RXD0
AIO
–
–
–
–
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Alternate Functions of Port E
The Port E pins with alternate functions are shown in Table 41.
Table 41. Port E Pins Alternate Functions
Port Pin
PE2
Alternate Function
OC1B (Timer/Counter1 Output CompareB Match Output)
ALE (Address Latch Enable to external memory)
PE1
ICP1 (Timer/Counter1 Input Capture Pin)
INT2 (External Interrupt 2 Input)
PE0
The alternate pin configuration is as follows:
• OC1B – Port E, Bit 2
OC1B, Output Compare Match B output: The PE2 pin can serve as an external output
for the Timer/Counter1 Output Compare B. The pin has to be configured as an output
(DDE0 set (one)) to serve this function. The OC1B pin is also the output pin for the PWM
mode timer function.
Table 42 relate the alternate functions of Port E to the overriding signals shown in Figure
32 on page 67.
• ALE – Port E, Bit 1
ALE is the external data memory Address Latch Enable signal.
• ICP1/INT2 – Port E, Bit 0
ICP1, Input Capture Pin: The PE0 pin can act as an Input Capture pin for
Timer/Counter1.
INT2, External Interrupt Source 2: The PE0 pin can serve as an external interrupt
source.
Table 42. Overriding Signals for Alternate Functions PE2..PE0
Signal Name
PUOE
PUOV
DDOE
DDOV
PVOE
PVOV
DIEOE
DIEOV
DI
PE2
PE1
SRE
0
PE0
0
0
0
0
0
SRE
1
0
0
0
OC1B ENABLE
SRE
ALE
0
0
OC1B
0
0
0
0
–
INT2 ENABLED
0
1
0
INT2 INPUT/ ICP1 INPUT
–
AIO
–
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ATmega162/V
Register Description for
I/O-Ports
Port A Data Register – PORTA
Bit
7
PORTA7
R/W
0
6
PORTA6
R/W
0
5
PORTA5
R/W
0
4
PORTA4
R/W
0
3
PORTA3
R/W
0
2
PORTA2
R/W
0
1
PORTA1
R/W
0
0
PORTA0
R/W
0
PORTA
DDRA
PINA
Read/Write
Initial Value
Port A Data Direction Register
– DDRA
Bit
7
DDA7
R/W
0
6
DDA6
R/W
0
5
DDA5
R/W
0
4
DDA4
R/W
0
3
DDA3
R/W
0
2
DDA2
R/W
0
1
DDA1
R/W
0
0
DDA0
R/W
0
Read/Write
Initial Value
Port A Input Pins Address –
PINA
Bit
7
PINA7
R
6
PINA6
R
5
PINA5
R
4
PINA4
R
3
PINA3
R
2
PINA2
R
1
PINA1
R
0
PINA0
R
Read/Write
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Port B Data Register – PORTB
Bit
7
PORTB7
R/W
0
6
PORTB6
R/W
0
5
PORTB5
R/W
0
4
PORTB4
R/W
0
3
PORTB3
R/W
0
2
PORTB2
R/W
0
1
PORTB1
R/W
0
0
PORTB0
R/W
0
PORTB
DDRB
PINB
Read/Write
Initial Value
Port B Data Direction Register
– DDRB
Bit
7
DDB7
R/W
0
6
DDB6
R/W
0
5
DDB5
R/W
0
4
DDB4
R/W
0
3
DDB3
R/W
0
2
DDB2
R/W
0
1
DDB1
R/W
0
0
DDB0
R/W
0
Read/Write
Initial Value
Port B Input Pins Address –
PINB
Bit
7
PINB7
R
6
PINB6
R
5
PINB5
R
4
PINB4
R
3
PINB3
R
2
PINB2
R
1
PINB1
R
0
PINB0
R
Read/Write
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Port C Data Register – PORTC
Bit
7
PORTC7
R/W
0
6
PORTC6
R/W
0
5
PORTC5
R/W
0
4
PORTC4
R/W
0
3
PORTC3
R/W
0
2
PORTC2
R/W
0
1
PORTC1
R/W
0
0
PORTC0
R/W
0
PORTC
Read/Write
Initial Value
Port C Data Direction Register
– DDRC
Bit
7
DDC7
R/W
0
6
DDC6
R/W
0
5
DDC5
R/W
0
4
DDC4
R/W
0
3
DDC3
R/W
0
2
DDC2
R/W
0
1
DDC1
R/W
0
0
DDC0
R/W
0
DDRC
Read/Write
Initial Value
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Port C Input Pins Address –
PINC
Bit
7
PINC7
R
6
PINC6
R
5
PINC5
R
4
PINC4
R
3
PINC3
R
2
PINC2
R
1
PINC1
R
0
PINC0
R
PINC
PORTD
DDRD
PIND
Read/Write
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Port D Data Register – PORTD
Bit
7
PORTD7
R/W
0
6
PORTD6
R/W
0
5
PORTD5
R/W
0
4
PORTD4
R/W
0
3
PORTD3
R/W
0
2
PORTD2
R/W
0
1
PORTD1
R/W
0
0
PORTD0
R/W
0
Read/Write
Initial Value
Port D Data Direction Register
– DDRD
Bit
7
DDD7
R/W
0
6
DDD6
R/W
0
5
DDD5
R/W
0
4
DDD4
R/W
0
3
DDD3
R/W
0
2
DDD2
R/W
0
1
DDD1
R/W
0
0
DDD0
R/W
0
Read/Write
Initial Value
Port D Input Pins Address –
PIND
Bit
7
PIND7
R
6
PIND6
R
5
PIND5
R
4
PIND4
R
3
PIND3
R
2
PIND2
R
1
PIND1
R
0
PIND0
R
Read/Write
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Port E Data Register – PORTE
Bit
7
–
6
–
5
–
4
–
3
–
2
PORTE2
R/W
0
1
PORTE1
R/W
0
0
PORTE0
R/W
0
PORTE
DDRE
PINE
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
Port E Data Direction Register
– DDRE
Bit
7
–
6
–
5
–
4
–
3
–
2
DDE2
R/W
0
1
DDE1
R/W
0
0
DDE0
R/W
0
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
Port E Input Pins Address –
PINE
Bit
7
–
6
–
5
–
4
–
3
–
2
PINE2
R
1
PINE1
R
0
PINE0
R
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
N/A
N/A
N/A
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ATmega162/V
External Interrupts
The External Interrupts are triggered by the INT0, INT1, INT2 pin, or any of the
PCINT15..0 pins. Observe that, if enabled, the interrupts will trigger even if the INT2..0
or PCINT15..0 pins are configured as outputs. This feature provides a way of generating
a software interrupt. The External Interrupts can be triggered by a falling or rising edge
or a low level (INT2 is only an edge triggered interrupt). This is set up as indicated in the
specification for the MCU Control Register – MCUCR and Extended MCU Control Reg-
ister – EMCUCR. When the external interrupt is enabled and is configured as level
triggered (only INT0/INT1), the interrupt will trigger as long as the pin is held low. The
pin change interrupt PCI1 will trigger if any enabled PCINT15..8 pin toggles. Pin change
interrupts PCI0 will trigger if any enabled PCINT7..0 pin toggles. The PCMSK1 and
PCMSK0 Registers control which pins contribute to the pin change interrupts. Note that
recognition of falling or rising edge interrupts on INT0 and INT1 requires the presence of
an I/O clock, described in “Clock Systems and their Distribution” on page 33. Low level
interrupts on INT0/INT1, the edge interrupt on INT2, and Pin change interrupts on
PCINT15..0 are detected asynchronously. This implies that these interrupts can be used
for waking the part also from sleep modes other than Idle mode. The I/O clock is halted
in all sleep modes except Idle mode.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the
changed level must be held for some time to wake up the MCU. This makes the MCU
less sensitive to noise. The changed level is sampled twice by the Watchdog Oscillator
clock. The period of the Watchdog Oscillator is 1 µs (nominal) at 5.0V and 25°C. The
frequency of the Watchdog Oscillator is voltage dependent as shown in “Electrical Char-
acteristics” on page 263. The MCU will wake up if the input has the required level during
this sampling or if it is held until the end of the start-up time. The start-up time is defined
by the SUT Fuses as described in “System Clock and Clock Options” on page 33. If the
level is sampled twice by the Watchdog Oscillator clock but disappears before the end
of the start-up time, the MCU will still wake up, but no interrupt will be generated. The
required level must be held long enough for the MCU to complete the wake up to trigger
the level interrupt.
MCU Control Register –
MCUCR
The MCU Control Register contains control bits for interrupt sense control and general
MCU functions.
Bit
7
6
SRW10
R/W
0
5
SE
R/W
0
4
3
ISC11
R/W
0
2
ISC10
R/W
0
1
ISC01
R/W
0
0
ISC00
R/W
0
SRE
R/W
0
SM1
R/W
0
MCUCR
Read/Write
Initial Value
• Bit 3, 2 – ISC11, ISC10: Interrupt Sense Control 1 Bit 1 and Bit 0
The External Interrupt 1 is activated by the external pin INT1 if the SREG I-bit and the
corresponding interrupt mask in the GICR are set. The level and edges on the external
INT1 pin that activate the interrupt are defined in Table 43. The value on the INT1 pin is
sampled before detecting edges. If edge or toggle interrupt is selected, pulses that last
longer than one clock period will generate an interrupt. Shorter pulses are not guaran-
teed to generate an interrupt. If low level interrupt is selected, the low level must be held
until the completion of the currently executing instruction to generate an interrupt.
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2513F–AVR–12/03
Table 43. Interrupt 1 Sense Control
ISC11
ISC10
Description
0
0
1
1
0
1
0
1
The low level of INT1 generates an interrupt request.
Any logical change on INT1 generates an interrupt request.
The falling edge of INT1 generates an interrupt request.
The rising edge of INT1 generates an interrupt request.
• Bit 1, 0 – ISC01, ISC00: Interrupt Sense Control 0 Bit 1 and Bit 0
The External Interrupt 0 is activated by the external pin INT0 if the SREG I-flag and the
corresponding interrupt mask are set. The level and edges on the external INT0 pin that
activate the interrupt are defined in Table 44. The value on the INT0 pin is sampled
before detecting edges. If edge or toggle interrupt is selected, pulses that last longer
than one clock period will generate an interrupt. Shorter pulses are not guaranteed to
generate an interrupt. If low level interrupt is selected, the low level must be held until
the completion of the currently executing instruction to generate an interrupt.
Table 44. Interrupt 0 Sense Control
ISC01
ISC00
Description
0
0
1
1
0
1
0
1
The low level of INT0 generates an interrupt request.
Any logical change on INT0 generates an interrupt request.
The falling edge of INT0 generates an interrupt request.
The rising edge of INT0 generates an interrupt request.
Extended MCU Control
Register – EMCUCR
Bit
7
6
SRL2
R/W
0
5
SRL1
R/W
0
4
SRL0
R/W
0
3
SRW01
R/W
0
2
SRW00
R/W
0
1
SRW11
R/W
0
0
SM0
R/W
0
ISC2
R/W
0
EMCUCR
Read/Write
Initial Value
• Bit 0 – ISC2: Interrupt Sense Control 2
The asynchronous External Interrupt 2 is activated by the external pin INT2 if the SREG
I-bit and the corresponding interrupt mask in GICR are set. If ISC2 is cleared (zero), a
falling edge on INT2 activates the interrupt. If ISC2 is set (one), a rising edge on INT2
activates the interrupt. Edges on INT2 are registered asynchronously. Pulses on INT2
wider than the minimum pulse width given in Table 45 will generate an interrupt. Shorter
pulses are not guaranteed to generate an interrupt. When changing the ISC2 bit, an
interrupt can occur. Therefore, it is recommended to first disable INT2 by clearing its
Interrupt Enable bit in the GICR Register. Then, the ISC2 bit can be changed. Finally,
the INT2 Interrupt Flag should be cleared by writing a logical one to its Interrupt Flag bit
(INTF2) in the GIFR Register before the interrupt is re-enabled.
Table 45. Asynchronous External Interrupt Characteristics
Symbol Parameter
Condition Min. Typ. Max. Units
Minimum pulse width for
asynchronous external interrupt
tINT
50
ns
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2513F–AVR–12/03
ATmega162/V
General Interrupt Control
Register – GICR
Bit
7
INT1
R/W
0
6
5
4
PCIE1
R/W
0
3
PCIE0
R/W
0
2
–
1
IVSEL
R/W
0
0
IVCE
R/W
0
INT0
R/W
0
INT2
R/W
0
GICR
Read/Write
Initial Value
R
0
• Bit 7 – INT1: External Interrupt Request 1 Enable
When the INT1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one),
the external pin interrupt is enabled. The Interrupt Sense Control1 bits 1/0 (ISC11 and
ISC10) in the MCU general Control Register (MCUCR) define whether the external
interrupt is activated on rising and/or falling edge of the INT1 pin or level sensed. Activity
on the pin will cause an interrupt request even if INT1 is configured as an output. The
corresponding interrupt of External Interrupt Request 1 is executed from the INT1 Inter-
rupt Vector.
• Bit 6 – INT0: External Interrupt Request 0 Enable
When the INT0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one),
the external pin interrupt is enabled. The Interrupt Sense Control0 bits 1/0 (ISC01 and
ISC00) in the MCU general Control Register (MCUCR) define whether the external
interrupt is activated on rising and/or falling edge of the INT0 pin or level sensed. Activity
on the pin will cause an interrupt request even if INT0 is configured as an output. The
corresponding interrupt of External Interrupt Request 0 is executed from the INT0 Inter-
rupt Vector.
• Bit 5 – INT2: External Interrupt Request 2 Enable
When the INT2 bit is set (one) and the I-bit in the Status Register (SREG) is set (one),
the external pin interrupt is enabled. The Interrupt Sense Control2 bit (ISC2) in the
Extended MCU Control Register (EMCUCR) defines whether the external interrupt is
activated on rising or falling edge of the INT2 pin. Activity on the pin will cause an inter-
rupt request even if INT2 is configured as an output. The corresponding interrupt of
External Interrupt Request 2 is executed from the INT2 Interrupt Vector.
• Bit 4 – PCIE1: Pin Change Interrupt Enable 1
When the PCIE1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one),
pin change interrupt 1 is enabled. Any change on any enabled PCINT15..8 pin will
cause an interrupt. The corresponding interrupt of Pin Change Interrupt Request is exe-
cuted from the PCI1 Interrupt Vector. PCINT15..8 pins are enabled individually by the
PCMSK1 Register.
• Bit 3 – PCIE0: Pin Change Interrupt Enable 0
When the PCIE0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one),
pin change interrupt 0 is enabled. Any change on any enabled PCINT7..0 pin will cause
an interrupt. The corresponding interrupt of Pin Change Interrupt Request is executed
from the PCI0 Interrupt Vector. PCINT7..0 pins are enabled individually by the PCMSK0
Register.
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2513F–AVR–12/03
General Interrupt Flag
Register – GIFR
Bit
7
INTF1
R/W
0
6
INTF0
R/W
0
5
INTF2
R/W
0
4
PCIF1
R/W
0
3
PCIF0
R/W
0
2
–
1
–
0
–
GIFR
Read/Write
Initial Value
R
0
R
0
R
0
• Bit 7 – INTF1: External Interrupt Flag 1
When an edge or logic change on the INT1 pin triggers an interrupt request, INTF1
becomes set (one). If the I-bit in SREG and the INT1 bit in GICR are set (one), the MCU
will jump to the corresponding Interrupt Vector. The flag is cleared when the interrupt
routine is executed. Alternatively, the flag can be cleared by writing a logical one to it.
This flag is always cleared when INT1 is configured as a level interrupt.
• Bit 6 – INTF0: External Interrupt Flag 0
When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0
becomes set (one). If the I-bit in SREG and the INT0 bit in GICR are set (one), the MCU
will jump to the corresponding Interrupt Vector. The flag is cleared when the interrupt
routine is executed. Alternatively, the flag can be cleared by writing a logical one to it.
This flag is always cleared when INT0 is configured as a level interrupt.
• Bit 5 – INTF2: External Interrupt Flag 2
When an event on the INT2 pin triggers an interrupt request, INTF2 becomes set (one).
If the I-bit in SREG and the INT2 bit in GICR are set (one), the MCU will jump to the cor-
responding Interrupt Vector. The flag is cleared when the interrupt routine is executed.
Alternatively, the flag can be cleared by writing a logical one to it. Note that when enter-
ing some sleep modes with the INT2 interrupt disabled, the input buffer on this pin will
be disabled. This may cause a logic change in internal signals which will set the INTF2
flag. See “Digital Input Enable and Sleep Modes” on page 66 for more information.
• Bit 4 – PCIF1: Pin Change Interrupt Flag 1
When a logic change on any PCINT15..8 pin triggers an interrupt request, PCIF1
becomes set (one). If the I-bit in SREG and the PCIE1 bit in GICR are set (one), the
MCU will jump to the corresponding Interrupt Vector. The flag is cleared when the inter-
rupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to
it.
• Bit 3 – PCIF0: Pin Change Interrupt Flag 0
When a logic change on any PCINT7..0 pin triggers an interrupt request, PCIF0
becomes set (one). If the I-bit in SREG and the PCIE0 bit in GICR are set (one), the
MCU will jump to the corresponding Interrupt Vector. The flag is cleared when the inter-
rupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to
it.
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Pin Change Mask Register 1 –
PCMSK1
Bit
7
PCINT15
R/W
0
6
PCINT14
R/W
0
5
PCINT13
R/W
0
4
PCINT12
R/W
3
PCINT11
R/W
0
2
PCINT10
R/W
0
1
PCINT9
R/W
0
0
PCINT9
R/W
0
PCMSK1
Read/Write
Initial Value
0
• Bit 7..0 – PCINT15..8: Pin Change Enable Mask 15..8
Each PCINT15..8 bit selects whether pin change interrupt is enabled on the correspond-
ing I/O pin. If PCINT15..8 is set and the PCIE1 bit in GICR is set, pin change interrupt is
enabled on the corresponding I/O pin. If PCINT15..8 is cleared, pin change interrupt on
the corresponding I/O pin is disabled.
Pin Change Mask Register 0 –
PCMSK0
Bit
7
PCINT7
R/W
0
6
PCINT6
R/W
0
5
PCINT5
R/W
0
4
PCINT4
R/W
0
3
PCINT3
R/W
0
2
PCINT2
R/W
0
1
PCINT1
R/W
0
0
PCINT0
R/W
0
PCMSK0
Read/Write
Initial Value
• Bit 7..0 – PCINT7..0: Pin Change Enable Mask 7..0
Each PCINT7..0 bit selects whether pin change interrupt is enabled on the correspond-
ing I/O pin. If PCINT7..0 is set and the PCIE0 bit in GICR is set, pin change interrupt is
enabled on the corresponding I/O pin. If PCINT7..0 is cleared, pin change interrupt on
the corresponding I/O pin is disabled.
The mapping between I/O pins and PCINT bits can be found in Figure 1 on page 2. Note
that the Pin Change Mask Register are located in Extended I/O. Thus, the pin change
interrupts are not supported in ATmega161 compatibility mode.
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8-bit Timer/Counter0 Timer/Counter0 is a general purpose, single channel, 8-bit Timer/Counter module. The
main features are:
• Single Channel Counter
with PWM
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Frequency Generator
• External Event Counter
• 10-bit Clock Prescaler
• Overflow and Compare Match Interrupt Sources (TOV0 and OCF0)
Overview
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 33. For the
actual placement of I/O pins, refer to “Pinout ATmega162” on page 2. CPU accessible
I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O
Register and bit locations are listed in the “8-bit Timer/Counter Register Description” on
page 99.
Figure 33. 8-bit Timer/Counter Block Diagram
TCCRn
count
TOVn
(Int.Req.)
clear
direction
Control Logic
Clock Select
clk
Tn
Edge
Detector
Tn
BOTTOM
TOP
( From Prescaler )
Timer/Counter
TCNTn
= 0
= 0xFF
OCn
(Int.Req.)
Waveform
Generation
OCn
=
OCRn
Registers
The Timer/Counter (TCNT0) and Output Compare Register (OCR0) are 8-bit registers.
Interrupt request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer
Interrupt Flag Register (TIFR). All interrupts are individually masked with the Timer
Interrupt Mask Register (TIMSK). TIFR and TIMSK are not shown in the figure since
these registers are shared by other timer units.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock
source on the T0 pin. The Clock Select logic block controls which clock source and edge
the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is
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inactive when no clock source is selected. The output from the clock select logic is
referred to as the timer clock (clkT0).
The double buffered Output Compare Register (OCR0) is compared with the
Timer/Counter value at all times. The result of the compare can be used by the Wave-
form Generator to generate a PWM or variable frequency output on the Output Compare
pin (OC0). See “Output Compare Unit” on page 90. for details. The Compare Match
event will also set the Compare Flag (OCF0) which can be used to generate an output
compare interrupt request.
Definitions
Many register and bit references in this section are written in general form. A lower case
“n” replaces the Timer/Counter number, in this case 0. However, when using the register
or bit defines in a program, the precise form must be used i.e., TCNT0 for accessing
Timer/Counter0 counter value and so on.
The definitions in Table 46 are also used extensively throughout the document.
Table 46. Definitions
BOTTOM The counter reaches the BOTTOM when it becomes 0x00.
MAX
TOP
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
The counter reaches the TOP when it becomes equal to the highest
value in the count sequence. The TOP value can be assigned to be the
fixed value 0xFF (MAX) or the value stored in the OCR0 Register. The
assignment is dependent on the mode of operation.
Timer/Counter Clock
Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock
source is selected by the Clock Select logic which is controlled by the Clock Select
(CS02:0) bits located in the Timer/Counter Control Register (TCCR0). For details on
clock sources and prescaler, see “Timer/Counter0, Timer/Counter1, and
Timer/Counter3 Prescalers” on page 103.
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Counter Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
Figure 34 shows a block diagram of the counter and its surroundings.
Figure 34. Counter Unit Block Diagram
TOVn
(Int.Req.)
DATA BUS
Clock Select
count
clear
Edge
Detector
Tn
clkTn
TCNTn
Control Logic
direction
( From Prescaler )
bottom
top
Signal description (internal signals):
count Increment or decrement TCNT0 by 1.
direction Select between increment and decrement.
clear
clkTn
top
Clear TCNT0 (set all bits to zero).
Timer/Counter clock, referred to as clkT0 in the following.
Signalize that TCNT0 has reached maximum value.
Signalize that TCNT0 has reached minimum value (zero).
bottom
Depending of the mode of operation used, the counter is cleared, incremented, or dec-
remented at each timer clock (clkT0). clkT0 can be generated from an external or internal
clock source, selected by the clock select bits (CS02:0). When no clock source is
selected (CS02:0 = 0) the timer is stopped. However, the TCNT0 value can be accessed
by the CPU, regardless of whether clkT0 is present or not. A CPU write overrides (has
priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the WGM01 and WGM00 bits
located in the Timer/Counter Control Register (TCCR0). There are close connections
between how the counter behaves (counts) and how waveforms are generated on the
output Compare Output OC0. For more details about advanced counting sequences
and waveform generation, see “Modes of Operation” on page 93.
The Timer/Counter Overflow (TOV0) Flag is set according to the mode of operation
selected by the WGM01:0 bits. TOV0 can be used for generating a CPU interrupt.
Output Compare Unit
The 8-bit comparator continuously compares TCNT0 with the Output Compare Register
(OCR0). Whenever TCNT0 equals OCR0, the comparator signals a match. A match will
set the Output Compare Flag (OCF0) at the next timer clock cycle. If enabled (OCIE0 =
1 and Global Interrupt Flag in SREG is set), the Output Compare Flag generates an out-
put compare interrupt. The OCF0 Flag is automatically cleared when the interrupt is
executed. Alternatively, the OCF0 Flag can be cleared by software by writing a logical
one to its I/O bit location. The waveform generator uses the match signal to generate an
output according to operating mode set by the WGM01:0 bits and Compare Output
mode (COM01:0) bits. The max and bottom signals are used by the waveform generator
for handling the special cases of the extreme values in some modes of operation (See
“Modes of Operation” on page 93.).
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Figure 35 shows a block diagram of the output compare unit.
Figure 35. Output Compare Unit, Block Diagram
DATA BUS
OCRn
TCNTn
=
(8-bit Comparator )
OCFn (Int.Req.)
top
bottom
FOCn
Waveform Generator
OCn
WGMn1:0
COMn1:0
The OCR0 Register is double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the Normal and Clear Timer on Compare (CTC) modes of operation,
the double buffering is disabled. The double buffering synchronizes the update of the
OCR0 Compare Register to either top or bottom of the counting sequence. The synchro-
nization prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby
making the output glitch-free.
The OCR0 Register access may seem complex, but this is not case. When the double
buffering is enabled, the CPU has access to the OCR0 Buffer Register, and if double
buffering is disabled the CPU will access the OCR0 directly.
Force Output Compare
In non-PWM waveform generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOC0) bit. Forcing Compare
Match will not set the OCF0 Flag or reload/clear the Timer, but the OC0 pin will be
updated as if a real Compare Match had occurred (the COM01:0 bits settings define
whether the OC0 pin is set, cleared or toggled).
Compare Match Blocking by
TCNT0 Write
All CPU write operations to the TCNT0 Register will block any Compare Match that
occur in the next timer clock cycle, even when the timer is stopped. This feature allows
OCR0 to be initialized to the same value as TCNT0 without triggering an interrupt when
the Timer/Counter clock is enabled.
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Using the Output Compare
Unit
Since writing TCNT0 in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNT0 when using the output
compare channel, independently of whether the Timer/Counter is running or not. If the
value written to TCNT0 equals the OCR0 value, the Compare Match will be missed,
resulting in incorrect waveform generation. Similarly, do not write the TCNT0 value
equal to BOTTOM when the counter is down-counting.
The setup of the OC0 should be performed before setting the Data Direction Register for
the port pin to output. The easiest way of setting the OC0 value is to use the Force Out-
put Compare (FOC0) strobe bits in Normal mode. The OC0 Register keeps its value
even when changing between Waveform Generation modes.
Be aware that the COM01:0 bits are not double buffered together with the compare
value. Changing the COM01:0 bits will take effect immediately.
Compare Match Output
Unit
The Compare Output mode (COM01:0) bits have two functions. The Waveform Genera-
tor uses the COM01:0 bits for defining the Output Compare (OC0) state at the next
Compare Match. Also, the COM01:0 bits control the OC0 pin output source. Figure 36
shows a simplified schematic of the logic affected by the COM01:0 bit setting. The I/O
Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the
general I/O Port Control Registers (DDR and PORT) that are affected by the COM01:0
bits are shown. When referring to the OC0 state, the reference is for the internal OC0
Register, not the OC0 pin. If a System Reset occur, the OC0 Register is reset to “0”.
Figure 36. Compare Match Output Unit, Schematics
COMn1
Waveform
Generator
COMn0
FOCn
D
Q
Q
1
0
OCn
Pin
OCn
D
PORT
D
Q
DDR
clkI/O
The general I/O port function is overridden by the Output Compare (OC0) from the
waveform generator if either of the COM01:0 bits are set. However, the OC0 pin direc-
tion (input or output) is still controlled by the Data Direction Register (DDR) for the port
pin. The Data Direction Register bit for the OC0 pin (DDR_OC0) must be set as output
before the OC0 value is visible on the pin. The port override function is independent of
the Waveform Generation mode.
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The design of the output compare pin logic allows initialization of the OC0 state before
the output is enabled. Note that some COM01:0 bit settings are reserved for certain
modes of operation. See “8-bit Timer/Counter Register Description” on page 99.
Compare Output Mode and
Waveform Generation
The Waveform Generator uses the COM01:0 bits differently in Normal, CTC, and PWM
modes. For all modes, setting the COM01:0 = 0 tells the Waveform Generator that no
action on the OC0 Register is to be performed on the next Compare Match. For Com-
pare Output actions in the non-PWM modes refer to Table 48 on page 100. For fast
PWM mode, refer to Table 49 on page 100, and for phase correct PWM refer to Table
50 on page 100.
A change of the COM01:0 bits state will have effect at the first Compare Match after the
bits are written. For non-PWM modes, the action can be forced to have immediate effect
by using the FOC0 strobe bits.
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGM01:0) and
Compare Output mode (COM01:0) bits. The Compare Output mode bits do not affect
the counting sequence, while the Waveform Generation mode bits do. The COM01:0
bits control whether the PWM output generated should be inverted or not (inverted or
non-inverted PWM). For non-PWM modes the COM01:0 bits control whether the output
should be set, cleared, or toggled at a Compare Match (See “Compare Match Output
Unit” on page 92.).
For detailed timing information refer to Figure 40, Figure 41, Figure 42 and Figure 43 in
“Timer/Counter Timing Diagrams” on page 97.
Normal Mode
The simplest mode of operation is the Normal mode (WGM01:0 = 0). In this mode the
counting direction is always up (incrementing), and no counter clear is performed. The
counter simply overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then
restarts from the bottom (0x00). In normal operation the Timer/Counter Overflow Flag
(TOV0) will be set in the same timer clock cycle as the TCNT0 becomes zero. The
TOV0 Flag in this case behaves like a ninth bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt that automatically clears the TOV0
Flag, the timer resolution can be increased by software. There are no special cases to
consider in the Normal mode, a new counter value can be written anytime.
The output compare unit can be used to generate interrupts at some given time. Using
the output compare to generate waveforms in Normal mode is not recommended, since
this will occupy too much of the CPU time.
Clear Timer on Compare
Match (CTC) Mode
In Clear Timer on Compare or CTC mode (WGM01:0 = 2), the OCR0 Register is used to
manipulate the counter resolution. In CTC mode the counter is cleared to zero when the
counter value (TCNT0) matches the OCR0. The OCR0 defines the top value for the
counter, hence also its resolution. This mode allows greater control of the Compare
Match output frequency. It also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in Figure 37. The counter value
(TCNT0) increases until a Compare Match occurs between TCNT0 and OCR0, and then
counter (TCNT0) is cleared.
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Figure 37. CTC Mode, Timing Diagram
OCn Interrupt Flag Set
TCNTn
OCn
(Toggle)
(COMn1:0 = 1)
1
2
3
4
Period
An interrupt can be generated each time the counter value reaches the TOP value by
using the OCF0 Flag. If the interrupt is enabled, the interrupt handler routine can be
used for updating the TOP value. However, changing TOP to a value close to BOTTOM
when the counter is running with none or a low prescaler value must be done with care
since the CTC mode does not have the double buffering feature. If the new value written
to OCR0 is lower than the current value of TCNT0, the counter will miss the Compare
Match. The counter will then have to count to its maximum value (0xFF) and wrap
around starting at 0x00 before the Compare Match can occur.
For generating a waveform output in CTC mode, the OC0 output can be set to toggle its
logical level on each Compare Match by setting the Compare Output mode bits to toggle
bitmode (COM01:0 = 1). The OC0 value will not be visible on the port pin unless the
data direction for the pin is set to output. The waveform generated will have a maximum
frequency of fOC0 = fclk_I/O/2 when OCR0 is set to zero (0x00). The waveform frequency
is defined by the following equation:
f
clk_I/O
f
= ----------------------------------------------
OCn
2 N (1 + OCRn)
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOV0 Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x00.
Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGM01:0 = 3) provides a high fre-
quency PWM waveform generation option. The fast PWM differs from the other PWM
option by its single-slope operation. The counter counts from BOTTOM to MAX then
restarts from BOTTOM. In non-inverting Compare Output mode, the Output Compare
(OC0) is cleared on the Compare Match between TCNT0 and OCR0, and set at BOT-
TOM. In inverting Compare Output mode, the output is set on Compare Match and
cleared at BOTTOM. Due to the single-slope operation, the operating frequency of the
fast PWM mode can be twice as high as the phase correct PWM mode that use dual-
slope operation. This high frequency makes the fast PWM mode well suited for power
regulation, rectification, and DAC applications. High frequency allows physically small
sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the MAX
value. The counter is then cleared at the following timer clock cycle. The timing diagram
for the fast PWM mode is shown in Figure 38. The TCNT0 value is in the timing diagram
shown as a histogram for illustrating the single-slope operation. The diagram includes
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non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0
slopes represent compare matches between OCR0 and TCNT0.
Figure 38. Fast PWM Mode, Timing Diagram
OCRn Interrupt Flag Set
OCRn Update ans
TOVn Interrupt Flag Set
TCNTn
(COMn1:0 = 2)
(COMn1:0 = 3)
OCn
OCn
1
2
3
4
5
6
7
Period
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches MAX. If
the interrupt is enabled, the interrupt handler routine can be used for updating the com-
pare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0
pin. Setting the COM01:0 bits to two will produce a non-inverted PWM and an inverted
PWM output can be generated by setting the COM01:0 to three (See Table 49 on page
100). The actual OC0 value will only be visible on the port pin if the data direction for the
port pin is set as output. The PWM waveform is generated by setting (or clearing) the
OC0 Register at the Compare Match between OCR0 and TCNT0, and clearing (or set-
ting) the OC0 Register at the timer clock cycle the counter is cleared (changes from
MAX to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
f
clk_I/O
f
= -----------------
OCnPWM
N 256
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR0 Register represents special cases when generating a
PWM waveform output in the fast PWM mode. If the OCR0 is set equal to BOTTOM, the
output will be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR0 equal
to MAX will result in a constantly high or low output (depending on the polarity of the out-
put set by the COM01:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OC0 to toggle its logical level on each Compare Match (COM01:0 = 1). The
waveform generated will have a maximum frequency of fOC0 = fclk_I/O/2 when OCR0 is
set to zero. This feature is similar to the OC0 toggle in CTC mode, except the double
buffer feature of the output compare unit is enabled in the fast PWM mode.
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Phase Correct PWM Mode
The phase correct PWM mode (WGM01:0 = 1) provides a high resolution phase correct
PWM waveform generation option. The phase correct PWM mode is based on a dual-
slope operation. The counter counts repeatedly from BOTTOM to MAX and then from
MAX to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OC0)
is cleared on the Compare Match between TCNT0 and OCR0 while up-counting, and
set on the Compare Match while down-counting. In inverting Output Compare mode, the
operation is inverted. The dual-slope operation has lower maximum operation frequency
than single slope operation. However, due to the symmetric feature of the dual-slope
PWM modes, these modes are preferred for motor control applications.
The PWM resolution for the phase correct PWM mode is fixed to eight bits. In phase
correct PWM mode the counter is incremented until the counter value matches MAX.
When the counter reaches MAX, it changes the count direction. The TCNT0 value will
be equal to MAX for one timer clock cycle. The timing diagram for the phase correct
PWM mode is shown on Figure 39. The TCNT0 value is in the timing diagram shown as
a histogram for illustrating the dual-slope operation. The diagram includes non-inverted
and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes repre-
sent compare matches between OCR0 and TCNT0.
Figure 39. Phase Correct PWM Mode, Timing Diagram
OCn Interrupt Flag Set
OCRn Update
TOVn Interrupt Flag Set
TCNTn
(COMn1:0 = 2)
OCn
(COMn1:0 = 3)
OCn
1
2
3
Period
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches BOT-
TOM. The Interrupt Flag can be used to generate an interrupt each time the counter
reaches the BOTTOM value.
In phase correct PWM mode, the compare unit allows generation of PWM waveforms on
the OC0 pin. Setting the COM01:0 bits to two will produce a non-inverted PWM. An
inverted PWM output can be generated by setting the COM01:0 to three (See Table 50
on page 100). The actual OC0 value will only be visible on the port pin if the data direc-
tion for the port pin is set as output. The PWM waveform is generated by clearing (or
setting) the OC0 Register at the Compare Match between OCR0 and TCNT0 when the
counter increments, and setting (or clearing) the OC0 Register at Compare Match
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between OCR0 and TCNT0 when the counter decrements. The PWM frequency for the
output when using phase correct PWM can be calculated by the following equation:
f
clk_I/O
f
= -----------------
OCnPCPWM
N 510
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
The extreme values for the OCR0 Register represent special cases when generating a
PWM waveform output in the phase correct PWM mode. If the OCR0 is set equal to
BOTTOM, the output will be continuously low and if set equal to MAX the output will be
continuously high for non-inverted PWM mode. For inverted PWM the output will have
the opposite logic values.
At the very start of period 2 in Figure 39 OCn has a transition from high to low even
though there is no Compare Match. The point of this transition is to guarantee symmetry
around BOTTOM. There are two cases that give a transition without Compare Match.
•
OCR0 changes its value from MAX, like in Figure 39. When the OCR0 value is MAX
the OCn pin value is the same as the result of a down-counting Compare Match. To
ensure symmetry around BOTTOM the OCn value at MAX must correspond to the
result of an up-counting Compare Match.
•
The timer starts counting from a value higher than the one in OCR0, and for that
reason misses the Compare Match and hence the OCn change that would have
happened on the way up.
Timer/Counter Timing
Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT0) is therefore
shown as a clock enable signal in the following figures. The figures include information
on when Interrupt Flags are set. Figure 40 contains timing data for basic Timer/Counter
operation. The figure shows the count sequence close to the MAX value in all modes
other than phase correct PWM mode.
Figure 40. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O/1)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 41 shows the same timing data, but with the prescaler enabled.
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Figure 41. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 42 shows the setting of OCF0 in all modes except CTC mode.
Figure 42. Timer/Counter Timing Diagram, Setting of OCF0, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
OCRn
OCFn
OCRn - 1
OCRn
OCRn + 1
OCRn + 2
OCRn Value
Figure 43 shows the setting of OCF0 and the clearing of TCNT0 in CTC mode.
Figure 43. Timer/Counter Timing Diagram, Clear Timer on Compare Match Mode, with
Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
(CTC)
TOP - 1
TOP
BOTTOM
BOTTOM + 1
OCRn
TOP
OCFn
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8-bit Timer/Counter
Register Description
Timer/Counter Control
Register – TCCR0
Bit
7
FOC0
W
6
WGM00
R/W
0
5
COM01
R/W
0
4
COM00
R/W
0
3
WGM01
R/W
0
2
CS02
R/W
0
1
CS01
R/W
0
0
CS00
R/W
0
TCCR0
Read/Write
Initial Value
0
• Bit 7 – FOC0: Force Output Compare
The FOC0 bit is only active when the WGM00 bit specifies a non-PWM mode. However,
for ensuring compatibility with future devices, this bit must be set to zero when TCCR0 is
written when operating in PWM mode. When writing a logical one to the FOC0 bit, an
immediate Compare Match is forced on the Waveform Generation unit. The OC0 output
is changed according to its COM01:0 bits setting. Note that the FOC0 bit is implemented
as a strobe. Therefore it is the value present in the COM01:0 bits that determines the
effect of the forced compare.
A FOC0 strobe will not generate any interrupt, nor will it clear the timer in CTC mode
using OCR0 as TOP.
The FOC0 bit is always read as zero.
• Bit 6, 3 – WGM01:0: Waveform Generation Mode
These bits control the counting sequence of the counter, the source for the maximum
(TOP) counter value, and what type of waveform generation to be used. Modes of oper-
ation supported by the Timer/Counter unit are: Normal mode, Clear Timer on Compare
match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes. See Table
47 and “Modes of Operation” on page 93.
Table 47. Waveform Generation Mode Bit Description(1)
WGM01 WGM00 Timer/Counter Mode
Update of TOV0 Flag
OCR0 at Set on
Mode
(CTC0)
(PWM0) of Operation
TOP
0xFF
0xFF
0
1
2
3
0
0
1
1
0
1
0
1
Normal
Immediate MAX
TOP BOTTOM
PWM, Phase Correct
CTC
OCR0 Immediate MAX
0xFF TOP MAX
Fast PWM
Note:
1. The CTC0 and PWM0 bit definition names are now obsolete. Use the WGM01:0 def-
initions. However, the functionality and location of these bits are compatible with
previous versions of the timer.
• Bit 5:4 – COM01:0: Compare Match Output Mode
These bits control the output compare pin (OC0) behavior. If one or both of the
COM01:0 bits are set, the OC0 output overrides the normal port functionality of the I/O
pin it is connected to. However, note that the Data Direction Register (DDR) bit corre-
sponding to the OC0 pin must be set in order to enable the output driver.
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When OC0 is connected to the pin, the function of the COM01:0 bits depends on the
WGM01:0 bit setting. Table 48 shows the COM01:0 bit functionality when the WGM01:0
bits are set to a Normal or CTC mode (non-PWM).
Table 48. Compare Output Mode, non-PWM Mode
COM01
COM00
Description
0
0
1
1
0
1
0
1
Normal port operation, OC0 disconnected.
Toggle OC0 on Compare Match.
Clear OC0 on Compare Match.
Set OC0 on Compare Match.
Table 49 shows the COM01:0 bit functionality when the WGM01:0 bits are set to fast
PWM mode.
Table 49. Compare Output Mode, fast PWM Mode(1)
COM01
COM00
Description
0
0
1
1
0
1
0
1
Normal port operation, OC0 disconnected.
Reserved
Clear OC0 on Compare Match, set OC0 at TOP.
Set OC0 on Compare Match, clear OC0 at TOP.
Note:
1. A special case occurs when OCR0 equals TOP and COM01 is set. In this case, the
Compare Match is ignored, but the set or clear is done at TOP. See “Fast PWM
Mode” on page 94 for more details.
Table 50 shows the COM01:0 bit functionality when the WGM01:0 bits are set to phase
correct PWM mode.
Table 50. Compare Output Mode, Phase Correct PWM Mode(1)
COM01
COM00
Description
0
0
1
0
1
0
Normal port operation, OC0 disconnected.
Reserved
Clear OC0 on Compare Match when up-counting. Set OC0 on
Compare Match when down-counting.
1
1
Set OC0 on Compare Match when up-counting. Clear OC0 on
Compare Match when down-counting.
Note:
1. A special case occurs when OCR0 equals TOP and COM01 is set. In this case, the
Compare Match is ignored, but the set or clear is done at TOP. See “Phase Correct
PWM Mode” on page 96 for more details.
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• Bit 2:0 – CS02:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter.
Table 51. Clock Select Bit Description
CS02
CS01
CS00
Description
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No clock source (Timer/Counter stopped).
clkI/O/(No prescaling)
clkI/O/8 (From prescaler)
clkI/O/64 (From prescaler)
clkI/O/256 (From prescaler)
clkI/O/1024 (From prescaler)
External clock source on T0 pin. Clock on falling edge.
External clock source on T0 pin. Clock on rising edge.
If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will
clock the counter even if the pin is configured as an output. This feature allows software
control of the counting.
Timer/Counter Register –
TCNT0
Bit
7
6
5
4
3
2
1
0
TCNT0[7:0]
TCNT0
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
The Timer/Counter Register gives direct access, both for read and write operations, to
the Timer/Counter unit 8-bit counter. Writing to the TCNT0 Register blocks (removes)
the Compare Match on the following timer clock. Modifying the counter (TCNT0) while
the counter is running, introduces a risk of missing a Compare Match between TCNT0
and the OCR0 Register.
Output Compare Register –
OCR0
Bit
7
6
5
4
3
2
1
0
OCR0[7:0]
OCR0
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
The Output Compare Register contains an 8-bit value that is continuously compared
with the counter value (TCNT0). A match can be used to generate an output compare
interrupt, or to generate a waveform output on the OC0 pin.
Timer/Counter Interrupt Mask
Register – TIMSK
Bit
7
TOIE1
R/W
0
6
OCIE1A
R/W
0
5
OCIE1B
R/W
0
4
OCIE2
R/W
0
3
TICIE1
R/W
0
2
TOIE2
R/W
0
1
TOIE0
R/W
0
0
OCIE0
R/W
0
TIMSK
Read/Write
Initial Value
• Bit 1 – TOIE0: Timer/Counter0 Overflow Interrupt Enable
When the TOIE0 bit is written to one, and the I-bit in the Status Register is set (one), the
Timer/Counter0 Overflow interrupt is enabled. The corresponding interrupt is executed if
an overflow in Timer/Counter0 occurs, i.e., when the TOV0 bit is set in the
Timer/Counter Interrupt Flag Register – TIFR.
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• Bit 0 – OCIE0: Timer/Counter0 Output Compare Match Interrupt Enable
When the OCIE0 bit is written to one, and the I-bit in the Status Register is set (one), the
Timer/Counter0 Compare Match interrupt is enabled. The corresponding interrupt is
executed if a Compare Match in Timer/Counter0 occurs, i.e., when the OCF0 bit is set in
the Timer/Counter Interrupt Flag Register – TIFR.
Timer/Counter Interrupt Flag
Register – TIFR
Bit
7
TOV1
R/W
0
6
OCF1A
R/W
0
5
OCF1B
R/W
0
4
OCF2
R/W
0
3
ICF1
R/W
0
2
TOV2
R/W
0
1
TOV0
R/W
0
0
OCF0
R/W
0
TIFR
Read/Write
Initial Value
• Bit 1 – TOV0: Timer/Counter0 Overflow Flag
The bit TOV0 is set (one) when an overflow occurs in Timer/Counter0. TOV0 is cleared
by hardware when executing the corresponding interrupt handling vector. Alternatively,
TOV0 is cleared by writing a logic one to the flag. When the SREG I-bit, TOIE0
(Timer/Counter0 Overflow Interrupt Enable), and TOV0 are set (one), the
Timer/Counter0 Overflow interrupt is executed. In phase correct PWM mode, this bit is
set when Timer/Counter0 changes counting direction at 0x00.
• Bit 0 – OCF0: Output Compare Flag 0
The OCF0 bit is set (one) when a Compare Match occurs between the Timer/Counter0
and the data in OCR0 – Output Compare Register0. OCF0 is cleared by hardware when
executing the corresponding interrupt handling vector. Alternatively, OCF0 is cleared by
writing a logic one to the flag. When the I-bit in SREG, OCIE0 (Timer/Counter0 Com-
pare match Interrupt Enable), and OCF0 are set (one), the Timer/Counter0 Compare
Match Interrupt is executed.
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Timer/Counter0,
Timer/Counter1, and
Timer/Counter3
Prescalers
Timer/Counter3, Timer/Counter1, and Timer/Counter0 share the same prescaler mod-
ule, but the Timer/Counters can have different prescaler settings. The description below
applies to Timer/Counter3, Timer/Counter1, and Timer/Counter0.
Internal Clock Source
The Timer/Counter can be clocked directly by the system clock (by setting the CSn2:0 =
1). This provides the fastest operation, with a maximum Timer/Counter clock frequency
equal to system clock frequency (fCLK_I/O). Alternatively, one of four taps from the pres-
caler can be used as a clock source. The prescaled clock has a frequency of either
fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024. In addition, Timer/Counter3 has the
option of choosing fCLK_I/O/16 and fCLK_I/O/32.
Prescaler Reset
The prescaler is free running, i.e., operates independently of the clock select logic of the
Timer/Counter, and it is shared by Timer/Counter3, Timer/Counter1, and
Timer/Counter0. Since the prescaler is not affected by the Timer/Counter’s clock select,
the state of the prescaler will have implications for situations where a prescaled clock is
used. One example of prescaling artifacts occurs when the Timer is enabled and
clocked by the prescaler (6 > CSn2:0 > 1). The number of system clock cycles from
when the Timer is enabled to the first count occurs can be from 1 to N+1 system clock
cycles, where N equals the prescaler divisor (8, 64, 256, or 1024, additional selections
for Timer/Counter3: 32 and 64).
It is possible to use the Prescaler Reset for synchronizing the Timer/Counter to program
execution. However, care must be taken if the other Timer/Counter that shares the
same prescaler also uses prescaling. A Prescaler Reset will affect the prescaler period
for all Timer/Counters it is connected to.
External Clock Source
An external clock source applied to the Tn/T0 pin can be used as Timer/Counter clock
(clkT1/clkT0) for Timer/Counter1 and Timer/Counter0. The Tn/T0 pin is sampled once
every system clock cycle by the pin synchronization logic. The synchronized (sampled)
signal is then passed through the edge detector. Figure 44 shows a functional equiva-
lent block diagram of the Tn/T0 synchronization and edge detector logic. The registers
are clocked at the positive edge of the internal system clock (clkI/O). The latch is trans-
parent in the high period of the internal system clock.
The edge detector generates one clkT1/clkT0 pulse for each positive (CSn2:0 = 7) or neg-
ative (CSn2:0 = 6) edge it detects.
Figure 44. Tn/T0 Pin Sampling
Tn_sync
(To Clock
Tn
D
Q
D
Q
D
Q
Select Logic)
LE
clkI/O
Synchronization
Edge Detector
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system
clock cycles from an edge has been applied to the Tn/T0 pin to the counter is updated.
Enabling and disabling of the clock input must be done when Tn/T0 has been stable for
at least one system clock cycle, otherwise it is a risk that a false Timer/Counter clock
pulse is generated.
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Each half period of the external clock applied must be longer than one system clock
cycle to ensure correct sampling. The external clock must be guaranteed to have less
than half the system clock frequency (fExtClk < fclk_I/O/2) given a 50/50% duty cycle. Since
the edge detector uses sampling, the maximum frequency of an external clock it can
detect is half the sampling frequency (Nyquist sampling theorem). However, due to vari-
ation of the system clock frequency and duty cycle caused by Oscillator source (crystal,
resonator, and capacitors) tolerances, it is recommended that maximum frequency of an
external clock source is less than fclk_I/O/2.5.
An external clock source can not be prescaled.
Figure 45. Prescaler for Timer/Counter0, Timer/Counter1, and Timer/Counter3(1)
CK
10-BIT T/C PRESCALER
Clear
PSR321
T1
T0
0
0
0
CS30
CS31
CS32
CS10
CS11
CS12
CS00
CS01
CS02
TIMER/COUNTER3 CLOCK SOURCE
TIMER/COUNTER1 CLOCK SOURCE
TIMER/COUNTER1 CLOCK SOURCE
clkT3
clkT1
clkT0
Note:
1. The synchronization logic on the input pins (Tn/T0) is shown in Figure 44.
Special Function IO Register –
SFIOR
Bit
7
6
XMBK
R/W
0
5
XMM2
R/W
0
4
XMM1
R/W
0
3
XMM0
R/W
0
2
1
PSR2
R/W
0
0
PSR310
R/W
0
TSM
R/W
0
PUD
R/W
0
SFIOR
Read/Write
Initial Value
• Bit 7 – TSM: Timer/Counter Synchronization Mode
Writing the TSM bit to one activates the Timer/Counter Synchronization mode. In this
mode, the value that is written to the PSR2 and PSR310 bits is kept, hence keeping the
corresponding prescaler reset signals asserted. This ensures that the corresponding
Timer/Counters are halted and can be configured to the same value without the risk of
one of them advancing during configuration. When the TSM bit is written to zero, the
PSR2 and PSR310 bits are cleared by hardware, and the Timer/Counters start counting
simultaneously.
• Bit 0 – PSR310: Prescaler Reset Timer/Counter3, Timer/Counter1, and
Timer/Counter0
When this bit is one, the Timer/Counter3, Timer/Counter1, and Timer/Counter0 pres-
caler will be reset. This bit is normally cleared immediately by hardware, except if the
TSM bit is set. Note that Timer/Counter3, Timer/Counter1, and Timer/Counter0 share
the same prescaler and a reset of this prescaler will affect all three timers.
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16-bit Timer/Counter The 16-bit Timer/Counter unit allows accurate program execution timing (event man-
agement), wave generation, and signal timing measurement. The main features are:
• True 16-bit Design (i.e., allows 16-bit PWM)
(Timer/Counter1 and
Timer/Counter3)
• Two Independent Output Compare Units
• Double Buffered Output Compare Registers
• One Input Capture Unit
• Input Capture Noise Canceler
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Variable PWM Period
• Frequency Generator
• External Event Counter
• Eight Independent Interrupt Sources (TOV1, OCF1A, OCF1B, ICF1, TOV3, OCF3A, OCF3B,
and ICF3)
Restriction in
ATmega161
Note that in ATmega161 compatibility mode, only one 16-bits Timer/Counter is available
(Timer/Counter1).
Compatibility Mode
Overview
Most register and bit references in this section are written in general form. A lower case
“n” replaces the Timer/Counter number, and a lower case “x” replaces the Output Com-
pare unit channel. However, when using the register or bit defines in a program, the
precise form must be used i.e., TCNT1 for accessing Timer/Counter1 counter value and
so on.
A simplified block diagram of the 16-bit Timer/Counter is shown in Figure 46. For the
actual placement of I/O pins, refer to “Pinout ATmega162” on page 2. CPU accessible
I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O
Register and bit locations are listed in the “16-bit Timer/Counter Register Description”
on page 127.
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Figure 46. 16-bit Timer/Counter Block Diagram(1)
Count
TOVn
(Int.Req.)
Clear
Control Logic
Clock Select
Direction
clkTn
Edge
Detector
Tn
TOP BOTTOM
( From Prescaler )
Timer/Counter
TCNTn
=
= 0
OCnA
(Int.Req.)
Waveform
Generation
OCnA
=
OCRnA
OCnB
(Int.Req.)
Fixed
TOP
Values
Waveform
Generation
OCnB
=
OCRnB
( From Analog
Comparator Ouput )
ICFn (Int.Req.)
Edge
Detector
Noise
Canceler
ICRn
ICPn
TCCRnA
TCCRnB
Note:
1. Refer to Figure 1 on page 2, Table 32 on page 71, and Table 38 on page 77 for
Timer/Counter1 pin placement and description.
Registers
The Timer/Counter (TCNTn), Output Compare Registers (OCRnA/B), and Input Capture
Register (ICRn) are all 16-bit registers. Special procedures must be followed when
accessing the 16-bit registers. These procedures are described in the section “Access-
ing 16-bit Registers” on page 108. The Timer/Counter Control Registers (TCCRnA/B)
are 8-bit registers and have no CPU access restrictions. Interrupt requests (abbreviated
to Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFR)
and Extended Timer Interrupt Flag Register (ETIFR). All interrupts are individually
masked with the Timer Interrupt Mask Register (TIMSK) and Extended Timer Interrupt
Mask Register (ETIMSK). (E)TIFR and (E)TIMSK are not shown in the figure since
these registers are shared by other Timer units.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock
source on the T1 pin. The Clock Select logic block controls which clock source and edge
the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is
inactive when no clock source is selected. The output from the Clock Select logic is
referred to as the Timer Clock (clkTn).
The double buffered Output Compare Registers (OCRnA/B) are compared with the
Timer/Counter value at all time. The result of the compare can be used by the waveform
generator to generate a PWM or variable frequency output on the Output Compare pin
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(OCnA/B). See “Output Compare Units” on page 114. The Compare Match event will
also set the Compare Match Flag (OCFnA/B) which can be used to generate an output
compare interrupt request.
The Input Capture Register can capture the Timer/Counter value at a given external
(edge triggered) event on either the Input Capture pin (ICPn) or on the Analog Compar-
ator pins (See “Analog Comparator” on page 194.) The Input Capture unit includes a
digital filtering unit (Noise Canceler) for reducing the chance of capturing noise spikes.
The TOP value, or maximum Timer/Counter value, can in some modes of operation be
defined by either the OCRnA Register, the ICRn Register, or by a set of fixed values.
When using OCRnA as TOP value in a PWM mode, the OCRnA Register can not be
used for generating a PWM output. However, the TOP value will in this case be double
buffered allowing the TOP value to be changed in run time. If a fixed TOP value is
required, the ICRn Register can be used as an alternative, freeing the OCRnA to be
used as PWM output.
Definitions
The following definitions are used extensively throughout the section:
Table 52. Definitions
BOTTOM The counter reaches the BOTTOM when it becomes 0x0000.
MAX
The counter reaches its MAXimum when it becomes 0xFFFF (decimal
65535).
TOP
The counter reaches the TOP when it becomes equal to the highest
value in the count sequence. The TOP value can be assigned to be one
of the fixed values: 0x00FF, 0x01FF, or 0x03FF, or to the value stored in
the OCRnA or ICRn Register. The assignment is dependent of the mode
of operation.
Compatibility
The 16-bit Timer/Counter has been updated and improved from previous versions of the
16-bit AVR Timer/Counter. This 16-bit Timer/Counter is fully compatible with the earlier
version regarding:
•
•
•
All 16-bit Timer/Counter related I/O Register address locations, including Timer
Interrupt Registers.
Bit locations inside all 16-bit Timer/Counter Registers, including Timer Interrupt
Registers.
Interrupt Vectors.
The following control bits have changed name, but have same functionality and register
location:
•
•
•
PWMn0 is changed to WGMn0.
PWMn1 is changed to WGMn1.
CTCn is changed to WGMn2.
The following bits are added to the 16-bit Timer/Counter Control Registers:
•
•
FOCnA and FOCnB are added to TCCRnA.
WGMn3 is added to TCCRnB.
The 16-bit Timer/Counter has improvements that will affect the compatibility in some
special cases.
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Accessing 16-bit
Registers
The TCNTn, OCRnA/B, and ICRn are 16-bit registers that can be accessed by the AVR
CPU via the 8-bit data bus. The 16-bit register must be byte accessed using two read or
write operations. Each 16-bit timer has a single 8-bit register for temporary storing of the
high byte of the 16-bit access. The same Temporary Register is shared between all 16-
bit registers within each 16-bit timer. Accessing the low byte triggers the 16-bit read or
write operation. When the low byte of a 16-bit register is written by the CPU, the high
byte stored in the temporary register, and the low byte written are both copied into the
16-bit register in the same clock cycle. When the low byte of a 16-bit register is read by
the CPU, the high byte of the 16-bit register is copied into the temporary register in the
same clock cycle as the low byte is read.
Not all 16-bit accesses uses the temporary register for the high byte. Reading the
OCRnA/B 16-bit registers does not involve using the temporary register.
To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read,
the low byte must be read before the high byte.
The following code examples show how to access the 16-bit Timer Registers assuming
that no interrupts updates the temporary register. The same principle can be used
directly for accessing the OCRnA/B and ICRn Registers. Note that when using “C”, the
compiler handles the 16-bit access.
Assembly Code Examples(1)
...
; Set TCNTn to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCNTnH,r17
out TCNTnL,r16
; Read TCNTn into r17:r16
in r16,TCNTnL
in r17,TCNTnH
...
C Code Examples(1)
unsigned int i;
...
/* Set TCNTn to 0x01FF */
TCNTn = 0x1FF;
/* Read TCNTn into i */
i = TCNTn;
...
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example returns the TCNTn value in the r17:r16 register pair.
It is important to notice that accessing 16-bit registers are atomic operations. If an inter-
rupt occurs between the two instructions accessing the 16-bit register, and the interrupt
code updates the temporary register by accessing the same or any other of the 16-bit
Timer Registers, then the result of the access outside the interrupt will be corrupted.
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Therefore, when both the main code and the interrupt code update the temporary regis-
ter, the main code must disable the interrupts during the 16-bit access.
The following code examples show how to do an atomic read of the TCNTn Register
contents. Reading any of the OCRnA/B or ICRn Registers can be done by using the
same principle.
Assembly Code Example(1)
TIM16_ReadTCNTn:
; Save Global Interrupt Flag
in r18,SREG
; Disable interrupts
cli
; Read TCNTn into r17:r16
in r16,TCNTnL
in r17,TCNTnH
; Restore Global Interrupt Flag
out SREG,r18
ret
C Code Example(1)
unsigned int TIM16_ReadTCNTn( void )
{
unsigned char sreg;
unsigned int i;
/* Save Global Interrupt Flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNTn into i */
i = TCNTn;
/* Restore Global Interrupt Flag */
SREG = sreg;
return i;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example returns the TCNTn value in the r17:r16 register pair.
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The following code examples show how to do an atomic write of the TCNTn Register
contents. Writing any of the OCRnA/B or ICRn Registers can be done by using the
same principle.
Assembly Code Example(1)
TIM16_WriteTCNTn:
; Save Global Interrupt Flag
in r18,SREG
; Disable interrupts
cli
; Set TCNTn to r17:r16
out TCNTnH,r17
out TCNTnL,r16
; Restore Global Interrupt Flag
out SREG,r18
ret
C Code Example(1)
void TIM16_WriteTCNTn( unsigned int i )
{
unsigned char sreg;
unsigned int i;
/* Save Global Interrupt Flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNTn to i */
TCNTn = i;
/* Restore Global Interrupt Flag */
SREG = sreg;
}
Note:
1. The example code assumes that the part specific header file is included.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”,
and “SBI” instructions must be replaced with instructions that allow access to
extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and
“CBR”.
The assembly code example requires that the r17:r16 register pair contains the value to
be written to TCNTn.
Reusing the Temporary High
Byte Register
If writing to more than one 16-bit register where the high byte is the same for all registers
written, then the high byte only needs to be written once. However, note that the same
rule of atomic operation described previously also applies in this case.
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Timer/Counter Clock
Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock
source is selected by the clock select logic which is controlled by the Clock Select
(CSn2:0) bits located in the Timer/Counter Control Register B (TCCRnB). For details on
clock sources and prescaler, see “Timer/Counter0, Timer/Counter1, and
Timer/Counter3 Prescalers” on page 103.
Counter Unit
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional
counter unit. Figure 47 shows a block diagram of the counter and its surroundings.
Figure 47. Counter Unit Block Diagram
DATA BUS (8-bit)
TOVn
(Int.Req.)
TEMP (8-bit)
Clock Select
Edge
Count
Tn
Detector
TCNTnH (8-bit)
TCNTnL (8-bit)
Clear
clkTn
Control Logic
Direction
TCNTn (16-bit Counter)
( From Prescaler )
TOP
BOTTOM
Signal description (internal signals):
Count Increment or decrement TCNTn by 1.
Direction Select between increment and decrement.
Clear
clkTn
TOP
Clear TCNTn (set all bits to zero).
Timer/Counter clock.
Signalize that TCNTn has reached maximum value.
BOTTOM Signalize that TCNTn has reached minimum value (zero).
The 16-bit counter is mapped into two 8-bit I/O memory locations: Counter High
(TCNTnH) containing the upper eight bits of the counter, and Counter Low (TCNTnL)
containing the lower eight bits. The TCNTnH Register can only be indirectly accessed
by the CPU. When the CPU does an access to the TCNTnH I/O location, the CPU
accesses the high byte temporary register (TEMP). The temporary register is updated
with the TCNTnH value when the TCNTnL is read, and TCNTnH is updated with the
temporary register value when TCNTnL is written. This allows the CPU to read or write
the entire 16-bit counter value within one clock cycle via the 8-bit data bus. It is impor-
tant to notice that there are special cases of writing to the TCNTn Register when the
counter is counting that will give unpredictable results. The special cases are described
in the sections where they are of importance.
Depending on the mode of operation used, the counter is cleared, incremented, or dec-
remented at each Timer Clock (clkTn). The clkTn can be generated from an external or
internal clock source, selected by the Clock Select bits (CSn2:0). When no clock source
is selected (CSn2:0 = 0) the Timer is stopped. However, the TCNTn value can be
accessed by the CPU, independent of whether clkTn is present or not. A CPU write over-
rides (has priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the Waveform Generation mode
bits (WGMn3:0) located in the Timer/Counter Control Registers A and B (TCCRnA and
TCCRnB). There are close connections between how the counter behaves (counts) and
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how waveforms are generated on the Output Compare outputs OCnx. For more details
about advanced counting sequences and waveform generation, see “Modes of Opera-
tion” on page 117.
The Timer/Counter Overflow Flag (TOVn) is set according to the mode of operation
selected by the WGMn3:0 bits. TOVn can be used for generating a CPU interrupt.
Input Capture Unit
The Timer/Counter incorporates an Input Capture unit that can capture external events
and give them a time-stamp indicating time of occurrence. The external signal indicating
an event, or multiple events, can be applied via the ICPn pin or alternatively, via the
Analog Comparator unit. The time-stamps can then be used to calculate frequency,
duty-cycle, and other features of the signal applied. Alternatively the time-stamps can be
used for creating a log of the events.
The Input Capture unit is illustrated by the block diagram shown in Figure 48. The ele-
ments of the block diagram that are not directly a part of the Input Capture unit are gray
shaded. The small “n” in register and bit names indicates the Timer/Counter number.
Figure 48. Input Capture Unit Block Diagram(1)
DATA BUS (8-bit)
TEMP (8-bit)
ICRnH (8-bit)
ICRnL (8-bit)
TCNTnH (8-bit)
TCNTnL (8-bit)
ICRn (16-bit Register)
TCNTn (16-bit Counter)
WRITE
ACO*
ACIC*
ICNC
ICES
Analog
Comparator
Noise
Canceler
Edge
Detector
ICFn (Int.Req.)
ICPn
Note:
1. The Analog Comparator Output (ACO) can only trigger the Timer/Counter1 ICP – not
Timer/Counter3.
When a change of the logic level (an event) occurs on the Input Capture pin (ICPn),
alternatively on the Analog Comparator output (ACO), and this change confirms to the
setting of the edge detector, a capture will be triggered. When a capture is triggered, the
16-bit value of the counter (TCNTn) is written to the Input Capture Register (ICRn). The
Input Capture Flag (ICFn) is set at the same system clock as the TCNTn value is copied
into ICRn Register. If enabled (TICIEn = 1), the Input Capture Flag generates an Input
Capture interrupt. The ICFn Flag is automatically cleared when the interrupt is executed.
Alternatively the ICFn Flag can be cleared by software by writing a logical one to its I/O
bit location.
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Reading the 16-bit value in the Input Capture Register (ICRn) is done by first reading the
low byte (ICRnL) and then the high byte (ICRnH). When the low byte is read the high
byte is copied into the high byte temporary register (TEMP). When the CPU reads the
ICRnH I/O location it will access the TEMP Register.
The ICRn Register can only be written when using a Waveform Generation mode that
utilizes the ICRn Register for defining the counter’s TOP value. In these cases the
Waveform Generation mode (WGMn3:0) bits must be set before the TOP value can be
written to the ICRn Register. When writing the ICRn Register the high byte must be writ-
ten to the ICRnH I/O location before the low byte is written to ICRnL.
For more information on how to access the 16-bit registers refer to “Accessing 16-bit
Registers” on page 108.
Input Capture Trigger Source
The main trigger source for the Input Capture unit is the Input Capture pin (ICPn).
Timer/Counter1 can alternatively use the Analog Comparator output as trigger source
for the Input Capture unit. The Analog Comparator is selected as trigger source by set-
ting the Analog Comparator Input Capture (ACIC) bit in the Analog Comparator Control
and Status Register (ACSR). Be aware that changing trigger source can trigger a cap-
ture. The Input Capture Flag must therefore be cleared after the change.
Both the Input Capture pin (ICPn) and the Analog Comparator output (ACO) inputs are
sampled using the same technique as for the Tn pin (Figure 44 on page 103). The edge
detector is also identical. However, when the noise canceler is enabled, additional logic
is inserted before the edge detector, which increases the delay by four system clock
cycles. Note that the input of the noise canceler and edge detector is always enabled
unless the Timer/Counter is set in a Waveform Generation mode that uses ICRn to
define TOP.
An Input Capture can be triggered by software by controlling the port of the ICPn pin.
Noise Canceler
The Noise Canceler improves noise immunity by using a simple digital filtering scheme.
The Noise Canceler input is monitored over four samples, and all four must be equal for
changing the output that in turn is used by the edge detector.
The Noise Canceler is enabled by setting the Input Capture Noise Canceler (ICNCn) bit
in Timer/Counter Control Register B (TCCRnB). When enabled the noise canceler intro-
duces additional four system clock cycles of delay from a change applied to the input, to
the update of the ICRn Register. The noise canceler uses the system clock and is there-
fore not affected by the prescaler.
Using the Input Capture Unit
The main challenge when using the Input Capture unit is to assign enough processor
capacity for handling the incoming events. The time between two events is critical. If the
processor has not read the captured value in the ICRn Register before the next event
occurs, the ICRn will be overwritten with a new value. In this case the result of the cap-
ture will be incorrect.
When using the Input Capture interrupt, the ICRn Register should be read as early in the
interrupt handler routine as possible. Even though the Input Capture interrupt has rela-
tively high priority, the maximum interrupt response time is dependent on the maximum
number of clock cycles it takes to handle any of the other interrupt requests.
Using the Input Capture unit in any mode of operation when the TOP value (resolution)
is actively changed during operation, is not recommended.
Measurement of an external signal’s duty cycle requires that the trigger edge is changed
after each capture. Changing the edge sensing must be done as early as possible after
the ICRn Register has been read. After a change of the edge, the Input Capture Flag
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(ICFn) must be cleared by software (writing a logical one to the I/O bit location). For
measuring frequency only, the clearing of the ICFn Flag is not required (if an interrupt
handler is used).
Output Compare Units
The 16-bit comparator continuously compares TCNTn with the Output Compare Regis-
ter (OCRnx). If TCNT equals OCRnx the comparator signals a match. A match will set
the Output Compare Flag (OCFnx) at the next timer clock cycle. If enabled (OCIEnx =
1), the Output Compare Flag generates an output compare interrupt. The OCFnx Flag is
automatically cleared when the interrupt is executed. Alternatively the OCFnx Flag can
be cleared by software by writing a logical one to its I/O bit location. The Waveform Gen-
erator uses the match signal to generate an output according to operating mode set by
the Waveform Generation mode (WGMn3:0) bits and Compare Output mode
(COMnx1:0) bits. The TOP and BOTTOM signals are used by the Waveform Generator
for handling the special cases of the extreme values in some modes of operation (See
“Modes of Operation” on page 117.)
A special feature of output compare unit A allows it to define the Timer/Counter TOP
value (i.e., counter resolution). In addition to the counter resolution, the TOP value
defines the period time for waveforms generated by the Waveform Generator.
Figure 49 shows a block diagram of the output compare unit. The small “n” in the regis-
ter and bit names indicates the device number (n = n for Timer/Counter n), and the “x”
indicates output compare unit (A/B). The elements of the block diagram that are not
directly a part of the output compare unit are gray shaded.
Figure 49. Output Compare Unit, Block Diagram
DATA BUS (8-bit)
TEMP (8-bit)
OCRnxH Buf. (8-bit)
OCRnxL Buf. (8-bit)
TCNTnH (8-bit)
TCNTnL (8-bit)
OCRnx Buffer (16-bit Register)
TCNTn (16-bit Counter)
OCRnxH (8-bit)
OCRnxL (8-bit)
OCRnx (16-bit Register)
=
(16-bit Comparator )
OCFnx (Int.Req.)
TOP
OCnx
Waveform Generator
BOTTOM
WGMn3:0
COMnx1:0
The OCRnx Register is double buffered when using any of the twelve Pulse Width Mod-
ulation (PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of
operation, the double buffering is disabled. The double buffering synchronizes the
update of the OCRnx Compare Register to either TOP or BOTTOM of the counting
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sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical
PWM pulses, thereby making the output glitch-free.
The OCRnx Register access may seem complex, but this is not case. When the double
buffering is enabled, the CPU has access to the OCRnx Buffer Register, and if double
buffering is disabled the CPU will access the OCRnx directly. The content of the OCR1x
(Buffer or Compare) Register is only changed by a write operation (the Timer/Counter
does not update this register automatically as the TCNT1 and ICR1 Register). Therefore
OCR1x is not read via the high byte temporary register (TEMP). However, it is a good
practice to read the low byte first as when accessing other 16-bit registers. Writing the
OCRnx Registers must be done via the TEMP Register since the compare of all 16 bits
is done continuously. The high byte (OCRnxH) has to be written first. When the high
byte I/O location is written by the CPU, the TEMP Register will be updated by the value
written. Then when the low byte (OCRnxL) is written to the lower eight bits, the high byte
will be copied into the upper eight bits of either the OCRnx buffer or OCRnx Compare
Register in the same system clock cycle.
For more information of how to access the 16-bit registers refer to “Accessing 16-bit
Registers” on page 108.
Force Output Compare
In non-PWM waveform generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOCnx) bit. Forcing Compare
Match will not set the OCFnx Flag or reload/clear the timer, but the OCnx pin will be
updated as if a real Compare Match had occurred (the COMn1:0 bits settings define
whether the OCnx pin is set, cleared or toggled).
Compare Match Blocking by
TCNTn Write
All CPU writes to the TCNTn Register will block any Compare Match that occurs in the
next timer clock cycle, even when the timer is stopped. This feature allows OCRnx to be
initialized to the same value as TCNTn without triggering an interrupt when the
Timer/Counter clock is enabled.
Using the Output Compare
Unit
Since writing TCNTn in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNTn when using any of the
output compare channels, independent of whether the Timer/Counter is running or not.
If the value written to TCNTn equals the OCRnx value, the Compare Match will be
missed, resulting in incorrect waveform generation. Do not write the TCNTn equal to
TOP in PWM modes with variable TOP values. The Compare Match for the TOP will be
ignored and the counter will continue to 0xFFFF. Similarly, do not write the TCNTn value
equal to BOTTOM when the counter is down-counting.
The setup of the OCnx should be performed before setting the Data Direction Register
for the port pin to output. The easiest way of setting the OCnx value is to use the Force
Output Compare (FOCnx) strobe bits in Normal mode. The OCnx Register keeps its
value even when changing between Waveform Generation modes.
Be aware that the COMnx1:0 bits are not double buffered together with the compare
value. Changing the COMnx1:0 bits will take effect immediately.
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Compare Match Output
Unit
The Compare Output mode (COMnx1:0) bits have two functions. The waveform genera-
tor uses the COMnx1:0 bits for defining the output compare (OCnx) state at the next
Compare Match. Secondly the COMnx1:0 bits control the OCnx pin output source. Fig-
ure 50 shows a simplified schematic of the logic affected by the COMnx1:0 bit setting.
The I/O Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of
the general I/O Port Control Registers (DDR and PORT) that are affected by the
COMnx1:0 bits are shown. When referring to the OCnx state, the reference is for the
internal OCnx Register, not the OCnx pin. If a System Reset occur, the OCnx Register is
reset to “0”.
Figure 50. Compare Match Output Unit, Schematic
COMnx1
Waveform
Generator
COMnx0
FOCnx
D
Q
1
0
OCnx
Pin
OCnx
D
Q
PORT
D
Q
DDR
clkI/O
The general I/O port function is overridden by the output compare (OCnx) from the
Waveform Generator if either of the COMnx1:0 bits are set. However, the OCnx pin
direction (input or output) is still controlled by the Data Direction Register (DDR) for the
port pin. The Data Direction Register bit for the OCnx pin (DDR_OCnx) must be set as
output before the OCnx value is visible on the pin. The port override function is generally
independent of the Waveform Generation mode, but there are some exceptions. Refer
to Table 53, Table 54 and Table 55 for details.
The design of the output compare pin logic allows initialization of the OCnx state before
the output is enabled. Note that some COMnx1:0 bit settings are reserved for certain
modes of operation. See “16-bit Timer/Counter Register Description” on page 127.
The COMnx1:0 bits have no effect on the Input Capture unit.
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Compare Output Mode and
Waveform Generation
The Waveform Generator uses the COMnx1:0 bits differently in normal, CTC, and PWM
modes. For all modes, setting the COMnx1:0 = 0 tells the Waveform Generator that no
action on the OCnx Register is to be performed on the next Compare Match. For Com-
pare Output actions in the non-PWM modes refer to Table 53 on page 127. For fast
PWM mode refer to Table 54 on page 128, and for phase correct and phase and fre-
quency correct PWM refer to Table 55 on page 128.
A change of the COMnx1:0 bits state will have effect at the first Compare Match after
the bits are written. For non-PWM modes, the action can be forced to have immediate
effect by using the FOCnx strobe bits.
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGMn3:0) and
Compare Output mode (COMnx1:0) bits. The Compare Output mode bits do not affect
the counting sequence, while the Waveform Generation mode bits do. The COMnx1:0
bits control whether the PWM output generated should be inverted or not (inverted or
non-inverted PWM). For non-PWM modes the COMnx1:0 bits control whether the out-
put should be set, cleared or toggle at a Compare Match (See “Compare Match Output
Unit” on page 116.)
For detailed timing information refer to “Timer/Counter Timing Diagrams” on page 125.
Normal Mode
The simplest mode of operation is the Normal mode (WGMn3:0 = 0). In this mode the
counting direction is always up (incrementing), and no counter clear is performed. The
counter simply overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and
then restarts from the BOTTOM (0x0000). In normal operation the Timer/Counter Over-
flow Flag (TOVn) will be set in the same timer clock cycle as the TCNTn becomes zero.
The TOVn Flag in this case behaves like a 17th bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt that automatically clears the TOVn
Flag, the timer resolution can be increased by software. There are no special cases to
consider in the normal mode, a new counter value can be written anytime.
The Input Capture unit is easy to use in Normal mode. However, observe that the maxi-
mum interval between the external events must not exceed the resolution of the counter.
If the interval between events are too long, the timer overflow interrupt or the prescaler
must be used to extend the resolution for the capture unit.
The Output Compare units can be used to generate interrupts at some given time. Using
the Output Compare to generate waveforms in Normal mode is not recommended,
since this will occupy too much of the CPU time.
Clear Timer on Compare
Match (CTC) Mode
In Clear Timer on Compare or CTC mode (WGMn3:0 = 4 or 12), the OCRnA or ICRn
Register are used to manipulate the counter resolution. In CTC mode the counter is
cleared to zero when the counter value (TCNTn) matches either the OCRnA (WGMn3:0
= 4) or the ICRn (WGMn3:0 = 12). The OCRnA or ICRn define the top value for the
counter, hence also its resolution. This mode allows greater control of the Compare
Match output frequency. It also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in Figure 51. The counter value
(TCNTn) increases until a Compare Match occurs with either OCRnA or ICRn, and then
counter (TCNTn) is cleared.
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Figure 51. CTC Mode, Timing Diagram
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
TCNTn
OCnA
(Toggle)
(COMnA1:0 = 1)
1
2
3
4
Period
An interrupt can be generated at each time the counter value reaches the TOP value by
either using the OCFnA or ICFn Flag according to the register used to define the TOP
value. If the interrupt is enabled, the interrupt handler routine can be used for updating
the TOP value. However, changing the TOP to a value close to BOTTOM when the
counter is running with none or a low prescaler value must be done with care since the
CTC mode does not have the double buffering feature. If the new value written to
OCRnA or ICRn is lower than the current value of TCNTn, the counter will miss the
Compare Match. The counter will then have to count to its maximum value (0xFFFF)
and wrap around starting at 0x0000 before the Compare Match can occur. In many
cases this feature is not desirable. An alternative will then be to use the fast PWM mode
using OCRnA for defining TOP (WGMn3:0 = 15) since the OCRnA then will be double
buffered.
For generating a waveform output in CTC mode, the OCnA output can be set to toggle
its logical level on each Compare Match by setting the Compare Output mode bits to
toggle mode (COMnA1:0 = 1). The OCnA value will not be visible on the port pin unless
the data direction for the pin is set to output (DDR_OCnA = 1). The waveform generated
will have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set to zero (0x0000).
The waveform frequency is defined by the following equation:
f
clk_I/O
f
= --------------------------------------------------
OCnA
2 N (1 + OCRnA)
The N variable represents the prescaler factor (1, 8, 64, 256, or 1024). For
Timer/Counter3 also prescaler factors 16 and 32 are available.
As for the Normal mode of operation, the TOVn Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x0000.
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Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGMn3:0 = 5,6,7,14, or 15) pro-
vides a high frequency PWM waveform generation option. The fast PWM differs from
the other PWM options by its single-slope operation. The counter counts from BOTTOM
to TOP then restarts from BOTTOM. In non-inverting Compare Output mode, the Output
Compare (OCnx) is set on the Compare Match between TCNTn and OCRnx, and
cleared at TOP. In inverting Compare Output mode output is cleared on Compare Match
and set at TOP. Due to the single-slope operation, the operating frequency of the fast
PWM mode can be twice as high as the phase correct and phase and frequency correct
PWM modes that use dual-slope operation. This high frequency makes the fast PWM
mode well suited for power regulation, rectification, and DAC applications. High fre-
quency allows physically small sized external components (coils, capacitors), hence
reduces total system cost.
The PWM resolution for fast PWM can be fixed to 8-, 9-, or 10-bit, or defined by either
ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to
0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM
resolution in bits can be calculated by using the following equation:
log(TOP + 1)
R
= ----------------------------------
FPWM
log(2)
In fast PWM mode the counter is incremented until the counter value matches either
one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 5, 6, or 7), the value in
ICRn (WGMn3:0 = 14), or the value in OCRnA (WGMn3:0 = 15). The counter is then
cleared at the following timer clock cycle. The timing diagram for the fast PWM mode is
shown in Figure 52. The figure shows fast PWM mode when OCRnA or ICRn is used to
define TOP. The TCNTn value is in the timing diagram shown as a histogram for illus-
trating the single-slope operation. The diagram includes non-inverted and inverted PWM
outputs. The small horizontal line marks on the TCNTn slopes represent compare
matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a Com-
pare Match occurs.
Figure 52. Fast PWM Mode, Timing Diagram
OCRnx / TOP Update
and TOVn Interrupt Flag
Set and OCnA Interrupt
Flag Set or ICFn
Interrupt Flag Set
(Interrupt on TOP)
TCNTn
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
OCnx
1
2
3
4
5
6
7
8
Period
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches TOP. In
addition the OCnA or ICFn Flag is set at the same timer clock cycle as TOVn is set
when either OCRnA or ICRn is used for defining the TOP value. If one of the interrupts
are enabled, the interrupt handler routine can be used for updating the TOP and com-
pare values.
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When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the compare registers. If the TOP value is lower
than any of the compare registers, a Compare Match will never occur between the
TCNTn and the OCRnx. Note that when using fixed TOP values the unused bits are
masked to zero when any of the OCRnx Registers are written.
The procedure for updating ICRn differs from updating OCRnA when used for defining
the TOP value. The ICRn Register is not double buffered. This means that if ICRn is
changed to a low value when the counter is running with none or a low prescaler value,
there is a risk that the new ICRn value written is lower than the current value of TCNTn.
The result will then be that the counter will miss the Compare Match at the TOP value.
The counter will then have to count to the MAX value (0xFFFF) and wrap around start-
ing at 0x0000 before the Compare Match can occur. The OCRnA Register however, is
double buffered. This feature allows the OCRnA I/O location to be written anytime.
When the OCRnA I/O location is written the value written will be put into the OCRnA
Buffer Register. The OCRnA Compare Register will then be updated with the value in
the Buffer Register at the next timer clock cycle the TCNTn matches TOP. The update is
done at the same timer clock cycle as the TCNTn is cleared and the TOVn Flag is set.
Using the ICRn Register for defining TOP works well when using fixed TOP values. By
using ICRn, the OCRnA Register is free to be used for generating a PWM output on
OCnA. However, if the base PWM frequency is actively changed (by changing the TOP
value), using the OCRnA as TOP is clearly a better choice due to its double buffer
feature.
In fast PWM mode, the compare units allow generation of PWM waveforms on the
OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and an
inverted PWM output can be generated by setting the COMnx1:0 to three (See Table
on page 128). The actual OCnx value will only be visible on the port pin if the data direc-
tion for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by
setting (or clearing) the OCnx Register at the Compare Match between OCRnx and
TCNTn, and clearing (or setting) the OCnx Register at the timer clock cycle the counter
is cleared (changes from TOP to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
f
clk_I/O
f
= ----------------------------------
OCnxPWM
N (1 + TOP)
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). For
Timer/Counter3 also prescaler factors 16 and 32 are available.
The extreme values for the OCRnx Register represents special cases when generating
a PWM waveform output in the fast PWM mode. If the OCRnx is set equal to BOTTOM
(0x0000) the output will be a narrow spike for each TOP+1 timer clock cycle. Setting the
OCRnx equal to TOP will result in a constant high or low output (depending on the polar-
ity of the output set by the COMnx1:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OCnA to toggle its logical level on each Compare Match (COMnA1:0 = 1).
This applies only if OCRnA is used to define the TOP value (WGMn3:0 = 15). The wave-
form generated will have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set
to zero (0x0000). This feature is similar to the OCnA toggle in CTC mode, except the
double buffer feature of the output compare unit is enabled in the fast PWM mode.
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Phase Correct PWM Mode
The phase correct Pulse Width Modulation or phase correct PWM mode (WGMn3:0 = 1,
2, 3, 10, or 11) provides a high resolution phase correct PWM waveform generation
option. The phase correct PWM mode is, like the phase and frequency correct PWM
mode, based on a dual-slope operation. The counter counts repeatedly from BOTTOM
(0x0000) to TOP and then from TOP to BOTTOM. In non-inverting Compare Output
mode, the Output Compare (OCnx) is cleared on the Compare Match between TCNTn
and OCRnx while up-counting, and set on the Compare Match while down-counting. In
inverting Output Compare mode, the operation is inverted. The dual-slope operation has
lower maximum operation frequency than single slope operation. However, due to the
symmetric feature of the dual-slope PWM modes, these modes are preferred for motor
control applications.
The PWM resolution for the phase correct PWM mode can be fixed to 8-, 9-, or 10-bit, or
defined by either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or
OCRnA set to 0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to
MAX). The PWM resolution in bits can be calculated by using the following equation:
log(TOP + 1)
R
= ----------------------------------
PCPWM
log(2)
In phase correct PWM mode the counter is incremented until the counter value matches
either one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 1, 2, or 3), the
value in ICRn (WGMn3:0 = 10), or the value in OCRnA (WGMn3:0 = 11). The counter
has then reached the TOP and changes the count direction. The TCNTn value will be
equal to TOP for one timer clock cycle. The timing diagram for the phase correct PWM
mode is shown on Figure 53. The figure shows phase correct PWM mode when OCRnA
or ICRn is used to define TOP. The TCNTn value is in the timing diagram shown as a
histogram for illustrating the dual-slope operation. The diagram includes non-inverted
and inverted PWM outputs. The small horizontal line marks on the TCNTn slopes repre-
sent compare matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be
set when a Compare Match occurs.
Figure 53. Phase Correct PWM Mode, Timing Diagram
OCRnx/TOP Update and
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
TOVn Interrupt Flag Set
(Interrupt on Bottom)
TCNTn
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
OCnx
1
2
3
4
Period
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches BOT-
TOM. When either OCRnA or ICRn is used for defining the TOP value, the OCnA or
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2513F–AVR–12/03
ICFn Flag is set accordingly at the same timer clock cycle as the OCRnx Registers are
updated with the double buffer value (at TOP). The Interrupt Flags can be used to gen-
erate an interrupt each time the counter reaches the TOP or BOTTOM value.
When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the compare registers. If the TOP value is lower
than any of the compare registers, a Compare Match will never occur between the
TCNTn and the OCRnx. Note that when using fixed TOP values, the unused bits are
masked to zero when any of the OCRnx Registers are written. As the third period shown
in Figure 53 illustrates, changing the TOP actively while the Timer/Counter is running in
the phase correct mode can result in an unsymmetrical output. The reason for this can
be found in the time of update of the OCRnx Register. Since the OCRnx update occurs
at TOP, the PWM period starts and ends at TOP. This implies that the length of the fall-
ing slope is determined by the previous TOP value, while the length of the rising slope is
determined by the new TOP value. When these two values differ the two slopes of the
period will differ in length. The difference in length gives the unsymmetrical result on the
output.
It is recommended to use the phase and frequency correct mode instead of the phase
correct mode when changing the TOP value while the Timer/Counter is running. When
using a static TOP value there are practically no differences between the two modes of
operation.
In phase correct PWM mode, the compare units allow generation of PWM waveforms on
the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and
an inverted PWM output can be generated by setting the COMnx1:0 to three (See Table
55 on page 128). The actual OCnx value will only be visible on the port pin if the data
direction for the port pin is set as output (DDR_OCnx). The PWM waveform is gener-
ated by setting (or clearing) the OCnx Register at the Compare Match between OCRnx
and TCNTn when the counter increments, and clearing (or setting) the OCnx Register at
Compare Match between OCRnx and TCNTn when the counter decrements. The PWM
frequency for the output when using phase correct PWM can be calculated by the fol-
lowing equation:
f
clk_I/O
f
= ---------------------------
OCnxPCPWM
2 N TOP
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). For
Timer/Counter3 also prescaler factors 16 and 32 are available.
The extreme values for the OCRnx Register represent special cases when generating a
PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to
BOTTOM the output will be continuously low and if set equal to TOP the output will be
continuously high for non-inverted PWM mode. For inverted PWM the output will have
the opposite logic values. If OCRnA is used to define the TOP value (WGMn3:0 = 11)
and COMnA1:0 = 1, the OCnA output will toggle with a 50% duty cycle.
Phase and Frequency Correct The phase and frequency correct Pulse Width Modulation, or phase and frequency cor-
PWM Mode
rect PWM mode (WGMn3:0 = 8 or 9) provides a high resolution phase and frequency
correct PWM waveform generation option. The phase and frequency correct PWM
mode is, like the phase correct PWM mode, based on a dual-slope operation. The
counter counts repeatedly from BOTTOM (0x0000) to TOP and then from TOP to BOT-
TOM. In non-inverting Compare Output mode, the Output Compare (OCnx) is cleared
on the Compare Match between TCNTn and OCRnx while up-counting, and set on the
Compare Match while down-counting. In inverting Compare Output mode, the operation
is inverted. The dual-slope operation gives a lower maximum operation frequency com-
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ATmega162/V
pared to the single-slope operation. However, due to the symmetric feature of the dual-
slope PWM modes, these modes are preferred for motor control applications.
The main difference between the phase correct, and the phase and frequency correct
PWM mode is the time the OCRnx Register is updated by the OCRnx Buffer Register,
(see Figure 53 and Figure 54).
The PWM resolution for the phase and frequency correct PWM mode can be defined by
either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to
0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM
resolution in bits can be calculated using the following equation:
log(TOP + 1)
R
= ----------------------------------
PFCPWM
log(2)
In phase and frequency correct PWM mode the counter is incremented until the counter
value matches either the value in ICRn (WGMn3:0 = 8), or the value in OCRnA
(WGMn3:0 = 9). The counter has then reached the TOP and changes the count direc-
tion. The TCNTn value will be equal to TOP for one timer clock cycle. The timing
diagram for the phase correct and frequency correct PWM mode is shown on Figure 54.
The figure shows phase and frequency correct PWM mode when OCRnA or ICRn is
used to define TOP. The TCNTn value is in the timing diagram shown as a histogram for
illustrating the dual-slope operation. The diagram includes non-inverted and inverted
PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare
matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a Com-
pare Match occurs.
Figure 54. Phase and Frequency Correct PWM Mode, Timing Diagram
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
OCRnx/TOP Update and
TOVn Interrupt Flag Set
(Interrupt on Bottom)
TCNTn
(COMnx1:0 = 2)
OCnx
(COMnx1:0 = 3)
OCnx
1
2
3
4
Period
The Timer/Counter Overflow Flag (TOVn) is set at the same timer clock cycle as the
OCRnx Registers are updated with the double buffer value (at BOTTOM). When either
OCRnA or ICRn is used for defining the TOP value, the OCnA or ICFn Flag set when
TCNTn has reached TOP. The Interrupt Flags can then be used to generate an interrupt
each time the counter reaches the TOP or BOTTOM value.
When changing the TOP value the program must ensure that the new TOP value is
higher or equal to the value of all of the compare registers. If the TOP value is lower
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2513F–AVR–12/03
than any of the compare registers, a Compare Match will never occur between the
TCNTn and the OCRnx.
As Figure 54 shows the output generated is, in contrast to the phase correct mode, sym-
metrical in all periods. Since the OCRnx Registers are updated at BOTTOM, the length
of the rising and the falling slopes will always be equal. This gives symmetrical output
pulses and is therefore frequency correct.
Using the ICRn Register for defining TOP works well when using fixed TOP values. By
using ICRn, the OCRnA Register is free to be used for generating a PWM output on
OCnA. However, if the base PWM frequency is actively changed by changing the TOP
value, using the OCRnA as TOP is clearly a better choice due to its double buffer
feature.
In phase and frequency correct PWM mode, the compare units allow generation of
PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a
non-inverted PWM and an inverted PWM output can be generated by setting the
COMnx1:0 to three (See Table 55 on page 128). The actual OCnx value will only be vis-
ible on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The
PWM waveform is generated by setting (or clearing) the OCnx Register at the Compare
Match between OCRnx and TCNTn when the counter increments, and clearing (or set-
ting) the OCnx Register at Compare Match between OCRnx and TCNTn when the
counter decrements. The PWM frequency for the output when using phase and fre-
quency correct PWM can be calculated by the following equation:
f
clk_I/O
f
= ---------------------------
OCnxPFCPWM
2 N TOP
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). For
Timer/Counter3 also prescaler factors 16 and 32 are available.
The extreme values for the OCRnx Register represents special cases when generating
a PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to
BOTTOM the output will be continuously low and if set equal to TOP the output will be
set to high for non-inverted PWM mode. For inverted PWM the output will have the
opposite logic values. If OCRnA is used to define the TOP value (WGMn3:0 = 9) and
COMnA1:0 = 1, the OCnA output will toggle with a 50% duty cycle.
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ATmega162/V
Timer/Counter Timing
Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkTn) is therefore
shown as a clock enable signal in the following figures. The figures include information
on when Interrupt Flags are set, and when the OCRnx Register is updated with the
OCRnx buffer value (only for modes utilizing double buffering). Figure 55 shows a timing
diagram for the setting of OCFnx.
Figure 55. Timer/Counter Timing Diagram, Setting of OCFnx, no Prescaling
clkI/O
clkTn
(clkI/O/1)
TCNTn
OCRnx
OCFnx
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
Figure 56 shows the same timing data, but with the prescaler enabled.
Figure 56. Timer/Counter Timing Diagram, Setting of OCFnx, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
OCRnx
OCFnx
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx Value
Figure 57 shows the count sequence close to TOP in various modes. When using phase
and frequency correct PWM mode the OCRnx Register is updated at BOTTOM. The
timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by
BOTTOM+1 and so on. The same renaming applies for modes that set the TOVn Flag
at BOTTOM.
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2513F–AVR–12/03
Figure 57. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O/1)
TCNTn
TOP - 1
TOP - 1
TOP
TOP
BOTTOM
TOP - 1
BOTTOM + 1
TOP - 2
(CTC and FPWM)
TCNTn
(PC and PFC PWM)
TOVn (FPWM)
and ICFn (if used
as TOP)
OCRnx
(Update at TOP)
Old OCRnx Value
New OCRnx Value
Figure 58 shows the same timing data, but with the prescaler enabled.
Figure 58. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
TOP - 1
TOP - 1
TOP
TOP
BOTTOM
TOP - 1
BOTTOM + 1
TOP - 2
(CTC and FPWM)
TCNTn
(PC and PFC PWM)
TOVn (FPWM)
and ICFn (if used
as TOP)
OCRnx
(Update at TOP)
Old OCRnx Value
New OCRnx Value
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ATmega162/V
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ATmega162/V
16-bit Timer/Counter
Register Description
Timer/Counter1 Control
Register A – TCCR1A
Bit
7
COM1A1
R/W
6
COM1A0
R/W
5
COM1B1
R/W
4
COM1B0
R/W
3
FOC1A
W
2
FOC1B
W
1
WGM11
R/W
0
0
WGM10
R/W
0
TCCR1A
Read/Write
Initial Value
0
0
0
0
0
0
Timer/Counter3 Control
Register A – TCCR3A
Bit
7
COM3A1
R/W
6
COM3A0
R/W
5
COM3B1
R/W
4
COM3B0
R/W
3
FOC3A
W
2
FOC3B
W
1
WGM31
R/W
0
0
WGM30
R/W
0
TCCR3A
Read/Write
Initial Value
0
0
0
0
0
0
• Bit 7:6 – COMnA1:0: Compare Output Mode for channel A
• Bit 5:4 – COMnB1:0: Compare Output Mode for channel B
The COMnA1:0 and COMnB1:0 control the Output Compare pins (OCnA and OCnB
respectively) behavior. If one or both of the COMnA1:0 bits are written to one, the OCnA
output overrides the normal port functionality of the I/O pin it is connected to. If one or
both of the COMnB1:0 bit are written to one, the OCnB output overrides the normal port
functionality of the I/O pin it is connected to. However, note that the Data Direction Reg-
ister (DDR) bit corresponding to the OCnA or OCnB pin must be set in order to enable
the output driver.
When the OCnA or OCnB is connected to the pin, the function of the COMnx1:0 bits is
dependent of the WGMn3:0 bits setting. Table 53 shows the COMnx1:0 bit functionality
when the WGMn3:0 bits are set to a normal or a CTC mode (non-PWM).
Table 53. Compare Output Mode, non-PWM
COMnA1/
COMnB1
COMnA0/
COMnB0
Description
0
0
1
1
0
1
0
1
Normal port operation, OCnA/OCnB disconnected.
Toggle OCnA/OCnB on Compare Match.
Clear OCnA/OCnB on Compare Match (Set output to low level).
Set OCnA/OCnB on Compare Match (Set output to high level).
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Table 54 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the
fast PWM mode.
Table 54. Compare Output Mode, Fast PWM(1)
COMnA1/
COMnB1
COMnA0/
COMnB0
Description
0
0
0
1
Normal port operation, OCnA/OCnB disconnected.
WGMn3:0 = 15: Toggle OCnA on Compare Match, OCnB
disconnected (normal port operation). For all other WGMn
settings, normal port operation, OCnA/OCnB disconnected.
1
1
0
1
Clear OCnA/OCnB on Compare Match, set OCnA/OCnB at TOP.
Set OCnA/OCnB on Compare Match, clear OCnA/OCnB at TOP.
Note:
1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is
set. In this case the Compare Match is ignored, but the set or clear is done at TOP.
See “Fast PWM Mode” on page 119. for more details.
Table 55 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the
phase correct or the phase and frequency correct, PWM mode.
Table 55. Compare Output Mode, Phase Correct and Phase and Frequency Correct
PWM(1)
COMnA1/
COMnB1
COMnA0
COMnB0
Description
0
0
0
1
Normal port operation, OCnA/OCnB disconnected.
WGMn3:0 = 9 or 14: Toggle OCnA on Compare Match, OCnB
disconnected (normal port operation). For all other WGMn
settings, normal port operation, OCnA/OCnB disconnected.
1
1
0
1
Clear OCnA/OCnB on Compare Match when up-counting. Set
OCnA/OCnB on Compare Match when down-counting.
Set OCnA/OCnB on Compare Match when up-counting. Clear
OCnA/OCnB on Compare Match when down-counting.
Note:
1. A special case occurs when OCRnA/OCRnB equals TOP and COMnA1/COMnB1 is
set. See “Phase Correct PWM Mode” on page 121. for more details.
• Bit 3 – FOCnA: Force Output Compare for channel A
• Bit 2 – FOCnB: Force Output Compare for channel B
The FOCnA/FOCnB bits are only active when the WGMn3:0 bits specifies a non-PWM
mode. However, for ensuring compatibility with future devices, these bits must be set to
zero when TCCRnA is written when operating in a PWM mode. When writing a logical
one to the FOCnA/FOCnB bit, an immediate Compare Match is forced on the Waveform
Generation unit. The OCnA/OCnB output is changed according to its COMnx1:0 bits
setting. Note that the FOCnA/FOCnB bits are implemented as strobes. Therefore it is
the value present in the COMnx1:0 bits that determine the effect of the forced compare.
A FOCnA/FOCnB strobe will not generate any interrupt nor will it clear the timer in Clear
Timer on Compare match (CTC) mode using OCRnA as TOP.
The FOCnA/FOCnB bits are always read as zero.
128
ATmega162/V
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ATmega162/V
• Bit 1:0 – WGMn1:0: Waveform Generation Mode
Combined with the WGMn3:2 bits found in the TCCRnB Register, these bits control the
counting sequence of the counter, the source for maximum (TOP) counter value, and
what type of waveform generation to be used, see Table 56. Modes of operation sup-
ported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare
match (CTC) mode, and three types of Pulse Width Modulation (PWM) modes. (See
“Modes of Operation” on page 117.)
Table 56. Waveform Generation Mode Bit Description(1)
WGMn2
(CTCn)
WGMn1
WGMn0
Update of TOVn Flag
OCRnx at Set on
Mode WGMn3
(PWMn1) (PWMn0) Timer/Counter Mode of Operation
TOP
0
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Normal
0xFFFF Immediate MAX
PWM, Phase Correct, 8-bit
PWM, Phase Correct, 9-bit
PWM, Phase Correct, 10-bit
CTC
0x00FF TOP
0x01FF TOP
0x03FF TOP
BOTTOM
2
BOTTOM
BOTTOM
3
4
OCRnA Immediate MAX
5
Fast PWM, 8-bit
0x00FF TOP
0x01FF TOP
0x03FF TOP
TOP
6
Fast PWM, 9-bit
TOP
7
Fast PWM, 10-bit
TOP
8
PWM, Phase and Frequency Correct ICRn
BOTTOM
BOTTOM
BOTTOM
BOTTOM
BOTTOM
9
PWM, Phase and Frequency Correct OCRnA BOTTOM
10
11
12
13
14
15
Note:
PWM, Phase Correct
PWM, Phase Correct
CTC
ICRn
TOP
OCRnA TOP
ICRn
–
Immediate MAX
Reserved
–
–
Fast PWM
ICRn
TOP
TOP
TOP
Fast PWM
OCRnA TOP
1. The CTCn and PWMn1:0 bit definition names are obsolete. Use the WGMn2:0 definitions. However, the functionality and
location of these bits are compatible with previous versions of the timer.
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2513F–AVR–12/03
Timer/Counter1 Control
Register B – TCCR1B
Bit
7
ICNC1
R/W
0
6
ICES1
R/W
0
5
–
4
WGM13
R/W
0
3
WGM12
R/W
0
2
CS12
R/W
0
1
CS11
R/W
0
0
CS10
R/W
0
TCCR1B
Read/Write
Initial Value
R
0
Timer/Counter3 Control
Register B – TCCR3B
Bit
7
ICNC3
R/W
0
6
ICES3
R/W
0
5
–
4
WGM33
R/W
0
3
WGM32
R/W
0
2
CS32
R/W
0
1
CS31
R/W
0
0
CS30
R/W
0
TCCR3B
Read/Write
Initial Value
R
0
• Bit 7 – ICNCn: Input Capture Noise Canceler
Setting this bit (to one) activates the Input Capture noise canceler. When the noise can-
celer is activated, the input from the Input Capture pin (ICPn) is filtered. The filter
function requires four successive equal valued samples of the ICPn pin for changing its
output. The Input Capture is therefore delayed by four Oscillator cycles when the noise
canceler is enabled.
• Bit 6 – ICESn: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICPn) that is used to trigger a cap-
ture event. When the ICESn bit is written to zero, a falling (negative) edge is used as
trigger, and when the ICESn bit is written to one, a rising (positive) edge will trigger the
capture.
When a capture is triggered according to the ICESn setting, the counter value is copied
into the Input Capture Register (ICRn). The event will also set the Input Capture Flag
(ICFn), and this can be used to cause an Input Capture Interrupt, if this interrupt is
enabled.
When the ICRn is used as TOP value (see description of the WGMn3:0 bits located in
the TCCRnA and the TCCRnB Register), the ICPn is disconnected and consequently
the Input Capture function is disabled.
• Bit 5 – Reserved Bit
This bit is reserved for future use. For ensuring compatibility with future devices, this bit
must be written to zero when TCCRnB is written.
• Bit 4:3 – WGMn3:2: Waveform Generation Mode
See TCCRnA Register description.
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ATmega162/V
• Bit 2:0 – CSn2:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see
Figure 55 and Figure 56.
Table 57. Clock Select Bit Description Timer/Counter1
CS12
CS11
CS10
Description
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No clock source. (Timer/Counter stopped).
clkI/O/1 (No prescaling)
clkI/O/8 (From prescaler)
clkI/O/64 (From prescaler)
clkI/O/256 (From prescaler)
clkI/O/1024 (From prescaler)
External clock source on T1 pin. Clock on falling edge.
External clock source on T1 pin. Clock on rising edge.
If external pin modes are used for the Timer/Counter1, transitions on the T1 pin will
clock the counter even if the pin is configured as an output. This feature allows software
control of the counting..
Table 58. Clock Select Bit Description Timer/Counter3
Description
CS32
CS31
CS30
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No clock source. (Timer/Counter stopped).
clkI/O / 1 (No prescaling)
clkI/O / 8 (From prescaler).
clkI/O / 64 (From prescaler).
clkI/O / 256 (From prescaler).
clkI/O / 1024 (From prescaler).
clkI/O / 16 (From prescaler).
clkI/O / 32 (From prescaler).
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2513F–AVR–12/03
Timer/Counter1 – TCNT1H
and TCNT1L
Bit
7
6
5
4
3
2
1
0
TCNT1[15:8]
TCNT1[7:0]
TCNT1H
TCNT1L
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
R/W
0
R/W
0
R/W
0
0
0
Timer/Counter3 – TCNT3H
and TCNT3L
Bit
7
6
5
4
3
2
1
0
TCNT3[15:8]
TCNT3[7:0]
TCNT3H
TCNT3L
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
R/W
0
R/W
0
R/W
0
0
0
The two Timer/Counter I/O locations (TCNTnH and TCNTnL, combined TCNTn) give
direct access, both for read and for write operations, to the Timer/Counter unit 16-bit
counter. To ensure that both the high and low bytes are read and written simultaneously
when the CPU accesses these registers, the access is performed using an 8-bit tempo-
rary high byte register (TEMP). This temporary register is shared by all the other 16-bit
registers. See “Accessing 16-bit Registers” on page 108.
Modifying the counter (TCNTn) while the counter is running introduces a risk of missing
a Compare Match between TCNTn and one of the OCRnx Registers.
Writing to the TCNTn Register blocks (removes) the Compare Match on the following
timer clock for all compare units.
Output Compare Register 1 A
– OCR1AH and OCR1AL
Bit
7
6
5
4
3
2
1
0
OCR1A[15:8]
OCR1A[7:0]
OCR1AH
OCR1AL
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
Output Compare Register 1 B
– OCR1BH and OCR1BL
Bit
7
6
5
4
3
2
1
0
OCR1B[15:8]
OCR1B[7:0]
OCR1BH
OCR1BL
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
Output Compare Register 3 A
– OCR3AH and OCR3AL
Bit
7
6
5
4
3
2
1
0
OCR3A[15:8]
OCR3A[7:0]
OCR3AH
OCR3AL
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
Output Compare Register 3 B
– OCR3BH and OCR3BL
Bit
7
6
5
4
3
2
1
0
OCR3B[15:8]
OCR3B[7:0]
OCR3BH
OCR3BL
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
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The Output Compare Registers contain a 16-bit value that is continuously compared
with the counter value (TCNTn). A match can be used to generate an output compare
interrupt, or to generate a waveform output on the OCnx pin.
The Output Compare Registers are 16-bit in size. To ensure that both the high and low
bytes are written simultaneously when the CPU writes to these registers, the access is
performed using an 8-bit temporary high byte register (TEMP). This temporary register
is shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 108.
Input Capture Register 1 –
ICR1H and ICR1L
Bit
7
6
5
4
3
2
1
0
ICR1[15:8]
ICR1[7:0]
ICR1H
ICR1L
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
Input Capture Register 3 –
ICR3H and ICR3L
Bit
7
6
5
4
3
2
1
0
ICR3[15:8]
ICR3[7:0]
ICR3H
ICR3L
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
The Input Capture is updated with the counter (TCNTn) value each time an event occurs
on the ICPn pin (or optionally on the Analog Comparator output for Timer/Counter1).
The Input Capture can be used for defining the counter TOP value.
The Input Capture Register is 16-bit in size. To ensure that both the high and low bytes
are read simultaneously when the CPU accesses these registers, the access is per-
formed using an 8-bit temporary high byte register (TEMP). This temporary register is
shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 108.
Timer/Counter Interrupt Mask
Register – TIMSK(1)
Bit
7
TOIE1
R/W
0
6
OCIE1A
R/W
0
5
OCIE1B
R/W
0
4
OCIE2
R/W
0
3
TICIE1
R/W
0
2
TOIE2
R/W
0
1
TOIE0
R/W
0
0
OCIE0
R/W
0
TIMSK
Read/Write
Initial Value
Note:
1. This register contains interrupt control bits for several Timer/Counters, but only
Timer1 bits are described in this section. The remaining bits are described in their
respective Timer sections.
• Bit 7 – TOIE1: Timer/Counter1, Overflow Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 overflow interrupt is enabled. The corresponding
Interrupt Vector (See “Interrupts” on page 56.) is executed when the TOV1 Flag, located
in TIFR, is set.
• Bit 6 – OCIE1A: Timer/Counter1, Output Compare A Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Output Compare A Match interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
OCF1A Flag, located in TIFR, is set.
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• Bit 5 – OCIE1B: Timer/Counter1, Output Compare B Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Output Compare B Match interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
OCF1B Flag, located in TIFR, is set.
• Bit 3 – TICIE1: Timer/Counter1, Input Capture Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Input Capture interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
ICF1 Flag, located in TIFR, is set.
Extended Timer/Counter
Interrupt Mask Register –
ETIMSK(1)
Bit
7
6
5
TICIE3
R/W
0
4
OCIE3A
R/W
0
3
OCIE3B
R/W
0
2
TOIE3
R/W
0
1
–
0
–
ETIMSK
Read/Write
Initial Value
R
0
R
0
R
0
R
0
Note:
1. This register contains interrupt control bits for several Timer/Counters, but only
Timer3 bits are described in this section. The remaining bits are described in their
respective Timer sections.
• Bit 5 – TICIE3: Timer/Counter3, Input Capture Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter3 Input Capture interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
ICF3 Flag, located in TIFR, is set.
• Bit 4 – OCIE3A: Timer/Counter3, Output Compare A Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter3 Output Compare A Match interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
OCF3A Flag, located in TIFR, is set.
• Bit 3 – OCIE3B: Timer/Counter3, Output Compare B Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter3 Output Compare B Match interrupt is enabled. The
corresponding Interrupt Vector (See “Interrupts” on page 56.) is executed when the
OCF3B Flag, located in TIFR, is set.
• Bit 2 – TOIE3: Timer/Counter3, Overflow Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter3 overflow interrupt is enabled. The corresponding
Interrupt Vector (See “Interrupts” on page 56.) is executed when the TOV3 Flag, located
in TIFR, is set.
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Timer/Counter Interrupt Flag
Register – TIFR(1)
Bit
7
TOV1
R/W
0
6
OCF1A
R/W
0
5
OC1FB
R/W
0
4
OCF2
R/W
0
3
ICF1
R/W
0
2
TOV2
R/W
0
1
TOV0
R/W
0
0
OCF0
R/W
0
TIFR
Read/Write
Initial Value
Note:
1. This register contains flag bits for several Timer/Counters, but only Timer1 bits are
described in this section. The remaining bits are described in their respective Timer
sections.
• Bit 7 – TOV1: Timer/Counter1, Overflow Flag
The setting of this flag is dependent of the WGMn3:0 bits setting. In Normal and CTC
modes, the TOV1 Flag is set when the timer overflows. Refer to Table 56 on page 129
for the TOV1 Flag behavior when using another WGMn3:0 bit setting.
TOV1 is automatically cleared when the Timer/Counter1 Overflow Interrupt Vector is
executed. Alternatively, TOV1 can be cleared by writing a logic one to its bit location.
• Bit 6 – OCF1A: Timer/Counter1, Output Compare A Match Flag
This flag is set in the timer clock cycle after the counter (TCNT1) value matches the Out-
put Compare Register A (OCR1A).
Note that a Forced Output Compare (FOC1A) strobe will not set the OCF1A Flag.
OCF1A is automatically cleared when the Output Compare Match A Interrupt Vector is
executed. Alternatively, OCF1A can be cleared by writing a logic one to its bit location.
• Bit 5 – OCF1B: Timer/Counter1, Output Compare B Match Flag
This flag is set in the timer clock cycle after the counter (TCNT1) value matches the Out-
put Compare Register B (OCR1B).
Note that a Forced Output Compare (FOC1B) strobe will not set the OCF1B Flag.
OCF1B is automatically cleared when the Output Compare Match B Interrupt Vector is
executed. Alternatively, OCF1B can be cleared by writing a logic one to its bit location.
• Bit 3 – ICF1: Timer/Counter1, Input Capture Flag
This flag is set when a capture event occurs on the ICP1 pin. When the Input Capture
Register (ICR1) is set by the WGMn3:0 to be used as the TOP value, the ICF1 Flag is
set when the counter reaches the TOP value.
ICF1 is automatically cleared when the Input Capture Interrupt Vector is executed. Alter-
natively, ICF1 can be cleared by writing a logic one to its bit location.
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Extended Timer/Counter
Interrupt Flag Register –
ETIFR(1)
Bit
7
6
5
ICF3
R/W
0
4
OCF3A
R/W
0
3
OC3FB
R/W
0
2
TOV3
R/W
0
1
–
0
–
ETIFR
Read/Write
Initial Value
R
0
R
0
R
0
R
0
Note:
1. This register contains flag bits for several Timer/Counters, but only Timer3 bits are
described in this section. The remaining bits are described in their respective Timer
sections.
• Bit 5 – ICF3: Timer/Counter3, Input Capture Flag
This flag is set when a capture event occurs on the ICP3 pin. When the Input Capture
Register (ICR3) is set by the WGMn3:0 to be used as the TOP value, the ICF3 Flag is
set when the counter reaches the TOP value.
ICF3 is automatically cleared when the Input Capture Interrupt Vector is executed. Alter-
natively, ICF3 can be cleared by writing a logic one to its bit location.
• Bit 4 – OCF3A: Timer/Counter3, Output Compare A Match Flag
This flag is set in the timer clock cycle after the counter (TCNT3) value matches the Out-
put Compare Register A (OCR3A).
Note that a Forced Output Compare (FOC3A) strobe will not set the OCF3A Flag.
OCF3A is automatically cleared when the Output Compare Match A Interrupt Vector is
executed. Alternatively, OCF3A can be cleared by writing a logic one to its bit location.
• Bit 3 – OCF3B: Timer/Counter3, Output Compare B Match Flag
This flag is set in the timer clock cycle after the counter (TCNT3) value matches the Out-
put Compare Register B (OCR3B).
Note that a Forced Output Compare (FOC3B) strobe will not set the OCF3B Flag.
OCF3B is automatically cleared when the Output Compare Match B Interrupt Vector is
executed. Alternatively, OCF3B can be cleared by writing a logic one to its bit location.
• Bit 2 – TOV3: Timer/Counter3, Overflow Flag
The setting of this flag is dependent of the WGMn3:0 bits setting. In normal and CTC
modes, the TOV3 Flag is set when the timer overflows. Refer to Table 56 on page 129
for the TOV3 Flag behavior when using another WGMn3:0 bit setting.
TOV3 is automatically cleared when the Timer/Counter3 Overflow Interrupt Vector is
executed. Alternatively, TOV3 can be cleared by writing a logic one to its bit location.
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8-bit Timer/Counter2 Timer/Counter2 is a general purpose, single channel, 8-bit Timer/Counter module. The
main features are:
• Single Channel Counter
with PWM and
Asynchronous
operation
• Clear Timer on Compare Match (Auto Reload)
• Glitch-free, Phase Correct Pulse Width Modulator (PWM)
• Frequency Generator
• 10-bit Clock Prescaler
• Overflow and Compare Match Interrupt Sources (TOV2 and OCF2)
• Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock
Overview
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 59. For the
actual placement of I/O pins, refer to “Pinout ATmega162” on page 2. CPU accessible
I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O
Register and bit locations are listed in the “8-bit Timer/Counter Register Description” on
page 148.
Figure 59. 8-bit Timer/Counter Block Diagram
TCCRn
count
TOVn
(Int.Req.)
clear
direction
Control Logic
clkTn
TOSC1
TOSC2
BOTTOM
TOP
T/C
Oscillator
Prescaler
Timer/Counter
TCNTn
= 0
= 0xFF
clkI/O
OCn
OCn
(Int.Req.)
Waveform
Generation
=
OCRn
clkI/O
Synchronized Status flags
Synchronization Unit
clkASY
Status flags
ASSRn
asynchronous mode
select (ASn)
Registers
The Timer/Counter (TCNT2) and Output Compare Register (OCR2) are 8-bit registers.
Interrupt request (shorten as Int.Req.) signals are all visible in the Timer Interrupt Flag
Register (TIFR). All interrupts are individually masked with the Timer Interrupt Mask
Register (TIMSK). TIFR and TIMSK are not shown in the figure since these registers are
shared by other timer units.
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The Timer/Counter can be clocked internally, via the prescaler, or asynchronously
clocked from the TOSC1/2 pins, as detailed later in this section. The asynchronous
operation is controlled by the Asynchronous Status Register (ASSR). The Clock Select
logic block controls which clock source the Timer/Counter uses to increment (or decre-
ment) its value. The Timer/Counter is inactive when no clock source is selected. The
output from the clock select logic is referred to as the Timer Clock (clkT2).
The double buffered Output Compare Register (OCR2) is compared with the
Timer/Counter value at all times. The result of the compare can be used by the wave-
form generator to generate a PWM or variable frequency output on the Output Compare
Pin (OC2). See “Output Compare Unit” on page 139. for details. The Compare Match
event will also set the Compare Flag (OCF2) which can be used to generate an output
compare interrupt request.
Definitions
Many register and bit references in this document are written in general form. A lower
case “n” replaces the Timer/Counter number, in this case 2. However, when using the
register or bit defines in a program, the precise form must be used i.e., TCNT2 for
accessing Timer/Counter2 counter value and so on.
The definitions in Table 59 are also used extensively throughout the section.
Table 59. Definitions
BOTTOM The counter reaches the BOTTOM when it becomes zero (0x00).
MAX
TOP
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
The counter reaches the TOP when it becomes equal to the highest
value in the count sequence. The TOP value can be assigned to be the
fixed value 0xFF (MAX) or the value stored in the OCR2 Register. The
assignment is dependent on the mode of operation.
Timer/Counter Clock
Sources
The Timer/Counter can be clocked by an internal synchronous or an external asynchro-
nous clock source. The clock source clkT2 is by default equal to the MCU clock, clkI/O.
When the AS2 bit in the ASSR Register is written to logic one, the clock source is taken
from the Timer/Counter Oscillator connected to TOSC1 and TOSC2. For details on
asynchronous operation, see “Asynchronous Status Register – ASSR” on page 152. For
details on clock sources and prescaler, see “Timer/Counter Prescaler” on page 156.
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Counter Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
Figure 60 shows a block diagram of the counter and its surrounding environment.
Figure 60. Counter Unit Block Diagram
TOVn
(Int.Req.)
DATA BUS
TOSC1
count
T/C
Oscillator
clk Tn
clear
TCNTn
Control Logic
Prescaler
direction
TOSC2
clk
bottom
top
I/O
Signal description (internal signals):
count Increment or decrement TCNT2 by 1.
direction Selects between increment and decrement.
clear
clkT2
top
Clear TCNT2 (set all bits to zero).
Timer/Counter clock.
Signalizes that TCNT2 has reached maximum value.
bottom
Signalizes that TCNT2 has reached minimum value (zero).
Depending on the mode of operation used, the counter is cleared, incremented, or dec-
remented at each timer clock (clkT2). clkT2 can be generated from an external or internal
clock source, selected by the Clock Select bits (CS22:0). When no clock source is
selected (CS22:0 = 0) the timer is stopped. However, the TCNT2 value can be accessed
by the CPU, regardless of whether clkT2 is present or not. A CPU write overrides (has
priority over) all counter clear or count operations.
The counting sequence is determined by the setting of the WGM21 and WGM20 bits
located in the Timer/Counter Control Register (TCCR2). There are close connections
between how the counter behaves (counts) and how waveforms are generated on the
Output Compare output OC2. For more details about advanced counting sequences
and waveform generation, see “Modes of Operation” on page 142.
The Timer/Counter Overflow Flag (TOV2) is set according to the mode of operation
selected by the WGM21:0 bits. TOV2 can be used for generating a CPU interrupt.
Output Compare Unit
The 8-bit comparator continuously compares TCNT2 with the Output Compare Register
(OCR2). Whenever TCNT2 equals OCR2, the comparator signals a match. A match will
set the Output Compare Flag (OCF2) at the next timer clock cycle. If enabled (OCIE2 =
1), the Output Compare Flag generates an output compare interrupt. The OCF2 Flag is
automatically cleared when the interrupt is executed. Alternatively, the OCF2 Flag can
be cleared by software by writing a logical one to its I/O bit location. The waveform gen-
erator uses the match signal to generate an output according to operating mode set by
the WGM21:0 bits and Compare Output mode (COM21:0) bits. The max and bottom sig-
nals are used by the waveform generator for handling the special cases of the extreme
values in some modes of operation (“Modes of Operation” on page 142).
Figure 61 shows a block diagram of the output compare unit.
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Figure 61. Output Compare Unit, Block Diagram
DATA BUS
OCRn
TCNTn
= (8-bit Comparator )
OCFn (Int.Req.)
top
bottom
Waveform Generator
OCxy
FOCn
WGMn1:0
COMn1:0
The OCR2 Register is double buffered when using any of the Pulse Width Modulation
(PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of operation,
the double buffering is disabled. The double buffering synchronizes the update of the
OCR2 Compare Register to either top or bottom of the counting sequence. The synchro-
nization prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby
making the output glitch-free.
The OCR2 Register access may seem complex, but this is not case. When the double
buffering is enabled, the CPU has access to the OCR2 Buffer Register, and if double
buffering is disabled the CPU will access the OCR2 directly.
Force Output Compare
In non-PWM waveform generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOC2) bit. Forcing Compare
Match will not set the OCF2 Flag or reload/clear the timer, but the OC2 pin will be
updated as if a real Compare Match had occurred (the COM21:0 bits settings define
whether the OC2 pin is set, cleared or toggled).
Compare Match Blocking by
TCNT2 Write
All CPU write operations to the TCNT2 Register will block any Compare Match that
occurs in the next timer clock cycle, even when the timer is stopped. This feature allows
OCR2 to be initialized to the same value as TCNT2 without triggering an interrupt when
the Timer/Counter clock is enabled.
Using the Output Compare
Unit
Since writing TCNT2 in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNT2 when using the output
compare channel, independently of whether the Timer/Counter is running or not. If the
value written to TCNT2 equals the OCR2 value, the Compare Match will be missed,
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resulting in incorrect Waveform Generation. Similarly, do not write the TCNT2 value
equal to BOTTOM when the counter is down-counting.
The Setup of the OC2 should be performed before setting the Data Direction Register
for the port pin to output. The easiest way of setting the OC2 value is to use the Force
Output Compare (FOC2) strobe bit in Normal mode. The OC2 Register keeps its value
even when changing between Waveform Generation modes.
Be aware that the COM21:0 bits are not double buffered together with the compare
value. Changing the COM21:0 bits will take effect immediately.
Compare Match Output
Unit
The Compare Output mode (COM21:0) bits have two functions. The waveform genera-
tor uses the COM21:0 bits for defining the Output Compare (OC2) state at the next
Compare Match. Also, the COM21:0 bits control the OC2 pin output source. Figure 62
shows a simplified schematic of the logic affected by the COM21:0 bit setting. The I/O
Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the
general I/O Port Control Registers (DDR and PORT) that are affected by the COM21:0
bits are shown. When referring to the OC2 state, the reference is for the internal OC2
Register, not the OC2 pin.
Figure 62. Compare Match Output Unit, Schematic
COMn1
Waveform
Generator
COMn0
FOCn
D
Q
Q
1
0
OCn
Pin
OCn
D
PORT
D
Q
DDR
clkI/O
The general I/O port function is overridden by the Output Compare (OC2) from the
waveform generator if either of the COM21:0 bits are set. However, the OC2 pin direc-
tion (input or output) is still controlled by the Data Direction Register (DDR) for the port
pin. The Data Direction Register bit for the OC2 pin (DDR_OC2) must be set as output
before the OC2 value is visible on the pin. The port override function is independent of
the Waveform Generation mode.
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The design of the Output Compare pin logic allows initialization of the OC2 state before
the output is enabled. Note that some COM21:0 bit settings are reserved for certain
modes of operation. See “8-bit Timer/Counter Register Description” on page 148.
Compare Output Mode and
Waveform Generation
The Waveform Generator uses the COM21:0 bits differently in Normal, CTC, and PWM
modes. For all modes, setting the COM21:0 = 0 tells the Waveform Generator that no
action on the OC2 Register is to be performed on the next Compare Match. For com-
pare output actions in the non-PWM modes refer to Table 61 on page 150. For fast
PWM mode, refer to Table 62 on page 150, and for phase correct PWM refer to Table
63 on page 150.
A change of the COM21:0 bits state will have effect at the first Compare Match after the
bits are written. For non-PWM modes, the action can be forced to have immediate effect
by using the FOC2 strobe bits.
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare
pins, is defined by the combination of the Waveform Generation mode (WGM21:0) and
Compare Output mode (COM21:0) bits. The Compare Output mode bits do not affect
the counting sequence, while the Waveform Generation mode bits do. The COM21:0
bits control whether the PWM output generated should be inverted or not (inverted or
non-inverted PWM). For non-PWM modes the COM21:0 bits control whether the output
should be set, cleared, or toggled at a Compare Match (See “Compare Match Output
Unit” on page 141.).
For detailed timing information refer to “Timer/Counter Timing Diagrams” on page 146.
Normal Mode
The simplest mode of operation is the Normal mode (WGM21:0 = 0). In this mode the
counting direction is always up (incrementing), and no counter clear is performed. The
counter simply overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then
restarts from the bottom (0x00). In normal operation the Timer/Counter Overflow Flag
(TOV2) will be set in the same timer clock cycle as the TCNT2 becomes zero. The
TOV2 Flag in this case behaves like a ninth bit, except that it is only set, not cleared.
However, combined with the timer overflow interrupt that automatically clears the TOV2
Flag, the timer resolution can be increased by software. There are no special cases to
consider in the normal mode, a new counter value can be written anytime.
The Output Compare unit can be used to generate interrupts at some given time. Using
the Output Compare to generate waveforms in Normal mode is not recommended,
since this will occupy too much of the CPU time.
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Clear Timer on Compare
Match (CTC) Mode
In Clear Timer on Compare or CTC mode (WGM21:0 = 2), the OCR2 Register is used to
manipulate the counter resolution. In CTC mode the counter is cleared to zero when the
counter value (TCNT2) matches the OCR2. The OCR2 defines the top value for the
counter, hence also its resolution. This mode allows greater control of the Compare
Match output frequency. It also simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in Figure 63. The counter value
(TCNT2) increases until a Compare Match occurs between TCNT2 and OCR2, and then
counter (TCNT2) is cleared.
Figure 63. CTC Mode, Timing Diagram
OCn Interrupt Flag Set
TCNTn
OCn
(Toggle)
(COMn1:0 = 1)
1
2
3
4
Period
An interrupt can be generated each time the counter value reaches the TOP value by
using the OCF2 Flag. If the interrupt is enabled, the interrupt handler routine can be
used for updating the TOP value. However, changing the TOP to a value close to BOT-
TOM when the counter is running with none or a low prescaler value must be done with
care since the CTC mode does not have the double buffering feature. If the new value
written to OCR2 is lower than the current value of TCNT2, the counter will miss the
Compare Match. The counter will then have to count to its maximum value (0xFF) and
wrap around starting at 0x00 before the Compare Match can occur.
For generating a waveform output in CTC mode, the OC2 output can be set to toggle its
logical level on each Compare Match by setting the Compare Output mode bits to toggle
mode (COM21:0 = 1). The OC2 value will not be visible on the port pin unless the data
direction for the pin is set to output. The waveform generated will have a maximum fre-
quency of fOC2 = fclk_I/O/2 when OCR2 is set to zero (0x00). The waveform frequency is
defined by the following equation:
f
clk_I/O
f
= ----------------------------------------------
OCn
2 N (1 + OCRn)
The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).
As for the Normal mode of operation, the TOV2 Flag is set in the same timer clock cycle
that the counter counts from MAX to 0x00.
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Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGM21:0 = 1) provides a high fre-
quency PWM waveform generation option. The fast PWM differs from the other PWM
option by its single-slope operation. The counter counts from BOTTOM to MAX then
restarts from BOTTOM. In non-inverting Compare Output mode, the Output Compare
(OC2) is cleared on the Compare Match between TCNT2 and OCR2, and set at BOT-
TOM. In inverting Compare Output mode, the output is set on Compare Match and
cleared at BOTTOM. Due to the single-slope operation, the operating frequency of the
fast PWM mode can be twice as high as the phase correct PWM mode that uses dual-
slope operation. This high frequency makes the fast PWM mode well suited for power
regulation, rectification, and DAC applications. High frequency allows physically small
sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the MAX
value. The counter is then cleared at the following timer clock cycle. The timing diagram
for the fast PWM mode is shown in Figure 64. The TCNT2 value is in the timing diagram
shown as a histogram for illustrating the single-slope operation. The diagram includes
non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT2
slopes represent compare matches between OCR2 and TCNT2.
Figure 64. Fast PWM Mode, Timing Diagram
OCRn Interrupt Flag Set
OCRn Update and
TOVn Interrupt Flag Set
TCNTn
(COMn1:0 = 2)
(COMn1:0 = 3)
OCn
OCn
1
2
3
4
5
6
7
Period
The Timer/Counter Overflow Flag (TOV2) is set each time the counter reaches MAX. If
the interrupt is enabled, the interrupt handler routine can be used for updating the com-
pare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC2
pin. Setting the COM21:0 bits to two will produce a non-inverted PWM and an inverted
PWM output can be generated by setting the COM21:0 to three (See Table 62 on page
150). The actual OC2 value will only be visible on the port pin if the data direction for the
port pin is set as output. The PWM waveform is generated by setting (or clearing) the
OC2 Register at the Compare Match between OCR2 and TCNT2, and clearing (or set-
ting) the OC2 Register at the timer clock cycle the counter is cleared (changes from
MAX to BOTTOM).
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The PWM frequency for the output can be calculated by the following equation:
f
clk_I/O
f
= -----------------
OCnPWM
N 256
The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).
The extreme values for the OCR2 Register represent special cases when generating a
PWM waveform output in the fast PWM mode. If the OCR2 is set equal to BOTTOM, the
output will be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR2 equal
to MAX will result in a constantly high or low output (depending on the polarity of the out-
put set by the COM21:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OC2 to toggle its logical level on each Compare Match (COM21:0 = 1). The
waveform generated will have a maximum frequency of foc2 = fclk_I/O/2 when OCR2 is set
to zero. This feature is similar to the OC2 toggle in CTC mode, except the double buffer
feature of the Output Compare unit is enabled in the fast PWM mode.
Phase Correct PWM Mode
The phase correct PWM mode (WGM21:0 = 3) provides a high resolution phase correct
PWM waveform generation option. The phase correct PWM mode is based on a dual-
slope operation. The counter counts repeatedly from BOTTOM to MAX and then from
MAX to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OC2)
is cleared on the Compare Match between TCNT2 and OCR2 while up-counting, and
set on the Compare Match while down-counting. In inverting output compare mode, the
operation is inverted. The dual-slope operation has lower maximum operation frequency
than single slope operation. However, due to the symmetric feature of the dual-slope
PWM modes, these modes are preferred for motor control applications.
The PWM resolution for the phase correct PWM mode is fixed to eight bits. In phase
correct PWM mode the counter is incremented until the counter value matches MAX.
When the counter reaches MAX, it changes the count direction. The TCNT2 value will
be equal to MAX for one timer clock cycle. The timing diagram for the phase correct
PWM mode is shown on Figure 65. The TCNT2 value is in the timing diagram shown as
a histogram for illustrating the dual-slope operation. The diagram includes non-inverted
and inverted PWM outputs. The small horizontal line marks on the TCNT2 slopes repre-
sent compare matches between OCR2 and TCNT2.
Figure 65. Phase Correct PWM Mode, Timing Diagram
OCn Interrupt Flag Set
OCRn Update
TOVn Interrupt Flag Set
TCNTn
(COMn1:0 = 2)
OCn
(COMn1:0 = 3)
OCn
1
2
3
Period
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The Timer/Counter Overflow Flag (TOV2) is set each time the counter reaches BOT-
TOM. The Interrupt Flag can be used to generate an interrupt each time the counter
reaches the BOTTOM value.
In phase correct PWM mode, the compare unit allows generation of PWM waveforms on
the OC2 pin. Setting the COM21:0 bits to two will produce a non-inverted PWM. An
inverted PWM output can be generated by setting the COM21:0 to three (See Table 63
on page 150). The actual OC2 value will only be visible on the port pin if the data direc-
tion for the port pin is set as output. The PWM waveform is generated by clearing (or
setting) the OC2 Register at the Compare Match between OCR2 and TCNT2 when the
counter increments, and setting (or clearing) the OC2 Register at Compare Match
between OCR2 and TCNT2 when the counter decrements. The PWM frequency for the
output when using phase correct PWM can be calculated by the following equation:
f
clk_I/O
f
= -----------------
OCnPCPWM
N 510
The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).
The extreme values for the OCR2 Register represent special cases when generating a
PWM waveform output in the phase correct PWM mode. If the OCR2 is set equal to
BOTTOM, the output will be continuously low and if set equal to MAX the output will be
continuously high for non-inverted PWM mode. For inverted PWM the output will have
the opposite logic values.
At the very start of period 2 in Figure 65 OCn has a transition from high to low even
though there is no Compare Match. The point of this transition is to guarantee symmetry
around BOTTOM. There are two cases that give a transition without a Compare Match.
•
OCR2 changes its value from MAX, like in Figure 65. When the OCR2 value is MAX
the OCn pin value is the same as the result of a down-counting Compare Match. To
ensure symmetry around BOTTOM the OCn value at MAX must correspond to the
result of an up-counting Compare Match.
•
The timer starts counting from a value higher than the one in OCR2, and for that
reason misses the Compare Match and hence the OCn change that would have
happened on the way up.
Timer/Counter Timing
Diagrams
The following figures show the Timer/Counter in synchronous mode, and the timer clock
(clkT2) is therefore shown as a clock enable signal. In asynchronous mode, clkI/O should
be replaced by the Timer/Counter Oscillator clock. The figures include information on
when Interrupt Flags are set. Figure 66 contains timing data for basic Timer/Counter
operation. The figure shows the count sequence close to the MAX value in all modes
other than phase correct PWM mode.
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Figure 66. Timer/Counter Timing Diagram, no Prescaling
clkI/O
clkTn
(clkI/O/1)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 67 shows the same timing data, but with the prescaler enabled.
Figure 67. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
TOVn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
Figure 68 shows the setting of OCF2 in all modes except CTC mode.
Figure 68. Timer/Counter Timing Diagram, Setting of OCF2, with Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
OCRn
OCFn
OCRn - 1
OCRn
OCRn + 1
OCRn + 2
OCRn Value
Figure 69 shows the setting of OCF2 and the clearing of TCNT2 in CTC mode.
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Figure 69. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with
Prescaler (fclk_I/O/8)
clkI/O
clkTn
(clkI/O/8)
TCNTn
(CTC)
TOP - 1
TOP
BOTTOM
BOTTOM + 1
OCRn
TOP
OCFn
8-bit Timer/Counter
Register Description
Timer/Counter Control
Register – TCCR2
Bit
7
FOC2
W
6
WGM20
R/W
0
5
COM21
R/W
0
4
COM20
R/W
0
3
WGM21
R/W
0
2
CS22
1
CS21
R/W
0
0
CS20
R/W
0
TCCR2
Read/Write
Initial Value
R/W
0
0
• Bit 7 – FOC2: Force Output Compare
The FOC2 bit is only active when the WGM bits specify a non-PWM mode. However, for
ensuring compatibility with future devices, this bit must be set to zero when TCCR2 is
written when operating in PWM mode. When writing a logical one to the FOC2 bit, an
immediate Compare Match is forced on the Waveform Generation unit. The OC2 output
is changed according to its COM21:0 bits setting. Note that the FOC2 bit is implemented
as a strobe. Therefore it is the value present in the COM21:0 bits that determines the
effect of the forced compare.
A FOC2 strobe will not generate any interrupt, nor will it clear the timer in CTC mode
using OCR2 as TOP.
The FOC2 bit is always read as zero.
• Bit 6, 3 – WGM21:0: Waveform Generation Mode
These bits control the counting sequence of the counter, the source for the maximum
(TOP) counter value, and what type of waveform generation to be used. Modes of oper-
ation supported by the Timer/Counter unit are: Normal mode, Clear Timer on Compare
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match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes. See Table
60 and “Modes of Operation” on page 142.
Table 60. Waveform Generation Mode Bit Description(1)
WGM21 WGM20 Timer/Counter Mode
Update of TOV2 Flag
OCR2 at Set on
Mode
(CTC2)
(PWM2) of Operation
TOP
0xFF
0xFF
0
1
2
3
0
0
1
1
0
1
0
1
Normal
Immediate MAX
TOP BOTTOM
PWM, Phase Correct
CTC
OCR2 Immediate MAX
0xFF TOP MAX
Fast PWM
Note:
1. The CTC2 and PWM2 bit definition names are now obsolete. Use the WGM21:0 def-
initions. However, the functionality and location of these bits are compatible with
previous versions of the timer.
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• Bit 5:4 – COM21:0: Compare Match Output Mode
These bits control the Output Compare pin (OC2) behavior. If one or both of the
COM21:0 bits are set, the OC2 output overrides the normal port functionality of the I/O
pin it is connected to. However, note that the Data Direction Register (DDR) bit corre-
sponding to OC2 pin must be set in order to enable the output driver.
When OC2 is connected to the pin, the function of the COM21:0 bits depends on the
WGM21:0 bit setting. Table 61 shows the COM21:0 bit functionality when the WGM21:0
bits are set to a normal or CTC mode (non-PWM).
Table 61. Compare Output Mode, non-PWM Mode
COM21
COM20
Description
0
0
1
1
0
1
0
1
Normal port operation, OC2 disconnected.
Toggle OC2 on Compare Match.
Clear OC2 on Compare Match.
Set OC2 on Compare Match.
Table 62 shows the COM21:0 bit functionality when the WGM21:0 bits are set to fast
PWM mode.
Table 62. Compare Output Mode, Fast PWM Mode(1)
COM21
COM20
Description
0
0
1
1
0
1
0
1
Normal port operation, OC2 disconnected.
Reserved
Clear OC2 on Compare Match, set OC2 at TOP.
Set OC2 on Compare Match, clear OC2 at TOP.
Note:
1. A special case occurs when OCR2 equals TOP and COM21 is set. In this case, the
Compare Match is ignored, but the set or clear is done at TOP. See “Fast PWM
Mode” on page 144 for more details.
Table 63 shows the COM21:0 bit functionality when the WGM21:0 bits are set to phase
correct PWM mode.
Table 63. Compare Output Mode, Phase Correct PWM Mode(1)
COM21 COM20 Description
0
0
1
0
1
0
Normal port operation, OC2 disconnected.
Reserved
Clear OC2 on Compare Match when up-counting. Set OC2 on Compare
Match when down-counting.
1
1
Set OC2 on Compare Match when up-counting. Clear OC2 on Compare
Match when down-counting.
Note:
1. A special case occurs when OCR2 equals TOP and COM21 is set. In this case, the
Compare Match is ignored, but the set or clear is done at TOP. See “Phase Correct
PWM Mode” on page 145 for more details.
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• Bit 2:0 – CS22:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see
Table 64.
Table 64. Clock Select Bit Description
Description
CS22
CS21
CS20
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No clock source (Timer/Counter stopped).
clkT2S/(No prescaling)
clkT2S/8 (From prescaler)
clkT2S/32 (From prescaler)
clkT2S/64 (From prescaler)
clkT2S/128 (From prescaler)
clkT2S/256 (From prescaler)
clkT2S/1024 (From prescaler)
Timer/Counter Register –
TCNT2
Bit
7
6
5
4
3
2
1
0
TCNT2[7:0]
TCNT2
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
The Timer/Counter Register gives direct access, both for read and write operations, to
the Timer/Counter unit 8-bit counter. Writing to the TCNT2 Register blocks (removes)
the Compare Match on the following timer clock. Modifying the counter (TCNT2) while
the counter is running, introduces a risk of missing a Compare Match between TCNT2
and the OCR2 Register.
Output Compare Register –
OCR2
Bit
7
6
5
4
3
2
1
0
OCR2[7:0]
OCR2
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
The Output Compare Register contains an 8-bit value that is continuously compared
with the counter value (TCNT2). A match can be used to generate an output compare
interrupt, or to generate a waveform output on the OC2 pin.
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Asynchronous operation
of the Timer/Counter
Asynchronous Status
Register – ASSR
Bit
7
–
6
–
5
–
4
–
3
2
1
0
AS2
R/W
0
TCN2UB
OCR2UB
TCR2UB
ASSR
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
R
0
R
0
• Bit 3 – AS2: Asynchronous Timer/Counter2
When AS2 is written to zero, Timer/Counter2 is clocked from the I/O clock, clkI/O. When
AS2 is written to one, Timer/Counter2 is clocked from a crystal Oscillator connected to
the Timer Oscillator 1 (TOSC1) pin. When the value of AS2 is changed, the contents of
TCNT2, OCR2, and TCCR2 might be corrupted.
• Bit 2 – TCN2UB: Timer/Counter2 Update Busy
When Timer/Counter2 operates asynchronously and TCNT2 is written, this bit becomes
set. When TCNT2 has been updated from the temporary storage register, this bit is
cleared by hardware. A logical zero in this bit indicates that TCNT2 is ready to be
updated with a new value.
• Bit 1 – OCR2UB: Output Compare Register2 Update Busy
When Timer/Counter2 operates asynchronously and OCR2 is written, this bit becomes
set. When OCR2 has been updated from the temporary storage register, this bit is
cleared by hardware. A logical zero in this bit indicates that OCR2 is ready to be
updated with a new value.
• Bit 0 – TCR2UB: Timer/Counter Control Register2 Update Busy
When Timer/Counter2 operates asynchronously and TCCR2 is written, this bit becomes
set. When TCCR2 has been updated from the temporary storage register, this bit is
cleared by hardware. A logical zero in this bit indicates that TCCR2 is ready to be
updated with a new value.
If a write is performed to any of the three Timer/Counter2 Registers while its update
Busy Flag is set, the updated value might get corrupted and cause an unintentional
interrupt to occur.
The mechanisms for reading TCNT2, OCR2, and TCCR2 are different. When reading
TCNT2, the actual timer value is read. When reading OCR2 or TCCR2, the value in the
temporary storage register is read.
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Asynchronous Operation of
Timer/Counter2
When Timer/Counter2 operates asynchronously, some considerations must be taken.
•
Warning: When switching between asynchronous and synchronous clocking of
Timer/Counter2, the Timer Registers TCNT2, OCR2, and TCCR2 might be
corrupted. A safe procedure for switching clock source is:
1. Disable the Timer/Counter2 interrupts by clearing OCIE2 and TOIE2.
2. Select clock source by setting AS2 as appropriate.
3. Write new values to TCNT2, OCR2, and TCCR2.
4. To switch to asynchronous operation: Wait for TCN2UB, OCR2UB, and
TCR2UB.
5. Clear the Timer/Counter2 Interrupt Flags.
6. Enable interrupts, if needed.
•
•
The Oscillator is optimized for use with a 32.768 kHz watch crystal. Applying an
external clock to the TOSC1 pin may result in incorrect Timer/Counter2 operation.
The CPU main clock frequency must be more than four times the Oscillator
frequency.
When writing to one of the registers TCNT2, OCR2, or TCCR2, the value is
transferred to a temporary register, and latched after two positive edges on TOSC1.
The user should not write a new value before the contents of the temporary register
have been transferred to its destination. Each of the three mentioned registers have
their individual temporary register, which means that e.g., writing to TCNT2 does not
disturb an OCR2 write in progress. To detect that a transfer to the destination
register has taken place, the Asynchronous Status Register – ASSR has been
implemented.
•
When entering Power-save or Extended Standby mode after having written to
TCNT2, OCR2, or TCCR2, the user must wait until the written register has been
updated if Timer/Counter2 is used to wake up the device. Otherwise, the MCU will
enter sleep mode before the changes are effective. This is particularly important if
the Output Compare2 interrupt is used to wake up the device, since the output
compare function is disabled during writing to OCR2 or TCNT2. If the write cycle is
not finished, and the MCU enters sleep mode before the OCR2UB bit returns to
zero, the device will never receive a Compare Match interrupt, and the MCU will not
wake up.
•
If Timer/Counter2 is used to wake the device up from Power-save or Extended
Standby mode, precautions must be taken if the user wants to re-enter one of these
modes: The interrupt logic needs one TOSC1 cycle to be reset. If the time between
wake-up and re-entering sleep mode is less than one TOSC1 cycle, the interrupt will
not occur, and the device will fail to wake up. If the user is in doubt whether the time
before re-entering Power-save or Extended Standby mode is sufficient, the following
algorithm can be used to ensure that one TOSC1 cycle has elapsed:
1. Write a value to TCCR2, TCNT2, or OCR2.
2. Wait until the corresponding Update Busy Flag in ASSR returns to zero.
3. Enter Power-save or Extended Standby mode.
•
When the asynchronous operation is selected, the 32.768 kHz Oscillator for
Timer/Counter2 is always running, except in Power-down and Standby modes. After
a Power-up Reset or wake-up from Power-down or Standby mode, the user should
be aware of the fact that this Oscillator might take as long as one second to stabilize.
The user is advised to wait for at least one second before using Timer/Counter2
after Power-up or wake-up from Power-down or Standby mode. The contents of all
Timer/Counter2 Registers must be considered lost after a wake-up from Power-
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down or Standby mode due to unstable clock signal upon start-up, no matter
whether the Oscillator is in use or a clock signal is applied to the TOSC1 pin.
•
•
Description of wake up from Power-save or Extended Standby mode when the
Timer is clocked asynchronously: When the interrupt condition is met, the wake up
process is started on the following cycle of the timer clock, that is, the Timer is
always advanced by at least one before the processor can read the counter value.
After wake-up, the MCU is halted for four cycles, it executes the interrupt routine,
and resumes execution from the instruction following SLEEP.
Reading of the TCNT2 Register shortly after wake-up from Power-save may give an
incorrect result. Since TCNT2 is clocked on the asynchronous TOSC clock, reading
TCNT2 must be done through a register synchronized to the internal I/O clock
domain. Synchronization takes place for every rising TOSC1 edge. When waking up
from Power-save mode, and the I/O clock (clkI/O) again becomes active, TCNT2 will
read as the previous value (before entering sleep) until the next rising TOSC1 edge.
The phase of the TOSC clock after waking up from Power-save mode is essentially
unpredictable, as it depends on the wake-up time. The recommended procedure for
reading TCNT2 is thus as follows:
1. Write any value to either of the registers OCR2 or TCCR2.
2. Wait for the corresponding Update Busy Flag to be cleared.
3. Read TCNT2.
•
During asynchronous operation, the synchronization of the Interrupt Flags for the
Asynchronous Timer takes three processor cycles plus one timer cycle. The Timer
is therefore advanced by at least one before the processor can read the Timer value
causing the setting of the Interrupt Flag. The output compare pin is changed on the
Timer clock and is not synchronized to the processor clock.
Timer/Counter Interrupt Mask
Register – TIMSK
Bit
7
TOIE1
R/W
0
6
OCIE1A
R/W
0
5
OCIE1B
R/W
0
4
OCIE2
R/W
0
3
TICIE1
R/W
0
2
TOIE2
R/W
0
1
TOIE0
R/W
0
0
OCIE0
R/W
0
TIMSK
Read/Write
Initial Value
• Bit 4 – OCIE2: Timer/Counter2 Output Compare Match Interrupt Enable
When the OCIE2 bit is written to one and the I-bit in the Status Register is set (one), the
Timer/Counter2 Compare Match interrupt is enabled. The corresponding interrupt is
executed if a Compare Match in Timer/Counter2 occurs, i.e., when the OCF2 bit is set in
the Timer/Counter Interrupt Flag Register – TIFR.
• Bit 2 – TOIE2: Timer/Counter2 Overflow Interrupt Enable
When the TOIE2 bit is written to one and the I-bit in the Status Register is set (one), the
Timer/Counter2 Overflow interrupt is enabled. The corresponding interrupt is executed if
an overflow in Timer/Counter2 occurs, i.e., when the TOV2 bit is set in the
Timer/Counter Interrupt Flag Register – TIFR.
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Timer/Counter Interrupt Flag
Register – TIFR
Bit
7
TOV1
R/W
0
6
OCF1A
R/W
0
5
OC1FB
R/W
0
4
OCF2
R/W
0
3
ICF1
R/W
0
2
TOV2
R/W
0
1
TOV0
R/W
0
0
OCF0
R/W
0
TIFR
Read/Write
Initial Value
• Bit 4 – OCF2: Output Compare Flag 2
The OCF2 bit is set (one) when a Compare Match occurs between the Timer/Counter2
and the data in OCR2 – Output Compare Register2. OCF2 is cleared by hardware when
executing the corresponding interrupt handling vector. Alternatively, OCF2 is cleared by
writing a logic one to the flag. When the I-bit in SREG, OCIE2 (Timer/Counter2 Com-
pare Match Interrupt Enable), and OCF2 are set (one), the Timer/Counter2 Compare
Match Interrupt is executed.
• Bit 2 – TOV2: Timer/Counter2 Overflow Flag
The TOV2 bit is set (one) when an overflow occurs in Timer/Counter2. TOV2 is cleared
by hardware when executing the corresponding interrupt handling vector. Alternatively,
TOV2 is cleared by writing a logic one to the flag. When the SREG I-bit, TOIE2
(Timer/Counter2 Overflow Interrupt Enable), and TOV2 are set (one), the
Timer/Counter2 Overflow interrupt is executed. In PWM mode, this bit is set when
Timer/Counter2 changes counting direction at 0x00.
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Timer/Counter Prescaler Figure 70. Prescaler for Timer/Counter2
clkI/O
clkT2S
10-BIT T/C PRESCALER
Clear
TOSC1
AS2
PSR2
0
CS20
CS21
CS22
TIMER/COUNTER2 CLOCK SOURCE
clkT2
The clock source for Timer/Counter2 is named clkT2S. clkT2S is by default connected to
the main system I/O clock clkIO. By setting the AS2 bit in ASSR, Timer/Counter2 is asyn-
chronously clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real
Time Counter (RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from
Port D. A crystal can then be connected between the TOSC1 and TOSC2 pins to serve
as an independent clock source for Timer/Counter2. The Oscillator is optimized for use
with a 32.768 kHz crystal. Applying an external clock source to TOSC1 is not
recommended.
For Timer/Counter2, the possible prescaled selections are: clkT2S/8, clkT2S/32, clkT2S/64,
clkT2S/128, clkT2S/256, and clkT2S/1024. Additionally, clkT2S as well as 0 (stop) may be
selected. Setting the PSR2 bit in SFIOR resets the prescaler. This allows the user to
operate with a predictable prescaler.
Special Function IO Register –
SFIOR
Bit
7
6
XMBK
R/W
0
5
XMM2
R/W
0
4
XMM1
R/W
0
3
XMM0
R/W
0
2
1
PSR2
R/W
0
0
PSR310
R/W
0
TSM
R/W
0
PUD
R/W
0
SFIOR
Read/Write
Initial Val-
ue
• Bit 1 – PSR2: Prescaler Reset Timer/Counter2
When this bit is one, the Timer/Counter2 prescaler will be reset. This bit is normally
cleared immediately by hardware. If this bit is written when Timer/Counter2 is operating
in asynchronous mode, the bit will remain one until the prescaler has been reset. The bit
will not be cleared by hardware if the TSM bit is set. Refer to the description of the “Bit 7
– TSM: Timer/Counter Synchronization Mode” on page 104 for a description of the
Timer/Counter Synchronization mode.
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ATmega162/V
Serial Peripheral
Interface – SPI
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer
between the ATmega162 and peripheral devices or between several AVR devices. The
ATmega162 SPI includes the following features:
• Full-duplex, Three-wire Synchronous Data Transfer
• Master or Slave Operation
• LSB First or MSB First Data Transfer
• Seven Programmable Bit Rates
• End of Transmission Interrupt Flag
• Write Collision Flag Protection
• Wake-up from Idle Mode
• Double Speed (CK/2) Master SPI Mode
Figure 71. SPI Block Diagram(1)
DIVIDER
/2/4/8/16/32/64/128
Note:
1. Refer to Figure 1 on page 2, and Table 32 on page 71 for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in Figure 72.
The system consists of two Shift Registers, and a Master clock generator. The SPI Mas-
ter initiates the communication cycle when pulling low the Slave Select SS pin of the
desired Slave. Master and Slave prepare the data to be sent in their respective Shift
Registers, and the Master generates the required clock pulses on the SCK line to inter-
change data. Data is always shifted from Master to Slave on the Master Out – Slave In,
MOSI, line, and from Slave to Master on the Master In – Slave Out, MISO, line. After
each data packet, the Master will synchronize the Slave by pulling high the Slave Select,
SS, line.
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When configured as a Master, the SPI interface has no automatic control of the SS line.
This must be handled by user software before communication can start. When this is
done, writing a byte to the SPI Data Register starts the SPI clock generator, and the
hardware shifts the eight bits into the Slave. After shifting one byte, the SPI clock gener-
ator stops, setting the End of Transmission Flag (SPIF). If the SPI Interrupt Enable bit
(SPIE) in the SPCR Register is set, an interrupt is requested. The Master may continue
to shift the next byte by writing it into SPDR, or signal the end of packet by pulling high
the Slave Select, SS line. The last incoming byte will be kept in the buffer register for
later use.
When configured as a Slave, the SPI interface will remain sleeping with MISO tri-stated
as long as the SS pin is driven high. In this state, software may update the contents of
the SPI Data Register, SPDR, but the data will not be shifted out by incoming clock
pulses on the SCK pin until the SS pin is driven low. As one byte has been completely
shifted, the End of Transmission Flag, SPIF is set. If the SPI interrupt enable bit, SPIE,
in the SPCR Register is set, an interrupt is requested. The Slave may continue to place
new data to be sent into SPDR before reading the incoming data. The last incoming byte
will be kept in the Buffer Register for later use.
Figure 72. SPI Master-slave Interconnection
MSB
MASTER
LSB
MSB
SLAVE
LSB
MISO
MOSI
MISO
MOSI
8-BIT SHIFT REGISTER
8-BIT SHIFT REGISTER
SHIFT
ENABLE
SPI
SCK
SS
SCK
CLOCK GENERATOR
SS
VCC
The system is single buffered in the transmit direction and double buffered in the receive
direction. This means that bytes to be transmitted cannot be written to the SPI Data
Register before the entire shift cycle is completed. When receiving data, however, a
received character must be read from the SPI Data Register before the next character
has been completely shifted in. Otherwise, the first byte is lost.
In SPI Slave mode, the control logic will sample the incoming signal of the SCK pin. To
ensure correct sampling of the clock signal, the frequency of the SPI clock should never
exceed fosc/4.
When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is
overridden according to Table 65. For more details on automatic port overrides, refer to
“Alternate Port Functions” on page 67.
Table 65. SPI Pin Overrides(1)
Pin
MOSI
MISO
SCK
SS
Direction, Master SPI
User Defined
Input
Direction, Slave SPI
Input
User Defined
Input
User Defined
User Defined
Input
Note:
1. See “Alternate Functions Of Port B” on page 71 for a detailed description of how to
define the direction of the user defined SPI pins.
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The following code examples show how to initialize the SPI as a Master and how to per-
form a simple transmission. DDR_SPI in the examples must be replaced by the actual
Data Direction Register controlling the SPI pins. DD_MOSI, DD_MISO, and DD_SCK
must be replaced by the actual data direction bits for these pins. E.g., if MOSI is placed
on pin PB5, replace DD_MOSI with DDB5 and DDR_SPI with DDRB.
Assembly Code Example(1)
SPI_MasterInit:
; Set MOSI and SCK output, all others input
ldi
out
r17,(1<<DD_MOSI)|(1<<DD_SCK)
DDR_SPI,r17
; Enable SPI, Master, set clock rate fck/16
ldi
out
ret
r17,(1<<SPE)|(1<<MSTR)|(1<<SPR0)
SPCR,r17
SPI_MasterTransmit:
; Start transmission of data (r16)
out
SPDR,r16
Wait_Transmit:
; Wait for transmission complete
sbis SPSR,SPIF
rjmp Wait_Transmit
ret
C Code Example(1)
void SPI_MasterInit(void)
{
/* Set MOSI and SCK output, all others input */
DDR_SPI = (1<<DD_MOSI)|(1<<DD_SCK);
/* Enable SPI, Master, set clock rate fck/16 */
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}
void SPI_MasterTransmit(char cData)
{
/* Start transmission */
SPDR = cData;
/* Wait for transmission complete */
while(!(SPSR & (1<<SPIF)))
;
}
Note:
1. The example code assumes that the part specific header file is included.
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The following code examples show how to initialize the SPI as a slave and how to per-
form a simple reception.
Assembly Code Example(1)
SPI_SlaveInit:
; Set MISO output, all others input
ldi
out
r17,(1<<DD_MISO)
DDR_SPI,r17
; Enable SPI
ldi
out
ret
r17,(1<<SPE)
SPCR,r17
SPI_SlaveReceive:
; Wait for reception complete
sbis SPSR,SPIF
rjmp SPI_SlaveReceive
; Read received data and return
in
r16,SPDR
ret
C Code Example(1)
void SPI_SlaveInit(void)
{
/* Set MISO output, all others input */
DDR_SPI = (1<<DD_MISO);
/* Enable SPI */
SPCR = (1<<SPE);
}
char SPI_SlaveReceive(void)
{
/* Wait for reception complete */
while(!(SPSR & (1<<SPIF)))
;
/* Return data register */
return SPDR;
}
Note:
1. The example code assumes that the part specific header file is included.
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SS Pin Functionality
Slave Mode
When the SPI is configured as a slave, the Slave Select (SS) pin is always input. When
SS is held low, the SPI is activated, and MISO becomes an output if configured so by
the user. All other pins are inputs. When SS is driven high, all pins are inputs, and the
SPI is passive, which means that it will not receive incoming data. Note that the SPI
logic will be reset once the SS pin is driven high.
The SS pin is useful for packet/byte synchronization to keep the slave bit counter syn-
chronous with the master clock generator. When the SS pin is driven high, the SPI Slave
will immediately reset the send and receive logic, and drop any partially received data in
the Shift Register.
Master Mode
When the SPI is configured as a Master (MSTR in SPCR is set), the user can determine
the direction of the SS pin.
If SS is configured as an output, the pin is a general output pin which does not affect the
SPI system. Typically, the pin will be driving the SS pin of the SPI Slave.
If SS is configured as an input, it must be held high to ensure Master SPI operation. If
the SS pin is driven low by peripheral circuitry when the SPI is configured as a Master
with the SS pin defined as an input, the SPI system interprets this as another Master
selecting the SPI as a slave And starting to send data to it. To avoid bus contention, the
SPI system takes the following actions:
1. The MSTR bit in SPCR is cleared and the SPI system becomes a Slave. As a
result of the SPI becoming a Slave, the MOSI and SCK pins become inputs.
2. The SPIF Flag in SPSR is set, and if the SPI interrupt is enabled, and the I-bit in
SREG is set, the interrupt routine will be executed.
Thus, when interrupt-driven SPI transmission is used in Master mode, and there exists a
possibility that SS is driven low, the interrupt should always check that the MSTR bit is
still set. If the MSTR bit has been cleared by a slave select, it must be set by the user to
re-enable SPI Master mode.
SPI Control Register – SPCR
Bit
7
SPIE
R/W
0
6
5
DORD
R/W
0
4
MSTR
R/W
0
3
CPOL
R/W
0
2
CPHA
R/W
0
1
SPR1
R/W
0
0
SPR0
R/W
0
SPE
R/W
0
SPCR
Read/Write
Initial Value
• Bit 7 – SPIE: SPI Interrupt Enable
This bit causes the SPI interrupt to be executed if SPIF bit in the SPSR Register is set
and the if the Global Interrupt Enable bit in SREG is set.
• Bit 6 – SPE: SPI Enable
When the SPE bit is written to one, the SPI is enabled. This bit must be set to enable
any SPI operations.
• Bit 5 – DORD: Data Order
When the DORD bit is written to one, the LSB of the data word is transmitted first.
When the DORD bit is written to zero, the MSB of the data word is transmitted first.
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• Bit 4 – MSTR: Master/Slave Select
This bit selects Master SPI mode when written to one, and Slave SPI mode when written
logic zero. If SS is configured as an input and is driven low while MSTR is set, MSTR will
be cleared, and SPIF in SPSR will become set. The user will then have to set MSTR to
re-enable SPI Master mode.
• Bit 3 – CPOL: Clock Polarity
When this bit is written to one, SCK is high when idle. When CPOL is written to zero,
SCK is low when idle. Refer to Figure 73 and Figure 74 for an example. The CPOL func-
tionality is summarized below:
Table 66. CPOL Functionality
CPOL
Leading Edge
Rising
Trailing Edge
Falling
0
1
Falling
Rising
• Bit 2 – CPHA: Clock Phase
The settings of the Clock Phase bit (CPHA) determine if data is sampled on the leading
(first) or trailing (last) edge of SCK. Refer to Figure 73 and Figure 74 for an example.
The CPHA functionality is summarized below:
Table 67. CPHA Functionality
CPHA
Leading Edge
Sample
Trailing Edge
Setup
0
1
Setup
Sample
• Bits 1, 0 – SPR1, SPR0: SPI Clock Rate Select 1 and 0
These two bits control the SCK rate of the device configured as a Master. SPR1 and
SPR0 have no effect on the Slave. The relationship between SCK and the Oscillator
Clock frequency fosc is shown in the following table:
Table 68. Relationship Between SCK and the Oscillator Frequency
SPI2X
SPR1
SPR0
SCK Frequency
fosc/4
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
fosc/16
fosc/64
fosc/128
fosc/2
fosc/8
fosc/32
fosc/64
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SPI Status Register – SPSR
Bit
7
SPIF
R
6
5
–
4
–
3
–
2
–
1
–
0
SPI2X
R/W
0
WCOL
SPSR
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
R
0
0
• Bit 7 – SPIF: SPI Interrupt Flag
When a serial transfer is complete, the SPIF Flag is set. An interrupt is generated if
SPIE in SPCR is set and global interrupts are enabled. If SS is an input and is driven low
when the SPI is in master mode, this will also set the SPIF Flag. SPIF is cleared by
hardware when executing the corresponding interrupt handling vector. Alternatively, the
SPIF bit is cleared by first reading the SPI Status Register with SPIF set, then accessing
the SPI Data Register (SPDR).
• Bit 6 – WCOL: Write COLlision Flag
The WCOL bit is set if the SPI Data Register (SPDR) is written during a data transfer.
The WCOL bit (and the SPIF bit) are cleared by first reading the SPI Status Register
with WCOL set, and then accessing the SPI Data Register.
• Bit 5..1 – Res: Reserved Bits
These bits are reserved bits in the ATmega162 and will always read as zero.
• Bit 0 – SPI2X: Double SPI Speed Bit
When this bit is written logic one the SPI speed (SCK Frequency) will be doubled when
the SPI is in Master mode (see Table 68). This means that the minimum SCK period will
be two CPU clock periods. When the SPI is configured as Slave, the SPI is only guaran-
teed to work at fosc/4 or lower.
The SPI interface on the ATmega162 is also used for program memory and EEPROM
downloading or uploading. See page 244 for SPI serial programming and verification.
SPI Data Register – SPDR
Bit
7
6
5
4
3
2
1
0
MSB
R/W
X
LSB
R/W
X
SPDR
Read/Write
Initial Value
R/W
X
R/W
X
R/W
X
R/W
X
R/W
X
R/W
X
Undefined
The SPI Data Register is a read/write register used for data transfer between the Regis-
ter File and the SPI Shift Register. Writing to the register initiates data transmission.
Reading the register causes the Shift Register receive buffer to be read.
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Data Modes
There are four combinations of SCK phase and polarity with respect to serial data,
which are determined by control bits CPHA and CPOL. The SPI data transfer formats
are shown in Figure 73 and Figure 74. Data bits are shifted out and latched in on oppo-
site edges of the SCK signal, ensuring sufficient time for data signals to stabilize. This is
clearly seen by summarizing Table 66 and Table 67, as done below:
Table 69. CPOL and CPHA Functionality
Leading Edge
Sample (Rising)
Setup (Rising)
Sample (Falling)
Setup (Falling)
Trailing Edge
Setup (Falling)
Sample (Falling)
Setup (Rising)
Sample (Rising)
SPI Mode
CPOL=0, CPHA=0
CPOL=0, CPHA=1
CPOL=1, CPHA=0
CPOL=1, CPHA=1
0
1
2
3
Figure 73. SPI Transfer Format with CPHA = 0
SCK (CPOL = 0)
mode 0
SCK (CPOL = 1)
mode 2
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0) MSB
LSB first (DORD = 1) LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
Figure 74. SPI Transfer Format with CPHA = 1
SCK (CPOL = 0)
mode 1
SCK (CPOL = 1)
mode 3
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0)
LSB first (DORD = 1)
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
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ATmega162/V
USART
The Universal Synchronous and Asynchronous serial Receiver and Transmitter
(USART) is a highly flexible serial communication device. The main features are:
• Full Duplex Operation (Independent Serial Receive and Transmit Registers)
• Asynchronous or Synchronous Operation
• Master or Slave Clocked Synchronous Operation
• High Resolution Baud Rate Generator
• Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits
• Odd or Even Parity Generation and Parity Check Supported by Hardware
• Data OverRun Detection
• Framing Error Detection
• Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter
• Three Separate Interrupts on TX Complete, TX Data Register Empty and RX Complete
• Multi-processor Communication Mode
• Double Speed Asynchronous Communication Mode
Dual USART
The ATmega162 has two USARTs, USART0 and USART1. The functionality for both
USARTs is described below.
USART0 and USART1 have different I/O Registers as shown in “Register Summary” on
page 303. Note that in ATmega161 compatibility mode, the double buffering of the
USART Receive Register is disabled. For details, see “AVR USART vs. AVR UART –
Compatibility” on page 167. Note also that the shared UBRRHI Register in ATmega161
has been split into two separate registers, UBRR0H and UBRR1H, in ATmega162.
A simplified block diagram of the USART Transmitter is shown in Figure 75. CPU acces-
sible I/O Registers and I/O pins are shown in bold.
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Figure 75. USART Block Diagram(1)
Clock Generator
UBRR[H:L]
OSC
BAUD RATE GENERATOR
SYNC LOGIC
PIN
CONTROL
XCK
TxD
RxD
Transmitter
TX
CONTROL
UDR (Transmit)
PARITY
GENERATOR
PIN
CONTROL
TRANSMIT SHIFT REGISTER
Receiver
CLOCK
RECOVERY
RX
CONTROL
DATA
RECOVERY
PIN
CONTROL
RECEIVE SHIFT REGISTER
PARITY
CHECKER
UDR (Receive)
UCSRA
UCSRB
UCSRC
Note:
1. Refer to Figure 1 on page 2, Table 34 on page 73, Table 39 on page 79, and Table
40 on page 79 for USART pin placement.
The dashed boxes in the block diagram separate the three main parts of the USART
(listed from the top): Clock Generator, Transmitter and Receiver. Control registers are
shared by all units. The Clock Generation logic consists of synchronization logic for
external clock input used by synchronous slave operation, and the baud rate generator.
The XCK (Transfer Clock) pin is only used by synchronous transfer mode. The Trans-
mitter consists of a single write buffer, a serial Shift Register, parity generator and
control logic for handling different serial frame formats. The write buffer allows a contin-
uous transfer of data without any delay between frames. The Receiver is the most
complex part of the USART module due to its clock and data recovery units. The recov-
ery units are used for asynchronous data reception. In addition to the recovery units, the
Receiver includes a Parity Checker, Control logic, a Shift Register and a two level
receive buffer (UDR). The receiver supports the same frame formats as the Transmitter,
and can detect Frame Error, Data OverRun and Parity Errors.
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AVR USART vs. AVR UART –
Compatibility
The USART is fully compatible with the AVR UART regarding:
•
•
•
•
•
Bit locations inside all USART Registers
Baud Rate Generation
Transmitter Operation
Transmit Buffer Functionality
Receiver Operation
However, the receive buffering has two improvements that will affect the compatibility in
some special cases:
•
A second Buffer Register has been added. The two buffer registers operate as a
circular FIFO buffer. Therefore the UDR must only be read once for each incoming
data! More important is the fact that the Error Flags (FE and DOR) and the ninth
data bit (RXB8) are buffered with the data in the receive buffer. Therefore the status
bits must always be read before the UDR Register is read. Otherwise the error
status will be lost since the buffer state is lost.
•
The Receiver Shift Register can now act as a third buffer level. This is done by
allowing the received data to remain in the serial Shift Register (see Figure 75) if the
Buffer Registers are full, until a new start bit is detected. The USART is therefore
more resistant to Data OverRun (DOR) error conditions.
The following control bits have changed name, but have same functionality and register
location:
•
•
CHR9 is changed to UCSZ2.
OR is changed to DOR.
Clock Generation
The Clock Generation logic generates the base clock for the Transmitter and Receiver.
The USART supports four modes of clock operation: Normal asynchronous, Double
Speed asynchronous, Master synchronous and Slave synchronous mode. The UMSEL
bit in USART Control and Status Register C (UCSRC) selects between asynchronous
and synchronous operation. Double Speed (asynchronous mode only) is controlled by
the U2X found in the UCSRA Register. When using synchronous mode (UMSEL = 1),
the Data Direction Register for the XCK pin (DDR_XCK) controls whether the clock
source is internal (Master mode) or external (Slave mode). The XCK pin is only active
when using synchronous mode.
Figure 76 shows a block diagram of the clock generation logic.
Figure 76. Clock Generation Logic, Block Diagram
UBRR
U2X
fosc
UBRR+1
Prescaling
Down-Counter
/ 2
/ 4
/ 2
0
1
0
1
OSC
txclk
UMSEL
rxclk
DDR_XCK
Sync
Register
Edge
Detector
xcki
0
1
XCK
Pin
xcko
DDR_XCK
UCPOL
1
0
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Signal description:
txclk Transmitter clock. (Internal Signal)
rxclk Receiver base clock. (Internal Signal)
xcki
Input from XCK pin (internal Signal). Used for synchronous slave operation.
xcko Clock output to XCK pin (Internal Signal). Used for synchronous master
operation.
fosc
XTAL pin frequency (System Clock).
Internal Clock Generation –
The Baud Rate Generator
Internal clock generation is used for the asynchronous and the synchronous master
modes of operation. The description in this section refers to Figure 76.
The USART Baud Rate Register (UBRR) and the down-counter connected to it function
as a programmable prescaler or baud rate generator. The down-counter, running at sys-
tem clock (fosc), is loaded with the UBRR value each time the counter has counted
down to zero or when the UBRRL Register is written. A clock is generated each time the
counter reaches zero. This clock is the baud rate generator clock output (=
fosc/(UBRR+1)). The Transmitter divides the baud rate generator clock output by 2, 8 or
16 depending on mode. The baud rate generator output is used directly by the receiver’s
clock and data recovery units. However, the recovery units use a state machine that
uses 2, 8 or 16 states depending on mode set by the state of the UMSEL, U2X and
DDR_XCK bits.
Table 70 contains equations for calculating the baud rate (in bits per second) and for
calculating the UBRR value for each mode of operation using an internally generated
clock source.
Table 70. Equations for Calculating Baud Rate Register Setting
Equation for Calculating
Baud Rate(1)
Equation for Calculating
UBRR Value
Operating Mode
Asynchronous Normal Mode
(U2X = 0)
f
f
OSC
OSC
BAUD = --------------------------------------
16(UBRR + 1)
UBRR = ----------------------- – 1
16BAUD
Asynchronous Double Speed
Mode (U2X = 1)
f
OSC
f
OSC
BAUD = -----------------------------------
UBRR = -------------------- – 1
8(UBRR + 1)
8BAUD
Synchronous Master Mode
f
OSC
f
OSC
BAUD = -----------------------------------
UBRR = -------------------- – 1
2(UBRR + 1)
2BAUD
Note:
BAUD Baud rate (in bits per second, bps)
fOSC System Oscillator clock frequency
1. The baud rate is defined to be the transfer rate in bit per second (bps).
UBRR Contents of the UBRRH and UBRRL Registers, (0 - 4095)
Some examples of UBRR values for some system clock frequencies are found in Table
78 (see page 190).
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Double Speed Operation
(U2X)
The transfer rate can be doubled by setting the U2X bit in UCSRA. Setting this bit only
has effect for the asynchronous operation. Set this bit to zero when using synchronous
operation.
Setting this bit will reduce the divisor of the baud rate divider from 16 to 8, effectively
doubling the transfer rate for asynchronous communication. Note however that the
Receiver will in this case only use half the number of samples (reduced from 16 to 8) for
data sampling and clock recovery, and therefore a more accurate baud rate setting and
system clock are required when this mode is used. For the Transmitter, there are no
downsides.
External Clock
External clocking is used by the synchronous slave modes of operation. The description
in this section refers to Figure 76 for details.
External clock input from the XCK pin is sampled by a synchronization register to mini-
mize the chance of meta-stability. The output from the synchronization register must
then pass through an edge detector before it can be used by the Transmitter and
Receiver. This process introduces a two CPU clock period delay and therefore the max-
imum external XCK clock frequency is limited by the following equation:
f
OSC
-----------
f
<
XCK
4
Note that fosc depends on the stability of the system clock source. It is therefore recom-
mended to add some margin to avoid possible loss of data due to frequency variations.
Synchronous Clock Operation When synchronous mode is used (UMSEL = 1), the XCK pin will be used as either clock
input (Slave) or clock output (Master). The dependency between the clock edges and
data sampling or data change is the same. The basic principle is that data input (on
RxD) is sampled at the opposite XCK clock edge of the edge the data output (TxD) is
changed.
Figure 77. Synchronous Mode XCK Timing.
UCPOL = 1
XCK
RxD / TxD
Sample
Sample
UCPOL = 0
XCK
RxD / TxD
The UCPOL bit UCRSC selects which XCK clock edge is used for data sampling and
which is used for data change. As Figure 77 shows, when UCPOL is zero the data will
be changed at rising XCK edge and sampled at falling XCK edge. If UCPOL is set, the
data will be changed at falling XCK edge and sampled at rising XCK edge.
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Frame Formats
A serial frame is defined to be one character of data bits with synchronization bits (start
and stop bits), and optionally a parity bit for error checking. The USART accepts all 30
combinations of the following as valid frame formats:
•
•
•
•
1 start bit
5, 6, 7, 8, or 9 data bits
no, even or odd parity bit
1 or 2 stop bits
A frame starts with the start bit followed by the least significant data bit. Then the next
data bits, up to a total of nine, are succeeding, ending with the most significant bit. If
enabled, the parity bit is inserted after the data bits, before the stop bits. When a com-
plete frame is transmitted, it can be directly followed by a new frame, or the
communication line can be set to an idle (high) state. Figure 78 illustrates the possible
combinations of the frame formats. Bits inside brackets are optional.
Figure 78. Frame Formats
FRAME
(IDLE)
St
0
1
2
3
4
[5]
[6]
[7]
[8]
[P] Sp1 [Sp2] (St / IDLE)
St
(n)
P
Start bit, always low.
Data bits (0 to 8).
Parity bit. Can be odd or even.
Stop bit, always high.
Sp
IDLE No transfers on the communication line (RxD or TxD). An IDLE line must be
high.
The frame format used by the USART is set by the UCSZ2:0, UPM1:0 and USBS bits in
UCSRB and UCSRC. The Receiver and Transmitter use the same setting. Note that
changing the setting of any of these bits will corrupt all ongoing communication for both
the Receiver and Transmitter.
The USART Character SiZe (UCSZ2:0) bits select the number of data bits in the frame.
The USART Parity mode (UPM1:0) bits enable and set the type of parity bit. The selec-
tion between one or two stop bits is done by the USART Stop Bit Select (USBS) bit. The
receiver ignores the second stop bit. An FE (Frame Error) will therefore only be detected
in the cases where the first stop bit is zero.
Parity Bit Calculation
The parity bit is calculated by doing an exclusive-or of all the data bits. If odd parity is
used, the result of the exclusive or is inverted. The relation between the parity bit and
data bits is as follows::
P
P
= d
= d
…
…
d
d
d
d
d
d
d
d
0
1
even
n – 1
n – 1
3
3
2
2
1
1
0
0
odd
Peven Parity bit using even parity
Podd
dn
Parity bit using odd parity
Data bit n of the character
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If used, the parity bit is located between the last data bit and first stop bit of a serial
frame.
USART Initialization
The USART has to be initialized before any communication can take place. The initial-
ization process normally consists of setting the baud rate, setting frame format and
enabling the Transmitter or the Receiver depending on the usage. For interrupt driven
USART operation, the Global Interrupt Flag should be cleared (and interrupts globally
disabled) when doing the initialization.
Before doing a re-initialization with changed baud rate or frame format, be sure that
there are no ongoing transmissions during the period the registers are changed. The
TXC Flag can be used to check that the Transmitter has completed all transfers, and the
RXC Flag can be used to check that there are no unread data in the receive buffer. Note
that the TXC Flag must be cleared before each transmission (before UDR is written) if it
is used for this purpose.
The following simple USART initialization code examples show one assembly and one
C function that are equal in functionality. The examples assume asynchronous opera-
tion using polling (no interrupts enabled) and a fixed frame format. The baud rate is
given as a function parameter. For the assembly code, the baud rate parameter is
assumed to be stored in the r17:r16 Registers. When the function writes to the UCSRC
Register, the URSEL bit (MSB) must be set due to the sharing of I/O location by UBRRH
and UCSRC.
Assembly Code Example(1)
USART_Init:
; Set baud rate
out
out
UBRRH, r17
UBRRL, r16
; Enable receiver and transmitter
ldi
out
r16, (1<<RXEN)|(1<<TXEN)
UCSRB,r16
; Set frame format: 8data, 2stop bit
ldi
out
ret
r16, (1<<URSEL)|(1<<USBS)|(3<<UCSZ0)
UCSRC,r16
C Code Example(1)
void USART_Init( unsigned int baud )
{
/* Set baud rate */
UBRRH = (unsigned char)(baud>>8);
UBRRL = (unsigned char)baud;
/* Enable receiver and transmitter */
UCSRB = (1<<RXEN)|(1<<TXEN);
/* Set frame format: 8data, 2stop bit */
UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);
}
Note:
1. The example code assumes that the part specific header file is included.
More advanced initialization routines can be made that include frame format as parame-
ters, disable interrupts and so on. However, many applications use a fixed setting of the
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Baud and Control Registers, and for these types of applications the initialization code
can be placed directly in the main routine, or be combined with initialization code for
other I/O modules.
Data Transmission – The The USART Transmitter is enabled by setting the Transmit Enable (TXEN) bit in the
UCSRB Register. When the Transmitter is enabled, the normal port operation of the
USART Transmitter
TxD pin is overridden by the USART and given the function as the transmitter’s serial
output. The baud rate, mode of operation and frame format must be set up once before
doing any transmissions. If synchronous operation is used, the clock on the XCK pin will
be overridden and used as transmission clock.
Sending Frames with 5 to 8
Data Bit
A data transmission is initiated by loading the transmit buffer with the data to be trans-
mitted. The CPU can load the transmit buffer by writing to the UDR I/O location. The
buffered data in the transmit buffer will be moved to the Shift Register when the Shift
Register is ready to send a new frame. The Shift Register is loaded with new data if it is
in idle state (no ongoing transmission) or immediately after the last stop bit of the previ-
ous frame is transmitted. When the Shift Register is loaded with new data, it will transfer
one complete frame at the rate given by the Baud Register, U2X bit or by XCK depend-
ing on mode of operation.
The following code examples show a simple USART transmit function based on polling
of the Data Register Empty (UDRE) Flag. When using frames with less than eight bits,
the most significant bits written to the UDR are ignored. The USART has to be initialized
before the function can be used. For the assembly code, the data to be sent is assumed
to be stored in Register R16
Assembly Code Example(1)
USART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Put data (r16) into buffer, sends the data
out
ret
UDR,r16
C Code Example(1)
void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) )
;
/* Put data into buffer, sends the data */
UDR = data;
}
Note:
1. The example code assumes that the part specific header file is included.
The function simply waits for the transmit buffer to be empty by checking the UDRE
Flag, before loading it with new data to be transmitted. If the Data Register Empty inter-
rupt is utilized, the interrupt routine writes the data into the buffer.
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Sending Frames with 9 Data
Bit
If 9-bit characters are used (UCSZ = 7), the ninth bit must be written to the TXB8 bit in
UCSRB before the low byte of the character is written to UDR. The following code
examples show a transmit function that handles 9-bit characters. For the assembly
code, the data to be sent is assumed to be stored in Registers R17:R16.
Assembly Code Example(1)
USART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Copy 9th bit from r17 to TXB8
cbi
UCSRB,TXB8
sbrc r17,0
sbi
UCSRB,TXB8
; Put LSB data (r16) into buffer, sends the data
out
ret
UDR,r16
C Code Example(1)
void USART_Transmit( unsigned int data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) )
;
/* Copy 9th bit to TXB8 */
UCSRB &= ~(1<<TXB8);
if ( data & 0x0100 )
UCSRB |= (1<<TXB8);
/* Put data into buffer, sends the data */
UDR = data;
}
Note:
1. These transmit functions are written to be general functions. They can be optimized if
the contents of the UCSRB is static. For example, only the TXB8 bit of the UCSRB
Register is used after initialization.
The ninth bit can be used for indicating an address frame when using multi processor
communication mode or for other protocol handling as for example synchronization.
Transmitter Flags and
Interrupts
The USART Transmitter has two flags that indicate its state: USART Data Register
Empty (UDRE) and Transmit Complete (TXC). Both flags can be used for generating
interrupts.
The Data Register Empty (UDRE) Flag indicates whether the transmit buffer is ready to
receive new data. This bit is set when the transmit buffer is empty, and cleared when the
transmit buffer contains data to be transmitted that has not yet been moved into the Shift
Register. For compatibility with future devices, always write this bit to zero when writing
the UCSRA Register.
When the Data Register Empty Interrupt Enable (UDRIE) bit in UCSRB is written to one,
the USART Data Register Empty Interrupt will be executed as long as UDRE is set (pro-
vided that global interrupts are enabled). UDRE is cleared by writing UDR. When
interrupt-driven data transmission is used, the Data Register Empty Interrupt routine
must either write new data to UDR in order to clear UDRE or disable the Data Register
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Empty Interrupt, otherwise a new interrupt will occur once the interrupt routine
terminates.
The Transmit Complete (TXC) Flag bit is set one when the entire frame in the Transmit
Shift Register has been shifted out and there are no new data currently present in the
transmit buffer. The TXC Flag bit is automatically cleared when a transmit complete
interrupt is executed, or it can be cleared by writing a one to its bit location. The TXC
Flag is useful in half-duplex communication interfaces (like the RS-485 standard), where
a transmitting application must enter Receive mode and free the communication bus
immediately after completing the transmission.
When the Transmit Compete Interrupt Enable (TXCIE) bit in UCSRB is set, the USART
Transmit Complete Interrupt will be executed when the TXC Flag becomes set (pro-
vided that global interrupts are enabled). When the transmit complete interrupt is used,
the interrupt handling routine does not have to clear the TXC Flag, this is done automat-
ically when the interrupt is executed.
Parity Generator
The Parity Generator calculates the parity bit for the serial frame data. When parity bit is
enabled (UPM1 = 1), the transmitter control logic inserts the parity bit between the last
data bit and the first stop bit of the frame that is sent.
Disabling the Transmitter
The disabling of the Transmitter (setting the TXEN to zero) will not become effective
until ongoing and pending transmissions are completed, i.e., when the Transmit Shift
Register and Transmit Buffer Register do not contain data to be transmitted. When dis-
abled, the Transmitter will no longer override the TxD pin.
Data Reception – The
USART Receiver
The USART Receiver is enabled by writing the Receive Enable (RXEN) bit in the
UCSRB Register to one. When the receiver is enabled, the normal pin operation of the
RxD pin is overridden by the USART and given the function as the receiver’s serial
input. The baud rate, mode of operation and frame format must be set up once before
any serial reception can be done. If synchronous operation is used, the clock on the
XCK pin will be used as transfer clock.
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Receiving Frames with 5 to 8
Data Bits
The Receiver starts data reception when it detects a valid start bit. Each bit that follows
the start bit will be sampled at the baud rate or XCK clock, and shifted into the Receive
Shift Register until the first stop bit of a frame is received. A second stop bit will be
ignored by the Receiver. When the first stop bit is received, i.e., a complete serial frame
is present in the Receive Shift Register, the contents of the Shift Register will be moved
into the receive buffer. The receive buffer can then be read by reading the UDR I/O
location.
The following code example shows a simple USART receive function based on polling
of the Receive Complete (RXC) Flag. When using frames with less than eight bits the
most significant bits of the data read from the UDR will be masked to zero. The USART
has to be initialized before the function can be used.
Assembly Code Example(1)
USART_Receive:
; Wait for data to be received
sbis UCSRA, RXC
rjmp USART_Receive
; Get and return received data from buffer
in
r16, UDR
ret
C Code Example(1)
unsigned char USART_Receive( void )
{
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC)) )
;
/* Get and return received data from buffer */
return UDR;
}
Note:
1. The example code assumes that the part specific header file is included.
The function simply waits for data to be present in the receive buffer by checking the
RXC Flag, before reading the buffer and returning the value.
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Receiving Frames with 9 Data If 9-bit characters are used (UCSZ=7) the ninth bit must be read from the RXB8 bit in
Bits
UCSRB before reading the low bits from the UDR. This rule applies to the FE, DOR and
UPE Status Flags as well. Read status from UCSRA, then data from UDR. Reading the
UDR I/O location will change the state of the receive buffer FIFO and consequently the
TXB8, FE, DOR and UPE bits, which all are stored in the FIFO, will change.
The following code example shows a simple USART receive function that handles both
nine bit characters and the status bits.
Assembly Code Example(1)
USART_Receive:
; Wait for data to be received
sbis UCSRA, RXC
rjmp USART_Receive
; Get status and 9th bit, then data from buffer
in
in
in
r18, UCSRA
r17, UCSRB
r16, UDR
; If error, return -1
andi r18,(1<<FE)|(1<<DOR)|(1<<UPE)
breq USART_ReceiveNoError
ldi
ldi
r17, HIGH(-1)
r16, LOW(-1)
USART_ReceiveNoError:
; Filter the 9th bit, then return
lsr
r17
andi r17, 0x01
ret
C Code Example(1)
unsigned int USART_Receive( void )
{
unsigned char status, resh, resl;
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC)) )
;
/* Get status and 9th bit, then data */
/* from buffer */
status = UCSRA;
resh = UCSRB;
resl = UDR;
/* If error, return -1 */
if ( status & (1<<FE)|(1<<DOR)|(1<<UPE) )
return -1;
/* Filter the 9th bit, then return */
resh = (resh >> 1) & 0x01;
return ((resh << 8) | resl);
}
Note:
1. The example code assumes that the part specific header file is included.
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The receive function example reads all the I/O Registers into the Register File before
any computation is done. This gives an optimal receive buffer utilization since the buffer
location read will be free to accept new data as early as possible.
Receive Compete Flag and
Interrupt
The USART Receiver has one flag that indicates the receiver state.
The Receive Complete (RXC) Flag indicates if there are unread data present in the
receive buffer. This flag is one when unread data exist in the receive buffer, and zero
when the receive buffer is empty (i.e., does not contain any unread data). If the Receiver
is disabled (RXEN = 0), the receive buffer will be flushed and consequently the RXC bit
will become zero.
When the Receive Complete Interrupt Enable (RXCIE) in UCSRB is set, the USART
Receive Complete Interrupt will be executed as long as the RXC Flag is set (provided
that global interrupts are enabled). When interrupt-driven data reception is used, the
receive complete routine must read the received data from UDR in order to clear the
RXC Flag, otherwise a new interrupt will occur once the interrupt routine terminates.
Receiver Error Flags
The USART Receiver has three Error Flags: Frame Error (FE), Data OverRun (DOR)
and Parity Error (UPE). All can be accessed by reading UCSRA. Common for the Error
Flags is that they are located in the receive buffer together with the frame for which they
indicate the error status. Due to the buffering of the Error Flags, the UCSRA must be
read before the receive buffer (UDR), since reading the UDR I/O location changes the
buffer read location. Another equality for the Error Flags is that they can not be altered
by software doing a write to the flag location. However, all flags must be set to zero
when the UCSRA is written for upward compatibility of future USART implementations.
None of the Error Flags can generate interrupts.
The Frame Error (FE) Flag indicates the state of the first stop bit of the next readable
frame stored in the receive buffer. The FE Flag is zero when the stop bit was correctly
read (as one), and the FE Flag will be one when the stop bit was incorrect (zero). This
flag can be used for detecting out-of-sync conditions, detecting break conditions and
protocol handling. The FE Flag is not affected by the setting of the USBS bit in UCSRC
since the receiver ignores all, except for the first, stop bits. For compatibility with future
devices, always set this bit to zero when writing to UCSRA.
The Data OverRun (DOR) Flag indicates data loss due to a receiver buffer full condition.
A Data OverRun occurs when the receive buffer is full (two characters), it is a new char-
acter waiting in the Receive Shift Register, and a new start bit is detected. If the DOR
Flag is set there was one or more serial frame lost between the frame last read from
UDR, and the next frame read from UDR. For compatibility with future devices, always
write this bit to zero when writing to UCSRA. The DOR Flag is cleared when the frame
received was successfully moved from the Shift Register to the receive buffer.
The Parity Error (UPE) Flag indicates that the next frame in the receive buffer had a Par-
ity Error when received. If parity check is not enabled the UPE bit will always be read
zero. For compatibility with future devices, always set this bit to zero when writing to
UCSRA. For more details see “Parity Bit Calculation” on page 170 and “Parity Checker”
on page 178.
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Parity Checker
The Parity Checker is active when the high USART Parity mode (UPM1) bit is set. Type
of parity check to be performed (odd or even) is selected by the UPM0 bit. When
enabled, the Parity Checker calculates the parity of the data bits in incoming frames and
compares the result with the parity bit from the serial frame. The result of the check is
stored in the receive buffer together with the received data and stop bits. The Parity
Error (UPE) Flag can then be read by software to check if the frame had a Parity Error.
The UPE bit is set if the next character that can be read from the receive buffer had a
parity error when received and the parity checking was enabled at that point (UPM1 =
1). This bit is valid until the receive buffer (UDR) is read.
Disabling the Receiver
In contrast to the Transmitter, disabling of the Receiver will be immediate. Data from
ongoing receptions will therefore be lost. When disabled (i.e., the RXEN is set to zero)
the receiver will no longer override the normal function of the RxD port pin. The receiver
buffer FIFO will be flushed when the receiver is disabled. Remaining data in the buffer
will be lost
Flushing the Receive Buffer
The receiver buffer FIFO will be flushed when the Receiver is disabled, i.e., the buffer
will be emptied of its contents. Unread data will be lost. If the buffer has to be flushed
during normal operation, due to for instance an error condition, read the UDR I/O loca-
tion until the RXC Flag is cleared. The following code example shows how to flush the
receive buffer.
Assembly Code Example(1)
USART_Flush:
sbis UCSRA, RXC
ret
in
r16, UDR
rjmp USART_Flush
C Code Example(1)
void USART_Flush( void )
{
unsigned char dummy;
while ( UCSRA & (1<<RXC) ) dummy = UDR;
}
Note:
1. The example code assumes that the part specific header file is included.
Asynchronous Data
Reception
The USART includes a clock recovery and a data recovery unit for handling asynchro-
nous data reception. The clock recovery logic is used for synchronizing the internally
generated baud rate clock to the incoming asynchronous serial frames at the RxD pin.
The data recovery logic samples and low pass filters each incoming bit, thereby improv-
ing the noise immunity of the receiver. The asynchronous reception operational range
depends on the accuracy of the internal baud rate clock, the rate of the incoming
frames, and the frame size in number of bits.
Asynchronous Clock
Recovery
The clock recovery logic synchronizes internal clock to the incoming serial frames. Fig-
ure 79 illustrates the sampling process of the start bit of an incoming frame. The sample
rate is 16 times the baud rate for Normal mode, and 8 times the baud rate for Double
Speed mode. The horizontal arrows illustrate the synchronization variation due to the
sampling process. Note the larger time variation when using the double speed mode
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(U2X = 1) of operation. Samples denoted zero are samples done when the RxD line is
idle (i.e., no communication activity).
Figure 79. Start Bit Sampling
RxD
IDLE
START
BIT 0
Sample
(U2X = 0)
0
0
1
1
2
3
2
4
5
3
6
7
4
8
9
5
10
11
6
12
13
7
14
15
8
16
1
1
2
3
Sample
(U2X = 1)
0
2
When the clock recovery logic detects a high (idle) to low (start) transition on the RxD
line, the start bit detection sequence is initiated. Let sample 1 denote the first zero-sam-
ple as shown in the figure. The clock recovery logic then uses samples 8, 9 and 10 for
Normal mode, and samples 4, 5 and 6 for Double Speed mode (indicated with sample
numbers inside boxes on the figure), to decide if a valid start bit is received. If two or
more of these three samples have logical high levels (the majority wins), the start bit is
rejected as a noise spike and the receiver starts looking for the next high to low-transi-
tion. If however, a valid start bit is detected, the clock recovery logic is synchronized and
the data recovery can begin. The synchronization process is repeated for each start bit.
Asynchronous Data Recovery When the receiver clock is synchronized to the start bit, the data recovery can begin.
The data recovery unit uses a state machine that has 16 states for each bit in Normal
mode and 8 states for each bit in Double Speed mode. Figure 80 shows the sampling of
the data bits and the parity bit. Each of the samples is given a number that is equal to
the state of the recovery unit.
Figure 80. Sampling of Data and Parity Bit
RxD
BIT n
Sample
(U2X = 0)
1
1
2
3
2
4
5
3
6
7
4
8
9
5
10
11
6
12
13
7
14
15
8
16
1
1
Sample
(U2X = 1)
The decision of the logic level of the received bit is taken by doing a majority voting of
the logic value to the three samples in the center of the received bit. The center samples
are emphasized on the figure by having the sample number inside boxes. The majority
voting process is done as follows: If two or all three samples have high levels, the
received bit is registered to be a logic 1. If two or all three samples have low levels, the
received bit is registered to be a logic 0. This majority voting process acts as a low pass
filter for the incoming signal on the RxD pin. The recovery process is then repeated until
a complete frame is received. Including the first stop bit. Note that the receiver only uses
the first stop bit of a frame.
Figure 81 shows the sampling of the stop bit and the earliest possible beginning of the
start bit of the next frame.
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Figure 81. Stop Bit Sampling and Next Start Bit Sampling
(A)
(B)
(C)
RxD
STOP 1
Sample
(U2X = 0)
1
1
2
3
2
4
5
3
6
7
4
8
9
5
10
0/1 0/1 0/1
Sample
(U2X = 1)
6
0/1
The same majority voting is done to the stop bit as done for the other bits in the frame. If
the stop bit is registered to have a logic 0 value, the Frame Error (FE) Flag will be set.
A new high to low transition indicating the start bit of a new frame can come right after
the last of the bits used for majority voting. For Normal Speed mode, the first low level
sample can be at point marked (A) in Figure 81. For Double Speed mode the first low
level must be delayed to (B). (C) marks a stop bit of full length. The early start bit detec-
tion influences the operational range of the receiver.
Asynchronous Operational
Range
The operational range of the receiver is dependent on the mismatch between the
received bit rate and the internally generated baud rate. If the Transmitter is sending
frames at too fast or too slow bit rates, or the internally generated baud rate of the
receiver does not have a similar (see Table 71) base frequency, the receiver will not be
able to synchronize the frames to the start bit.
The following equations can be used to calculate the ratio of the incoming data rate and
internal receiver baud rate.
(D + 2)S
(D + 1)S + S
(D + 1)S
S – 1 + D S + S
R
= -----------------------------------
R
= ------------------------------------------
fast
slow
M
F
D
S
Sum of character size and parity size (D = 5 to 10 bit)
Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double Speed
mode.
SF
First sample number used for majority voting. SF = 8 for Normal Speed and
SF = 4 for Double Speed mode.
SM Middle sample number used for majority voting. SM = 9 for Normal Speed and
SM = 5 for Double Speed mode.
Rslow is the ratio of the slowest incoming data rate that can be accepted in relation to the
receiver baud rate. Rfast is the ratio of the fastest incoming data rate that can be
accepted in relation to the receiver baud rate.
Table 71 and Table 72 list the maximum receiver baud rate error that can be tolerated.
Note that normal speed mode has higher toleration of baud rate variations.
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Table 71. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode
(U2X = 0)
D
Recommended Max.
Receiver Error (%)
# (Data+Parity Bit) Rslow (%) Rfast (%) Max. Total Error (%)
5
6
93.20
94.12
94.81
95.36
95.81
96.17
106.67
105.79
105.11
104.58
104.14
103.78
+6.67/-6.8%
+5.79/-5.88
+5.11/-5.19
+4.58/-4.54
+4.14/-4.19
+3.7 /-3.83
± 3.0
± 2.5
± 2.0
± 2.0
± 1.5
± 1.5
7
8
9
10
Table 72. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode
(U2X = 1)
D
Recommended Max.
Receiver Error (%)
# (Data+Parity Bit) Rslow (%) Rfast (%) Max. Total Error (%)
5
6
94.12
94.92
95.52
96.00
96.39
96.70
105.66
104.92
104.35
103.90
103.53
103.23
+5.66/-5.88
+4.92/-5.08
+4.35/-4.48
+3.90/-4.00
+3.53/-3.61
+3.23/-3.30
± 2.5
± 2.0
± 1.5
± 1.5
± 1.5
± 1.0
7
8
9
10
The recommendations of the maximum receiver baud rate error was made under the
assumption that the Receiver and Transmitter equally divides the maximum total error.
There are two possible sources for the receivers baud rate error. The receiver’s system
clock (XTAL) will always have some minor instability over the supply voltage range and
the temperature range. When using a crystal to generate the system clock, this is rarely
a problem, but for a resonator the system clock may differ more than 2% depending of
the resonators tolerance. The second source for the error is more controllable. The baud
rate generator can not always do an exact division of the system frequency to get the
baud rate wanted. In this case an UBRR value that gives an acceptable low error can be
used if possible.
Multi-processor
Communication Mode
Setting the Multi-processor Communication mode (MPCM) bit in UCSRA enables a fil-
tering function of incoming frames received by the USART Receiver. Frames that do not
contain address information will be ignored and not put into the receive buffer. This
effectively reduces the number of incoming frames that has to be handled by the CPU,
in a system with multiple MCUs that communicate via the same serial bus. The Trans-
mitter is unaffected by the MPCM setting, but has to be used differently when it is a part
of a system utilizing the Multi-processor Communication mode.
If the receiver is set up to receive frames that contain 5 to 8 data bits, then the first stop
bit indicates if the frame contains data or address information. If the receiver is set up for
frames with nine data bits, then the ninth bit (RXB8) is used for identifying address and
data frames. When the frame type bit (the first stop or the ninth bit) is one, the frame
contains an address. When the frame type bit is zero the frame is a data frame.
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The Multi-processor Communication mode enables several slave MCUs to receive data
from a Master MCU. This is done by first decoding an address frame to find out which
MCU has been addressed. If a particular slave MCU has been addressed, it will receive
the following data frames as normal, while the other slave MCUs will ignore the received
frames until another address frame is received.
Using MPCM
For an MCU to act as a Master MCU, it can use a 9-bit character frame format (UCSZ =
7). The ninth bit (TXB8) must be set when an address frame (TXB8 = 1) or cleared when
a data frame (TXB = 0) is being transmitted. The slave MCUs must in this case be set to
use a 9-bit character frame format.
The following procedure should be used to exchange data in Multi-processor Communi-
cation mode:
1. All Slave MCUs are in Multi-processor Communication mode (MPCM in UCSRA
is set).
2. The Master MCU sends an address frame, and all slaves receive and read this
frame. In the slave MCUs, the RXC Flag in UCSRA will be set as normal.
3. Each Slave MCU reads the UDR Register and determines if it has been
selected. If so, it clears the MPCM bit in UCSRA, otherwise it waits for the next
address byte and keeps the MPCM setting.
4. The addressed MCU will receive all data frames until a new address frame is
received. The other Slave MCUs, which still have the MPCM bit set, will ignore
the data frames.
5. When the last data frame is received by the addressed MCU, the addressed
MCU sets the MPCM bit and waits for a new address frame from master. The
process then repeats from 2.
Using any of the 5- to 8-bit character frame formats is possible, but impractical since the
receiver must change between using n and n+1 character frame formats. This makes
full-duplex operation difficult since the Transmitter and Receiver uses the same charac-
ter size setting. If 5 to 8 bit character frames are used, the Transmitter must be set to
use two stop bit (USBS = 1) since the first stop bit is used for indicating the frame type.
Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCM bit.
The MPCM bit shares the same I/O location as the TXC Flag and this might accidentally
be cleared when using SBI or CBI instructions.
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ATmega162/V
Accessing UBRRH/
UCSRC Registers
The UBRRH Register shares the same I/O location as the UCSRC Register. Therefore
some special consideration must be taken when accessing this I/O location.
Write Access
When doing a write access of this I/O location, the high bit of the value written, the
USART Register Select (URSEL) bit, controls which one of the two registers that will be
written. If URSEL is zero during a write operation, the UBRRH value will be updated. If
URSEL is one, the UCSRC setting will be updated.
The following code examples show how to access the two registers.
Assembly Code Examples(1)
...
; Set UBRRH to 2
ldi r16,0x02
out UBRRH,r16
...
; Set the USBS and the UCSZ1 bit to one, and
; the remaining bits to zero.
ldi r16,(1<<URSEL)|(1<<USBS)|(1<<UCSZ1)
out UCSRC,r16
...
C Code Examples(1)
...
/* Set UBRRH to 2 */
UBRRH = 0x02;
...
/* Set the USBS and the UCSZ1 bit to one, and */
/* the remaining bits to zero. */
UCSRC = (1<<URSEL)|(1<<USBS)|(1<<UCSZ1);
...
Note:
1. The example code assumes that the part specific header file is included.
As the code examples illustrate, write accesses of the two registers are relatively unaf-
fected of the sharing of I/O location.
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Read Access
Doing a read access to the UBRRH or the UCSRC Register is a more complex opera-
tion. However, in most applications, it is rarely necessary to read any of these registers.
The read access is controlled by a timed sequence. Reading the I/O location once
returns the UBRRH Register contents. If the register location was read in previous sys-
tem clock cycle, reading the register in the current clock cycle will return the UCSRC
contents. Note that the timed sequence for reading the UCSRC is an atomic operation.
Interrupts must therefore be controlled (e.g., by disabling interrupts globally) during the
read operation.
The following code example shows how to read the UCSRC Register contents.
Assembly Code Example(1)
USART_ReadUCSRC:
; Read UCSRC
in r16,UBRRH
in r16,UCSRC
ret
C Code Example(1)
unsigned char USART_ReadUCSRC( void )
{
unsigned char ucsrc;
/* Read UCSRC */
ucsrc = UBRRH;
ucsrc = UCSRC;
return ucsrc;
}
Note:
1. The example code assumes that the part specific header file is included.
The assembly code example returns the UCSRC value in r16.
Reading the UBRRH contents is not an atomic operation and therefore it can be read as
an ordinary register, as long as the previous instruction did not access the register
location.
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ATmega162/V
USART Register
Description
USART I/O Data Register –
UDR
Bit
7
6
5
4
3
2
1
0
RXB[7:0]
TXB[7:0]
UDR (Read)
UDR (Write)
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers
share the same I/O address referred to as USART Data Register or UDR. The Transmit
Data Buffer Register (TXB) will be the destination for data written to the UDR Register
location. Reading the UDR Register location will return the contents of the Receive Data
Buffer Register (RXB).
For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter
and set to zero by the Receiver.
The transmit buffer can only be written when the UDRE Flag in the UCSRA Register is
set. Data written to UDR when the UDRE Flag is not set, will be ignored by the USART
Transmitter. When data is written to the transmit buffer, and the Transmitter is enabled,
the Transmitter will load the data into the Transmit Shift Register when the Shift Register
is empty. Then the data will be serially transmitted on the TxD pin.
The receive buffer consists of a two level FIFO. The FIFO will change its state whenever
the receive buffer is accessed. Due to this behavior of the receive buffer, do not use
read modify write instructions (SBI and CBI) on this location. Be careful when using bit
test instructions (SBIC and SBIS), since these also will change the state of the FIFO.
USART Control and Status
Register A – UCSRA
Bit
7
RXC
R
6
5
UDRE
R
4
FE
R
3
DOR
R
2
UPE
R
1
0
MPCM
R/W
0
TXC
R/W
0
U2X
R/W
0
UCSRA
Read/Write
Initial Value
0
1
0
0
0
• Bit 7 – RXC: USART Receive Complete
This flag bit is set when there are unread data in the receive buffer and cleared when the
receive buffer is empty (i.e., does not contain any unread data). If the receiver is dis-
abled, the receive buffer will be flushed and consequently the RXC bit will become zero.
The RXC Flag can be used to generate a Receive Complete interrupt (see description of
the RXCIE bit).
• Bit 6 – TXC: USART Transmit Complete
This flag bit is set when the entire frame in the Transmit Shift Register has been shifted
out and there are no new data currently present in the transmit buffer (UDR). The TXC
Flag bit is automatically cleared when a transmit complete interrupt is executed, or it can
be cleared by writing a one to its bit location. The TXC Flag can generate a Transmit
Complete interrupt (see description of the TXCIE bit).
• Bit 5 – UDRE: USART Data Register Empty
The UDRE Flag indicates if the transmit buffer (UDR) is ready to receive new data. If
UDRE is one, the buffer is empty, and therefore ready to be written. The UDRE Flag can
generate a Data Register Empty interrupt (see description of the UDRIE bit).
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2513F–AVR–12/03
UDRE is set after a Reset to indicate that the transmitter is ready.
• Bit 4 – FE: Frame Error
This bit is set if the next character in the receive buffer had a Frame Error when
received. I.e., when the first stop bit of the next character in the receive buffer is zero.
This bit is valid until the receive buffer (UDR) is read. The FE bit is zero when the stop
bit of received data is one. Always set this bit to zero when writing to UCSRA.
• Bit 3 – DOR: Data OverRun
This bit is set if a Data OverRun condition is detected. A data overrun occurs when the
receive buffer is full (two characters), it is a new character waiting in the reCeive Shift
Register, and a new start bit is detected. This bit is valid until the receive buffer (UDR) is
read. Always set this bit to zero when writing to UCSRA.
• Bit 2 – UPE: Parity Error
This bit is set if the next character in the receive buffer had a Parity Error when received
and the Parity Checking was enabled at that point (UPM1 = 1). This bit is valid until the
receive buffer (UDR) is read. Always set this bit to zero when writing to UCSRA.
• Bit 1 – U2X: Double the USART Transmission Speed
This bit only has effect for the asynchronous operation. Write this bit to zero when using
synchronous operation.
Writing this bit to one will reduce the divisor of the baud rate divider from 16 to 8 effec-
tively doubling the transfer rate for asynchronous communication.
• Bit 0 – MPCM: Multi-processor Communication Mode
This bit enables the Multi-processor Communication mode. When the MPCM bit is writ-
ten to one, all the incoming frames received by the USART receiver that do not contain
address information will be ignored. The transmitter is unaffected by the MPCM setting.
For more detailed information see “Multi-processor Communication Mode” on page 181.
USART Control and Status
Register B – UCSRB
Bit
7
RXCIE
R/W
0
6
TXCIE
R/W
0
5
UDRIE
R/W
0
4
RXEN
R/W
0
3
TXEN
R/W
0
2
UCSZ2
R/W
0
1
RXB8
R
0
TXB8
R/W
0
UCSRB
Read/Write
Initial Value
0
• Bit 7 – RXCIE: RX Complete Interrupt Enable
Writing this bit to one enables interrupt on the RXC Flag. A USART Receive Complete
interrupt will be generated only if the RXCIE bit is written to one, the Global Interrupt
Flag in SREG is written to one and the RXC bit in UCSRA is set.
• Bit 6 – TXCIE: TX Complete Interrupt Enable
Writing this bit to one enables interrupt on the TXC Flag. A USART Transmit Complete
interrupt will be generated only if the TXCIE bit is written to one, the Global Interrupt
Flag in SREG is written to one and the TXC bit in UCSRA is set.
186
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ATmega162/V
• Bit 5 – UDRIE: USART Data Register Empty Interrupt Enable
Writing this bit to one enables interrupt on the UDRE Flag. A Data Register Empty inter-
rupt will be generated only if the UDRIE bit is written to one, the Global Interrupt Flag in
SREG is written to one and the UDRE bit in UCSRA is set.
• Bit 4 – RXEN: Receiver Enable
Writing this bit to one enables the USART Receiver. The Receiver will override normal
port operation for the RxD pin when enabled. Disabling the Receiver will flush the
receive buffer invalidating the FE, DOR and UPE Flags.
• Bit 3 – TXEN: Transmitter Enable
Writing this bit to one enables the USART Transmitter. The Transmitter will override nor-
mal port operation for the TxD pin when enabled. The disabling of the Transmitter
(writing TXEN to zero) will not become effective until ongoing and pending transmis-
sions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register
do not contain data to be transmitted. When disabled, the Transmitter will no longer
override the TxD port.
• Bit 2 – UCSZ2: Character Size
The UCSZ2 bits combined with the UCSZ1:0 bit in UCSRC sets the number of data bits
(character size) in a frame the Receiver and Transmitter use.
• Bit 1 – RXB8: Receive Data Bit 8
RXB8 is the ninth data bit of the received character when operating with serial frames
with nine data bits. Must be read before reading the low bits from UDR.
• Bit 0 – TXB8: Transmit Data Bit 8
TXB8 is the 9th data bit in the character to be transmitted when operating with serial
frames with 9 data bits. Must be written before writing the low bits to UDR.
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2513F–AVR–12/03
USART Control and Status
Register C – UCSRC(1)
Bit
7
URSEL
R/W
1
6
UMSEL
R/W
0
5
UPM1
R/W
0
4
UPM0
R/W
0
3
USBS
R/W
0
2
UCSZ1
R/W
1
1
UCSZ0
R/W
1
0
UCPOL
R/W
0
UCSRC
Read/Write
Initial Value
Note:
1. The UCSRC Register shares the same I/O location as the UBRRH Register. See the
“Accessing UBRRH/ UCSRC Registers” on page 183 section which describes how to
access this register.
• Bit 7 – URSEL: Register Select
This bit selects between accessing the UCSRC or the UBRRH Register. It is read as
one when reading UCSRC. The URSEL must be one when writing the UCSRC.
• Bit 6 – UMSEL: USART Mode Select
This bit selects between asynchronous and synchronous mode of operation.
Table 73. UMSEL Bit Settings
UMSEL
Mode
0
1
Asynchronous Operation
Synchronous Operation
• Bit 5:4 – UPM1:0: Parity Mode
These bits enable and set type of parity generation and check. If enabled, the transmit-
ter will automatically generate and send the parity of the transmitted data bits within
each frame. The receiver will generate a parity value for the incoming data and compare
it to the UPM0 setting. If a mismatch is detected, the UPE Flag in UCSRA will be set.
Table 74. UPM Bits Settings
UPM1
UPM0
Parity Mode
0
0
1
1
0
1
0
1
Disabled
Reserved
Enabled, Even Parity
Enabled, Odd Parity
• Bit 3 – USBS: Stop Bit Select
This bit selects the number of stop bits to be inserted by the transmitter. The receiver
ignores this setting.
Table 75. USBS Bit Settings
USBS
Stop Bit(s)
1-bit
0
1
2-bit
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ATmega162/V
• Bit 2:1 – UCSZ1:0: Character Size
The UCSZ1:0 bits combined with the UCSZ2 bit in UCSRB sets the number of data bits
(Character Size) in a frame the receiver and transmitter use.
Table 76. UCSZ Bits Settings
UCSZ2
UCSZ1
UCSZ0
Character Size
5-bit
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
6-bit
7-bit
8-bit
Reserved
Reserved
Reserved
9-bit
• Bit 0 – UCPOL: Clock Polarity
This bit is used for synchronous mode only. Write this bit to zero when asynchronous
mode is used. The UCPOL bit sets the relationship between data output change and
data input sample, and the synchronous clock (XCK).
Table 77. UCPOL Bit Settings
Transmitted Data Changed
UCPOL (Output of TxD Pin)
Received Data Sampled
(Input on RxD Pin)
0
1
Rising XCK Edge
Falling XCK Edge
Falling XCK Edge
Rising XCK Edge
USART Baud Rate Registers –
UBRRL and UBRRH(1)
Bit
15
14
13
12
11
10
9
8
URSEL
–
–
–
UBRR[11:8]
UBRRH
UBRRL
UBRR[7:0]
7
R/W
R/W
0
6
R
5
R
4
R
3
R/W
R/W
0
2
R/W
R/W
0
1
R/W
R/W
0
0
R/W
R/W
0
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
0
0
0
0
0
0
0
0
Note:
1. The UBRRH Register shares the same I/O location as the UCSRC Register. See the
“Accessing UBRRH/ UCSRC Registers” on page 183 section which describes how to
access this register.
• Bit 15 – URSEL: Register Select
This bit selects between accessing the UBRRH or the UCSRC Register. It is read as
zero when reading UBRRH. The URSEL must be zero when writing the UBRRH.
• Bit 14:12 – Reserved Bits
These bits are reserved for future use. For compatibility with future devices, these bit
must be written to zero when UBRRH is written.
189
2513F–AVR–12/03
• Bit 11:0 – UBRR11:0: USART Baud Rate Register
This is a 12-bit register which contains the USART baud rate. The UBRRH contains the
four most significant bits, and the UBRRL contains the eight least significant bits of the
USART baud rate. Ongoing transmissions by the transmitter and receiver will be cor-
rupted if the baud rate is changed. Writing UBRRL will trigger an immediate update of
the baud rate prescaler.
Examples of Baud Rate
Setting
For standard crystal and resonator frequencies, the most commonly used baud rates for
asynchronous operation can be generated by using the UBRR settings in Table 78.
UBRR values which yield an actual baud rate differing less than 0.5% from the target
baud rate, are bold in the table. Higher error ratings are acceptable, but the receiver will
have less noise resistance when the error ratings are high, especially for large serial
frames (see “Asynchronous Operational Range” on page 180). The error values are cal-
culated using the following equation:
BaudRateClosest Match
Error[%] = ------------------------------------------------------ – 1 • 100%
BaudRate
Table 78. Examples of UBRR Settings for Commonly Used Oscillator Frequencies
fosc = 1.0000 MHz fosc = 1.8432 MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRR UBRR UBRR UBRR
fosc = 2.0000 MHz
U2X = 0 U2X = 1
UBRR UBRR
Baud
Rate
(bps)
Error
0.2%
0.2%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
Error
0.2%
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-25.0%
0.0%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
Error
0.2%
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
Error
0.2%
0.2%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
–
2400
25
12
6
51
25
12
8
47
23
11
7
95
47
23
15
11
7
51
25
12
8
103
51
25
16
12
8
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
3
2
6
5
6
1
3
3
3
1
2
2
5
2
6
0
1
1
3
1
3
–
1
1
2
1
2
–
–
0
0
1
0
1
–
–
–
–
0
–
–
–
–
–
–
–
–
–
–
–
0
0.0%
Max. (1)
62.5 kbps
UBRR = 0, Error = 0.0%
125 kbps
115.2 kbps
230.4 kbps
125 kbps
250 kbps
1.
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ATmega162/V
Table 79. Examples of UBRR Settings for Commonly Used Oscillator Frequencies (Continued)
osc = 3.6864 MHz fosc = 4.0000 MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRR UBRR UBRR UBRR
f
fosc = 7.3728 MHz
Baud
Rate
(bps)
U2X = 0
U2X = 1
UBRR
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
–
Error
0.2%
0.2%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
8.5%
0.0%
–
Error
0.2%
0.2%
0.2%
-0.8%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
0.0%
0.0%
–
UBRR
191
95
47
31
23
15
11
7
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
-7.8%
2400
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
95
47
23
15
11
7
191
95
47
31
23
15
11
7
103
51
25
16
12
8
207
103
51
34
25
16
12
8
383
191
95
63
47
31
23
15
11
7
5
6
3
3
2
5
2
6
5
1
3
1
3
3
0
1
0
1
1
3
0
1
0
1
1
3
0.5M
1M
–
0
–
0
0
1
–
–
–
–
–
–
–
0
Max. (1)
230.4 kbps
UBRR = 0, Error = 0.0%
460.8 kbps
250 kbps
0.5 Mbps
460.8 kbps
921.6 kbps
1.
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2513F–AVR–12/03
Table 80. Examples of UBRR Settings for Commonly Used Oscillator Frequencies (Continued)
osc = 8.0000 MHz fosc = 11.0592 MHz fosc = 14.7456 MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRR UBRR UBRR UBRR UBRR UBRR
f
Baud
Rate
(bps)
Error
0.2%
0.2%
0.2%
-0.8%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
0.0%
0.0%
–
Error
-0.1%
0.2%
0.2%
0.6%
0.2%
-0.8%
0.2%
2.1%
0.2%
-3.5%
8.5%
0.0%
0.0%
0.0%
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
-7.8%
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
5.3%
-7.8%
-7.8%
2400
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
207
103
51
34
25
16
12
8
416
207
103
68
51
34
25
16
12
8
287
143
71
47
35
23
17
11
8
575
287
143
95
71
47
35
23
17
11
5
383
191
95
63
47
31
23
15
11
7
767
383
191
127
95
63
47
31
23
15
7
6
3
5
1
3
2
3
1
3
2
5
3
6
0.5M
1M
0
1
–
2
1
3
–
0
–
–
–
0
1
Max. (1)
0.5 Mbps
UBRR = 0, Error = 0.0%
1 Mbps
691.2 kbps
1.3824 Mbps
921.6 kbps
1.8432 Mbps
1.
192
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Table 81. Examples of UBRR Settings for Commonly Used Oscillator Frequencies (Continued)
osc = 16.0000 MHz fosc = 18.4320 MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRR UBRR UBRR UBRR
f
fosc = 20.0000 MHz
Baud
Rate
(bps)
U2X = 0
U2X = 1
UBRR
Error
-0.1%
0.2%
0.2%
0.6%
0.2%
-0.8%
0.2%
2.1%
0.2%
-3.5%
8.5%
0.0%
0.0%
0.0%
Error
0.0%
-0.1%
0.2%
-0.1%
0.2%
0.6%
0.2%
-0.8%
0.2%
2.1%
-3.5%
0.0%
0.0%
0.0%
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
2.4%
-7.8%
–
UBRR
520
259
129
86
64
42
32
21
15
10
4
Error
0.0%
0.2%
0.2%
-0.2%
0.2%
0.9%
-1.4%
-1.4%
1.7%
-1.4%
8.5%
0.0%
–
Error
0.0%
0.0%
0.2%
-0.2%
0.2%
-0.2%
0.2%
0.9%
-1.4%
-1.4%
-1.4%
0.0%
0.0%
–
2400
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
416
207
103
68
51
34
25
16
12
8
832
416
207
138
103
68
51
34
25
16
8
479
239
119
79
59
39
29
19
14
9
959
479
239
159
119
79
59
39
29
19
9
1041
520
259
173
129
86
64
42
32
21
3
4
10
3
7
4
8
4
9
0.5M
1M
1
3
–
4
–
4
0
1
–
–
–
–
–
–
Max. (1)
1 Mbps
UBRR = 0, Error = 0.0%
2 Mbps
1.152 Mbps
2.304 Mbps
1.25 Mbps
2.5 Mbps
1.
193
2513F–AVR–12/03
Analog Comparator
The Analog Comparator compares the input values on the positive pin AIN0 and nega-
tive pin AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on
the negative pin AIN1, the Analog Comparator Output, ACO, is set. The comparator’s
output can be set to trigger the Timer/Counter1 Input Capture function. In addition, the
comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The
user can select Interrupt triggering on comparator output rise, fall or toggle. A block dia-
gram of the comparator and its surrounding logic is shown in Figure 82.
Figure 82. Analog Comparator Block Diagram(1)
BANDGAP
REFERENCE
ACBG
Note:
1. Refer to Figure 1 on page 2 and Table 32 on page 71 for Analog Comparator pin
placement.
Analog Comparator Control
and Status Register – ACSR
Bit
7
6
ACBG
R/W
0
5
ACO
R
4
ACI
R/W
0
3
ACIE
R/W
0
2
ACIC
R/W
0
1
ACIS1
R/W
0
0
ACIS0
R/W
0
ACD
R/W
0
ACSR
Read/Write
Initial Value
N/A
• Bit 7 – ACD: Analog Comparator Disable
When this bit is written logic one, the power to the Analog Comparator is switched off.
This bit can be set at any time to turn off the Analog Comparator. This will reduce power
consumption in Active and Idle mode. When changing the ACD bit, the Analog Compar-
ator Interrupt must be disabled by clearing the ACIE bit in ACSR. Otherwise an interrupt
can occur when the bit is changed.
• Bit 6 – ACBG: Analog Comparator Bandgap Select
When this bit is set, a fixed bandgap reference voltage replaces the positive input to the
Analog Comparator. When this bit is cleared, AIN0 is applied to the positive input of the
Analog Comparator. See “Internal Voltage Reference” on page 51.
• Bit 5 – ACO: Analog Comparator Output
The output of the Analog Comparator is synchronized and then directly connected to
ACO. The synchronization introduces a delay of 1 - 2 clock cycles.
• Bit 4 – ACI: Analog Comparator Interrupt Flag
This bit is set by hardware when a comparator output event triggers the interrupt mode
defined by ACIS1 and ACIS0. The Analog Comparator interrupt routine is executed if
194
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ATmega162/V
the ACIE bit is set and the I-bit in SREG is set. ACI is cleared by hardware when execut-
ing the corresponding interrupt handling vector. Alternatively, ACI is cleared by writing a
logic one to the flag.
• Bit 3 – ACIE: Analog Comparator Interrupt Enable
When the ACIE bit is written logic one and the I-bit in the Status Register is set, the Ana-
log Comparator interrupt is activated. When written logic zero, the interrupt is disabled.
• Bit 2 – ACIC: Analog Comparator Input Capture Enable
When written logic one, this bit enables the Input Capture function in Timer/Counter1 to
be triggered by the Analog Comparator. The comparator output is in this case directly
connected to the Input Capture front-end logic, making the comparator utilize the noise
canceler and edge select features of the Timer/Counter1 Input Capture interrupt. When
written logic zero, no connection between the Analog Comparator and the Input Capture
function exists. To make the comparator trigger the Timer/Counter1 Input Capture inter-
rupt, the TICIE1 bit in the Timer Interrupt Mask Register (TIMSK) must be set.
• Bits 1, 0 – ACIS1, ACIS0: Analog Comparator Interrupt Mode Select
These bits determine which comparator events that trigger the Analog Comparator inter-
rupt. The different settings are shown in Table 82.
Table 82. ACIS1/ACIS0 Settings
ACIS1
ACIS0
Interrupt Mode
0
0
1
1
0
1
0
1
Comparator Interrupt on Output Toggle.
Reserved
Comparator Interrupt on Falling Output Edge.
Comparator Interrupt on Rising Output Edge.
When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be dis-
abled by clearing its Interrupt Enable bit in the ACSR Register. Otherwise an interrupt
can occur when the bits are changed.
195
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JTAG Interface and
On-chip Debug
System
Features
• JTAG (IEEE std. 1149.1 Compliant) Interface
• Boundary-scan Capabilities According to the IEEE std. 1149.1 (JTAG) Standard
• Debugger Access to:
– All Internal Peripheral Units
– Internal and External RAM
– The Internal Register File
– Program Counter
– EEPROM and Flash Memories
• Extensive On-chip Debug Support for Break Conditions, Including
– AVR Break Instruction
– Break on Change of Program Memory Flow
– Single Step Break
– Program Memory Breakpoints on Single Address or Address Range
– Data Memory Breakpoints on Single Address or Address Range
• Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface
• On-chip Debugging Supported by AVR Studio®
Overview
The AVR IEEE std. 1149.1 compliant JTAG interface can be used for
•
•
•
Testing PCBs by using the JTAG Boundary-scan capability.
Programming the non-volatile memories, Fuses and Lock bits.
On-chip debugging.
A brief description is given in the following sections. Detailed descriptions for Program-
ming via the JTAG interface, and using the Boundary-scan Chain can be found in the
sections “Programming via the JTAG Interface” on page 249 and “IEEE 1149.1 (JTAG)
Boundary-scan” on page 203, respectively. The On-chip Debug support is considered
being private JTAG instructions, and distributed within ATMEL and to selected third
party vendors only.
Figure 83 shows a block diagram of the JTAG interface and the On-chip Debug system.
The TAP Controller is a state machine controlled by the TCK and TMS signals. The TAP
Controller selects either the JTAG Instruction Register or one of several Data Registers
as the scan chain (Shift Register) between the TDI – input and TDO – output. The
Instruction Register holds JTAG instructions controlling the behavior of a Data Register.
The ID-Register, Bypass Register, and the Boundary-scan Chain are the Data Registers
used for board-level testing. The JTAG Programming Interface (actually consisting of
several physical and virtual Data Registers) is used for serial programming via the JTAG
interface. The Internal Scan Chain and Break Point Scan Chain are used for On-chip
debugging only.
Test Access Port – TAP
The JTAG interface is accessed through four of the AVR’s pins. In JTAG terminology,
these pins constitute the Test Access Port – TAP. These pins are:
•
TMS: Test mode select. This pin is used for navigating through the TAP-controller
state machine.
•
•
TCK: Test Clock. JTAG operation is synchronous to TCK.
TDI: Test Data In. Serial input data to be shifted in to the Instruction Register or Data
Register (Scan Chains).
•
TDO: Test Data Out. Serial output data from Instruction Register or Data Register.
196
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ATmega162/V
The IEEE std. 1149.1 also specifies an optional TAP signal; TRST – Test ReSeT –
which is not provided.
When the JTAGEN fuse is unprogrammed, these four TAP pins are normal port pins
and the TAP controller is in reset. When programmed and the JTD bit in MCUCSR is
cleared, the TAP input signals are internally pulled high and the JTAG is enabled for
Boundary-scan and programming. In this case, the TAP output pin (TDO) is left floating
in states where the JTAG TAP controller is not shifting data, and must therefore be con-
nected to a pull-up resistor or other hardware having pull-ups (for instance the TDI-input
of the next device in the scan chain). The device is shipped with this fuse programmed.
For the On-chip Debug system, in addition to the JTAG interface pins, the RESET pin is
monitored by the debugger to be able to detect External Reset sources. The debugger
can also pull the RESET pin low to reset the whole system, assuming only open collec-
tors on the reset line are used in the application.
Figure 83. Block Diagram
I/O PORT 0
DEVICE BOUNDARY
BOUNDARY SCAN CHAIN
TDI
JTAG PROGRAMMING
INTERFACE
TDO
TCK
TMS
TAP
CONTROLLER
AVR CPU
INTERNAL
FLASH
MEMORY
Address
Data
SCAN
CHAIN
PC
Instruction
INSTRUCTION
REGISTER
ID
REGISTER
BREAKPOINT
UNIT
M
U
X
FLOW CONTROL
UNIT
BYPASS
REGISTER
DIGITAL
PERIPHERAL
UNITS
ANALOG
PERIPHERIAL
UNITS
Analog inputs
BREAKPOINT
SCAN CHAIN
JTAG / AVR CORE
COMMUNICATION
INTERFACE
ADDRESS
DECODER
OCD STATUS
AND CONTROL
Control & Clock lines
I/O PORT n
197
2513F–AVR–12/03
Figure 84. TAP Controller State Diagram
1
Test-Logic-Reset
0
1
1
1
0
Run-Test/Idle
Select-DR Scan
Select-IR Scan
0
0
1
1
Capture-DR
Capture-IR
0
0
Shift-IR
1
Shift-DR
0
0
1
Exit1-DR
0
1
1
Exit1-IR
0
Pause-DR
1
0
Pause-IR
1
0
0
0
Exit2-DR
1
Exit2-IR
1
Update-DR
Update-IR
1
1
0
0
198
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ATmega162/V
TAP Controller
The TAP controller is a 16-state finite state machine that controls the operation of the
Boundary-scan circuitry, JTAG programming circuitry, or On-chip Debug system. The
state transitions depicted in Figure 84 depend on the signal present on TMS (shown
adjacent to each state transition) at the time of the rising edge at TCK. The initial state
after a Power-on Reset is Test-Logic-Reset.
As a definition in this document, the LSB is shifted in and out first for all Shift Registers.
Assuming Run-Test/Idle is the present state, a typical scenario for using the JTAG inter-
face is:
•
At the TMS input, apply the sequence 1, 1, 0, 0 at the rising edges of TCK to enter
the Shift Instruction Register – Shift-IR state. While in this state, shift the four bits of
the JTAG instructions into the JTAG Instruction Register from the TDI input at the
rising edge of TCK. The TMS input must be held low during input of the 3 LSBs in
order to remain in the Shift-IR state. The MSB of the instruction is shifted in when
this state is left by setting TMS high. While the instruction is shifted in from the TDI
pin, the captured IR-state 0x01 is shifted out on the TDO pin. The JTAG Instruction
selects a particular Data Register as path between TDI and TDO and controls the
circuitry surrounding the selected Data Register.
•
•
Apply the TMS sequence 1, 1, 0 to re-enter the Run-Test/Idle state. The instruction
is latched onto the parallel output from the Shift Register path in the Update-IR
state. The Exit-IR, Pause-IR, and Exit2-IR states are only used for navigating the
state machine.
At the TMS input, apply the sequence 1, 0, 0 at the rising edges of TCK to enter the
Shift Data Register – Shift-DR state. While in this state, upload the selected data
register (selected by the present JTAG instruction in the JTAG Instruction Register)
from the TDI input at the rising edge of TCK. In order to remain in the Shift-DR state,
the TMS input must be held low during input of all bits except the MSB. The MSB of
the data is shifted in when this state is left by setting TMS high. While the Data
Register is shifted in from the TDI pin, the parallel inputs to the Data Register
captured in the Capture-DR state is shifted out on the TDO pin.
•
Apply the TMS sequence 1, 1, 0 to re-enter the Run-Test/Idle state. If the selected
data register has a latched parallel-output, the latching takes place in the Update-
DR state. The Exit-DR, Pause-DR, and Exit2-DR states are only used for navigating
the state machine.
As shown in the state diagram, the Run-Test/Idle state need not be entered between
selecting JTAG instruction and using Data Registers, and some JTAG instructions may
select certain functions to be performed in the Run-Test/Idle, making it unsuitable as an
Idle state.
Note:
Independent of the initial state of the TAP Controller, the Test-Logic-Reset state can
always be entered by holding TMS high for five TCK clock periods.
For detailed information on the JTAG specification, refer to the literature listed in “Bibli-
ography” on page 202.
Using the Boundary-
scan Chain
A complete description of the Boundary-scan capabilities are given in the section “IEEE
1149.1 (JTAG) Boundary-scan” on page 203.
199
2513F–AVR–12/03
Using the On-chip Debug As shown in Figure 83, the hardware support for On-chip Debugging consists mainly of
system
•
A scan chain on the interface between the internal AVR CPU and the internal
peripheral units
•
•
Break Point unit
Communication interface between the CPU and JTAG system
All read or modify/write operations needed for implementing the Debugger are done by
applying AVR instructions via the internal AVR CPU Scan Chain. The CPU sends the
result to an I/O memory mapped location which is part of the communication interface
between the CPU and the JTAG system.
The Break Point unit implements Break on Change of program flow, Single Step Break,
two Program memory Break Points, and two Combined Break Points. Together, the four
Break Points can be configured as either:
•
•
•
•
4 single Program Memory Break Points
3 Single Program Memory Break Point + 1 single Data Memory Break Point
2 single Program Memory Break Points + 2 single Data Memory Break Points
2 single Program Memory Break Points + 1 Program Memory Break Point with mask
(“range Break Point”)
•
2 single Program Memory Break Points + 1 Data Memory Break Point with mask
(“range Break Point”)
A debugger, like the AVR Studio®, may however use one or more of these resources for
its internal purpose, leaving less flexibility to the end-user.
A list of the On-chip Debug specific JTAG instructions is given in “On-chip debug spe-
cific JTAG instructions” on page 201.
The JTAGEN Fuse must be programmed to enable the JTAG Test Access Port. In addi-
tion, the OCDEN Fuse must be programmed and no Lock bits must be set for the On-
chip debug system to work. As a security feature, the On-chip debug system is disabled
when either of the LB1 or LB2 Lock bits are set. Otherwise, the On-chip debug system
would have provided a backdoor into a secured device.
The AVR Studio enables the user to fully control execution of programs on an AVR
device with On-chip Debug capability, AVR In-Circuit Emulator, or the built-in AVR
Instruction Set Simulator. AVR Studio supports source level execution of Assembly pro-
grams assembled with Atmel Corporation’s AVR Assembler and C programs compiled
with third party vendors’ compilers.
AVR Studio runs under Microsoft® Windows® 95/98/2000, Windows NT®, and
Windows XP®.
For a full description of the AVR Studio, please refer to the AVR Studio User Guide.
Only highlights are presented in this document.
All necessary execution commands are available in AVR Studio, both on source level
and on disassembly level. The user can execute the program, single step through the
code either by tracing into or stepping over functions, step out of functions, place the
cursor on a statement and execute until the statement is reached, stop the execution,
and reset the execution target. In addition, the user can have an unlimited number of
code Break Points (using the BREAK instruction) and up to two data memory Break
Points, alternatively combined as a mask (range) Break Point.
200
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ATmega162/V
On-chip debug specific
JTAG instructions
The On-chip debug support is considered being private JTAG instructions, and distrib-
uted within ATMEL and to selected 3rd party vendors only. Instruction opcodes are
listed for reference.
PRIVATE0; 0x8
PRIVATE1; 0x9
PRIVATE2; 0xA
PRIVATE3; 0xB
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
On-chip Debug Related
Register in I/O Memory
On-chip Debug Register –
OCDR
Bit
7
MSB/IDRD
R/W
6
5
4
3
2
1
0
LSB
R/W
0
OCDR
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
0
The OCDR Register provides a communication channel from the running program in the
microcontroller to the debugger. The CPU can transfer a byte to the debugger by writing
to this location. At the same time, an internal flag; I/O Debug Register Dirty – IDRD – is
set to indicate to the debugger that the register has been written. When the CPU reads
the OCDR Register the 7 LSB will be from the OCDR Register, while the MSB is the
IDRD bit. The debugger clears the IDRD bit when it has read the information.
In some AVR devices, this register is shared with a standard I/O location. In this case,
the OCDR Register can only be accessed if the OCDEN Fuse is programmed, and the
debugger enables access to the OCDR Register. In all other cases, the standard I/O
location is accessed.
Refer to the debugger documentation for further information on how to use this register.
Using the JTAG
Programming
Capabilities
Programming of AVR parts via JTAG is performed via the 4-pin JTAG port, TCK, TMS,
TDI and TDO. These are the only pins that need to be controlled/observed to perform
JTAG programming (in addition to power pins). It is not required to apply 12V externally.
The JTAGEN Fuse must be programmed and the JTD bit in the MCUSR Register must
be cleared to enable the JTAG Test Access Port.
The JTAG programming capability supports:
•
•
•
•
Flash programming and verifying.
EEPROM programming and verifying.
Fuse programming and verifying.
Lock bit programming and verifying.
The Lock bit security is exactly as in parallel programming mode. If the Lock bits LB1 or
LB2 are programmed, the OCDEN Fuse cannot be programmed unless first doing a
chip erase. This is a security feature that ensures no backdoor exists for reading out the
content of a secured device.
The details on programming through the JTAG interface and programming specific
JTAG instructions are given in the section “Programming via the JTAG Interface” on
page 249.
201
2513F–AVR–12/03
Bibliography
For more information about general Boundary-scan, the following literature can be
consulted:
•
IEEE: IEEE Std. 1149.1-1990. IEEE Standard Test Access Port and Boundary-scan
Architecture, IEEE, 1993
•
Colin Maunder: The Board Designers Guide to Testable Logic Circuits, Addison-
Wesley, 1992
202
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ATmega162/V
IEEE 1149.1 (JTAG)
Boundary-scan
Features
• JTAG (IEEE std. 1149.1 Compliant) Interface
• Boundary-scan Capabilities According to the JTAG Standard
• Full Scan of all Port Functions as well as Analog Circuitry Having Off-chip Connections
• Supports the Optional IDCODE Instruction
• Additional Public AVR_RESET Instruction to Reset the AVR
System Overview
The Boundary-scan chain has the capability of driving and observing the logic levels on
the digital I/O pins, as well as the boundary between digital and analog logic for analog
circuitry having Off-chip connections. At system level, all ICs having JTAG capabilities
are connected serially by the TDI/TDO signals to form a long Shift Register. An external
controller sets up the devices to drive values at their output pins, and observe the input
values received from other devices. The controller compares the received data with the
expected result. In this way, Boundary-scan provides a mechanism for testing intercon-
nections and integrity of components on Printed Circuits Boards by using the four TAP
signals only.
The four IEEE 1149.1 defined mandatory JTAG instructions IDCODE, BYPASS, SAM-
PLE/PRELOAD, and EXTEST, as well as the AVR specific public JTAG instruction
AVR_RESET can be used for testing the Printed Circuit Board. Initial scanning of the
Data Register path will show the ID-code of the device, since IDCODE is the default
JTAG instruction. It may be desirable to have the AVR device in Reset during Test
mode. If not Reset, inputs to the device may be determined by the scan operations, and
the internal software may be in an undetermined state when exiting the test mode.
Entering Reset, the outputs of any Port Pin will instantly enter the high impedance state,
making the HIGHZ instruction redundant. If needed, the BYPASS instruction can be
issued to make the shortest possible scan chain through the device. The device can be
set in the Reset state either by pulling the external RESET pin low, or issuing the
AVR_RESET instruction with appropriate setting of the Reset Data Register.
The EXTEST instruction is used for sampling external pins and loading output pins with
data. The data from the output latch will be driven out on the pins as soon as the
EXTEST instruction is loaded into the JTAG IR-Register. Therefore, the SAMPLE/PRE-
LOAD should also be used for setting initial values to the scan ring, to avoid damaging
the board when issuing the EXTEST instruction for the first time. SAMPLE/PRELOAD
can also be used for taking a snapshot of the external pins during normal operation of
the part.
The JTAGEN Fuse must be programmed and the JTD bit in the I/O Register MCUCSR
must be cleared to enable the JTAG Test Access Port.
When using the JTAG interface for Boundary-scan, using a JTAG TCK clock frequency
higher than the internal chip frequency is possible. The chip clock is not required to run.
203
2513F–AVR–12/03
Data Registers
The data registers relevant for Boundary-scan operations are:
•
•
•
•
Bypass Register
Device Identification Register
Reset Register
Boundary-scan Chain
Bypass Register
The Bypass Register consists of a single Shift Register stage. When the Bypass Regis-
ter is selected as path between TDI and TDO, the register is reset to 0 when leaving the
Capture-DR controller state. The Bypass Register can be used to shorten the scan
chain on a system when the other devices are to be tested.
Device Identification Register Figure 85 shows the structure of the Device Identification Register.
Figure 85. The Format of the Device Identification Register
MSB
LSB
0
Bit
31
28
27
12
11
1
Device ID
Version
4 bits
Part Number
16 bits
Manufacturer ID
1
11 bits
1 bit
Version
Version is a 4-bit number identifying the revision of the component. The relevant version
number is shown in Table 83.
Table 83. JTAG Version Numbers
Version
JTAG Version number (Hex)
ATmega162 revision A
ATmega162 revision B
ATmega162 revision C
ATmega162 revision D
0x0
0x1
0x2
0x3
Part Number
The part number is a 16-bit code identifying the component. The JTAG Part Number for
ATmega162 is listed in Table 84.
Table 84. AVR JTAG Part Number
Part number
JTAG Part Number (Hex)
ATmega162
0x9404
Manufacturer ID
The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufac-
turer ID for ATMEL is listed in Table 85.
Table 85. Manufacturer ID
Manufacturer
JTAG Man. ID (Hex)
ATMEL
0x01F
Reset Register
The Reset Register is a test data register used to reset the part. Since the AVR tri-states
Port Pins when reset, the Reset Register can also replace the function of the unimple-
mented optional JTAG instruction HIGHZ.
A high value in the Reset Register corresponds to pulling the external Reset low. The
part is reset as long as there is a high value present in the Reset Register. Depending
204
ATmega162/V
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ATmega162/V
on the Fuse settings for the clock options, the part will remain reset for a Reset Time-out
Period (refer to “Clock Sources” on page 34) after releasing the Reset Register. The
output from this data register is not latched, so the reset will take place immediately, as
shown in Figure 86.
Figure 86. Reset Register
To
TDO
From Other Internal and
External Reset Sources
From
TDI
Internal Reset
D
Q
ClockDR · AVR_RESET
Boundary-scan Chain
The Boundary-scan Chain has the capability of driving and observing the logic levels on
the digital I/O pins, as well as the boundary between digital and analog logic for analog
circuitry having Off-chip connections.
See “Boundary-scan Chain” on page 207 for a complete description.
Boundary-scan Specific The Instruction Register is 4-bit wide, supporting up to 16 instructions. Listed below are
the JTAG instructions useful for Boundary-scan operation. Note that the optional HIGHZ
JTAG Instructions
instruction is not implemented, but all outputs with tri-state capability can be set in high-
impedant state by using the AVR_RESET instruction, since the initial state for all port
pins is tri-state.
As a definition in this datasheet, the LSB is shifted in and out first for all Shift Registers.
The OPCODE for each instruction is shown behind the instruction name in hex format.
The text describes which Data Register is selected as path between TDI and TDO for
each instruction.
EXTEST; 0x0
Mandatory JTAG instruction for selecting the Boundary-scan Chain as Data Register for
testing circuitry external to the AVR package. For port-pins, Pull-up Disable, Output
Control, Output Data, and Input Data are all accessible in the scan chain. For analog cir-
cuits having Off-chip connections, the interface between the analog and the digital logic
is in the scan chain. The contents of the latched outputs of the Boundary-scan chain is
driven out as soon as the JTAG IR-Register is loaded with the EXTEST instruction.
The active states are:
•
•
•
Capture-DR: Data on the external pins are sampled into the Boundary-scan Chain.
Shift-DR: The Internal Scan Chain is shifted by the TCK input.
Update-DR: Data from the scan chain is applied to output pins.
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IDCODE; 0x1
Optional JTAG instruction selecting the 32-bit ID-register as data register. The ID-Regis-
ter consists of a version number, a device number and the manufacturer code chosen
by JEDEC. This is the default instruction after Power-up.
The active states are:
•
Capture-DR: Data in the IDCODE Register is sampled into the Boundary-scan
Chain.
•
Shift-DR: The IDCODE scan chain is shifted by the TCK input.
SAMPLE_PRELOAD; 0x2
Mandatory JTAG instruction for preloading the output latches and taking a snapshot of
the input/output pins without affecting the system operation. However, the output latches
are not connected to the pins. The Boundary-scan Chain is selected as Data Register.
The active states are:
•
•
•
Capture-DR: Data on the external pins are sampled into the Boundary-scan Chain.
Shift-DR: The Boundary-scan Chain is shifted by the TCK input.
Update-DR: Data from the Boundary-scan chain is applied to the output latches.
However, the output latches are not connected to the pins.
AVR_RESET; 0xC
The AVR specific public JTAG instruction for forcing the AVR device into the Reset
mode or releasing the JTAG Reset source. The TAP controller is not reset by this
instruction. The one bit Reset Register is selected as data register. Note that the reset
will be active as long as there is a logic 'one' in the Reset Chain. The output from this
chain is not latched.
The active states are:
•
Shift-DR: The Reset Register is shifted by the TCK input.
BYPASS; 0xF
Mandatory JTAG instruction selecting the Bypass Register for data register.
The active states are:
•
•
Capture-DR: Loads a logic “0” into the Bypass Register.
Shift-DR: The Bypass Register cell between TDI and TDO is shifted.
Boundary-scan Related
Register in I/O Memory
MCU Control and Status
Register – MCUCSR
The MCU Control and Status Register contains control bits for general MCU functions,
and provides information on which reset source caused an MCU Reset.
Bit
7
6
–
5
SM2
R
4
3
2
1
0
JTD
R/W
0
JTRF
R/W
WDRF
R/W
BORF
R/W
EXTRF
R/W
PORF
R/W
MCUCSR
Read/Write
Initial Value
R/W
0
0
See Bit Description
• Bit 7 – JTD: JTAG Interface Disable
When this bit is zero, the JTAG interface is enabled if the JTAGEN Fuse is programmed.
If this bit is one, the JTAG interface is disabled. In order to avoid unintentional disabling
or enabling of the JTAG interface, a timed sequence must be followed when changing
this bit: The application software must write this bit to the desired value twice within four
cycles to change its value.
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If the JTAG interface is left unconnected to other JTAG circuitry, the JTD bit should be
set to one. The reason for this is to avoid static current at the TDO pin in the JTAG
interface.
• Bit 4 – JTRF: JTAG Reset Flag
This bit is set if a reset is being caused by a logic one in the JTAG Reset Register
selected by the JTAG instruction AVR_RESET. This bit is reset by a Power-on Reset, or
by writing a logic zero to the flag.
Boundary-scan Chain
The Boundary-scan Chain has the capability of driving and observing the logic levels on
the digital I/O pins, as well as the boundary between digital and analog logic for analog
circuitry having Off-chip connection.
Scanning the Digital Port Pins Figure 87 shows the Boundary-scan Cell for a bi-directional port pin with pull-up func-
tion. The cell consists of a standard Boundary-scan cell for the Pull-up Enable – PUExn
– function, and a bi-directional pin cell that combines the three signals Output Control –
OCxn, Output Data – ODxn, and Input Data – IDxn, into only a two-stage Shift Register.
The port and pin indexes are not used in the following description
The Boundary-scan logic is not included in the figures in the datasheet. Figure 88 shows
a simple digital Port Pin as described in the section “I/O-Ports” on page 62. The Bound-
ary-scan details from Figure 87 replaces the dashed box in Figure 88.
When no alternate port function is present, the Input Data – ID – corresponds to the
PINxn Register value (but ID has no synchronizer), Output Data corresponds to the
PORT Register, Output Control corresponds to the Data Direction – DD Register, and
the Pull-up Enable – PUExn – corresponds to logic expression PUD · DDxn · PORTxn.
Digital alternate port functions are connected outside the dotted box in Figure 88 to
make the scan chain read the actual pin value. For Analog function, there is a direct
connection from the external pin to the analog circuit, and a scan chain is inserted on
the interface between the digital logic and the analog circuitry.
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Figure 87. Boundary-scan Cell for Bi-directional Port Pin with Pull-up Function.
ShiftDR
To Next Cell
EXTEST
Vcc
Pullup Enable (PUE)
0
1
FF2
Q
LD2
0
1
D
D
Q
G
Output Control (OC)
FF1
D Q
LD1
0
1
0
1
D
G
Q
Output Data (OD)
0
1
FF0
D
LD0
0
1
Port Pin (PXn)
0
1
Q
D
G
Q
Input Data (ID)
From Last Cell
ClockDR
UpdateDR
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Figure 88. General Port Pin Schematic Diagram
See Boundary-Scan Description
for Details!
PUExn
PUD
Q
D
DDxn
Q CLR
WDx
RDx
RESET
OCxn
Q
D
Pxn
PORTxn
ODxn
Q CLR
WRx
RRx
IDxn
RESET
SLEEP
SYNCHRONIZER
RPx
D
Q
D
L
Q
Q
PINxn
Q
CLK I/O
PUD:
PULLUP DISABLE
WDx:
RDx:
WRITE DDRx
PUExn:
OCxn:
ODxn:
IDxn:
PULLUP ENABLE for pin Pxn
OUTPUT CONTROL for pin Pxn
OUTPUT DATA to pin Pxn
INPUT DATA from pin Pxn
SLEEP CONTROL
READ DDRx
WRx:
RRx:
WRITE PORTx
READ PORTx REGISTER
READ PORTx PIN
I/O CLOCK
RPx:
CLK I/O :
SLEEP:
Scanning the RESET pin
The RESET pin accepts 5V active low logic for standard reset operation, and 12V active
high logic for high voltage parallel programming. An observe-only cell as shown in Fig-
ure 89 is inserted both for the 5V reset signal; RSTT, and the 12V reset signal; RSTHV.
Figure 89. Observe-only Cell
To
Next
ShiftDR
Cell
From System Pin
To System Logic
FF1
0
1
D
Q
From
ClockDR
Previous
Cell
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Scanning the Clock Pins
The AVR devices have many clock options selectable by fuses. These are: Internal RC
Oscillator, External Clock, (High Frequency) Crystal Oscillator, Low Frequency Crystal
Oscillator, and Ceramic Resonator.
Figure 90 shows how each Oscillator with external connection is supported in the scan
chain. The Enable signal is supported with a general Boundary-scan cell, while the
Oscillator/clock output is attached to an observe-only cell. In addition to the main clock,
the Timer Oscillator is scanned in the same way. The output from the internal RC Oscil-
lator is not scanned, as this Oscillator does not have external connections.
Figure 90. Boundary-scan Cells for Oscillators and Clock Options
XTAL1/TOSC1
XTAL2/TOSC2
To
Next
Cell
To
ShiftDR
EXTEST
Next
Cell
Oscillator
ShiftDR
From Digital Logic
0
1
To System Logic
ENABLE
OUTPUT
0
1
FF1
D
Q
D
G
Q
0
1
D
Q
From
ClockDR
UpdateDR
Previous
Cell
From
ClockDR
Previous
Cell
Table 86 summaries the scan registers for the external clock pin XTAL1, oscillators with
XTAL1/XTAL2 connections as well as 32 kHz Timer Oscillator.
Table 86. Scan Signals for the Oscillator(1)(2)(3)
Scanned Clock
Line when Not
Enable Signal Scanned Clock Line Clock Option
Used
EXTCLKEN
OSCON
EXTCLK (XTAL1)
OSCCK
External Clock
0
0
External Crystal
External Ceramic Resonator
OSC32EN
TOSKON
OSC32CK
TOSCK
Low Freq. External Crystal
32 kHz Timer Oscillator
0
0
Notes: 1. Do not enable more than one clock source as main clock at a time.
2. Scanning an Oscillator output gives unpredictable results as there is a frequency drift
between the Internal Oscillator and the JTAG TCK clock. If possible, scanning an
external clock is preferred.
3. The clock configuration is programmed by fuses. As a fuse is not changed run-time,
the clock configuration is considered fixed for a given application. The user is advised
to scan the same clock option as to be used in the final system. The enable signals
are supported in the scan chain because the system logic can disable clock options
in sleep modes, thereby disconnecting the Oscillator pins from the scan path if not
provided. The INTCAP selection is not supported in the scan-chain, so the boundary
scan chain can not make a XTAL Oscillator requiring internal capacitors to run unless
the fuses are correctly programmed.
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Scanning the Analog
Comparator
The relevant Comparator signals regarding Boundary-scan are shown in Figure 91. The
Boundary-scan cell from Figure 92 is attached to each of these signals. The signals are
described in Table 87.
The Comparator need not be used for pure connectivity testing, since all analog inputs
are shared with a digital port pin as well.
Figure 91. Analog Comparator
BANDGAP
REFERENCE
ACBG
ACO
AC_IDLE
Figure 92. General Boundary-scan Cell used for Signals for Comparator
To
Next
ShiftDR
Cell
EXTEST
From Digital Logic/
From Analog Ciruitry
0
1
To Snalog Circuitry/
To Digital Logic
0
1
D
Q
D
G
Q
From
ClockDR
UpdateDR
Previous
Cell
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Table 87. Boundary-scan Signals for the Analog Comparator
Direction as
seen from the
Comparator
Recommended Output Values when
Signal
Name
Input when Not
in Use
Recommended
Inputs are Used
Description
AC_IDLE
input
output
input
Turns off Analog
comparator
when true
1
Depends upon µC
code being executed
ACO
Analog
Comparator
Output
Will become
input to µC code
being executed
0
ACBG
Bandgap
Reference
enable
0
Depends upon µC
code being executed
ATmega162 Boundary-
scan Order
Table 88 shows the Scan order between TDI and TDO when the Boundary-scan chain
is selected as data path. Bit 0 is the LSB; the first bit scanned in, and the first bit
scanned out. The scan order follows the pinout order as far as possible. Therefore, the
bits of Port A and Port E is scanned in the opposite bit order of the other ports. Excep-
tions from the rules are the Scan chains for the analog circuits, which constitute the
most significant bits of the scan chain regardless of which physical pin they are con-
nected to. In Figure 87, PXn. Data corresponds to FF0, PXn. Control corresponds to
FF1, and PXn. Pullup_enable corresponds to FF2. Bit 4, 5, 6, and 7of Port C is not in the
scan chain, since these pins constitute the TAP pins when the JTAG is enabled.
Table 88. ATmega162 Boundary-scan Order
Bit Number
105
104
103
102
101
100
99
Signal Name
AC_IDLE
Module
Comparator
ACO
ACBG
PB0.Data
Port B
PB0.Control
PB0.Pullup_Enable
PB1.Data
98
PB1.Control
PB1.Pullup_Enable
PB2.Data
97
96
95
PB2.Control
PB2.Pullup_Enable
PB3.Data
94
93
92
PB3.Control
PB3.Pullup_Enable
PB4.Data
91
90
89
PB4.Control
PB4.Pullup_Enable
88
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Table 88. ATmega162 Boundary-scan Order (Continued)
Bit Number
87
Signal Name
PB5.Data
Module
Port B
86
PB5.Control
PB5.Pullup_Enable
PB6.Data
85
84
83
PB6.Control
PB6.Pullup_Enable
PB7.Data
82
81
80
PB7.Control
PB7.Pullup_Enable
RSTT
79
78
Reset Logic
(Observe-only)
77
RSTHV
76
TOSC
32 kHz Timer Oscillator
Port D
75
TOSCON
74
PD0.Data
73
PD0.Control
PD0.Pullup_Enable
PD1.Data
72
71
70
PD1.Control
PD1.Pullup_Enable
PD2.Data
69
68
67
PD2.Control
PD2.Pullup_Enable
PD3.Data
66
65
64
PD3.Control
PD3.Pullup_Enable
PD4.Data
63
62
61
PD4.Control
PD4.Pullup_Enable
PD5.Data
60
59
Port D
58
PD5.Control
PD5.Pullup_Enable
PD6.Data
57
56
55
PD6.Control
PD6.Pullup_Enable
PD7.Data
54
53
52
PD7.Control
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Table 88. ATmega162 Boundary-scan Order (Continued)
Bit Number
51
Signal Name
PD7.Pullup_Enable
EXTCLKEN
Module
Port D
50
Enable signals for main
Clock/Oscillators
49
OSCON
48
OSC32EN
47
EXTCLK (XTAL1)
OSCCK
Clock input and Oscillators
for the main clock (Observe-
only)
46
45
OSC32CK
44
PC0.Data
Port C
43
PC0.Control
PC0.Pullup_Enable
PC1.Data
42
41
40
PC1.Control
PC1.Pullup_Enable
PC2.Data
39
38
37
PC2.Control
PC2.Pullup_Enable
PC3.Data
36
35
34
PC3.Control
PC3.Pullup_Enable
PE2.Data
33
32
Port E
31
PE2.Control
PE2.Pullup_Enable
PE1.Data
30
29
28
PE1.Control
PE1.Pullup_Enable
PE0.Data
27
26
25
PE0.Control
PE0.Pullup_Enable
PA7.Data
24
23
Port A
22
PA7.Control
21
PA7.Pullup_Enable
PA6.Data
20
19
PA6.Control
18
PA6.Pullup_Enable
PA5.Data
17
16
PA5.Control
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ATmega162/V
Table 88. ATmega162 Boundary-scan Order (Continued)
Bit Number
Signal Name
PA5.Pullup_Enable
PA4.Data
Module
15
14
13
12
11
10
9
Port A
PA4.Control
PA4.Pullup_Enable
PA3.Data
PA3.Control
PA3.Pullup_Enable
PA2.Data
8
7
PA2.Control
6
PA2.Pullup_Enable
PA1.Data
5
4
PA1.Control
3
PA1.Pullup_Enable
PA0.Data
2
1
PA0.Control
0
PA0.Pullup_Enable
Note:
1. PRIVATE_SIGNAL1 should always be scanned in as zero.
Boundary-scan
Description Language
Files
Boundary-scan Description Language (BSDL) files describe Boundary-scan capable
devices in a standard format used by automated test-generation software. The order
and function of bits in the Boundary-scan Data Register are included in this description.
A BSDL file for ATmega162 is available.
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2513F–AVR–12/03
Boot Loader Support The Boot Loader Support provides a real Read-While-Write Self-programming mecha-
nism for downloading and uploading program code by the MCU itself. This feature
allows flexible application software updates controlled by the MCU using a Flash-resi-
dent Boot Loader program. The Boot Loader program can use any available data
– Read-While-Write
Self-programming
interface and associated protocol to read code and write (program) that code into the
Flash memory, or read the code from the program memory. The program code within
the Boot Loader section has the capability to write into the entire Flash, including the
Boot Loader memory. The Boot Loader can thus even modify itself, and it can also
erase itself from the code if the feature is not needed anymore. The size of the Boot
Loader memory is configurable with Fuses and the Boot Loader has two separate sets
of Boot Lock bits which can be set independently. This gives the user a unique flexibility
to select different levels of protection.
Features
• Read-While-Write Self-programming
• Flexible Boot Memory Size
• High Security (Separate Boot Lock Bits for a Flexible Protection)
• Separate Fuse to Select Reset Vector
• Optimized Page(1) Size
• Code Efficient Algorithm
• Efficient Read-Modify-Write Support
Note:
1. A page is a section in the Flash consisting of several bytes (see Table 106 on page
235) used during programming. The page organization does not affect normal
operation.
Application and Boot
Loader Flash Sections
The Flash memory is organized in two main sections, the Application section and the
Boot Loader section (see Figure 94). The size of the different sections is configured by
the BOOTSZ Fuses as shown in Table 94 on page 228 and Figure 94. These two sec-
tions can have different level of protection since they have different sets of Lock bits.
Application Section
The Application section is the section of the Flash that is used for storing the application
code. The protection level for the application section can be selected by the Application
Boot Lock bits (Boot Lock bits 0), see Table 90 on page 219. The Application section
can never store any Boot Loader code since the SPM instruction is disabled when exe-
cuted from the Application section.
BLS – Boot Loader Section
While the Application section is used for storing the application code, the The Boot
Loader software must be located in the BLS since the SPM instruction can initiate a pro-
gramming when executing from the BLS only. The SPM instruction can access the
entire Flash, including the BLS itself. The protection level for the Boot Loader section
can be selected by the Boot Loader Lock bits (Boot Lock bits 1), see Table 91 on page
219.
Read-While-Write and No Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot
Loader software update is dependent on which address that is being programmed. In
addition to the two sections that are configurable by the BOOTSZ Fuses as described
above, the Flash is also divided into two fixed sections, the Read-While-Write (RWW)
section and the No Read-While-Write (NRWW) section. The limit between the RWW-
and NRWW sections is given in Table 95 on page 228 and Figure 94 on page 218. The
main difference between the two sections is:
Read-While-Write Flash
Sections
•
When erasing or writing a page located inside the RWW section, the NRWW section
can be read during the operation.
•
When erasing or writing a page located inside the NRWW section, the CPU is halted
during the entire operation.
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ATmega162/V
Note that the user software can never read any code that is located inside the RWW
section during a Boot Loader software operation. The syntax “Read-While-Write sec-
tion” refers to which section that is being programmed (erased or written), not which
section that actually is being read during a Boot Loader software update.
RWW – Read-While-Write
Section
If a Boot Loader software update is programming a page inside the RWW section, it is
possible to read code from the Flash, but only code that is located in the NRWW sec-
tion. During an ongoing programming, the software must ensure that the RWW section
never is being read. If the user software is trying to read code that is located inside the
RWW section (i.e., by a call/jmp/lpm or an interrupt) during programming, the software
might end up in an unknown state. To avoid this, the interrupts should either be disabled
or moved to the Boot Loader section. The Boot Loader section is always located in the
NRWW section. The RWW Section Busy bit (RWWSB) in the Store Program Memory
Control Register (SPMCR) will be read as logical one as long as the RWW section is
blocked for reading. After a programming is completed, the RWWSB must be cleared by
software before reading code located in the RWW section. See “Store Program Memory
Control Register – SPMCR” on page 220. for details on how to clear RWWSB.
NRWW – No Read-While-Write The code located in the NRWW section can be read when the Boot Loader software is
Section
updating a page in the RWW section. When the Boot Loader code updates the NRWW
section, the CPU is halted during the entire Page Erase or Page Write operation.
Table 89. Read-While-Write Features
Which Section does the Z-
pointer Address During the
Programming?
Which Section Can be
Read During
Read-While-
Write
Supported?
Is the CPU
Halted?
Programming?
RWW section
NRWW section
None
No
Yes
No
NRWW section
Yes
Figure 93. Read-While-Write vs. No Read-While-Write
Read-While-Write
(RWW) Section
Z-pointer
Addresses NRWW
Section
Z-pointer
No Read-While-Write
(NRWW) Section
Addresses RWW
Section
CPU is Halted
During the Operation
Code Located in
NRWW Section
Can be Read During
the Operation
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2513F–AVR–12/03
Figure 94. Memory Sections(1)
Program Memory
BOOTSZ = '10'
Program Memory
BOOTSZ = '11'
0x0000
0x0000
Application Flash Section
Application Flash Section
End RWW
End RWW
Start NRWW
Start NRWW
Application Flash Section
Boot Loader Flash Section
Application Flash Section
Boot Loader Flash Section
End Application
End Application
Start Boot Loader
Flashend
Start Boot Loader
Flashend
0x0000
Program Memory
BOOTSZ = '01'
Program Memory
BOOTSZ = '00'
0x0000
Application Flash Section
Application flash Section
End RWW, End Application
End RWW
Start NRWW, Start Boot Loader
Start NRWW
Application Flash Section
Boot Loader Flash Section
End Application
Boot Loader Flash Section
Start Boot Loader
Flashend
Flashend
Note:
1. The parameters are given in Table 94 on page 228.
Boot Loader Lock Bits
If no Boot Loader capability is needed, the entire Flash is available for application code.
The Boot Loader has two separate sets of Boot Lock bits which can be set indepen-
dently. This gives the user a unique flexibility to select different levels of protection.
The user can select:
•
•
•
•
To protect the entire Flash from a software update by the MCU
To protect only the Boot Loader Flash section from a software update by the MCU
To protect only the Application Flash section from a software update by the MCU
Allow software update in the entire Flash
See Table 90 and Table 91 for further details. The Boot Lock bits can be set in software
and in Serial or Parallel Programming mode, but they can be cleared by a chip erase
command only. The general Write Lock (Lock bit mode 2) does not control the program-
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ATmega162/V
ming of the Flash memory by SPM instruction. Similarly, the general Read/Write Lock
(Lock bit mode 1) does not control reading nor writing by LPM/SPM, if it is attempted.
Table 90. Boot Lock Bit0 Protection Modes (Application Section)(1)
BLB0 Mode BLB02 BLB01 Protection
No restrictions for SPM or LPM accessing the Application
section.
1
2
1
1
1
0
SPM is not allowed to write to the Application section.
SPM is not allowed to write to the Application section, and
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
3
4
0
0
0
1
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
Note:
1. “1” means unprogrammed, “0” means programmed
Table 91. Boot Lock Bit1 Protection Modes (Boot Loader Section)(1)
BLB1 Mode BLB12 BLB11 Protection
No restrictions for SPM or LPM accessing the Boot Loader
section.
1
2
1
1
1
0
SPM is not allowed to write to the Boot Loader section.
SPM is not allowed to write to the Boot Loader section,
and LPM executing from the Application section is not
allowed to read from the Boot Loader section. If Interrupt
Vectors are placed in the Application section, interrupts
are disabled while executing from the Boot Loader section.
3
4
0
0
0
1
LPM executing from the Application section is not allowed
to read from the Boot Loader section. If Interrupt Vectors
are placed in the Application section, interrupts are
disabled while executing from the Boot Loader section.
Note:
1. “1” means unprogrammed, “0” means programmed
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Entering the Boot Loader Entering the Boot Loader takes place by a jump or call from the application program.
This may be initiated by a trigger such as a command received via USART, or SPI inter-
Program
face. Alternatively, the Boot Reset Fuse can be programmed so that the Reset Vector is
pointing to the Boot Flash start address after a reset. In this case, the Boot Loader is
started after a reset. After the application code is loaded, the program can start execut-
ing the application code. Note that the fuses cannot be changed by the MCU itself. This
means that once the Boot Reset Fuse is programmed, the Reset Vector will always
point to the Boot Loader Reset and the fuse can only be changed through the Serial or
Parallel Programming interface.
Table 92. Boot Reset Fuse(1)
BOOTRST
Reset Address
1
0
Reset Vector = Application Reset (address 0x0000).
Reset Vector = Boot Loader Reset (see Table 94 on page 228).
Note:
1. “1” means unprogrammed, “0” means programmed
Store Program Memory
Control Register – SPMCR
The Store Program Memory Control Register contains the control bits needed to control
the Boot Loader operations.
Bit
7
SPMIE
R/W
0
6
5
–
4
RWWSRE
R/W
3
BLBSET
R/W
0
2
PGWRT
R/W
0
1
PGERS
R/W
0
0
SPMEN
R/W
0
RWWSB
SPMCR
Read/Write
Initial Value
R
0
R
0
0
• Bit 7 – SPMIE: SPM Interrupt Enable
When the SPMIE bit is written to one, and the I-bit in the Status Register is set (one), the
SPM ready interrupt will be enabled. The SPM ready Interrupt will be executed as long
as the SPMEN bit in the SPMCR Register is cleared.
• Bit 6 – RWWSB: Read-While-Write Section Busy
When a Self-programming (Page Erase or Page Write) operation to the RWW section is
initiated, the RWWSB will be set (one) by hardware. When the RWWSB bit is set, the
RWW section cannot be accessed. The RWWSB bit will be cleared if the RWWSRE bit
is written to one after a Self-programming operation is completed. Alternatively the
RWWSB bit will automatically be cleared if a page load operation is initiated.
• Bit 5 – Res: Reserved Bit
This bit is a reserved bit in the ATmega162 and always read as zero.
• Bit 4 – RWWSRE: Read-While-Write Section Read Enable
When programming (Page Erase or Page Write) to the RWW section, the RWW section
is blocked for reading (the RWWSB will be set by hardware). To re-enable the RWW
section, the user software must wait until the programming is completed (SPMEN will be
cleared). Then, if the RWWSRE bit is written to one at the same time as SPMEN, the
next SPM instruction within four clock cycles re-enables the RWW section. The RWW
section cannot be re-enabled while the Flash is busy with a Page Erase or a Page Write
(SPMEN is set). If the RWWSRE bit is written while the Flash is being loaded, the Flash
load operation will abort and the data loaded will be lost.
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• Bit 3 – BLBSET: Boot Lock Bit Set
If this bit is written to one at the same time as SPMEN, the next SPM instruction within
four clock cycles sets Boot Lock bits, according to the data in R0. The data in R1 and
the address in the Z-pointer are ignored. The BLBSET bit will automatically be cleared
upon completion of the Lock bit set, or if no SPM instruction is executed within four clock
cycles.
An LPM instruction within three cycles after BLBSET and SPMEN are set in the SPMCR
Register, will read either the Lock bits or the Fuse bits (depending on Z0 in the Z-
pointer) into the destination register. See “Reading the Fuse and Lock Bits from Soft-
ware” on page 224 for details.
• Bit 2 – PGWRT: Page Write
If this bit is written to one at the same time as SPMEN, the next SPM instruction within
four clock cycles executes Page Write, with the data stored in the temporary buffer. The
page address is taken from the high part of the Z-pointer. The data in R1 and R0 are
ignored. The PGWRT bit will auto–clear upon completion of a Page Write, or if no SPM
instruction is executed within four clock cycles. The CPU is halted during the entire
Page Write operation if the NRWW section is addressed.
• Bit 1 – PGERS: Page Erase
If this bit is written to one at the same time as SPMEN, the next SPM instruction within
four clock cycles executes Page Erase. The page address is taken from the high part of
the Z-pointer. The data in R1 and R0 are ignored. The PGERS bit will auto-clear upon
completion of a Page Erase, or if no SPM instruction is executed within four clock
cycles. The CPU is halted during the entire Page Write operation if the NRWW section is
addressed.
• Bit 0 – SPMEN: Store Program Memory Enable
This bit enables the SPM instruction for the next four clock cycles. If written to one
together with either RWWSRE, BLBSET, PGWRT’ or PGERS, the following SPM
instruction will have a special meaning, see description above. If only SPMEN is written,
the following SPM instruction will store the value in R1:R0 in the temporary page buffer
addressed by the Z-pointer. The LSB of the Z-pointer is ignored. The SPMEN bit will
auto-clear upon completion of an SPM instruction, or if no SPM instruction is executed
within four clock cycles. During Page Erase and Page Write, the SPMEN bit remains
high until the operation is completed.
Writing any other combination than “10001”, “01001”, “00101”, “00011” or “00001” in the
lower five bits will have no effect.
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Addressing the Flash
During Self-
programming
The Z-pointer is used to address the SPM commands.
Bit
15
Z15
Z7
7
14
Z14
Z6
6
13
Z13
Z5
5
12
Z12
Z4
4
11
Z11
Z3
3
10
Z10
Z2
2
9
Z9
Z1
1
8
Z8
Z0
0
ZH (R31)
ZL (R30)
Since the Flash is organized in pages (see Table 106 on page 235), the Program
Counter can be treated as having two different sections. One section, consisting of the
least significant bits, is addressing the words within a page, while the most significant
bits are addressing the pages. This is shown in Figure 95. Note that the Page Erase and
Page Write operations are addressed independently. Therefore it is of major importance
that the Boot Loader software addresses the same page in both the Page Erase and
Page Write operation. Once a programming operation is initiated, the address is latched
and the Z-pointer can be used for other operations.
The only SPM operation that does not use the Z-pointer is Setting the Boot Loader Lock
bits. The content of the Z-pointer is ignored and will have no effect on the operation. The
LPM instruction does also use the Z-pointer to store the address. Since this instruction
addresses the Flash byte-by-byte, also the LSB (bit Z0) of the Z-pointer is used.
Figure 95. Addressing the Flash during SPM(1)
BIT 15
ZPCMSB
ZPAGEMSB
1
0
0
Z - REGISTER
PCMSB
PAGEMSB
PCWORD
PROGRAM
COUNTER
PCPAGE
PAGE ADDRESS
WITHIN THE FLASH
WORD ADDRESS
WITHIN A PAGE
PROGRAM MEMORY
PAGE
PAGE
INSTRUCTION WORD
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
Notes: 1. The different variables used in Figure 95 are listed in Table 96 on page 229.
2. PCPAGE and PCWORD are listed in Table 106 on page 235.
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Self-programming the
Flash
The program memory is updated in a page by page fashion. Before programming a
page with the data stored in the temporary page buffer, the page must be erased. The
temporary page buffer is filled one word at a time using SPM and the buffer can be filled
either before the Page Erase command or between a Page Erase and a Page Write
operation:
Alternative 1, fill the buffer before a Page Erase
•
•
•
Fill temporary page buffer
Perform a Page Erase
Perform a Page Write
Alternative 2, fill the buffer after Page Erase
•
•
•
Perform a Page Erase
Fill temporary page buffer
Perform a Page Write
If only a part of the page needs to be changed, the rest of the page must be stored (for
example in the temporary page buffer) before the erase, and then be rewritten. When
using alternative 1, the Boot Loader provides an effective Read-Modify-Write feature
which allows the user software to first read the page, do the necessary changes, and
then write back the modified data. If alternative 2 is used, it is not possible to read the
old data while loading since the page is already erased. The temporary page buffer can
be accessed in a random sequence. It is essential that the page address used in both
the Page Erase and Page Write operation is addressing the same page. See “Simple
Assembly Code Example for a Boot Loader” on page 226 for an assembly code
example.
Performing Page Erase by
SPM
To execute Page Erase, set up the address in the Z-pointer, write “X0000011” to
SPMCR and execute SPM within four clock cycles after writing SPMCR. The data in R1
and R0 is ignored. The page address must be written to PCPAGE in the Z-register.
Other bits in the Z-pointer will be ignored during this operation.
•
Page Erase to the RWW section: The NRWW section can be read during the Page
Erase.
•
Page Erase to the NRWW section: The CPU is halted during the operation.
Filling the Temporary Buffer
(Page Loading)
To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write
“00000001” to SPMCR and execute SPM within four clock cycles after writing SPMCR.
The content of PCWORD in the Z-register is used to address the data in the temporary
buffer. The temporary buffer will auto-erase after a Page Write operation or by writing
the RWWSRE bit in SPMCR. It is also erased after a System Reset. Note that it is not
possible to write more than one time to each address without erasing the temporary
buffer.
Note:
If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded
will be lost.
Performing a Page Write
To execute Page Write, set up the address in the Z-pointer, write “X0000101” to
SPMCR and execute SPM within four clock cycles after writing SPMCR. The data in R1
and R0 is ignored. The page address must be written to PCPAGE. Other bits in the Z-
pointer must be written zero during this operation.
•
Page Write to the RWW section: The NRWW section can be read during the Page
Write.
•
Page Write to the NRWW section: The CPU is halted during the operation.
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Using the SPM Interrupt
If the SPM interrupt is enabled, the SPM interrupt will generate a constant interrupt
when the SPMEN bit in SPMCR is cleared. This means that the interrupt can be used
instead of polling the SPMCR Register in software. When using the SPM interrupt, the
Interrupt Vectors should be moved to the BLS section to avoid that an interrupt is
accessing the RWW section when it is blocked for reading. How to move the interrupts
is described in “Interrupts” on page 56.
Consideration while Updating Special care must be taken if the user allows the Boot Loader section to be updated by
BLS
leaving Boot Lock bit11 unprogrammed. An accidental write to the Boot Loader itself can
corrupt the entire Boot Loader, and further software updates might be impossible. If it is
not necessary to change the Boot Loader software itself, it is recommended to program
the Boot Lock bit11 to protect the Boot Loader software from any internal software
changes.
Prevent Reading the RWW
Section During Self-
programming
During Self-programming (either Page Erase or Page Write), the RWW section is
always blocked for reading. The user software itself must prevent that this section is
addressed during the self programming operation. The RWWSB in the SPMCR will be
set as long as the RWW section is busy. During Self-programming the Interrupt Vector
table should be moved to the BLS as described in “Interrupts” on page 56, or the inter-
rupts must be disabled. Before addressing the RWW section after the programming is
completed, the user software must clear the RWWSB by writing the RWWSRE. See
“Simple Assembly Code Example for a Boot Loader” on page 226 for an example.
Setting the Boot Loader Lock To set the Boot Loader Lock bits, write the desired data to R0, write “X0001001” to
Bits by SPM
SPMCR and execute SPM within four clock cycles after writing SPMCR. The only
accessible Lock bits are the Boot Lock bits that may prevent the Application and Boot
Loader section from any software update by the MCU.
Bit
7
6
5
4
3
2
1
0
R0
1
1
BLB12
BLB11
BLB02
BLB01
1
1
See Table 90 and Table 91 for how the different settings of the Boot Loader bits affect
the Flash access.
If bits 5..2 in R0 are cleared (zero), the corresponding Boot Lock bit will be programmed
if an SPM instruction is executed within four cycles after BLBSET and SPMEN are set in
SPMCR. The Z-pointer is don’t care during this operation, but for future compatibility it is
recommended to load the Z-pointer with 0x0001 (same as used for reading the Lock
bits). For future compatibility it is also recommended to set bits 7, 6, 1, and 0 in R0 to “1”
when writing the Lock bits. When programming the Lock bits the entire Flash can be
read during the operation.
EEPROM Write Prevents
Writing to SPMCR
Note that an EEPROM write operation will block all software programming to Flash.
Reading the Fuses and Lock bits from software will also be prevented during the
EEPROM write operation. It is recommended that the user checks the status bit (EEWE)
in the EECR Register and verifies that the bit is cleared before writing to the SPMCR
Register.
Reading the Fuse and Lock
Bits from Software
It is possible to read both the Fuse and Lock bits from software. To read the Lock bits,
load the Z-pointer with 0x0001 and set the BLBSET and SPMEN bits in SPMCR. When
an LPM instruction is executed within three CPU cycles after the BLBSET and SPMEN
bits are set in SPMCR, the value of the Lock bits will be loaded in the destination regis-
ter. The BLBSET and SPMEN bits will auto-clear upon completion of reading the Lock
bits or if no LPM instruction is executed within three CPU cycles or no SPM instruction is
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executed within four CPU cycles. When BLBSET and SPMEN are cleared, LPM will
work as described in the Instruction set Manual.
Bit
7
6
5
4
3
2
1
0
Rd
–
–
BLB12
BLB11
BLB02
BLB01
LB2
LB1
The algorithm for reading the Fuse Low byte is similar to the one described above for
reading the Lock bits. To read the Fuse Low byte, load the Z-pointer with 0x0000 and
set the BLBSET and SPMEN bits in SPMCR. When an LPM instruction is executed
within three cycles after the BLBSET and SPMEN bits are set in the SPMCR, the value
of the Fuse Low byte (FLB) will be loaded in the destination register as shown below.
Refer to Table 101 on page 232 for a detailed description and mapping of the Fuse Low
byte.
Bit
7
6
5
4
3
2
1
0
Rd
FLB7
FLB6
FLB5
FLB4
FLB3
FLB2
FLB1
FLB0
Similarly, when reading the Fuse High byte, load 0x0003 in the Z-pointer. When an LPM
instruction is executed within three cycles after the BLBSET and SPMEN bits are set in
the SPMCR, the value of the Fuse High byte (FHB) will be loaded in the destination reg-
ister as shown below. Refer to Table 99 on page 231 for detailed description and
mapping of the Fuse High byte.
Bit
7
6
5
4
3
2
1
0
Rd
FHB7
FHB6
FHB5
FHB4
FHB3
FHB2
FHB1
FHB0
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an LPM
instruction is executed within three cycles after the BLBSET and SPMEN bits are set in
the SPMCR, the value of the Extended Fuse byte (EFB) will be loaded in the destination
register as shown below. Refer to Table 99 on page 231 for detailed description and
mapping of the Extended Fuse byte.
Bit
7
6
5
4
3
2
1
0
Rd
–
–
–
EFB4
EFB3
EFB2
EFB1
–
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that
are unprogrammed, will be read as one.
Preventing Flash Corruption
During periods of low VCC, the Flash program can be corrupted because the supply volt-
age is too low for the CPU and the Flash to operate properly. These issues are the same
as for board level systems using the Flash, and the same design solutions should be
applied.
A Flash program corruption can be caused by two situations when the voltage is too low.
First, a regular write sequence to the Flash requires a minimum voltage to operate cor-
rectly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage
for executing instructions is too low.
Flash corruption can easily be avoided by following these design recommendations (one
is sufficient):
1. If there is no need for a Boot Loader update in the system, program the Boot
Loader Lock bits to prevent any Boot Loader software updates.
2. Keep the AVR RESET active (low) during periods of insufficient power supply
voltage. This can be done by enabling the internal Brown-out Detector (BOD) if
the operating voltage matches the detection level. If not, an external low VCC
Reset Protection circuit can be used. If a Reset occurs while a write operation is
in progress, the write operation will be completed provided that the power supply
voltage is sufficient.
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3. Keep the AVR core in Power-down sleep mode during periods of low VCC. This
will prevent the CPU from attempting to decode and execute instructions, effec-
tively protecting the SPMCR Register and thus the Flash from unintentional
writes.
Programming Time for Flash
When Using SPM
The calibrated RC Oscillator is used to time Flash accesses. Table 93 shows the typical
programming time for Flash accesses from the CPU.
Table 93. SPM Programming Time
Symbol
Min Programming Time Max Programming Time
3.7ms 4.5ms
Flash Write (Page Erase, Page Write,
and Write Lock bits by SPM)
Simple Assembly Code
Example for a Boot Loader
;-the routine writes one page of data from RAM to Flash
; the first data location in RAM is pointed to by the Y pointer
; the first data location in Flash is pointed to by the Z-pointer
;-error handling is not included
;-the routine must be placed inside the boot space
; (at least the Do_spm sub routine). Only code inside NRWW section can
; be read during self-programming (page erase and page write).
;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24),
; loophi (r25), spmcrval (r20)
; storing and restoring of registers is not included in the routine
; register usage can be optimized at the expense of code size
;-It is assumed that either the interrupt table is moved to the Boot
; loader section or that the interrupts are disabled.
.equ PAGESIZEB = PAGESIZE*2
;PAGESIZEB is page size in BYTES, not
; words
.org SMALLBOOTSTART
Write_page:
; page erase
ldi
spmcrval, (1<<PGERS) | (1<<SPMEN)
call Do_spm
; re-enable the RWW section
ldi
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
call Do_spm
; transfer data from RAM to Flash page buffer
ldi
ldi
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
;init loop variable
;not required for PAGESIZEB<=256
Wrloop:
ld
r0, Y+
ld
r1, Y+
ldi
spmcrval, (1<<SPMEN)
call Do_spm
adiw ZH:ZL, 2
sbiw loophi:looplo, 2
brne Wrloop
;use subi for PAGESIZEB<=256
; execute page write
subi ZL, low(PAGESIZEB)
sbci ZH, high(PAGESIZEB)
;restore pointer
;not required for PAGESIZEB<=256
ldi
spmcrval, (1<<PGWRT) | (1<<SPMEN)
call Do_spm
; re-enable the RWW section
ldi
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
call Do_spm
; read back and check, optional
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ldi
ldi
looplo, low(PAGESIZEB)
loophi, high(PAGESIZEB)
;init loop variable
;not required for PAGESIZEB<=256
;restore pointer
subi YL, low(PAGESIZEB)
sbci YH, high(PAGESIZEB)
Rdloop:
lpm
ld
r0, Z+
r1, Y+
cpse r0, r1
jmp Error
sbiw loophi:looplo, 1
brne Rdloop
;use subi for PAGESIZEB<=256
; return to RWW section
; verify that RWW section is safe to read
Return:
in
temp1, SPMCR
sbrs temp1, RWWSB
; If RWWSB is set, the RWW section is not
; ready yet
ret
; re-enable the RWW section
ldi
spmcrval, (1<<RWWSRE) | (1<<SPMEN)
call Do_spm
rjmp Return
Do_spm:
; check for previous SPM complete
Wait_spm:
in
temp1, SPMCR
sbrc temp1, SPMEN
rjmp Wait_spm
; input: spmcrval determines SPM action
; disable interrupts if enabled, store status
in
temp2, SREG
cli
; check that no EEPROM write access is present
Wait_ee:
sbic EECR, EEWE
rjmp Wait_ee
; SPM timed sequence
out
spm
SPMCR, spmcrval
; restore SREG (to enable interrupts if originally enabled)
out
ret
SREG, temp2
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ATmega162 Boot Loader
Parameters
In Table 94 through Table 96, the parameters used in the description of the self pro-
gramming are given.
Table 94. Boot Size Configuration(1)
Boot Reset
Boot
Loader
Flash
Address
(Start Boot
Loader
Application
Flash
Section
End
Application
Section
Boot
Size
BOOTSZ1
BOOTSZ0
Pages
Section
Section)
128
words
0x0000 -
0x1F7F
0x1F80 -
0x1FFF
1
1
2
0x1F7F
0x1EFF
0x1DFF
0x1BFF
0x1F80
0x1F00
0x1E00
0x1C00
256
words
0x0000 -
0x1EFF
0x1F00 -
0x1FFF
1
0
0
0
1
0
4
512
words
0x0000 -
0x1DFF
0x1E00 -
0x1FFF
8
1024
words
0x0000 -
0x1BFF
0x1C00-
0x1FFF
16
Note:
1. The different BOOTSZ Fuse configurations are shown in Figure 94
Table 95. Read-While-Write Limit
Section
Pages
112
Address
Read-While-Write section (RWW)
No Read-While-Write section (NRWW)
0x0000 - 0x1BFF
0x1C00 - 0x1FFF
16
Note:
1. For details about these two section, see “NRWW – No Read-While-Write Section” on
page 217 and “RWW – Read-While-Write Section” on page 217
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Table 96. Explanation of Different Variables Used in Figure 95 and the Mapping to the
Z-pointer(1)
Corresponding
Variable
Z-value
Description
12
5
Most significant bit in the Program Counter.
(The Program Counter is 13 bits PC[12:0])
PCMSB
Most significant bit which is used to address
the words within one page (64 words in a page
requires 6 bits PC [5:0]).
PAGEMSB
ZPCMSB
Z13
Z6
Bit in Z-register that is mapped to PCMSB.
Because Z0 is not used, the ZPCMSB equals
PCMSB + 1.
Bit in Z-register that is mapped to PCMSB.
Because Z0 is not used, the ZPAGEMSB
equals PAGEMSB + 1.
ZPAGEMSB
PCPAGE
PC[12:6]
PC[5:0]
Z13:Z7
Z6:Z1
Program Counter page address: Page select,
for Page Erase and Page Write
Program Counter word address: Word select,
for filling temporary buffer (must be zero during
Page Write operation)
PCWORD
Note:
1. Z15:Z14: always ignored
Z0: should be zero for all SPM commands, byte select for the LPM instruction.
See “Addressing the Flash During Self-programming” on page 222 for details about
the use of Z-pointer during Self-programming.
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Memory
Programming
Program And Data
Memory Lock Bits
The ATmega162 provides six Lock bits which can be left unprogrammed (“1”) or can be
programmed (“0”) to obtain the additional features listed in Table 98. The Lock bits can
only be erased to “1” with the Chip Erase command.
Table 97. Lock Bit Byte(1)
Bit no
Description
–
Default Value
Lock Bit Byte
7
6
5
4
3
2
1
0
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
–
BLB12
BLB11
BLB02
BLB01
LB2
Boot Lock bit
Boot Lock bit
Boot Lock bit
Boot Lock bit
Lock bit
LB1
Lock bit
Note:
Table 98. Lock Bit Protection Modes(1)(2)
Memory Lock Bits Protection Type
1. “1” means unprogrammed, “0” means programmed
LB Mode
LB2
LB1
1
1
1
No memory lock features enabled.
Further programming of the Flash and EEPROM is
disabled in Parallel and SPI/JTAG Serial Programming
mode. The Fuse bits are locked in both Serial and Parallel
Programming mode(1).
2
1
0
0
0
Further programming and verification of the Flash and
EEPROM is disabled in Parallel and SPI/JTAG Serial
Programming mode. Also the Boot Lock bits and the Fuse
bits are locked in both Serial and Parallel Programming
mode(1).
3
BLB0 Mode BLB02 BLB01
No restrictions for SPM or LPM accessing the Application
section.
1
2
1
1
1
0
SPM is not allowed to write to the Application section.
SPM is not allowed to write to the Application section, and
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
3
4
0
0
0
1
LPM executing from the Boot Loader section is not
allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts
are disabled while executing from the Application section.
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Table 98. Lock Bit Protection Modes(1)(2) (Continued)
Memory Lock Bits
Protection Type
BLB1 Mode BLB12 BLB11
No restrictions for SPM or LPM accessing the Boot Loader
section.
1
2
1
1
1
0
SPM is not allowed to write to the Boot Loader section.
SPM is not allowed to write to the Boot Loader section,
and LPM executing from the Application section is not
allowed to read from the Boot Loader section. If Interrupt
Vectors are placed in the Application section, interrupts
are disabled while executing from the Boot Loader section.
3
4
0
0
0
1
LPM executing from the Application section is not allowed
to read from the Boot Loader section. If Interrupt Vectors
are placed in the Application section, interrupts are
disabled while executing from the Boot Loader section.
Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Fuse Bits
The ATmega162 has three Fuse bytes. Table 100 and Table 101 describe briefly the
functionality of all the fuses and how they are mapped into the Fuse bytes. Note that the
fuses are read as logical zero, “0”, if they are programmed.
Table 99. Extended Fuse Byte(1)(2)
Fuse Low Byte
Bit no Description
Default Value
–
7
6
5
–
–
–
1
1
1
–
–
ATmega161 compatibility
mode
M161C
4
3
2
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
Brown-out Detector
trigger level
BODLEVEL2(2)
BODLEVEL1(2)
Brown-out Detector
trigger level
Brown-out Detector
trigger level
BODLEVEL0(2)
–
1
0
1 (unprogrammed)
1
–
Notes: 1. See “ATmega161 Compatibility Mode” on page 5 for details.
2. See Table 19 on page 49 for BODLEVEL Fuse decoding.
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Table 100. Fuse High Byte
Fuse Low Byte Bit no Description
Default Value
1 (unprogrammed, OCD
disabled)
OCDEN(3)
JTAGEN(4)
7
6
Enable OCD
Enable JTAG
0 (programmed, JTAG
enabled)
Enable Serial Program and Data
Downloading
0 (programmed, SPI prog.
enabled)
SPIEN(1)
WDTON
EESAVE
5
4
3
Watchdog Timer always on
1 (unprogrammed)
EEPROM memory is preserved
through the Chip Erase
1 (unprogrammed,
EEPROM not preserved)
Select Boot Size (see Table 94 for
details)
BOOTSZ1
2
0 (programmed)(2)
Select Boot Size (see Table 94 for
details)
BOOTSZ0
BOOTRST
1
0
0 (programmed)(2)
1 (unprogrammed)
Select Reset Vector
Notes: 1. The SPIEN Fuse is not accessible in SPI Serial Programming mode.
2. The default value of BOOTSZ1:0 results in maximum Boot Size. See Table 94 on
page 228 for details.
3. Never ship a product with the OCDEN Fuse programmed regardless of the setting of
Lock bits and the JTAGEN Fuse. A programmed OCDEN Fuse enables some parts of
the clock system to be running in all sleep modes. This may increase the power
consumption.
4. If the JTAG interface is left unconnected, the JTAGEN fuse should if possible be dis-
abled. This to avoid static current at the TDO pin in the JTAG interface.
Table 101. Fuse Low Byte
Fuse Low Byte Bit no Description
Default value
CKDIV8(4)
CKOUT(3)
SUT1
7
6
5
4
3
2
1
0
Divide clock by 8
Clock Output
0 (programmed)
1 (unprogrammed)
1 (unprogrammed)(1)
0 (programmed)(1)
0 (programmed)(2)
0 (programmed)(2)
1 (unprogrammed)(2)
0 (programmed)(2)
Select start-up time
Select start-up time
Select Clock source
Select Clock source
Select Clock source
Select Clock source
SUT0
CKSEL3
CKSEL2
CKSEL1
CKSEL0
Notes: 1. The default value of SUT1:0 results in maximum start-up time for the default clock
source. See Table 12 on page 37 for details.
2. The default setting of CKSEL3:0 results in Internal RC Oscillator @ 8 MHz. See
Table 5 on page 34 for details.
3. The CKOUT Fuse allow the system clock to be output on PortB 0. See “Clock output
buffer” on page 38 for details.
4. See “System Clock Prescaler” on page 39 for details.
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are
locked if Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the
Lock bits.
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Latching of Fuses
The Fuse values are latched when the device enters Programming mode and changes
of the Fuse values will have no effect until the part leaves Programming mode. This
does not apply to the EESAVE Fuse which will take effect once it is programmed. The
Fuses are also latched on Power-up in Normal mode.
Signature Bytes
All Atmel microcontrollers have a 3-byte signature code which identifies the device. This
code can be read in both Serial and Parallel mode, also when the device is locked. The
three bytes reside in a separate address space.
For the ATmega162 the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x001: 0x94 (indicates 16KB Flash memory).
3. 0x002: 0x04 (indicates ATmega162 device when 0x001 is 0x94).
Calibration Byte
The ATmega162 has a one-byte calibration value for the internal RC Oscillator. This
byte resides in the high byte of address 0x000 in the signature address space. During
Reset, this byte is automatically written into the OSCCAL Register to ensure correct fre-
quency of the calibrated RC Oscillator.
Parallel Programming
Parameters, Pin
Mapping, and
This section describes how to parallel program and verify Flash Program memory,
EEPROM Data memory, Memory Lock bits, and Fuse bits in the ATmega162. Pulses
are assumed to be at least 250 ns unless otherwise noted.
Commands
Signal Names
In this section, some pins of the ATmega162 are referenced by signal names describing
their functionality during parallel programming, see Figure 96 and Table 102. Pins not
described in the following table are referenced by pin names.
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a posi-
tive pulse. The bit coding is shown in Table 104.
When pulsing WR or OE, the command loaded determines the action executed. The dif-
ferent Commands are shown in Table 105.
Figure 96. Parallel Programming
+5V
RDY/BSY
OE
PD1
PD2
PD3
PD4
PD5
PD6
PD7
VCC
PB7 - PB0
DATA
WR
BS1
XA0
XA1
PAGEL
+12 V
BS2
RESET
PA0
XTAL1
GND
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Table 102. Pin Name Mapping
Signal Name in
Programming Mode Pin Name I/O Function
0: Device is busy programming, 1: Device is ready
for new command
RDY/BSY
PD1
O
OE
PD2
PD3
I
I
Output Enable (Active low)
Write Pulse (Active low)
WR
Byte Select 1 (“0” selects low byte, “1” selects high
byte)
BS1
PD4
I
XA0
XA1
PD5
PD6
PD7
I
I
I
XTAL Action Bit 0
XTAL Action Bit 1
PAGEL
Program Memory and EEPROM data Page Load
Byte Select 2 (“0” selects low byte, “1” selects 2’nd
high byte)
BS2
PA0
I
DATA
PB7 - 0
I/O Bi-directional Data bus (Output when OE is low)
Table 103. Pin Values used to Enter Programming Mode
Pin
PAGEL
XA1
Symbol
Value
Prog_enable[3]
Prog_enable[2]
Prog_enable[1]
Prog_enable[0]
0
0
0
0
XA0
BS1
Table 104. XA1 and XA0 Coding
XA1 XA0 Action when XTAL1 is Pulsed
0
0
1
1
0
1
0
1
Load Flash or EEPROM address (High or low address byte determined by BS1)
Load Data (High or Low data byte for Flash determined by BS1).
Load Command
No Action, Idle
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Table 105. Command Byte Bit Coding
Command Byte
1000 0000
0100 0000
0010 0000
0001 0000
0001 0001
0000 1000
0000 0100
0000 0010
0000 0011
Command Executed
Chip Erase
Write Fuse Bits
Write Lock Bits
Write Flash
Write EEPROM
Read Signature Bytes and Calibration byte
Read Fuse and Lock Bits
Read Flash
Read EEPROM
Table 106. No. of Words in a Page and no. of Pages in the Flash
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
8K words (16K bytes)
64 words
PC[5:0]
128
PC[12:6]
12
Table 107. No. of Words in a Page and no. of Pages in the EEPROM
EEPROM Size
Page Size
PCWORD
No. of pages
PCPAGE
EEAMSB
512 bytes
4 bytes
EEA[1:0]
128
EEA[8:2]
8
Parallel Programming
Enter Programming Mode
The following algorithm puts the device in Parallel Programming mode:
1. Apply 4.5 - 5.5V between VCC and GND, and wait at least 100 µs.
2. Set RESET to “0” and toggle XTAL1 at least six times.
3. Set the Prog_enable pins listed in Table 103 on page 234 to “0000” and wait at
least 100 ns.
4. Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns
after +12V has been applied to RESET, will cause the device to fail entering Pro-
gramming mode.
Considerations for Efficient
Programming
The loaded command and address are retained in the device during programming. For
efficient programming, the following should be considered.
•
•
•
The command needs only be loaded once when writing or reading multiple memory
locations.
Skip writing the data value 0xFF, that is the contents of the entire EEPROM (unless
the EESAVE Fuse is programmed) and Flash after a Chip Erase.
Address high byte needs only be loaded before programming or reading a new 256-
word window in Flash or 256 byte EEPROM. This consideration also applies to
Signature bytes reading.
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Chip Erase
The Chip Erase will erase the Flash and EEPROM(1) memories plus Lock bits. The Lock
bits are not reset until the program memory has been completely erased. The Fuse bits
are not changed. A Chip Erase must be performed before the Flash or EEPROM are
reprogrammed.
Note:
1. The EEPRPOM memory is preserved during chip erase if the EESAVE Fuse is
programmed.
Load Command “Chip Erase”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “1000 0000”. This is the command for Chip Erase.
4. Give XTAL1 a positive pulse. This loads the command.
5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low.
6. Wait until RDY/BSY goes high before loading a new command.
Programming the Flash
The Flash is organized in pages, see Table 106 on page 235. When programming the
Flash, the program data is latched into a page buffer. This allows one page of program
data to be programmed simultaneously. The following procedure describes how to pro-
gram the entire Flash memory:
A. Load Command “Write Flash”
1. Set XA1, XA0 to “10”. This enables command loading.
2. Set BS1 to “0”.
3. Set DATA to “0001 0000”. This is the command for Write Flash.
4. Give XTAL1 a positive pulse. This loads the command.
B. Load Address Low byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “0”. This selects low address.
3. Set DATA = Address low byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the address low byte.
C. Load Data Low Byte
1. Set XA1, XA0 to “01”. This enables data loading.
2. Set DATA = Data low byte (0x00 - 0xFF).
3. Give XTAL1 a positive pulse. This loads the data byte.
D. Load Data High Byte
1. Set BS1 to “1”. This selects high data byte.
2. Set XA1, XA0 to “01”. This enables data loading.
3. Set DATA = Data high byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the data byte.
E. Latch Data
1. Set BS1 to “1”. This selects high data byte.
2. Give PAGEL a positive pulse. This latches the data bytes (See Figure 98 for sig-
nal waveforms).
F. Repeat B through E until the entire buffer is filled or until all data within the page is
loaded.
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While the lower bits in the address are mapped to words within the page, the higher bits
address the pages within the FLASH. This is illustrated in Figure 97 on page 237. Note
that if less than eight bits are required to address words in the page (pagesize < 256),
the most significant bit(s) in the address low byte are used to address the page when
performing a Page Write.
G. Load Address High byte
1. Set XA1, XA0 to “00”. This enables address loading.
2. Set BS1 to “1”. This selects high address.
3. Set DATA = Address high byte (0x00 - 0xFF).
4. Give XTAL1 a positive pulse. This loads the address high byte.
H. Program Page
1. Give WR a negative pulse. This starts programming of the entire page of data.
RDY/BSY goes low.
2. Wait until RDY/BSY goes high. (See Figure 98 for signal waveforms)
I. Repeat B through H until the entire Flash is programmed or until all data has been
programmed.
J. End Page Programming
1. 1. Set XA1, XA0 to “10”. This enables command loading.
2. Set DATA to “0000 0000”. This is the command for No Operation.
3. Give XTAL1 a positive pulse. This loads the command, and the internal write sig-
nals are reset.
Figure 97. Addressing the Flash which is Organized in Pages(1)
PCMSB
PAGEMSB
PROGRAM
COUNTER
PCPAGE
PCWORD
PAGE ADDRESS
WITHIN THE FLASH
WORD ADDRESS
WITHIN A PAGE
PROGRAM MEMORY
PAGE
PAGE
INSTRUCTION WORD
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
Note:
1. PCPAGE and PCWORD are listed in Table 106 on page 235.
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Figure 98. Programming the Flash Waveforms
F
A
B
C
D
E
B
C
D
E
G
H
0x10
ADDR. LOW DATA LOW
DATA HIGH
ADDR. LOW DATA LOW
DATA HIGH
XX
ADDR. HIGH
XX
XX
DATA
XA1
XA0
BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
BS2
Note:
“XX” is don’t care. The letters refer to the programming description above.
Programming the EEPROM
The EEPROM is organized in pages, see Table 107 on page 235. When programming
the EEPROM, the program data is latched into a page buffer. This allows one page of
data to be programmed simultaneously. The programming algorithm for the EEPROM
data memory is as follows (refer to “Programming the Flash” on page 236 for details on
Command, Address and Data loading):
1. A: Load Command “0001 0001”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. C: Load Data (0x00 - 0xFF).
5. E: Latch data (give PAGEL a positive pulse).
K: Repeat 3 through 5 until the entire buffer is filled.
L: Program EEPROM page
1. Set BS to “0”.
2. Give WR a negative pulse. This starts programming of the EEPROM page.
RDY/BSY goes low.
3. Wait until to RDY/BSY goes high before programming the next page
(See Figure 99 for signal waveforms).
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Figure 99. Programming the EEPROM Waveforms
K
A
G
B
C
E
B
C
E
L
0x11
ADDR. HIGH ADDR. LOW
DATA
ADDR. LOW
DATA
XX
XX
DATA
XA1
XA0
BS1
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
BS2
Reading the Flash
The algorithm for reading the Flash memory is as follows (refer to “Programming the
Flash” on page 236 for details on Command and Address loading):
1. A: Load Command “0000 0010”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. Set OE to “0”, and BS1 to “0”. The Flash word low byte can now be read at DATA.
5. Set BS to “1”. The Flash word high byte can now be read at DATA.
6. Set OE to “1”.
Reading the EEPROM
The algorithm for reading the EEPROM memory is as follows (refer to “Programming the
Flash” on page 236 for details on Command and Address loading):
1. A: Load Command “0000 0011”.
2. G: Load Address High Byte (0x00 - 0xFF).
3. B: Load Address Low Byte (0x00 - 0xFF).
4. Set OE to “0”, and BS1 to “0”. The EEPROM Data byte can now be read at
DATA.
5. Set OE to “1”.
Programming the Fuse Low
Bits
The algorithm for programming the Fuse Low bits is as follows (refer to “Programming
the Flash” on page 236 for details on Command and Data loading):
1. A: Load Command “0100 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “0” and BS2 to “0”. This selects low data byte.
4. Give WR a negative pulse and wait for RDY/BSY to go high.
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Programming the Fuse High
Bits
The algorithm for programming the Fuse high bits is as follows (refer to “Programming
the Flash” on page 236 for details on Command and Data loading):
1. A: Load Command “0100 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “1” and BS2 to “0”. This selects high data byte.
4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. Set BS1 to “0”. This selects low data byte.
Programming the Extended
Fuse Bits
The algorithm for programming the Extended Fuse bits is as follows (refer to “Program-
ming the Flash” on page 236 for details on Command and Data loading):
1. 1. A: Load Command “0100 0000”.
2. 2. C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse
bit.
3. 3. Set BS1 to “0” and BS2 to “1”. This selects extended data byte.
4. 4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. 5. Set BS2 to “0”. This selects low data byte.
Figure 100. Programming the FUSES Waveforms
Write Fuse Low byte
Write Fuse high byte
Write Extended Fuse byte
A
C
A
C
A
C
0x40
DATA
XX
0x40
DATA
XX
0x40
DATA
XX
DATA
XA1
XA0
BS1
BS2
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
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Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (refer to “Programming the
Flash” on page 236 for details on Command and Data loading):
1. A: Load Command “0010 0000”.
2. C: Load Data Low Byte. Bit n = “0” programs the Lock bit. If LB mode 3 is pro-
grammed (LB1 and LB2 is programmed), it is not possible to program the Boot
Lock Bits by any external Programming mode.
3. Give WR a negative pulse and wait for RDY/BSY to go high.
The Lock bits can only be cleared by executing Chip Erase.
Reading the Fuse and Lock
Bits
The algorithm for reading the Fuse and Lock bits is as follows (refer to “Programming
the Flash” on page 236 for details on Command loading):
1. A: Load Command “0000 0100”.
2. Set OE to “0”, BS2 to “0” and BS1 to “0”. The status of the Fuse Low bits can
now be read at DATA (“0” means programmed).
3. Set OE to “0”, BS2 to “1” and BS1 to “1”. The status of the Fuse High bits can
now be read at DATA (“0” means programmed).
4. Set OE to “0”, BS2 to “1” and BS1 to “0”. The status of the Extended Fuse bits
can now be read at DATA (“0” means programmed).
5. Set OE to “0”, BS2 to “0” and BS1 to “1”. The status of the Lock bits can now be
read at DATA (“0” means programmed).
6. Set OE to “1”.
Figure 101. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
0
Fuse Low Byte
Extended Fuse Byte
Lock Bits
0
1
1
0
DATA
BS2
BS1
Fuse High Byte
1
BS2
Reading the Signature Bytes
The algorithm for reading the signature bytes is as follows (refer to “Programming the
Flash” on page 236 for details on Command and Address loading):
1. A: Load Command “0000 1000”.
2. B: Load Address Low Byte (0x00 - 0x02).
3. Set OE to “0”, and BS to “0”. The selected Signature byte can now be read at
DATA.
4. Set OE to “1”.
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Reading the Calibration Byte
The algorithm for reading the calibration byte is as follows (refer to “Programming the
Flash” on page 236 for details on Command and Address loading):
1. A: Load Command “0000 1000”.
2. B: Load Address Low Byte, 0x00.
3. Set OE to “0”, and BS1 to “1”. The Calibration byte can now be read at DATA.
4. Set OE to “1”.
Parallel Programming
Characteristics
Figure 102. Parallel Programming Timing, Including some General Timing
Requirements
tXLWL
tXHXL
XTAL1
tDVXH
tXLDX
Data & Contol
(DATA, XA0/1, BS1, BS2)
tBVPH
tPLBX tBVWL
tWLBX
PAGEL
tPHPL
tWLWH
WR
tPLWL
WLRL
RDY/BSY
tWLRH
Figure 103. Parallel Programming Timing, Loading Sequence with Timing
Requirements(1)
LOAD DATA
LOAD ADDRESS
(LOW BYTE)
LOAD DATA
(LOW BYTE)
LOAD DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
tXLPH
tXLXH
tPLXH
XTAL1
BS1
PAGEL
DATA
ADDR0 (low byte)
DATA (low byte)
DATA (high byte)
ADDR1 (low byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 102 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to loading operation.
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Figure 104. Parallel Programming Timing, Reading Sequence (within the Same Page)
with Timing Requirements(1)
LOAD ADDRESS
(LOW BYTE)
READ DATA
(LOW BYTE)
READ DATA
(HIGH BYTE)
LOAD ADDRESS
(LOW BYTE)
tXLOL
XTAL1
BS1
tBVDV
tOLDV
OE
tOHDZ
ADDR1 (low byte)
DATA (high byte)
DATA
ADDR0 (low byte)
DATA (low byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 102 (i.e., tDVXH, tXHXL, and tXLDX) also apply
to reading operation.
Table 108. Parallel Programming Characteristics, VCC = 5 V ± 10%
Symbol
VPP
Parameter
Min
Typ
Max
12.5
250
Units
V
Programming Enable Voltage
Programming Enable Current
Data and Control Valid before XTAL1 High
XTAL1 Low to XTAL1 High
XTAL1 Pulse Width High
11.5
IPP
µA
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
µs
ms
ms
ns
tDVXH
tXLXH
tXHXL
tXLDX
tXLWL
tXLPH
tPLXH
tBVPH
tPHPL
tPLBX
tWLBX
tPLWL
tBVWL
tWLWH
tWLRL
tWLRH
tWLRH_CE
tXLOL
67
200
150
67
0
Data and Control Hold after XTAL1 Low
XTAL1 Low to WR Low
XTAL1 Low to PAGEL high
PAGEL low to XTAL1 high
BS1 Valid before PAGEL High
PAGEL Pulse Width High
BS1 Hold after PAGEL Low
BS2/1 Hold after WR Low
PAGEL Low to WR Low
0
150
67
150
67
67
67
67
150
0
BS1 Valid to WR Low
WR Pulse Width Low
WR Low to RDY/BSY Low
WR Low to RDY/BSY High(1)
WR Low to RDY/BSY High for Chip Erase(2)
XTAL1 Low to OE Low
1
4.5
9
3.7
7.5
0
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Table 108. Parallel Programming Characteristics, VCC = 5 V ± 10% (Continued)
Symbol
tBVDV
Parameter
Min
Typ
Max
250
250
250
Units
ns
BS1 Valid to DATA valid
OE Low to DATA Valid
OE High to DATA Tri-stated
0
tOLDV
ns
tOHDZ
ns
Notes: 1. tWLRH is valid for the Write Flash, Write EEPROM, Write Fuse Bits and Write Lock
Bits commands.
2.
tWLRH_CE is valid for the Chip Erase command.
Serial Downloading
SPI Serial Programming
Pin Mapping
Table 109. Pin Mapping SPI Serial Programming
Symbol
MOSI
MISO
SCK
Pins
PB5
PB6
PB7
I/O
I
Description
Serial Data in
Serial Data out
Serial Clock
O
I
Both the Flash and EEPROM memory arrays can be programmed using the serial SPI
bus while RESET is pulled to GND. The serial interface consists of pins SCK, MOSI
(input) and MISO (output). After RESET is set low, the Programming Enable instruction
needs to be executed first before program/erase operations can be executed. NOTE, in
Table 109 on page 244, the pin mapping for SPI programming is listed. Not all parts use
the SPI pins dedicated for the internal SPI interface.
Figure 105. SPI Serial Programming and Verify(1)
VCC
MOSI
MISO
SCK
XTAL1
RESET
GND
Note:
1. If the device is clocked by the Internal Oscillator, it is no need to connect a clock
source to the XTAL1 pin.
When programming the EEPROM, an auto-erase cycle is built into the self-timed pro-
gramming operation (in the Serial mode ONLY) and there is no need to first execute the
Chip Erase instruction. The Chip Erase operation turns the content of every memory
location in both the Program and EEPROM arrays into 0xFF.
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Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high
periods for the serial clock (SCK) input are defined as follows:
Low:> 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
High:> 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
SPI Serial Programming
Algorithm
When writing serial data to the ATmega162, data is clocked on the rising edge of SCK.
When reading data from the ATmega162, data is clocked on the falling edge of SCK.
See Figure 106.
To program and verify the ATmega162 in the SPI Serial Programming mode, the follow-
ing sequence is recommended (See four byte instruction formats in Table 111):
1. Power-up sequence:
Apply power between VCC and GND while RESET and SCK are set to “0”. In
some systems, the programmer can not guarantee that SCK is held low during
Power-up. In this case, RESET must be given a positive pulse of at least two
CPU clock cycles duration after SCK has been set to “0”.
2. Wait for at least 20 ms and enable SPI Serial Programming by sending the Pro-
gramming Enable serial instruction to pin MOSI.
3. The SPI Serial Programming instructions will not work if the communication is
out of synchronization. When in sync. the second byte (0x53), will echo back
when issuing the third byte of the Programming Enable instruction. Whether the
echo is correct or not, all four bytes of the instruction must be transmitted. If the
0x53 did not echo back, give RESET a positive pulse and issue a new Program-
ming Enable command.
4. The Flash is programmed one page at a time. The page size is found in Table
106 on page 235. The memory page is loaded one byte at a time by supplying
the 6 LSB of the address and data together with the Load Program Memory
Page instruction. To ensure correct loading of the page, the data low byte must
be loaded before data high byte is applied for a given address. The Program
Memory Page is stored by loading the Write Program Memory Page instruction
with the 8 MSB of the address. If polling is not used, the user must wait at least
tWD_FLASH before issuing the next page. (See Table 110.) Accessing the SPI
serial programming interface before the Flash write operation completes can
result in incorrect programming.
5. The EEPROM array can either be programmed one page at a time or it can be
programmed byte by byte.
For Page Programming, the following algorithm is used:
The EEPROM memory page is loaded one byte at a time by supplying the 2 LSB of
the address and data together with the Load EEPROM Memory Page instruction.
The EEPROM Memory Page is stored by loading the Write EEPROM Memory Page
instruction with the 8 MSB of the address. If polling is not used, the user must wait at
least tWD_EEPROM before issuing the next page. (See Table 100.) Accessing the SPI
Serial Programming interface before the EEPROM write operation completes can
result in incorrect programming.
Alternatively, the EEPROM can be programmed bytewise:
The EEPROM array is programmed one byte at a time by supplying the address
and data together with the Write EEPROM instruction. An EEPROM memory loca-
tion is first automatically erased before new data is written. If polling is not used, the
user must wait at least tWD_EEPROM before issuing the next byte. (See Table 110.) In
a chip erased device, no 0xFFs in the data file(s) need to be programmed.
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6. Any memory location can be verified by using the Read instruction which returns
the content at the selected address at serial output MISO.
7. At the end of the programming session, RESET can be set high to commence
normal operation.
8. Power-off sequence (if needed):
Set RESET to “1”.
Turn VCC power off.
Data Polling Flash
When a page is being programmed into the Flash, reading an address location within
the page being programmed will give the value 0xFF. At the time the device is ready for
a new page, the programmed value will read correctly. This is used to determine when
the next page can be written. Note that the entire page is written simultaneously and any
address within the page can be used for polling. Data polling of the Flash will not work
for the value 0xFF, so when programming this value, the user will have to wait for at
least tWD_FLASH before programming the next page. As a chip erased device contains
0xFF in all locations, programming of addresses that are meant to contain 0xFF, can be
skipped. See Table 110 for tWD_FLASH value.
Data Polling EEPROM
When a new byte has been written and is being programmed into EEPROM, reading the
address location being programmed will give the value 0xFF. At the time the device is
ready for a new byte, the programmed value will read correctly. This is used to deter-
mine when the next byte can be written. This will not work for the value 0xFF, but the
user should have the following in mind: As a chip erased device contains 0xFF in all
locations, programming of addresses that are meant to contain 0xFF, can be skipped.
This does not apply if the EEPROM is re-programmed without chip erasing the device.
In this case, data polling cannot be used for the value 0xFF, and the user will have to
wait at least tWD_EEPROM before programming the next byte. See Table 110 for
tWD_EEPROM value.
Table 110. Minimum Wait Delay before Writing the Next Flash or EEPROM Location
Symbol
Minimum Wait Delay
4.5 ms
tWD_FLASH
tWD_EEPROM
tWD_ERASE
tWD_FUSE
9.0 ms
9.0 ms
4.5 ms
Figure 106. SPI Serial Programming Waveforms
SERIAL DATA INPUT
MSB
LSB
LSB
(MOSI)
SERIAL DATA OUTPUT
MSB
(MISO)
SERIAL CLOCK INPUT
(SCK)
SAMPLE
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ATmega162/V
Table 111. SPI Serial Programming Instruction Set(1)
Instruction
Instruction Format
Operation
Byte 1
Byte 2
Byte 3
Byte4
1010 1100
0101 0011
xxxx xxxx
xxxx xxxx
Enable SPI Serial Programming
after RESET goes low.
Programming Enable
Chip Erase
1010 1100
100x xxxx
xxxx xxxx
xxxx xxxx
Chip Erase EEPROM and Flash.
0010 H000
00aa aaaa
bbbb bbbb
oooo oooo
Read H (high or low) data o from
Program memory at word address
a:b.
Read Program Memory
0100 H000
00xx xxxx
xxbb bbbb
iiii iiii
Write H (high or low) data i to
Program Memory page at word
address b. Data low byte must be
loaded before Data high byte is
applied within the same address.
Load Program Memory
Page
Write Program Memory
Page
0100 1100
1010 0000
1100 0000
1100 0001
00aa aaaa
00xx xxaa
00xx xxaa
0000 0000
bbxx xxxx
bbbb bbbb
bbbb bbbb
0000 00bb
xxxx xxxx
oooo oooo
iiii iiii
iiii iiii
Write Program Memory Page at
address a:b.
Read data o from EEPROM
memory at address a:b.
Read EEPROM Memory
Write EEPROM Memory
(byte access)
Write data i to EEPROM memory
at address a:b.
Load data i to EEPROM memory
page buffer. After data is loaded,
program EEPROM page.
Load EEPROM Memory
Page (page access)
Write EEPROM Memory
Page (page access)
1100 0010
0101 1000
00xx xxaa
bbbb bb00
xxxx xxxx
Write EEPROM page at address
a:b.
0000 0000
xxxx xxxx
xxoo oooo
Read Lock bits. “0” = programmed,
“1” = unprogrammed. See Table
97 on page 230 for details.
Read Lock Bits
1010 1100
111x xxxx
xxxx xxxx
11ii iiii
Write Lock bits. Set bits = “0” to
program Lock bits. See Table 97
on page 230 for details.
Write Lock Bits
0011 0000
1010 1100
00xx xxxx
1010 0000
xxxx xxbb
oooo oooo
iiii iiii
Read Signature Byte o at address
b.
Read Signature Byte
Write Fuse Bits
xxxx xxxx
Set bits = “0” to program, “1” to
unprogram. See Table 101 on
page 232 for details.
1010 1100
1010 1100
0101 0000
1010 1000
1010 0100
0000 0000
xxxx xxxx
xxxx xxxx
xxxx xxxx
iiii iiii
xxxx xxii
oooo oooo
Set bits = “0” to program, “1” to
unprogram. See Table 100 on
page 232 for details.
Write Fuse High Bits
Write Extended Fuse Bits
Read Fuse Bits
Set bits = “0” to program, “1” to
unprogram. See Table 99 on
page 231 for details.
Read Fuse bits. “0” = programmed,
“1” = unprogrammed. See Table
101 on page 232 for details.
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Table 111. SPI Serial Programming Instruction Set(1) (Continued)
Instruction
Instruction Format
Operation
Byte 1
Byte 2
Byte 3
Byte4
0101 1000
0000 1000
0000 1000
xxxx xxxx
oooo oooo
Read Fuse high bits. “0” = pro-
grammed, “1” = unprogrammed.
See Table 100 on page 232 for
details.
Read Fuse High Bits
0101 0000
xxxx xxxx
oooo oooo
Read Extended Fuse bits. “0” =
pro-grammed, “1” =
Read Extended Fuse Bits
Read Calibration Byte
Poll RDY/BSY
unprogrammed. See Table 99 on
page 231 for details.
0011 1000
1111 0000
00xx xxxx
0000 0000
0000 0000
xxxx xxxx
oooo oooo
Read Calibration Byte
xxxx xxxo
If o = “1”, a programming operation
is still busy. Wait until this bit
returns to “0” before applying
another command.
Note:
1. a = address high bits, b = address low bits, H = 0 – Low byte, 1 – High Byte, o = data out, i = data in, x = don’t care
SPI Serial Programming
Characteristics
For characteristics of the SPI module, see “SPI Timing Characteristics” on page 267.
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ATmega162/V
Programming via the
JTAG Interface
Programming through the JTAG interface requires control of the four JTAG specific
pins: TCK, TMS, TDI, and TDO. Control of the Reset and clock pins is not required.
To be able to use the JTAG interface, the JTAGEN Fuse must be programmed. The
device is default shipped with the Fuse programmed. In addition, the JTD bit in
MCUCSR must be cleared. Alternatively, if the JTD bit is set, the External Reset can be
forced low. Then, the JTD bit will be cleared after two chip clocks, and the JTAG pins
are available for programming. This provides a means of using the JTAG pins as normal
port pins in running mode while still allowing In-System Programming via the JTAG
interface. Note that this technique can not be used when using the JTAG pins for
Boundary-scan or On-chip Debug. In these cases the JTAG pins must be dedicated for
this purpose.
As a definition in this datasheet, the LSB is shifted in and out first of all Shift Registers.
Programming Specific JTAG
Instructions
The Instruction Register is 4-bit wide, supporting up to 16 instructions. The JTAG
instructions useful for Programming are listed below.
The OPCODE for each instruction is shown behind the instruction name in hex format.
The text describes which Data Register is selected as path between TDI and TDO for
each instruction.
The Run-Test/Idle state of the TAP controller is used to generate internal clocks. It can
also be used as an idle state between JTAG sequences. The state machine sequence
for changing the instruction word is shown in Figure 107.
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2513F–AVR–12/03
Figure 107. State machine sequence for changing the instruction word
1
Test-Logic-Reset
0
1
1
1
0
Run-Test/Idle
Select-DR Scan
Select-IR Scan
0
0
1
1
Capture-DR
Capture-IR
0
0
Shift-IR
1
Shift-DR
0
0
1
Exit1-DR
0
1
1
Exit1-IR
0
Pause-DR
1
0
Pause-IR
1
0
0
0
Exit2-DR
1
Exit2-IR
1
Update-DR
Update-IR
1
1
0
0
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AVR_RESET (0xC)
The AVR specific public JTAG instruction for setting the AVR device in the Reset mode
or taking the device out from the Reset mode. The TAP controller is not reset by this
instruction. The one bit Reset Register is selected as data register. Note that the reset
will be active as long as there is a logic “one” in the Reset Chain. The output from this
chain is not latched.
The active states are:
•
Shift-DR: The Reset Register is shifted by the TCK input.
PROG_ENABLE (0x4)
The AVR specific public JTAG instruction for enabling programming via the JTAG port.
The 16-bit Programming Enable Register is selected as data register. The active states
are the following:
•
•
Shift-DR: The programming enable signature is shifted into the Data Register.
Update-DR: The programming enable signature is compared to the correct value,
and Programming mode is entered if the signature is valid.
PROG_COMMANDS (0x5)
The AVR specific public JTAG instruction for entering programming commands via the
JTAG port. The 15-bit Programming Command Register is selected as data register.
The active states are the following:
•
•
Capture-DR: The result of the previous command is loaded into the Data Register.
Shift-DR: The Data Register is shifted by the TCK input, shifting out the result of the
previous command and shifting in the new command.
•
•
Update-DR: The programming command is applied to the Flash inputs.
Run-Test/Idle: One clock cycle is generated, executing the applied command (not
always required, see Table 112 below).
PROG_PAGELOAD (0x6)
The AVR specific public JTAG instruction to directly load the Flash data page via the
JTAG port. The 1024 bit Virtual Flash Page Load Register is selected as register. This is
a virtual scan chain with length equal to the number of bits in one Flash page. Internally
the Shift Register is 8-bit. Unlike most JTAG instructions, the Update-DR state is not
used to transfer data from the Shift Register. The data are automatically transferred to
the Flash page buffer byte-by-byte in the Shift-DR state by an internal state machine.
This is the only active state:
•
Shift-DR: Flash page data are shifted in from TDI by the TCK input, and
automatically loaded into the Flash page one byte at a time.
Note:
The JTAG instruction PROG_PAGELOAD can only be used if the AVR device is the first
device in JTAG scan chain. If the AVR cannot be the first device in the scan chain, the
byte-wise programming algorithm must be used.
PROG_PAGEREAD (0x7)
The AVR specific public JTAG instruction to read one full Flash data page via the JTAG
port. The 1032 bit Virtual Flash Page Read Register is selected as data register. This is
a virtual scan chain with length equal to the number of bits in one Flash page plus eight.
Internally the Shift Register is 8-bit. Unlike most JTAG instructions, the Capture-DR
state is not used to transfer data to the Shift Register. The data are automatically trans-
ferred from the Flash page buffer byte-by-byte in the Shift-DR state by an internal state
machine. This is the only active state:
•
Shift-DR: Flash data are automatically read one byte at a time and shifted out on
TDO by the TCK input. The TDI input is ignored.
Note:
The JTAG instruction PROG_PAGEREAD can only be used if the AVR device is the first
device in JTAG scan chain. If the AVR cannot be the first device in the scan chain, the
byte-wise programming algorithm must be used.
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Data Registers
The Data Registers are selected by the JTAG Instruction Registers described in section
“Programming Specific JTAG Instructions” on page 249. The Data Registers relevant for
programming operations are:
•
•
•
•
•
Reset Register
Programming Enable Register.
Programming Command Register.
Virtual Flash Page Load Register.
Virtual Flash Page Read Register.
Reset Register
The Reset Register is a test data register used to reset the part during programming. It
is required to reset the part before entering Programming mode.
A high value in the Reset Register corresponds to pulling the external reset low. The
part is reset as long as there is a high value present in the Reset Register. Depending
on the fuse settings for the clock options, the part will remain reset for a Reset Time-out
period (refer to “Clock Sources” on page 34) after releasing the Reset Register. The out-
put from this data register is not latched, so the reset will take place immediately, as
shown in Figure 86 on page 205.
Programming Enable Register The Programming Enable Register is a 16-bit register. The contents of this register is
compared to the programming enable signature, binary code 1010_0011_0111_0000.
When the contents of the register is equal to the programming enable signature, pro-
gramming via the JTAG port is enabled. The register is reset to 0 on Power-on Reset,
and should always be reset when leaving Programming mode.
Figure 108. Programming Enable Register
TDI
0xA370
D
D
Q
A
T
A
Programming Enable
=
ClockDR & PROG_ENABLE
TDO
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ATmega162/V
Programming Command
Register
The Programming Command Register is a 15-bit register. This register is used to seri-
ally shift in programming commands, and to serially shift out the result of the previous
command, if any. The JTAG Programming Instruction Set is shown in Table 112. The
state sequence when shifting in the programming commands is illustrated in Figure 110.
Figure 109. Programming Command Register
TDI
S
T
R
O
B
E
S
Flash
A
EEPROM
D
Fuses
D
R
E
S
S
/
Lock Bits
D
A
T
A
TDO
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Table 112. JTAG Programming Instruction Set
Instruction
TDI sequence
TDO sequence
Notes
1a. Chip eRase
0100011_10000000
0110001_10000000
0110011_10000000
0110011_10000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
1b. Poll for Chip Erase complete
2a. Enter Flash Write
0110011_10000000
0100011_00010000
0000111_aaaaaaaa
0000011_bbbbbbbb
0010011_iiiiiiii
xxxxxox_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(2)
(9)
2b. Load Address High Byte
2c. Load Address Low Byte
2d. Load Data Low Byte
2e. Load Data High Byte
2f. Latch Data
0010111_iiiiiiii
0110111_00000000
1110111_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(1)
(1)
2g. Write Flash Page
0110111_00000000
0110101_00000000
0110111_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
2h. Poll for Page Write complete
3a. Enter Flash Read
0110111_00000000
0100011_00000010
0000111_aaaaaaaa
0000011_bbbbbbbb
xxxxxox_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(2)
(9)
3b. Load Address High Byte
3c. Load Address Low Byte
3d. Read Data Low and High Byte
0110010_00000000
0110110_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
xxxxxxx_oooooooo
low byte
high byte
4a. Enter EEPROM Write
4b. Load Address High Byte
4c. Load Address Low Byte
4d. Load Data Byte
0100011_00010001
0000111_aaaaaaaa
0000011_bbbbbbbb
0010011_iiiiiiii
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(9)
4e. Latch Data
0110111_00000000
1110111_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(1)
(1)
4f. Write EEPROM Page
0110011_00000000
0110001_00000000
0110011_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
4g. Poll for Page Write complete
5a. Enter EEPROM Read
0110011_00000000
0100011_00000011
0000111_aaaaaaaa
0000011_bbbbbbbb
xxxxxox_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(2)
(9)
5b. Load Address High Byte
5c. Load Address Low Byte
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ATmega162/V
Table 112. JTAG Programming Instruction Set (Continued)
Instruction
TDI sequence
TDO sequence
Notes
5d. Read Data Byte
0110011_bbbbbbbb
0110010_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
6a. Enter Fuse Write
0100011_01000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
6b. Load Data Low Byte(6)
0010011_iiiiiiii
(3)
(1)
6c. Write Fuse Extended Byte
0111011_00000000
0111001_00000000
0111011_00000000
0111011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
6d. Poll for Fuse Write complete
6e. Load Data Low Byte(7)
6f. Write Fuse High byte
0110111_00000000
xxxxxox_xxxxxxxx
(2)
(3)
(1)
0010011_iiiiiiii
xxxxxxx_xxxxxxxx
0110111_00000000
0110101_00000000
0110111_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
6g. Poll for Fuse Write complete
6h. Load Data Low Byte(8)
6i. Write Fuse Low Byte
0110111_00000000
xxxxxox_xxxxxxxx
(2)
(3)
(1)
0010011_iiiiiiii
xxxxxxx_xxxxxxxx
0110011_00000000
0110001_00000000
0110011_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
6j. Poll for Fuse Write complete
7a. Enter Lock Bit Write
7b. Load Data Byte(9)
0110011_00000000
0100011_00100000
0010011_11iiiiii
xxxxxox_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
(2)
(4)
(1)
7c. Write Lock Bits
0110011_00000000
0110001_00000000
0110011_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
7d. Poll for Lock Bit Write complete
8a. Enter Fuse/Lock Bit Read
8b. Read Fuse Extended Byte(6)
0110011_00000000
0100011_00000100
xxxxxox_xxxxxxxx
(2)
xxxxxxx_xxxxxxxx
0111010_00000000
0111111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
8c. Read Fuse High Byte(7)
8d. Read Fuse Low Byte(8)
8e. Read Lock Bits(9)
0111110_00000000
0111111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
0110010_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
0110110_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
(5)
xxxxxxx_xxoooooo
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Table 112. JTAG Programming Instruction Set (Continued)
Instruction
TDI sequence
TDO sequence
Notes
8f. Read Fuses and Lock Bits
0111010_00000000
0111110_00000000
0110010_00000000
0110110_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
xxxxxxx_oooooooo
xxxxxxx_oooooooo
xxxxxxx_oooooooo
(5)
Fuse ext. byte
Fuse high byte
Fuse low byte
Lock bits
9a. Enter Signature Byte Read
9b. Load Address Byte
0100011_00001000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
0000011_bbbbbbbb
9c. Read Signature Byte
0110010_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
10a. Enter Calibration Byte Read
10b. Load Address Byte
0100011_00001000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
0000011_bbbbbbbb
10c. Read Calibration Byte
0110110_00000000
0110111_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_oooooooo
11a. Load No Operation Command
0100011_00000000
0110011_00000000
xxxxxxx_xxxxxxxx
xxxxxxx_xxxxxxxx
Notes: 1. This command sequence is not required if the seven MSB are correctly set by the previous command sequence (which is
normally the case).
2. Repeat until o = “1”.
3. Set bits to “0” to program the corresponding Fuse, “1” to unprogram the Fuse.
4. Set bits to “0” to program the corresponding lock bit, “1” to leave the Lock bit unchanged.
5. “0” = programmed, “1” = unprogrammed.
6. The bit mapping for Fuses Extended byte is listed in Table 99 on page 231.
7. The bit mapping for Fuses High byte is listed in Table 100 on page 232.
8. The bit mapping for Fuses Low byte is listed in Table 101 on page 232.
9. The bit mapping for Lock Bits byte is listed in Table 97 on page 230.
10. Address bits exceeding PCMSB and EEAMSB (Table 106 and Table 107) are don’t care
Note:
a = address high bits
b = address low bits
H = 0 – Low byte, 1 – High Byte
o = data out
i = data in
x = don’t care
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ATmega162/V
Figure 110. State Machine Sequence for Changing/Reading the Data Word
1
Test-Logic-Reset
0
1
1
1
0
Run-Test/Idle
Select-DR Scan
Select-IR Scan
0
0
1
1
Capture-DR
Capture-IR
0
0
Shift-DR
0
Shift-IR
0
1
Exit1-DR
0
1
1
1
Exit1-IR
0
Pause-IR
1
Pause-DR
1
0
0
0
0
Exit2-DR
1
Exit2-IR
1
Update-DR
Update-IR
1
1
0
0
Virtual Flash Page Load
Register
The Virtual Flash Page Load Register is a virtual scan chain with length equal to the
number of bits in one Flash page. Internally the Shift Register is 8-bit, and the data are
automatically transferred to the Flash page buffer byte-by-byte. Shift in all instruction
words in the page, starting with the LSB of the first instruction in the page and ending
with the MSB of the last instruction in the page. This provides an efficient way to load the
entire Flash page buffer before executing Page Write.
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Figure 111. Virtual Flash Page Load Register
STROBES
State
Machine
ADDRESS
TDI
Flash
EEPROM
Fuses
Lock Bits
D
A
T
A
TDO
Virtual Flash Page Read
Register
The Virtual Flash Page Read Register is a virtual scan chain with length equal to the
number of bits in one Flash page plus eight. Internally the Shift Register is 8-bit, and the
data are automatically transferred from the Flash data page byte-by-byte. The first eight
cycles are used to transfer the first byte to the internal Shift Register, and the bits that
are shifted out during these right cycles should be ignored. Following this initialization,
data are shifted out starting with the LSB of the first instruction in the page and ending
with the MSB of the last instruction in the page. This provides an efficient way to read
one full Flash page to verify programming.
258
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ATmega162/V
Figure 112. Virtual Flash Page Read Register
STROBES
State
Machine
ADDRESS
TDI
Flash
EEPROM
Fuses
Lock Bits
D
A
T
A
TDO
Programming Algorithm
All references below of type “1a”, “1b”, and so on, refer to Table 112.
Entering Programming Mode
1. Enter JTAG instruction AVR_RESET and shift one in the Reset Register.
2. Enter instruction PROG_ENABLE and shift 1010_0011_0111_0000 in the Pro-
gramming Enable Register.
Leaving Programming Mode
1. Enter JTAG instruction PROG_COMMANDS.
2. Disable all programming instructions by using no operation instruction 11a.
3. Enter instruction PROG_ENABLE and shift 0000_0000_0000_0000 in the Pro-
gramming Enable Register.
4. Enter JTAG instruction AVR_RESET and shift 0 in the Reset Register.
Performing Chip Erase
Programming the Flash
1. Enter JTAG instruction PROG_COMMANDS.
2. Start Chip Erase using programming instruction 1a.
3. Poll for Chip Erase complete using programming instruction 1b, or wait for
tWLRH_CE (refer to Table 108 on page 243).
Before programming the Flash a Chip Erase must be performed. See “Performing Chip
Erase” on page 259.
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Flash write using programming instruction 2a.
3. Load address high byte using programming instruction 2b.
4. Load address low byte using programming instruction 2c.
5. Load data using programming instructions 2d, 2e and 2f.
6. Repeat steps 4 and 5 for all instruction words in the page.
7. Write the page using programming instruction 2g.
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2513F–AVR–12/03
8. Poll for Flash write complete using programming instruction 2h, or wait for
tWLRH_FLASH (refer to Table 108 on page 243).
9. Repeat steps 3 to 7 until all data have been programmed.
A more efficient data transfer can be achieved using the PROG_PAGELOAD
instruction:
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Flash write using programming instruction 2a.
3. Load the page address using programming instructions 2b and 2c. PCWORD
(refer to Table 106 on page 235) is used to address within one page and must be
written as 0.
4. Enter JTAG instruction PROG_PAGELOAD.
5. Load the entire page by shifting in all instruction words in the page, starting with
the LSB of the first instruction in the page and ending with the MSB of the last
instruction in the page.
6. Enter JTAG instruction PROG_COMMANDS.
7. Write the page using programming instruction 2g.
8. Poll for Flash write complete using programming instruction 2h, or wait for
tWLRH_FLASH (refer to Table 108 on page 243).
9. Repeat steps 3 to 8 until all data have been programmed.
Reading the Flash
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Flash read using programming instruction 3a.
3. Load address using programming instructions 3b and 3c.
4. Read data using programming instruction 3d.
5. Repeat steps 3 and 4 until all data have been read.
A more efficient data transfer can be achieved using the PROG_PAGEREAD
instruction:
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Flash read using programming instruction 3a.
3. Load the page address using programming instructions 3b and 3c. PCWORD
(refer to Table 106 on page 235) is used to address within one page and must be
written as 0.
4. Enter JTAG instruction PROG_PAGEREAD.
5. Read the entire page by shifting out all instruction words in the page, starting
with the LSB of the first instruction in the page and ending with the MSB of the
last instruction in the page. Remember that the first 8 bits shifted out should be
ignored.
6. Enter JTAG instruction PROG_COMMANDS.
7. Repeat steps 3 to 6 until all data have been read.
260
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Programming the EEPROM
Before programming the EEPROM a Chip Erase must be performed. See “Performing
Chip Erase” on page 259.
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable EEPROM write using programming instruction 4a.
3. Load address high byte using programming instruction 4b.
4. Load address low byte using programming instruction 4c.
5. Load data using programming instructions 4d and 4e.
6. Repeat steps 4 and 5 for all data bytes in the page.
7. Write the data using programming instruction 4f.
8. Poll for EEPROM write complete using programming instruction 4g, or wait for
tWLRH (refer to Table 108 on page 243).
9. Repeat steps 3 to 8 until all data have been programmed.
Note:
The PROG_PAGELOAD instruction can not be used when programming the EEPROM
Reading the EEPROM
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable EEPROM read using programming instruction 5a.
3. Load address using programming instructions 5b and 5c.
4. Read data using programming instruction 5d.
5. Repeat steps 3 and 4 until all data have been read.
Note:
The PROG_PAGEREAD instruction can not be used when reading the EEPROM
Programming the Fuses
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Fuse write using programming instruction 6a.
3. Load data low byte using programming instructions 6b. A bit value of “0” will pro-
gram the corresponding Fuse, a “1” will unprogram the Fuse.
4. Write Fuse extended byte using programming instruction 6c.
5. Poll for Fuse write complete using programming instruction 6d, or wait for tWLRH
(refer to Table 108 on page 243).
6. Load data low byte using programming instructions 6e. A bit value of “0” will pro-
gram the corresponding Fuse, a “1” will unprogram the Fuse.
7. Write Fuse High byte using programming instruction 6f.
8. Poll for Fuse write complete using programming instruction 6g, or wait for tWLRH
(refer to Table 108 on page 243).
9. Load data low byte using programming instructions 6h. A “0” will program the
Fuse, a “1” will unprogram the Fuse.
10. Write Fuse Low byte using programming instruction 6i.
11. Poll for Fuse write complete using programming instruction 6j, or wait for tWLRH
(refer to Table 108 on page 243).
Programming the Lock Bits
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Lock bit write using programming instruction 7a.
3. Load data using programming instructions 7b. A bit value of “0” will program the
corresponding Lock bit, a “1” will leave the Lock bit unchanged.
4. Write Lock bits using programming instruction 7c.
5. Poll for Lock bit write complete using programming instruction 7d, or wait for
tWLRH (refer to Table 108 on page 243).
261
2513F–AVR–12/03
Reading the Fuses and Lock
Bits
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Fuse/Lock bit read using programming instruction 8a.
3. To read all Fuses and Lock bits, use programming instruction 8f.
To only read Fuse Extended byte, use programming instruction 8b.
To only read Fuse High byte, use programming instruction 8c.
To only read Fuse Low byte, use programming instruction 8d.
To only read Lock bits, use programming instruction 8e.
Reading the Signature Bytes
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Signature byte read using programming instruction 9a.
3. Load address 0x00 using programming instruction 9b.
4. Read first signature byte using programming instruction 9c.
5. Repeat steps 3 and 4 with address 0x01 and address 0x02 to read the second
and third signature bytes, respectively.
Reading the Calibration Byte
1. Enter JTAG instruction PROG_COMMANDS.
2. Enable Calibration byte read using programming instruction 10a.
3. Load address 0x00 using programming instruction 10b.
4. Read the calibration byte using programming instruction 10c.
262
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Electrical Characteristics
Absolute Maximum Ratings*
*NOTICE:
Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent dam-
age to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect device
reliability.
Operating Temperature.................................. -55°C to +125°C
Storage Temperature..................................... -65°C to +150°C
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V
Voltage on RESET with respect to Ground......-0.5V to +13.0V
Maximum Operating Voltage ............................................ 6.0V
DC Current per I/O Pin ............................................... 40.0 mA
DC Current VCC and GND Pins................................ 200.0 mA
DC Characteristics
TA = -40°C to 85°C, VCC = 1.8V to 5.5V (unless otherwise noted)
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
(1)
(1)
VCC = 1.8 - 2.4V
VCC = 2.4 - 5.5V
-0.5
-0.5
0.2 VCC
0.3 VCC
VIL
Input Low Voltage, Except XTAL1 pin
Input Low Voltage, XTAL1 pin
V
V
V
(1)
VIL1
VCC = 1.8 - 5.5V
-0.5
0.1 VCC
(2)
(2)
Input High Voltage, Except XTAL1
and RESET pin
VCC = 1.8 - 2.4V
VCC = 2.4 - 5.5V
0.7 VCC
0.6 VCC
VCC + 0.5
VCC + 0.5
VIH
(2)
(2)
VCC = 1.8 - 2.4V
VCC = 2.4 - 5.5V
0.8 VCC
0.7 VCC
VCC + 0.5
VCC + 0.5
VIH1
VIH2
VOL
Input High Voltage, XTAL1 pin
Input High Voltage, RESET pin
V
V
(2)
VCC = 1.8 - 5.5V
0.9 VCC
VCC + 0.5
Output Low Voltage(3), Ports A, B, C,
D, and E
IOL = 20 mA, VCC = 5V
IOL = 10 mA, VCC = 3V
0.7
0.5
V
V
Output High Voltage(4), Ports A, B, C,
D, and E
IOL = -20 mA, VCC = 5V
IOL = -5 mA, VCC = 3V
4.2
2.3
V
V
VOH
IIL
Vcc = 5.5V, pin low
(absolute value)
Input Leakage Current I/O Pin
Input Leakage Current I/O Pin
1
1
µA
µA
Vcc = 5.5V, pin high
(absolute value)
IIH
RRST
Rpu
Reset Pull-up Resistor
I/O Pin Pull-up Resistor
30
20
60
50
kΩ
kΩ
263
2513F–AVR–12/03
TA = -40°C to 85°C, VCC = 1.8V to 5.5V (unless otherwise noted) (Continued)
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
Active 1 MHz, VCC = 2V
(ATmega162V)
0.8
mA
Active 4 MHz, VCC = 3V
(ATmega162/V)
5
16
0.3
2
mA
mA
mA
mA
Active 8 MHz, VCC = 5V
(ATmega162)
Power Supply Current
Idle 1 MHz, VCC = 2V
(ATmega162V)
ICC
Idle 4 MHz, VCC = 3V
(ATmega162/V)
Idle 8 MHz, VCC = 5V
(ATmega162)
8
mA
µA
µA
mV
nA
ns
WDT Enabled,
VCC = 3.0V
< 10
< 1.5
< 10
14
2
Power-down mode
WDT Disabled,
VCC = 3.0V
Analog Comparator Input Offset
Voltage
VCC = 5V
Vin = VCC/2
VACIO
IACLK
tACID
40
50
Analog Comparator Input Leakage
Current
VCC = 5V
Vin = VCC/2
-50
Analog Comparator Propagation
Delay
VCC = 2.7V
VCC = 4.0V
750
500
Notes: 1. “Max” means the highest value where the pin is guaranteed to be read as low
2. “Min” means the lowest value where the pin is guaranteed to be read as high
3. Although each I/O port can sink more than the test conditions (20 mA at Vcc = 5V, 10 mA at Vcc = 3V) under steady state
conditions (non-transient), the following must be observed:
PDIP Package:
1] The sum of all IOL, for all ports, should not exceed 300 mA.
2] The sum of all IOL, for port B0 - B7, D0 - D7, and XTAL2, should not exceed 150 mA.
3] The sum of all IOL, for ports A0 - A7, E0 - E2, C0 - C7, should not exceed 150 mA.
TQFP and MLF Package:
1] The sum of all IOL, for all ports, should not exceed 400 mA.
2] The sum of all IOL, for ports B0 - B7, D0 - D7, and XTAL2, should not exceed 200 mA.
3] The sum of all IOL, for ports C0 - C7 and E1 - E2, should not exceed 200 mA.
4] The sum of all IOL, for ports A0 - A7 and E0, should not exceed 200 mA.
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater
than the listed test condition.
4. Although each I/O port can source more than the test conditions (20 mA at Vcc = 5V, 10 mA at Vcc = 3V) under steady state
conditions (non-transient), the following must be observed:
PDIP Package:
1] The sum of all IOH, for all ports, should not exceed 300 mA.
2] The sum of all IOH, for port B0 - B7, D0 - D7, and XTAL2, should not exceed 150 mA.
3] The sum of all IOH, for ports A0 - A7, E0 - E2, C0 - C7, should not exceed 150 mA.
TQFP and MLF Package:
1] The sum of all IOH, for all ports, should not exceed 400 mA.
2] The sum of all IOH, for ports B0 - B7, D0 - D7, and XTAL2, should not exceed 200 mA.
3] The sum of all IOH, for ports C0 - C7 and E1 - E2, should not exceed 200 mA.
4] The sum of all IOH, for ports A0 - A7 and E0, should not exceed 200 mA.
If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current
greater than the listed test condition.
264
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 113. Absolute Maximum Frequency as a function of VCC, ATmega162V
Frequency
16 MHz
8 MHz
1 MHz
Safe Operating
Area
VCC
1.8V
2.4V 2.7V
4.5V
5.5V
Figure 114. Absolute Maximum Frequency as a function of VCC, ATmega162
Frequency
16 MHz
8 MHz
Safe Operating
Area
1 MHz
VCC
1.8V
2.4V 2.7V
4.5V
5.5V
265
2513F–AVR–12/03
External Clock Drive
Waveforms
Figure 115. External Clock Drive Waveforms
VIH1
VIL1
External Clock Drive
Table 113. External Clock Drive
VCC = 1.8 - 5.5V VCC =2.7 - 5.5V VCC = 4.5 - 5.5V
Symbol Parameter
Min.
Max.
Min.
Max.
Min.
Max.
Units
Oscillator
0
1
0
8
0
16
MHz
1/tCLCL
tCLCL
tCHCX
tCLCX
tCLCH
tCHCL
Frequency
Clock Period
High Time
Low Time
Rise Time
Fall Time
1000
400
125
50
62.5
25
ns
ns
ns
µs
µs
400
50
25
2.0
2.0
1.6
1.6
0.5
0.5
Change in
period from one
clock cycle to
the next
2
2
2
%
∆tCLCL
266
ATmega162/V
2513F–AVR–12/03
ATmega162/V
SPI Timing
See Figure 116 and Figure 117 for details.
Characteristics
Table 114. SPI Timing Parameters
Description
SCK period
SCK high/low
Rise/Fall time
Setup
Mode
Master
Master
Master
Master
Master
Master
Master
Master
Slave
Min
Typ
Max
1
2
See Table 68
50% duty cycle
3
3.6
10
4
5
Hold
10
ns
6
Out to SCK
SCK to out
SCK to out high
SS low to out
SCK period
SCK high/low(1)
Rise/Fall time
Setup
0.5 • tsck
10
7
8
10
9
15
10
11
12
13
14
15
16
17
18
Slave
4 • tck
2 • tck
Slave
Slave
1.6
µs
ns
Slave
10
tck
Hold
Slave
SCK to out
SCK to SS high
SS high to tri-state
SS low to SCK
Slave
15
10
Slave
20
Slave
Slave
2 • tck
Note:
1. In SPI Programming mode, the minimum SCK high/low period is:
– 2 tCLCL for fCK < 12 MHz
– 3 tCLCL for fCK > 12 MHz.
Figure 116. SPI Interface Timing Requirements (Master Mode)
SS
6
1
SCK
(CPOL = 0)
2
2
SCK
(CPOL = 1)
4
5
3
MISO
(Data Input)
MSB
...
LSB
7
8
MOSI
(Data Output)
MSB
...
LSB
267
2513F–AVR–12/03
Figure 117. SPI Interface Timing Requirements (Slave Mode)
18
SS
10
16
9
SCK
(CPOL = 0)
11
11
SCK
(CPOL = 1)
13
14
12
MOSI
(Data Input)
MSB
...
LSB
15
17
MISO
(Data Output)
MSB
...
LSB
X
268
ATmega162/V
2513F–AVR–12/03
ATmega162/V
External Data Memory Timing
Table 115. External Data Memory Characteristics, 4.5 - 5.5 Volts, no Wait-state
8 MHz Oscillator
Variable Oscillator
Symbol
1/tCLCL
tLHLL
Parameter
Min
Max
Min
Max
Unit
MHz
ns
0
1
2
Oscillator Frequency
ALE Pulse Width
0.0
16
115
1.0tCLCL-10
0.5tCLCL-5(1)
tAVLL
Address Valid A to ALE Low
57.5
ns
Address Hold After ALE Low,
write access
5
5
5
3a
tLLAX_ST
ns
Address Hold after ALE Low,
read access
5
3b
4
tLLAX_LD
tAVLLC
tAVRL
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Address Valid C to ALE Low
Address Valid to RD Low
Address Valid to WR Low
ALE Low to WR Low
ALE Low to RD Low
57.5
115
115
47.5
47.5
40
0.5tCLCL-5(1)
1.0tCLCL-10
1.0tCLCL-10
0.5tCLCL-15(2)
0.5tCLCL-15(2)
40
5
6
tAVWL
tLLWL
7
67.5
67.5
0.5tCLCL+5(2)
0.5tCLCL+5(2)
8
tLLRL
9
tDVRH
tRLDV
Data Setup to RD High
Read Low to Data Valid
Data Hold After RD High
RD Pulse Width
10
11
12
13
14
15
16
75
1.0tCLCL-50
tRHDX
tRLRH
tDVWL
tWHDX
tDVWH
tWLWH
0
0
115
42.5
115
125
115
1.0tCLCL-10
0.5tCLCL-20(1)
1.0tCLCL-10
1.0tCLCL
Data Setup to WR Low
Data Hold After WR High
Data Valid to WR High
WR Pulse Width
1.0tCLCL-10
Notes: 1. This assumes 50% clock duty cycle. The half period is actually the high time of the external clock, XTAL1.
2. This assumes 50% clock duty cycle. The half period is actually the low time of the external clock, XTAL1.
Table 116. External Data Memory Characteristics, 4.5 - 5.5 Volts, 1 Cycle Wait-state
8 MHz Oscillator
Variable Oscillator
Min Max
Symbol
Parameter
Min
Max
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
16
10 tRLDV
12 tRLRH
15 tDVWH
16 tWLWH
200
2.0tCLCL-50
240
240
240
2.0tCLCL-10
2.0tCLCL
ns
Data Valid to WR High
WR Pulse Width
ns
2.0tCLCL-10
ns
269
2513F–AVR–12/03
Table 117. External Data Memory Characteristics, 4.5 - 5.5 Volts, SRWn1 = 1, SRWn0 = 0
4 MHz Oscillator Variable Oscillator
Symbol
Parameter
Min
Max
Min
Max
16
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
10 tRLDV
12 tRLRH
15 tDVWH
16 tWLWH
325
3.0tCLCL-50
365
375
365
3.0tCLCL-10
3.0tCLCL
ns
Data Valid to WR High
WR Pulse Width
ns
3.0tCLCL-10
ns
Table 118. External Data Memory Characteristics, 4.5 - 5.5 Volts, SRWn1 = 1, SRWn0 = 1
4 MHz Oscillator Variable Oscillator
Symbol
Parameter
Min
Max
Min
Max
16
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
10 tRLDV
12 tRLRH
14 tWHDX
15 tDVWH
16 tWLWH
325
3.0tCLCL-50
365
240
375
365
3.0tCLCL-10
2.0tCLCL-10
3.0tCLCL
ns
Data Hold After WR High
Data Valid to WR High
WR Pulse Width
ns
ns
3.0tCLCL-10
ns
Table 119. External Data Memory Characteristics, 2.7 - 5.5 Volts, no Wait-state
4 MHz Oscillator
Variable Oscillator
Symbol
1/tCLCL
tLHLL
Parameter
Min
Max
Min
0.0
Max
Unit
MHz
ns
0
1
2
Oscillator Frequency
ALE Pulse Width
8
235
115
tCLCL-15
0.5tCLCL-10(1)
tAVLL
Address Valid A to ALE Low
ns
Address Hold After ALE Low,
write access
5
5
5
3a tLLAX_ST
ns
Address Hold after ALE Low,
read access
5
3b tLLAX_LD
ns
ns
ns
ns
ns
ns
ns
ns
ns
4
5
6
7
8
9
tAVLLC
tAVRL
tAVWL
tLLWL
tLLRL
Address Valid C to ALE Low
Address Valid to RD Low
Address Valid to WR Low
ALE Low to WR Low
115
235
235
115
115
45
0.5tCLCL-10(1)
1.0tCLCL-15
1.0tCLCL-15
0.5tCLCL-10(2)
0.5tCLCL-10(2)
45
130
130
0.5tCLCL+5(2)
0.5tCLCL+5(2)
ALE Low to RD Low
tDVRH
Data Setup to RD High
Read Low to Data Valid
Data Hold After RD High
10 tRLDV
11 tRHDX
190
1.0tCLCL-60
0
0
270
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Table 119. External Data Memory Characteristics, 2.7 - 5.5 Volts, no Wait-state (Continued)
4 MHz Oscillator Variable Oscillator
Min Max
Symbol
12 tRLRH
Parameter
Min
Max
Unit
ns
RD Pulse Width
235
105
235
250
235
1.0tCLCL-15
0.5tCLCL-20(1)
1.0tCLCL-15
1.0tCLCL
13 tDVWL
14 tWHDX
15 tDVWH
16 tWLWH
Data Setup to WR Low
Data Hold After WR High
Data Valid to WR High
WR Pulse Width
ns
ns
ns
1.0tCLCL-15
ns
Notes: 1. This assumes 50% clock duty cycle. The half period is actually the high time of the external clock, XTAL1.
2. This assumes 50% clock duty cycle. The half period is actually the low time of the external clock, XTAL1.
Table 120. External Data Memory Characteristics, 2.7 - 5.5 Volts, SRWn1 = 0, SRWn0 = 1
4 MHz Oscillator
Variable Oscillator
Min Max
Symbol
Parameter
Min
Max
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
8
10 tRLDV
12 tRLRH
15 tDVWH
16 tWLWH
440
2.0tCLCL-60
485
500
485
2.0tCLCL-15
2.0tCLCL
ns
Data Valid to WR High
WR Pulse Width
ns
2.0tCLCL-15
ns
Table 121. External Data Memory Characteristics, 2.7 - 5.5 Volts, SRWn1 = 1, SRWn0 = 0
4 MHz Oscillator Variable Oscillator
Symbol
Parameter
Min
Max
Min
Max
8
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
10 tRLDV
12 tRLRH
15 tDVWH
16 tWLWH
690
3.0tCLCL-60
735
750
735
3.0tCLCL-15
3.0tCLCL
ns
Data Valid to WR High
WR Pulse Width
ns
3.0tCLCL-15
ns
Table 122. External Data Memory Characteristics, 2.7 - 5.5 Volts, SRWn1 = 1, SRWn0 = 1
4 MHz Oscillator Variable Oscillator
Symbol
Parameter
Min
Max
Min
Max
8
Unit
MHz
ns
0
1/tCLCL
Oscillator Frequency
Read Low to Data Valid
RD Pulse Width
0.0
10 tRLDV
12 tRLRH
14 tWHDX
15 tDVWH
16 tWLWH
690
3.0tCLCL-60
735
485
750
735
3.0tCLCL-15
2.0tCLCL-15
3.0tCLCL
ns
Data Hold After WR High
Data Valid to WR High
WR Pulse Width
ns
ns
3.0tCLCL-15
ns
271
2513F–AVR–12/03
Figure 118. External Memory Timing (SRWn1 = 0, SRWn0 = 0
T1
T2
T3
T4
System Clock (CLKCPU
)
1
ALE
4
2
7
A15:8 Prev. addr.
Address
15
3a
13
DA7:0 Prev. data
Address
6
XX
Data
16
14
WR
3b
9
11
DA7:0 (XMBK = 0)
Address
5
Data
10
8
12
RD
Figure 119. External Memory Timing (SRWn1 = 0, SRWn0 = 1)
T1
T2
T3
T4
T5
System Clock (CLKCPU
)
1
ALE
4
2
7
A15:8 Prev. addr.
Address
15
3a
13
Data
16
DA7:0 Prev. data
Address
6
XX
14
WR
3b
9
11
DA7:0 (XMBK = 0)
Address
5
Data
10
8
12
RD
272
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 120. External Memory Timing (SRWn1 = 1, SRWn0 = 0)
T1
T2
T3
T4
T5
T6
System Clock (CLKCPU
)
1
ALE
4
2
7
Address
15
A15:8 Prev. addr.
3a
13
DA7:0 Prev. data
Address
6
XX
Data
16
14
WR
9
3b
11
DA7:0 (XMBK = 0)
Address
5
Data
10
8
12
RD
Figure 121. External Memory Timing (SRWn1 = 1, SRWn0 = 1)(1)
T1
T2
T3
T4
T5
T6
T7
System Clock (CLKCPU
)
1
ALE
4
2
7
Address
15
A15:8 Prev. addr.
3a
13
DA7:0 Prev. data
Address
6
XX
Data
16
14
WR
9
3b
11
DA7:0 (XMBK = 0)
Address
5
Data
10
8
12
RD
Note:
1. The ALE pulse in the last period (T4 - T7) is only present if the next instruction
accesses the RAM (internal or external).
273
2513F–AVR–12/03
ATmega162 Typical
Characteristics
The following charts show typical behavior. These figures are not tested during manu-
facturing. All current consumption measurements are performed with all I/O pins
configured as inputs and with internal pull-ups enabled. A sine wave generator with rail-
to-rail output is used as clock source. The CKSEL Fuses are programmed to select
external clock.
The power consumption in Power-down mode is independent of clock selection.
The current consumption is a function of several factors such as: Operating voltage,
operating frequency, loading of I/O pins, switching rate of I/O pins, code executed and
ambient temperature. The dominating factors are operating voltage and frequency.
The current drawn from capacitive loaded pins may be estimated (for one pin) as
CL*VCC*f where CL = load capacitance, VCC = operating voltage and f = average switch-
ing frequency of I/O pin.
The parts are characterized at frequencies higher than test limits. Parts are not guaran-
teed to function properly at frequencies higher than the ordering code indicates.
The difference between current consumption in Power-down mode with Watchdog
Timer enabled and Power-down mode with Watchdog Timer disabled represents the dif-
ferential current drawn by the Watchdog Timer.
Active Supply Current
Figure 122. Active Supply Current vs. Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz
3
2.5
2
5.5V
5.0V
4.5V
4.0V
1.5
1
3.3V
2.7V
1.8V
0.5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
274
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 123. Active Supply Current vs. Frequency (1 - 20 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
1- 20 MHz
45
40
35
30
25
20
15
10
5
5.5V
5.0V
4.5V
4.0V
3.3V
2.7V
1.8V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
Figure 124. Active Supply Current vs. VCC (Internal RC Oscillator, 8 MHz)
ACTIVE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 8 MHz
20
18
16
14
12
10
8
85°C
25°C
-40°C
6
4
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
275
2513F–AVR–12/03
Figure 125. Active Supply Current vs. VCC (32 kHz External Oscillator)
ACTIVE SUPPLY CURRENT vs. VCC
32kHz EXTERNAL OSCILLATOR
300
250
200
150
100
50
25°C
85°C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Idle Supply Current
Figure 126. Idle Supply Current vs. Frequency (0.1 - 1.0 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz
1.2
5.5V
5.0V
1
0.8
0.6
0.4
0.2
0
4.5V
4.0V
3.3V
2.7V
1.8V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
276
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 127. Idle Supply Current vs. Frequency (1 - 20 MHz)
IDLE SUPPLY CURRENT vs. FREQUENCY
1 - 20 MHz
25
20
15
10
5
5.5V
5.0V
4.5V
4.0V
3.3V
2.7V
1.8V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
Figure 128. Idle Supply Current vs. VCC (Internal RC Oscillator, 8 MHz)
IDLE SUPPLY CURRENT vs. VCC
INTERNAL RC OSCILLATOR, 8 MHz
9
85°C
25°C
-40°C
8
7
6
5
4
3
2
1
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
277
2513F–AVR–12/03
Figure 129. Idle Supply Current vs. VCC (32 kHz External Oscillator)
IDLE SUPPLY CURRENT vs. VCC
32kHz EXTERNAL OSCILLATOR
70
60
50
40
30
20
10
0
85°C
25°C
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Power-down Supply Current
Figure 130. Power-down Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-DOWN SUPPLY CURRENT vs. VCC
WATCHDOG TIMER DISABLED
3
85°C
2.5
2
1.5
1
-40°C
25°C
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
278
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 131. Power-down Supply Current vs. VCC (Watchdog Timer Enabled)
POWER-DOWN SUPPLY CURRENT vs. VCC
WATCHDOG TIMER ENABLED
25
20
15
10
5
85°C
25°C
-40°C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Power-save Supply Current
Figure 132. Power-save Supply Current vs. VCC (Watchdog Timer Disabled)
POWER-SAVE SUPPLY CURRENT vs. VCC
WATCHDOG TIMER DISABLED
30
85°C
25°C
25
20
15
10
5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
279
2513F–AVR–12/03
Standby Supply Current
Figure 133. Standby Supply Current vs. VCC (455 kHz Resonator, Watchdog Timer
Disabled)
STANDBY SUPPLY CURRENT vs. VCC
455 kHz RESONATOR, WATCHDOG TIMER DISABLED
70
60
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 134. Standby Supply Current vs. VCC (1 MHz Resonator, Watchdog Timer
Disabled)
STANDBY SUPPLY CURRENT vs. VCC
1 MHz RESONATOR, WATCHDOG TIMER DISABLED
60
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
280
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 135. Standby Supply Current vs. VCC (2 MHz Resonator, Watchdog Timer
Disabled)
STANDBY SUPPLY CURRENT vs. VCC
2 MHz XTAL, WATCHDOG TIMER DISABLED
90
80
70
60
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 136. Standby Supply Current vs. VCC (2 MHz Xtal, Watchdog Timer Disabled)
STANDBY SUPPLY CURRENT vs. VCC
2 MHz XTAL, WATCHDOG TIMER DISABLED
90
80
70
60
50
40
30
20
10
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
281
2513F–AVR–12/03
Figure 137. Standby Supply Current vs. VCC (4 MHz Resonator, Watchdog Timer
Disabled)
STANDBY SUPPLY CURRENT vs. VCC
4 MHz RESONATOR, WATCHDOG TIMER DISABLED
140
120
100
80
60
40
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 138. Standby Supply Current vs. VCC (4 MHz Xtal, Watchdog Timer Disabled)
STANDBY SUPPLY CURRENT vs. VCC
4 MHz XTAL, WATCHDOG TIMER DISABLED
140
120
100
80
60
40
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
282
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 139. Standby Supply Current vs. VCC (6 MHz Resonator, Watchdog Timer
Disabled)
STANDBY SUPPLY CURRENT vs. VCC
6 MHz RESONATOR, WATCHDOG TIMER DISABLED
180
160
140
120
100
80
60
40
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
CC (V)
Figure 140. Standby Supply Current vs. VCC (6 MHz Xtal, Watchdog Timer Disabled)
STANDBY SUPPLY CURRENT vs. VCC
6 MHz XTAL, WATCHDOG TIMER DISABLED
200
180
160
140
120
100
80
60
40
20
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
283
2513F–AVR–12/03
Pin Pull-up
Figure 141. I/O Pin Pull-up Resistor Current vs. Input Voltage (VCC = 5V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
Vcc = 5V
160
85°C
140
25°C
120
-40°C
100
80
60
40
20
0
0
1
2
3
4
5
6
VIO (V)
Figure 142. I/O Pin Pull-up Resistor Current vs. Input Voltage (VCC = 2.7V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
Vcc = 2.7V
80
85°C
70
25°C
-40°C
60
50
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
VIO (V)
284
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 143. I/O Pin Pull-up Resistor Current vs. Input Voltage (VCC = 1.8V)
I/O PIN PULL-UP RESISTOR CURRENT vs. INPUT VOLTAGE
Vcc = 1.8V
60
50
85°C
25°C
40
30
20
10
0
-40°C
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VOP (V)
Figure 144. Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 5V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
Vcc = 5V
120
-40°C
25°C
100
85°C
80
60
40
20
0
6
0
1
2
3
4
5
VRESET (V)
285
2513F–AVR–12/03
Figure 145. Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 2.7V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
Vcc = 2.7V
60
-40°C
25°C
50
85°C
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
V
RESET (V)
Figure 146. Reset Pull-up Resistor Current vs. Reset Pin Voltage (VCC = 1.8V)
RESET PULL-UP RESISTOR CURRENT vs. RESET PIN VOLTAGE
Vcc = 1.8V
40
-40°C
35
25°C
30
85°C
25
20
15
10
5
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
V
RESET (V)
286
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Pin Driver Strength
Figure 147. I/O Pin Source Current vs. Output Voltage (VCC = 5V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
Vcc = 5V
90
80
70
60
50
40
30
20
10
0
-40°C
25°C
85°C
0
1
2
3
4
5
6
VOH (V)
Figure 148. I/O Pin Source Current vs. Output Voltage (VCC = 2.7V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
Vcc = 2.7V
30
-40°C
25
25°C
85°C
20
15
10
5
0
0
0.5
1
1.5
2
2.5
3
V
OH (V)
287
2513F–AVR–12/03
Figure 149. I/O Pin Source Current vs. Output Voltage (VCC = 1.8V)
I/O PIN SOURCE CURRENT vs. OUTPUT VOLTAGE
Vcc = 1.8V
-40°C
85°C
8
25°C
7
6
5
4
3
2
1
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
VOH (V)
Figure 150. I/O Pin Sink Current vs. Output Voltage (VCC = 5V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
Vcc = 5V
90
80
70
60
50
40
30
20
10
0
-40°C
25°C
85°C
0
0.5
1
1.5
2
2.5
VOL (V)
288
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 151. I/O Pin Sink Current vs. Output Voltage (VCC = 2.7V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
Vcc = 2.7V
35
30
25
20
15
10
5
-40°C
25°C
85°C
0
0
0.5
1
1.5
2
2.5
V
OL (V)
Figure 152. I/O Pin Sink Current vs. Output Voltage (VCC = 1.8V)
I/O PIN SINK CURRENT vs. OUTPUT VOLTAGE
Vcc = 1.8V
12
-40°C
25°C
10
8
85°C
6
4
2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
V
OL (V)
289
2513F–AVR–12/03
Pin Thresholds and
Hysteresis
Figure 153. I/O Pin Input Threshold Voltage vs. VCC (VIH, I/O Pin Read as “1”)
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIH, I/O PIN READ AS '1'
3
2.5
2
85°C
25°C
-40°C
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 154. I/O Pin Input Threshold Voltage vs. VCC (VIL, I/O Pin Read as “0”)
I/O PIN INPUT THRESHOLD VOLTAGE vs. VCC
VIL, I/O PIN READ AS '0'
3
85°C
25°C
-40°C
2.5
2
1.5
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
290
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 155. I/O Pin Input Hysteresis vs. VCC
I/O PIN INPUT HYSTERESIS vs. VCC
0.6
0.5
0.4
0.3
0.2
0.1
0
-40°C
25°C
85°C
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
CC (V)
Figure 156. Reset Input Threshold Voltage vs. VCC (VIH, Reset Pin Read as “1”)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIH, RESET PIN READ AS '1'
3
2.5
2
-40°C
1.5
25°C
85°C
1
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
CC (V)
291
2513F–AVR–12/03
Figure 157. Reset Input Threshold Voltage vs. VCC (VIL, Reset Pin Read as “0”)
RESET INPUT THRESHOLD VOLTAGE vs. VCC
VIL, RESET PIN READ AS '0'
2.5
2
1.5
1
85°C
25°C
-40°C
0.5
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
CC (V)
Figure 158. Reset Input Pin Hysteresis vs. VCC
RESET INPUT PIN HYSTERESIS vs. VCC
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-40°C
25°C
85°C
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
292
ATmega162/V
2513F–AVR–12/03
ATmega162/V
BOD Thresholds and Analog
Comparator Offset
Figure 159. BOD Thresholds vs. Temperature (BOD Level is 4.3V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 4.3V
4.6
4.5
4.4
4.3
4.2
4.1
4
Rising VCC
Falling VCC
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (˚C)
Figure 160. BOD Thresholds vs. Temperature (BOD Level is 2.7V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 2.7V
3
2.9
Rising VCC
2.8
Falling VCC
2.7
2.6
2.5
2.4
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (˚C)
293
2513F–AVR–12/03
Figure 161. BOD Thresholds vs. Temperature (BOD Level is 2.3V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 2.3V
2.6
2.5
Rising VCC
2.4
Falling VCC
2.3
2.2
2.1
2
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (˚C)
Figure 162. BOD Thresholds vs. Temperature (BOD Level is 1.8V)
BOD THRESHOLDS vs. TEMPERATURE
BODLEVEL IS 1.8V
2.1
2
Rising VCC
1.9
1.8
Falling VCC
1.7
1.6
1.5
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (˚C)
294
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 163. Bandgap Voltage vs. VCC
BANDGAP VOLTAGE vs. VCC
1.14
1.13
1.12
1.11
1.1
85°C
25°C
-40°C
1.09
1.08
1.5
2
2.5
3
3.5
4
4.5
5
5.5
Vcc (V)
Figure 164. Analog Comparator Offset Voltage vs. Common Mode Voltage (VCC = 5V)
ANALOG COMPARATOR OFFSET VOLTAGE vs. COMMON MODE VOLTAGE
VCC = 5V
0.01
85°C
0.009
25°C
0.008
-40°C
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Common Mode Voltage (V)
295
2513F–AVR–12/03
Figure 165. Analog Comparator Offset Voltage vs. Common Mode Voltage
(VCC = 2.7V)
ANALOG COMPARATOR OFFSET VOLTAGE vs. COMMON MODE VOLTAGE
VCC = 2.7V
0.006
85°C
0.005
25°C
0.004
-40°C
0.003
0.002
0.001
0
-0.001
0
0.5
1
1.5
2
2.5
3
Common Mode Voltage (V)
Internal Oscillator Speed
Figure 166. Watchdog Oscillator Frequency vs. VCC
WATCHDOG OSCILLATOR FREQUENCY vs. VCC
1300
1250
1200
1150
1100
1050
1000
-40°C
25°C
85°C
1.5
2
2.5
3
3.5
4
4.5
5
5.5
V
CC (V)
296
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 167. Calibrated 8 MHz RC Oscillator Frequency vs. Temperature
CALIBRATED 8MHz RC OSCILLATOR FREQUENCY vs. TEMPERATURE
8.4
8.3
8.2
8.1
8
5.5V
4.0V
2.7V
1.8V
7.9
7.8
7.7
7.6
7.5
-60
-40
-20
0
20
40
60
80
100
Ta (˚C)
Figure 168. Calibrated 8 MHz RC Oscillator Frequency vs.VCC
CALIBRATED 8MHz RC OSCILLATOR FREQUENCY vs. VCC
10
9.5
9
8.5
8
85°C
25°C
-40°C
7.5
7
6.5
6
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
297
2513F–AVR–12/03
Figure 169. Calibrated 8 MHz RC Oscillator Frequency vs. Osccal Value
CALIBRATED 8MHz RC OSCILLATOR FREQUENCY vs. OSCCAL VALUE
16
14
12
10
8
6
4
0
16
32
48
64
80
96
112
OSCCAL VALUE
Current Consumption of
Peripheral Units
Figure 170. Brownout Detector Current vs. VCC
BROWNOUT DETECTOR CURRENT vs. VCC
35
30
25
20
15
10
5
-40°C
85°C
25°C
0
-5
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
298
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Figure 171. 32 kHz TOSC Current vs. VCC (Watchdog Timer Disabled)
32kHz TOSC CURRENT vs. VCC
WATCHDOG TIMER DISABLED
30
25
20
15
10
5
85°C
25°C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 172. Watchdog TImer Current vs. VCC
WATCHDOG TIMER CURRENT vs. VCC
20
18
16
14
12
10
8
85°C
25°C
-40°C
6
4
2
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
299
2513F–AVR–12/03
Figure 173. Analog Comparator Current vs. VCC
ANALOG COMPARATOR CURRENT vs. VCC
80
70
60
50
40
30
20
10
0
-40°C
25°C
85°C
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
Figure 174. Programming Current vs. VCC
PROGRAMMING CURRENT vs. Vcc
25
20
15
10
5
-40°C
25°C
85°C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
300
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Current Consumption in
Figure 175. Reset Supply Current vs. Frequency (0.1 - 1.0 MHz, Excluding Current
Reset and Reset Pulsewidth
Through The Reset Pull-up)
RESET SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz, EXCLUDING CURRENT THROUGH THE RESET PULLUP
4.5
5.5V
4
5.0V
3.5
3
4.5V
4.0V
2.5
2
3.3V
2.7V
1.5
1
1.8V
0.5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
Figure 176. Reset Supply Current vs. Frequency (1 - 20 MHz, Excluding Current
Through The Reset Pull-up)
RESET SUPPLY CURRENT vs. FREQUENCY
1 - 20 MHz, EXCLUDING CURRENT THROUGH THE RESET PULLUP
35
5.5V
30
5.0V
25
4.5V
20
4.0V
15
10
3.3V
5
2.7V
1.8V
0
0
2
4
6
8
10
12
14
16
18
20
Frequency (MHz)
301
2513F–AVR–12/03
Figure 177. Reset Pulse Width vs. VCC
RESET PULSE WIDTH vs. VCC
2500
2000
1500
1000
500
85°C
25°C
-40°C
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VCC (V)
302
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Register Summary
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Page
(0xFF)
..
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
TCCR3A
TCCR3B
TCNT3H
TCNT3L
OCR3AH
OCR3AL
OCR3BH
OCR3BL
Reserved
Reserved
ICR3H
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
(0x9E)
(0x9D)
(0x9C)
(0x9B)
(0x9A)
(0x99)
(0x98)
(0x97)
(0x96)
(0x95)
(0x94)
(0x93)
(0x92)
(0x91)
(0x90)
(0x8F)
(0x8E)
(0x8D)
(0x8C)
(0x8B)
(0x8A)
(0x89)
(0x88)
(0x87)
(0x86)
(0x85)
(0x84)
(0x83)
(0x82)
(0x81)
(0x80)
(0x7F)
(0x7E)
(0x7D)
(0x7C)
(0x7B)
(0x7A)
(0x79)
(0x78)
(0x77)
(0x76)
(0x75)
(0x74)
(0x73)
(0x72)
(0x71)
(0x70)
(0x6F)
(0x6E)
(0x6D)
(0x6C)
(0x6B)
(0x6A)
(0x69)
(0x68)
(0x67)
(0x66)
(0x65)
(0x64)
(0x63)
(0x62)
(0x61)
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
COM3B1
–
–
–
–
–
–
COM3A1
ICNC3
COM3A0
ICES3
COM3B0
WGM33
FOC3A
WGM32
FOC3B
CS32
WGM31
CS31
WGM30
CS30
130
127
132
132
132
132
132
132
Timer/Counter3 – Counter Register High Byte
Timer/Counter3 – Counter Register Low Byte
Timer/Counter3 – Output Compare Register A High Byte
Timer/Counter3 – Output Compare Register A Low Byte
Timer/Counter3 – Output Compare Register B High Byte
Timer/Counter3 – Output Compare Register B Low Byte
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Timer/Counter3 – Input Capture Register High Byte
Timer/Counter3 – Input Capture Register Low Byte
133
133
ICR3L
Reserved
Reserved
ETIMSK
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
TICIE3
OCIE3A
OCIE3B
TOIE3
–
–
134
135
ETIFR
–
–
ICF3
OCF3A
OCF3B
TOV3
–
–
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
PCMSK1
PCMSK0
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
CLKPR
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
PCINT15
PCINT14
PCINT13
PCINT12
PCINT11
PCINT10
PCINT9
PCINT8
87
87
PCINT7
PCINT6
PCINT5
PCINT4
PCINT3
PCINT2
PCINT1
PCINT0
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
CLKPCE
CLKPS3
CLKPS2
CLKPS1
CLKPS0
39
303
2513F–AVR–12/03
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Page
(0x60)
Reserved
SREG
–
–
T
–
H
–
S
–
V
–
N
–
–
0x3F (0x5F)
0x3E (0x5E)
0x3D (0x5D)
I
Z
C
8
SPH
SP15
SP7
SP14
SP6
SP13
SP5
SP12
SP4
SP11
SP3
SP10
SP2
SP9
SP1
SP8
SP0
11
SPL
11
UBRR1[11:8]
UBRR1H
UCSR1C
GICR
URSEL1
URSEL1
INT1
189
0x3C(2)(0x5C)(2)
UMSEL1
INT0
UPM11
INT2
UPM10
PCIE1
PCIF1
OCIE2
OCF2
USBS1
PCIE0
PCIF0
UCSZ11
–
UCSZ10
IVSEL
–
UCPOL1
IVCE
188
0x3B (0x5B)
0x3A (0x5A)
0x39 (0x59)
0x38 (0x58)
0x37 (0x57)
0x36 (0x56)
0x35 (0x55)
0x34 (0x54)
0x33 (0x53)
0x32 (0x52)
0x31 (0x51)
60, 85
GIFR
INTF1
TOIE1
TOV1
SPMIE
SM0
INTF0
OCIE1A
OCF1A
RWWSB
SRL2
INTF2
OCIE1B
OCF1B
–
–
–
86
TIMSK
TIFR
TICIE1
ICF1
TOIE2
TOV2
PGWRT
SRW00
ISC10
BORF
CS02
TOIE0
TOV0
PGERS
SRW11
ISC01
EXTRF
CS01
OCIE0
OCF0
SPMEN
ISC2
101, 133, 154
102, 135, 155
220
28,42,84
28,41,83
41,50,206
99
SPMCR
EMCUCR
MCUCR
MCUCSR
TCCR0
TCNT0
OCR0
RWWSRE
SRL0
BLBSET
SRW01
ISC11
SRL1
SE
SRE
SRW10
–
SM1
ISC00
PORF
CS00
JTD
SM2
JTRF
WDRF
WGM01
FOC0
WGM00
COM01
COM00
Timer/Counter0 (8 Bits)
Timer/Counter0 Output Compare Register
101
101
30,69,104,156
127
130
132
132
132
132
132
132
148
152
133
133
151
151
52
0x30 (0x50)
0x2F (0x4F)
0x2E (0x4E)
0x2D (0x4D)
0x2C (0x4C)
0x2B (0x4B)
0x2A (0x4A)
0x29 (0x49)
0x28 (0x48)
0x27 (0x47)
0x26 (0x46)
0x25 (0x45)
0x24 (0x44)
0x23 (0x43)
0x22 (0x42)
0x21 (0x41)
SFIOR
TCCR1A
TCCR1B
TCNT1H
TCNT1L
OCR1AH
OCR1AL
OCR1BH
OCR1BL
TCCR2
ASSR
TSM
COM1A1
ICNC1
XMBK
COM1A0
ICES1
XMM2
COM1B1
–
XMM1
COM1B0
WGM13
XMM0
FOC1A
WGM12
PUD
FOC1B
CS12
PSR2
WGM11
CS11
PSR310
WGM10
CS10
Timer/Counter1 – Counter Register High Byte
Timer/Counter1 – Counter Register Low Byte
Timer/Counter1 – Output Compare Register A High Byte
Timer/Counter1 – Output Compare Register A Low Byte
Timer/Counter1 – Output Compare Register B High Byte
Timer/Counter1 – Output Compare Register B Low Byte
FOC2
–
WGM20
–
COM21
–
COM20
–
WGM21
AS2
CS22
CS21
CS20
TCON2UB
OCR2UB
TCR2UB
ICR1H
ICR1L
Timer/Counter1 – Input Capture Register High Byte
Timer/Counter1 – Input Capture Register Low Byte
Timer/Counter2 (8 Bits)
TCNT2
OCR2
Timer/Counter2 Output Compare Register
WDTCR
UBRR0H
UCSR0C
EEARH
EEARL
EEDR
–
–
–
WDCE
WDE
WDP2
WDP1
WDP0
URSEL0
URSEL0
–
–
UMSEL0
–
–
UPM01
–
–
UPM00
–
UBRR0[11:8]
189
188
18
0x20(2) (0x40)(2)
USBS0
–
UCSZ01
–
UCSZ00
–
UCPOL0
EEAR8
0x1F (0x3F)
0x1E (0x3E)
0x1D (0x3D)
0x1C (0x3C)
0x1B (0x3B)
0x1A (0x3A)
0x19 (0x39)
0x18 (0x38)
0x17 (0x37)
0x16 (0x36)
0x15 (0x35)
0x14 (0x34)
0x13 (0x33)
0x12 (0x32)
0x11 (0x31)
0x10 (0x30)
0x0F (0x2F)
0x0E (0x2E)
0x0D (0x2D)
0x0C (0x2C)
0x0B (0x2B)
0x0A (0x2A)
0x09 (0x29)
0x08 (0x28)
0x07 (0x27)
0x06 (0x26)
0x05 (0x25)
EEPROM Address Register Low Byte
EEPROM Data Register
18
19
EECR
–
–
–
–
EERIE
PORTA3
DDA3
EEMWE
PORTA2
DDA2
EEWE
PORTA1
DDA1
EERE
PORTA0
DDA0
19
PORTA
DDRA
PORTA7
DDA7
PORTA6
DDA6
PORTA5
DDA5
PORTA4
DDA4
81
81
PINA
PINA7
PORTB7
DDB7
PINA6
PORTB6
DDB6
PINA5
PORTB5
DDB5
PINA4
PORTB4
DDB4
PINA3
PINA2
PINA1
PINA0
81
PORTB
DDRB
PORTB3
DDB3
PORTB2
DDB2
PORTB1
DDB1
PORTB0
DDB0
81
81
PINB
PINB7
PORTC7
DDC7
PINB6
PORTC6
DDC6
PINB5
PORTC5
DDC5
PINB4
PORTC4
DDC4
PINB3
PINB2
PINB1
PINB0
81
PORTC
DDRC
PORTC3
DDC3
PORTC2
DDC2
PORTC1
DDC1
PORTC0
DDC0
81
81
PINC
PINC7
PORTD7
DDD7
PINC6
PORTD6
DDD6
PINC5
PORTD5
DDD5
PINC4
PORTD4
DDD4
PINC3
PINC2
PINC1
PORTD1
DDD1
PINC0
PORTD0
DDD0
82
PORTD
DDRD
PORTD3
DDD3
PORTD2
DDD2
82
82
PIND
PIND7
PIND6
PIND5
PIND4
PIND3
PIND2
PIND1
PIND0
82
SPDR
SPI Data Register
163
163
161
185
185
186
189
194
82
SPSR
SPIF
SPIE
WCOL
SPE
–
–
–
–
–
SPI2X
SPR0
SPCR
DORD
MSTR
CPOL
CPHA
SPR1
UDR0
USART0 I/O Data Register
UCSR0A
UCSR0B
UBRR0L
ACSR
RXC0
TXC0
UDRE0
UDRIE0
FE0
DOR0
UPE0
U2X0
MPCM0
TXB80
RXCIE0
TXCIE0
RXEN0
TXEN0
UCSZ02
RXB80
USART0 Baud Rate Register Low Byte
ACD
ACBG
ACO
ACI
ACIE
ACIC
PORTE2
DDE2
ACIS1
PORTE1
DDE1
ACIS0
PORTE0
DDE0
PORTE
DDRE
–
–
–
–
–
–
–
–
–
–
–
–
82
PINE
–
–
–
–
PINE2
CAL2
PINE1
CAL1
PINE0
CAL0
82
OSCCAL
OCDR
CAL6
CAL5
CAL4
CAL3
37
0x04(1) (0x24)(1)
On-chip Debug Register
201
185
185
0x03 (0x23)
0x02 (0x22)
UDR1
USART1 I/O Data Register
UCSR1A
RXC1
TXC1
UDRE1
FE1
DOR1
UPE1
U2X1
MPCM1
304
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Page
0x01 (0x21)
0x00 (0x20)
UCSR1B
UBRR1L
RXCIE1
TXCIE1
UDRIE1
RXEN1
TXEN1
UCSZ12
RXB81
TXB81
186
189
USART1 Baud Rate Register Low Byte
Notes: 1. When the OCDEN Fuse is unprogrammed, the OSCCAL Register is always accessed on this address. Refer to the debug-
ger specific documentation for details on how to use the OCDR Register.
2. Refer to the USART description for details on how to access UBRRH and UCSRC.
3. For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses
should never be written.
4. Some of the Status Flags are cleared by writing a logical one to them. Note that the CBI and SBI instructions will operate on
all bits in the I/O Register, writing a one back into any flag read as set, thus clearing the flag. The CBI and SBI instructions
work with registers 0x00 to 0x1F only.
305
2513F–AVR–12/03
Instruction Set Summary
Flags
#Clocks
Operands
Description
Operation
Mnemonics
ARITHMETIC AND LOGIC INSTRUCTIONS
ADD
Rd, Rr
Rd, Rr
Rdl,K
Rd, Rr
Rd, K
Rd, Rr
Rd, K
Rdl,K
Rd, Rr
Rd, K
Rd, Rr
Rd, K
Rd, Rr
Rd
Add two Registers
Rd ← Rd + Rr
Z,C,N,V,H
Z,C,N,V,H
Z,C,N,V,S
Z,C,N,V,H
Z,C,N,V,H
Z,C,N,V,H
Z,C,N,V,H
Z,C,N,V,S
Z,N,V
1
1
2
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
ADC
Add with Carry two Registers
Add Immediate to Word
Subtract two Registers
Subtract Constant from Register
Subtract with Carry two Registers
Subtract with Carry Constant from Reg.
Subtract Immediate from Word
Logical AND Registers
Logical AND Register and Constant
Logical OR Registers
Rd ← Rd + Rr + C
Rdh:Rdl ← Rdh:Rdl + K
Rd ← Rd - Rr
ADIW
SUB
SUBI
SBC
Rd ← Rd - K
Rd ← Rd - Rr - C
Rd ← Rd - K - C
Rdh:Rdl ← Rdh:Rdl - K
Rd ← Rd • Rr
SBCI
SBIW
AND
ANDI
OR
Rd ← Rd • K
Z,N,V
Rd ← Rd v Rr
Z,N,V
ORI
Logical OR Register and Constant
Exclusive OR Registers
One’s Complement
Rd ← Rd v K
Z,N,V
EOR
COM
NEG
SBR
Rd ← Rd Rr
Z,N,V
Rd ← 0xFF − Rd
Rd ← 0x00 − Rd
Rd ← Rd v K
Z,C,N,V
Z,C,N,V,H
Z,N,V
Rd
Two’s Complement
Rd,K
Rd,K
Rd
Set Bit(s) in Register
CBR
Clear Bit(s) in Register
Increment
Rd ← Rd • (0xFF - K)
Rd ← Rd + 1
Z,N,V
INC
Z,N,V
DEC
Rd
Decrement
Rd ← Rd − 1
Z,N,V
TST
Rd
Test for Zero or Minus
Clear Register
Rd ← Rd • Rd
Z,N,V
CLR
Rd
Rd ← Rd Rd
Rd ← 0xFF
Z,N,V
SER
Rd
Set Register
None
MUL
MULS
MULSU
FMUL
FMULS
FMULSU
Rd, Rr
Rd, Rr
Rd, Rr
Rd, Rr
Rd, Rr
Rd, Rr
Multiply Unsigned
R1:R0 ← Rd x Rr
R1:R0 ← Rd x Rr
R1:R0 ← Rd x Rr
R1:R0 ← (Rd x Rr) << 1
R1:R0 ← (Rd x Rr) << 1
R1:R0 ← (Rd x Rr) << 1
Z,C
Multiply Signed
Z,C
Multiply Signed with Unsigned
Fractional Multiply Unsigned
Fractional Multiply Signed
Fractional Multiply Signed with Unsigned
Z,C
Z,C
Z,C
Z,C
BRANCH INSTRUCTIONS
RJMP
IJMP
k
Relative Jump
PC ← PC + k + 1
None
None
None
None
None
None
None
I
2
2
Indirect Jump to (Z)
PC ← Z
JMP
k
k
Direct Jump
PC ← k
3
RCALL
ICALL
CALL
RET
Relative Subroutine Call
Indirect Call to (Z)
PC ← PC + k + 1
3
PC ← Z
3
k
Direct Subroutine Call
Subroutine Return
PC ← k
4
PC ← STACK
4
RETI
Interrupt Return
PC ← STACK
4
CPSE
CP
Rd,Rr
Compare, Skip if Equal
Compare
if (Rd = Rr) PC ← PC + 2 or 3
Rd − Rr
None
Z, N,V,C,H
Z, N,V,C,H
Z, N,V,C,H
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
1/2/3
1
Rd,Rr
CPC
Rd,Rr
Compare with Carry
Rd − Rr − C
1
CPI
Rd,K
Compare Register with Immediate
Skip if Bit in Register Cleared
Skip if Bit in Register is Set
Skip if Bit in I/O Register Cleared
Skip if Bit in I/O Register is Set
Branch if Status Flag Set
Branch if Status Flag Cleared
Branch if Equal
Rd − K
1
SBRC
SBRS
SBIC
SBIS
Rr, b
if (Rr(b)=0) PC ← PC + 2 or 3
if (Rr(b)=1) PC ← PC + 2 or 3
if (P(b)=0) PC ← PC + 2 or 3
if (P(b)=1) PC ← PC + 2 or 3
if (SREG(s) = 1) then PC←PC+k + 1
if (SREG(s) = 0) then PC←PC+k + 1
if (Z = 1) then PC ← PC + k + 1
if (Z = 0) then PC ← PC + k + 1
if (C = 1) then PC ← PC + k + 1
if (C = 0) then PC ← PC + k + 1
if (C = 0) then PC ← PC + k + 1
if (C = 1) then PC ← PC + k + 1
if (N = 1) then PC ← PC + k + 1
if (N = 0) then PC ← PC + k + 1
if (N V= 0) then PC ← PC + k + 1
if (N V= 1) then PC ← PC + k + 1
if (H = 1) then PC ← PC + k + 1
if (H = 0) then PC ← PC + k + 1
if (T = 1) then PC ← PC + k + 1
if (T = 0) then PC ← PC + k + 1
if (V = 1) then PC ← PC + k + 1
if (V = 0) then PC ← PC + k + 1
1/2/3
1/2/3
1/2/3
1/2/3
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
Rr, b
P, b
P, b
s, k
s, k
k
BRBS
BRBC
BREQ
BRNE
BRCS
BRCC
BRSH
BRLO
BRMI
BRPL
BRGE
BRLT
BRHS
BRHC
BRTS
BRTC
BRVS
BRVC
k
Branch if Not Equal
k
Branch if Carry Set
k
Branch if Carry Cleared
Branch if Same or Higher
Branch if Lower
k
k
k
Branch if Minus
k
Branch if Plus
k
Branch if Greater or Equal, Signed
Branch if Less Than Zero, Signed
Branch if Half Carry Flag Set
Branch if Half Carry Flag Cleared
Branch if T Flag Set
k
k
k
k
k
Branch if T Flag Cleared
Branch if Overflow Flag is Set
Branch if Overflow Flag is Cleared
k
k
306
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Flags
None
#Clocks
Operands
Description
Operation
Mnemonics
BRIE
BRID
k
k
Branch if Interrupt Enabled
Branch if Interrupt Disabled
if ( I = 1) then PC ← PC + k + 1
if ( I = 0) then PC ← PC + k + 1
1/2
1/2
None
DATA TRANSFER INSTRUCTIONS
MOV
MOVW
LDI
LD
Rd, Rr
Rd, Rr
Rd, K
Move Between Registers
Copy Register Word
Rd ← Rr
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
-
Rd+1:Rd ← Rr+1:Rr
Load Immediate
Rd ← K
Rd, X
Load Indirect
Rd ← (X)
LD
Rd, X+
Rd, - X
Rd, Y
Load Indirect and Post-Inc.
Load Indirect and Pre-Dec.
Load Indirect
Rd ← (X), X ← X + 1
X ← X - 1, Rd ← (X)
Rd ← (Y)
LD
LD
LD
Rd, Y+
Rd, - Y
Rd,Y+q
Rd, Z
Load Indirect and Post-Inc.
Load Indirect and Pre-Dec.
Load Indirect with Displacement
Load Indirect
Rd ← (Y), Y ← Y + 1
Y ← Y - 1, Rd ← (Y)
Rd ← (Y + q)
Rd ← (Z)
LD
LDD
LD
LD
Rd, Z+
Rd, -Z
Rd, Z+q
Rd, k
Load Indirect and Post-Inc.
Load Indirect and Pre-Dec.
Load Indirect with Displacement
Load Direct from SRAM
Store Indirect
Rd ← (Z), Z ← Z+1
Z ← Z - 1, Rd ← (Z)
Rd ← (Z + q)
Rd ← (k)
LD
LDD
LDS
ST
X, Rr
(X) ← Rr
ST
X+, Rr
- X, Rr
Y, Rr
Store Indirect and Post-Inc.
Store Indirect and Pre-Dec.
Store Indirect
(X) ← Rr, X ← X + 1
X ← X - 1, (X) ← Rr
(Y) ← Rr
ST
ST
ST
Y+, Rr
- Y, Rr
Y+q,Rr
Z, Rr
Store Indirect and Post-Inc.
Store Indirect and Pre-Dec.
Store Indirect with Displacement
Store Indirect
(Y) ← Rr, Y ← Y + 1
Y ← Y - 1, (Y) ← Rr
(Y + q) ← Rr
ST
STD
ST
(Z) ← Rr
ST
Z+, Rr
-Z, Rr
Z+q,Rr
k, Rr
Store Indirect and Post-Inc.
Store Indirect and Pre-Dec.
Store Indirect with Displacement
Store Direct to SRAM
Load Program Memory
Load Program Memory
Load Program Memory and Post-Inc
Store Program Memory
In Port
(Z) ← Rr, Z ← Z + 1
Z ← Z - 1, (Z) ← Rr
(Z + q) ← Rr
ST
STD
STS
LPM
LPM
LPM
SPM
IN
(k) ← Rr
R0 ← (Z)
Rd, Z
Rd ← (Z)
Rd, Z+
Rd ← (Z), Z ← Z+1
(Z) ← R1:R0
Rd, P
P, Rr
Rr
Rd ← P
1
1
2
2
OUT
PUSH
POP
Out Port
P ← Rr
Push Register on Stack
Pop Register from Stack
STACK ← Rr
Rd ← STACK
Rd
BIT AND BIT-TEST INSTRUCTIONS
SBI
P,b
P,b
Rd
Rd
Rd
Rd
Rd
Rd
s
Set Bit in I/O Register
Clear Bit in I/O Register
Logical Shift Left
I/O(P,b) ← 1
None
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
CBI
I/O(P,b) ← 0
None
LSL
Rd(n+1) ← Rd(n), Rd(0) ← 0
Z,C,N,V
LSR
ROL
ROR
ASR
SWAP
BSET
BCLR
BST
BLD
SEC
CLC
SEN
CLN
SEZ
CLZ
SEI
Logical Shift Right
Rd(n) ← Rd(n+1), Rd(7) ← 0
Z,C,N,V
Rotate Left Through Carry
Rotate Right Through Carry
Arithmetic Shift Right
Swap Nibbles
Rd(0)←C,Rd(n+1)← Rd(n),C←Rd(7)
Z,C,N,V
Rd(7)←C,Rd(n)← Rd(n+1),C←Rd(0)
Z,C,N,V
Rd(n) ← Rd(n+1), n=0..6
Z,C,N,V
Rd(3..0)←Rd(7..4),Rd(7..4)←Rd(3..0)
None
Flag Set
SREG(s) ← 1
SREG(s) ← 0
T ← Rr(b)
Rd(b) ← T
C ← 1
SREG(s)
s
Flag Clear
SREG(s)
Rr, b
Rd, b
Bit Store from Register to T
Bit load from T to Register
Set Carry
T
None
C
C
N
N
Z
Clear Carry
C ← 0
Set Negative Flag
N ← 1
Clear Negative Flag
Set Zero Flag
N ← 0
Z ← 1
Clear Zero Flag
Z ← 0
Z
Global Interrupt Enable
Global Interrupt Disable
Set Signed Test Flag
Clear Signed Test Flag
Set Twos Complement Overflow.
Clear Twos Complement Overflow
Set T in SREG
I ← 1
I
CLI
I ← 0
I
SES
CLS
SEV
CLV
SET
CLT
SEH
S ← 1
S
S
V
V
T
S ← 0
V ← 1
V ← 0
T ← 1
Clear T in SREG
T ← 0
T
Set Half Carry Flag in SREG
H ← 1
H
307
2513F–AVR–12/03
Flags
#Clocks
Operands
Description
Operation
Mnemonics
Clear Half Carry Flag in SREG
CLH
H ← 0
H
1
MCU CONTROL INSTRUCTIONS
NOP
No Operation
Sleep
None
None
None
None
1
1
SLEEP
WDR
(see specific descr. for Sleep function)
(see specific descr. for WDR/Timer)
For On-chip Debug Only
Watchdog Reset
Break
1
BREAK
N/A
308
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Ordering Information
Speed (MHz)
Power Supply
Ordering Code
Package
Operation Range
8(2)
1.8 - 5.5V
ATmega162V-8AI
ATmega162V-8PI
ATmega162V-8MI
44A
40P6
44M1
Industrial
(-40°C to 85°C)
16(3)
2.7 - 5.5V
ATmega162-16AI
ATmega162-16PI
ATmega162-16MI
44A
40P6
44M1
Industrial
(-40°C to 85°C)
Notes: 1. This device can also be supplied in wafer form. Please contact your local Atmel sales office for detailed ordering information
and minimum quantities.
2. See Figure 113 on page 265.
3. See Figure 114 on page 265.
Package Type
44A
44-lead, Thin (1.0 mm) Plastic Gull Wing Quad Flat Package (TQFP)
40-pin, 0.600” Wide, Plastic Dual Inline Package (PDIP)
40P6
44M1
44-pad, 7 x 7 x 1.0 mm body, lead pitch 0.50 mm, Micro Lead Frame Package (MLF)
309
2513F–AVR–12/03
Packaging Information
44A
PIN 1
B
PIN 1 IDENTIFIER
E1
E
e
D1
D
C
0˚~7˚
A2
A
A1
L
COMMON DIMENSIONS
(Unit of Measure = mm)
MIN
–
MAX
1.20
NOM
NOTE
SYMBOL
A
–
–
A1
A2
D
0.05
0.95
11.75
9.90
11.75
9.90
0.30
0.09
0.45
0.15
1.00
12.00
10.00
12.00
10.00
–
1.05
12.25
D1
E
10.10 Note 2
12.25
Notes:
1. This package conforms to JEDEC reference MS-026, Variation ACB.
2. Dimensions D1 and E1 do not include mold protrusion. Allowable
protrusion is 0.25 mm per side. Dimensions D1 and E1 are maximum
plastic body size dimensions including mold mismatch.
E1
B
10.10 Note 2
0.45
C
–
0.20
3. Lead coplanarity is 0.10 mm maximum.
L
–
0.75
e
0.80 TYP
10/5/2001
TITLE
DRAWING NO. REV.
2325 Orchard Parkway
San Jose, CA 95131
44A, 44-lead, 10 x 10 mm Body Size, 1.0 mm Body Thickness,
0.8 mm Lead Pitch, Thin Profile Plastic Quad Flat Package (TQFP)
44A
B
R
310
ATmega162/V
2513F–AVR–12/03
ATmega162/V
40P6
D
PIN
1
E1
A
SEATING PLANE
A1
L
B
B1
e
E
COMMON DIMENSIONS
(Unit of Measure = mm)
0º ~ 15º REF
C
MIN
–
MAX
4.826
–
NOM
NOTE
SYMBOL
A
–
eB
A1
D
0.381
52.070
15.240
13.462
0.356
1.041
3.048
0.203
15.494
–
–
52.578 Note 2
15.875
E
–
E1
B
–
13.970 Note 2
0.559
–
B1
L
–
1.651
Notes:
1. This package conforms to JEDEC reference MS-011, Variation AC.
2. Dimensions D and E1 do not include mold Flash or Protrusion.
Mold Flash or Protrusion shall not exceed 0.25 mm (0.010").
–
3.556
C
–
–
0.381
eB
e
17.526
2.540 TYP
09/28/01
DRAWING NO. REV.
40P6
TITLE
2325 Orchard Parkway
San Jose, CA 95131
40P6, 40-lead (0.600"/15.24 mm Wide) Plastic Dual
Inline Package (PDIP)
B
R
311
2513F–AVR–12/03
44M1
D
Marked Pin# 1 ID
E
SEATING PLANE
A1
A3
TOP VIEW
A
L
Pin #1 Corner
SIDE VIEW
D2
COMMON DIMENSIONS
(Unit of Measure = mm)
MIN
0.80
–
MAX
1.00
0.05
NOM
0.90
NOTE
SYMBOL
E2
A
A1
A3
b
0.02
0.25 REF
0.23
0.18
5.00
5.00
0.35
0.30
5.40
5.40
0.75
D
7.00 BSC
5.20
D2
E
e
b
7.00 BSC
5.20
BOTTOM VIEW
E2
e
0.50 BSC
0.55
L
Notes: 1. JEDEC Standard MO-220, Fig. 1 (SAW Singulation) VKKD-1.
01/15/03
DRAWING NO. REV.
TITLE
2325 Orchard Parkway
San Jose, CA 95131
44M1, 44-pad, 7 x 7 x 1.0 mm Body, Lead Pitch 0.50 mm
Micro Lead Frame Package (MLF)
44M1
C
R
312
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Erratas
The revision letter in this section refers to the revision of the ATmega162 device.
ATmega162, all rev.
There are no errata for this revision of ATmega162. However, a proposal for solving
problems regarding the JTAG instruction IDCODE is presented below.
IDCODE masks data from TDI input
The public but optional JTAG instruction IDCODE is not implemented correctly
according to IEEE1149.1; a logic one is scanned into the shift register instead of the
TDI input while shifting the Device ID Register. Hence, captured data from the pre-
ceding devices in the boundary scan chain are lost and replaced by all-ones, and
data to succeeding devices are replaced by all-ones during Update-DR.
If ATmega162 is the only device in the scan chain, the problem is not visible.
Problem Fix/ Workaround
Select the Device ID Register of the ATmega162 (Either by issuing the IDCODE
instruction or by entering the Test-Logic-Reset state of the TAP controller) to read
out the contents of its Device ID Register and possibly data from succeeding
devices of the scan chain. Note that data to succeeding devices cannot be entered
during this scan, but data to preceding devices can. Issue the BYPASS instruction
to the ATmega162 to select its Bypass Register while reading the Device ID Regis-
ters of preceding devices of the boundary scan chain. Never read data from
succeeding devices in the boundary scan chain or upload data to the succeeding
devices while the Device ID Register is selected for the ATmega162. Note that the
IDCODE instruction is the default instruction selected by the Test-Logic-Reset state
of the TAP-controller.
Alternative Problem Fix/ Workaround
If the Device IDs of all devices in the boundary scan chain must be captured simul-
taneously (for instance if blind interrogation is used), the boundary scan chain can
be connected in such way that the ATmega162 is the fist device in the chain.
Update-DR will still not work for the succeeding devices in the boundary scan chain
as long as IDCODE is present in the JTAG Instruction Register, but the Device ID
registered cannot be uploaded in any case.
313
2513F–AVR–12/03
Datasheet Change
Log for ATmega162
Please note that the referring page numbers in this section are referring to this docu-
ment. The referring revision in this section are referring to the document revision.
Changes from Rev.
2513E-09/03 to Rev.
2513F-12/03
1. Updated “Calibrated Internal RC Oscillator” on page 36.
Changes from Rev.
2513D-04/03 to Rev.
2513E-09/03
1. Removed “Preliminary” from the datasheet.
2. Added note on Figure 1 on page 2.
3. Renamed and updated “On-chip Debug System” to “JTAG Interface and
On-chip Debug System” on page 44.
4. Updated Table 18 on page 47 and Table 19 on page 49.
5. Updated “Test Access Port – TAP” on page 196 regarding JTAGEN.
6. Updated description for the JTD bit on page 206.
7. Added note on JTAGEN in Table 100 on page 232.
8. Updated Absolute Maximum Ratings* and DC Characteristics in “Electrical
Characteristics” on page 263.
9. Added a proposal for solving problems regarding the JTAG instruction
IDCODE in “Erratas” on page 313.
Changes from Rev.
2513C-09/02 to Rev.
2513D-04/03
1. Updated the “Ordering Information” on page 309 and “Packaging Informa-
tion” on page 310.
2. Updated “Features” on page 1.
3. Added characterization plots under “ATmega162 Typical Characteristics” on
page 274.
4. Added Chip Erase as a first step under “Programming the Flash” on page 259
and “Programming the EEPROM” on page 261.
5. Changed CAL7, the highest bit in the OSCCAL Register, to a reserved bit on
page 37 and in “Register Summary” on page 303.
6. Changed CPCE to CLKPCE on page 39.
7. Corrected code examples on page 54.
8. Corrected OCn waveforms in Figure 52 on page 119.
9. Various minor Timer1 corrections.
10. Added note under “Filling the Temporary Buffer (Page Loading)” on page 223
about writing to the EEPROM during an SPM Page Load.
314
ATmega162/V
2513F–AVR–12/03
ATmega162/V
11. Added section “EEPROM Write During Power-down Sleep Mode” on page 22.
12. Added information about PWM symmetry for Timer0 on page 97 and Timer2
on page 146.
13. Updated Table 18 on page 47, Table 20 on page 49, Table 36 on page 76, Table
83 on page 204, Table 110 on page 246, Table 113 on page 266, and Table 114
on page 267.
14. Added Figures for “Absolute Maximum Frequency as a function of VCC,
ATmega162” on page 265.
15. Updated Figure 29 on page 63, Figure 32 on page 67, and Figure 88 on page
209.
16. Removed Table 114, “External RC Oscillator, Typical Frequencies(1),” on
page 265.
17. Updated “Electrical Characteristics” on page 263.
Changes from Rev.
2513B-09/02 to Rev.
2513C-09/02
1. Changed the Endurance on the Flash to 10,000 Write/Erase Cycles.
Changes from Rev.
2513A-05/02 to Rev.
2513B-09/02
1. Added information for ATmega162U.
Information about ATmega162U included in “Features” on page 1, Table 19,
“BODLEVEL Fuse Coding,” on page 49, and “Ordering Information” on page 309.
315
2513F–AVR–12/03
316
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Table of Contents
Features................................................................................................ 1
Pin Configurations............................................................................... 2
Disclaimer............................................................................................................. 2
Overview............................................................................................... 3
Block Diagram ...................................................................................................... 3
ATmega161 and ATmega162 Compatibility......................................................... 4
Pin Descriptions.................................................................................................... 5
About Code Examples.......................................................................................... 6
AVR CPU Core ..................................................................................... 7
Introduction........................................................................................................... 7
Architectural Overview.......................................................................................... 7
ALU – Arithmetic Logic Unit.................................................................................. 8
Status Register ..................................................................................................... 8
General Purpose Register File ........................................................................... 10
Stack Pointer ...................................................................................................... 11
Instruction Execution Timing............................................................................... 12
Reset and Interrupt Handling.............................................................................. 12
AVR ATmega162 Memories .............................................................. 15
In-System Reprogrammable Flash Program Memory ........................................ 15
SRAM Data Memory........................................................................................... 16
EEPROM Data Memory...................................................................................... 18
I/O Memory......................................................................................................... 23
External Memory Interface.................................................................................. 24
XMEM Register Description................................................................................ 28
System Clock and Clock Options .................................................... 33
Clock Systems and their Distribution.................................................................. 33
Clock Sources..................................................................................................... 34
Default Clock Source.......................................................................................... 34
Crystal Oscillator................................................................................................. 34
Low-frequency Crystal Oscillator........................................................................ 36
Calibrated Internal RC Oscillator ........................................................................ 36
External Clock..................................................................................................... 38
Clock output buffer.............................................................................................. 38
Timer/Counter Oscillator..................................................................................... 39
System Clock Prescaler...................................................................................... 39
Power Management and Sleep Modes............................................. 41
Idle Mode............................................................................................................ 42
Power-down Mode.............................................................................................. 42
Power-save Mode............................................................................................... 43
Standby Mode..................................................................................................... 43
i
2513F–AVR–12/03
Extended Standby Mode .................................................................................... 43
Minimizing Power Consumption ......................................................................... 44
System Control and Reset................................................................ 46
Internal Voltage Reference................................................................................. 51
Watchdog Timer ................................................................................................. 51
Timed Sequences for Changing the Configuration of the Watchdog Timer ....... 55
Interrupts............................................................................................ 56
Interrupt Vectors in ATmega162......................................................................... 56
I/O-Ports.............................................................................................. 62
Introduction......................................................................................................... 62
Ports as General Digital I/O................................................................................ 63
Alternate Port Functions ..................................................................................... 67
Register Description for I/O-Ports....................................................................... 81
External Interrupts............................................................................. 83
8-bit Timer/Counter0 with PWM........................................................ 88
Overview............................................................................................................. 88
Timer/Counter Clock Sources............................................................................. 89
Counter Unit........................................................................................................ 90
Output Compare Unit.......................................................................................... 90
Compare Match Output Unit............................................................................... 92
Modes of Operation ............................................................................................ 93
Timer/Counter Timing Diagrams......................................................................... 97
8-bit Timer/Counter Register Description ........................................................... 99
Timer/Counter0, Timer/Counter1, and Timer/Counter3 Prescalers ...
103
16-bit Timer/Counter (Timer/Counter1 and Timer/Counter3)....... 105
Restriction in ATmega161 Compatibility Mode................................................. 105
Overview........................................................................................................... 105
Accessing 16-bit Registers ............................................................................... 108
Timer/Counter Clock Sources........................................................................... 111
Counter Unit...................................................................................................... 111
Input Capture Unit............................................................................................. 112
Output Compare Units...................................................................................... 114
Compare Match Output Unit............................................................................. 116
Modes of Operation .......................................................................................... 117
Timer/Counter Timing Diagrams....................................................................... 125
16-bit Timer/Counter Register Description ....................................................... 127
8-bit Timer/Counter2 with PWM and Asynchronous operation... 137
ii
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Overview........................................................................................................... 137
Timer/Counter Clock Sources........................................................................... 138
Counter Unit...................................................................................................... 139
Output Compare Unit........................................................................................ 139
Compare Match Output Unit............................................................................. 141
Modes of Operation .......................................................................................... 142
Timer/Counter Timing Diagrams....................................................................... 146
8-bit Timer/Counter Register Description ......................................................... 148
Asynchronous operation of the Timer/Counter................................................. 152
Timer/Counter Prescaler................................................................................... 156
Serial Peripheral Interface – SPI..................................................... 157
SS Pin Functionality.......................................................................................... 161
Data Modes ...................................................................................................... 164
USART .............................................................................................. 165
Dual USART ..................................................................................................... 165
Clock Generation.............................................................................................. 167
Frame Formats ................................................................................................. 170
USART Initialization.......................................................................................... 171
Data Transmission – The USART Transmitter ................................................. 172
Data Reception – The USART Receiver .......................................................... 174
Asynchronous Data Reception ......................................................................... 178
Multi-processor Communication Mode ............................................................. 181
Accessing UBRRH/
UCSRC Registers............................................................................................. 183
USART Register Description ............................................................................ 185
Examples of Baud Rate Setting........................................................................ 190
Analog Comparator ......................................................................... 194
JTAG Interface and On-chip Debug System ................................. 196
Features............................................................................................................ 196
Overview........................................................................................................... 196
Test Access Port – TAP.................................................................................... 196
TAP Controller .................................................................................................. 199
Using the Boundary-scan Chain....................................................................... 199
Using the On-chip Debug system..................................................................... 200
On-chip debug specific JTAG instructions........................................................ 201
On-chip Debug Related Register in I/O Memory .............................................. 201
Using the JTAG Programming Capabilities ...................................................... 201
Bibliography...................................................................................................... 202
IEEE 1149.1 (JTAG) Boundary-scan .............................................. 203
Features............................................................................................................ 203
System Overview.............................................................................................. 203
iii
2513F–AVR–12/03
Data Registers.................................................................................................. 204
Boundary-scan Specific JTAG Instructions ...................................................... 205
Boundary-scan Chain ....................................................................................... 207
ATmega162 Boundary-scan Order................................................................... 212
Boundary-scan Description Language Files..................................................... 215
Boot Loader Support – Read-While-Write Self-programming ..... 216
Features............................................................................................................ 216
Application and Boot Loader Flash Sections.................................................... 216
Read-While-Write and No Read-While-Write Flash Sections........................... 216
Boot Loader Lock Bits....................................................................................... 218
Entering the Boot Loader Program................................................................... 220
Addressing the Flash During Self-programming............................................... 222
Self-programming the Flash ............................................................................. 223
Memory Programming..................................................................... 230
Program And Data Memory Lock Bits .............................................................. 230
Fuse Bits........................................................................................................... 231
Signature Bytes ................................................................................................ 233
Calibration Byte ................................................................................................ 233
Parallel Programming Parameters, Pin Mapping, and Commands .................. 233
Parallel Programming ....................................................................................... 235
Serial Downloading........................................................................................... 244
SPI Serial Programming Pin Mapping .............................................................. 244
Programming via the JTAG Interface ............................................................... 249
Electrical Characteristics................................................................ 263
Absolute Maximum Ratings*............................................................................. 263
DC Characteristics............................................................................................ 263
External Clock Drive Waveforms...................................................................... 266
External Clock Drive ......................................................................................... 266
SPI Timing Characteristics ............................................................................... 267
External Data Memory Timing .......................................................................... 269
ATmega162 Typical Characteristics .............................................. 274
Register Summary........................................................................... 303
Instruction Set Summary ................................................................ 306
Ordering Information....................................................................... 309
Packaging Information.................................................................... 310
44A ................................................................................................................... 310
40P6 ................................................................................................................. 311
44M1................................................................................................................. 312
iv
ATmega162/V
2513F–AVR–12/03
ATmega162/V
Erratas .............................................................................................. 313
ATmega162, all rev........................................................................................... 313
Datasheet Change Log for ATmega162......................................... 314
Changes from Rev. 2513E-09/03 to Rev. 2513F-12/03 ................................... 314
Changes from Rev. 2513D-04/03 to Rev. 2513E-09/03................................... 314
Changes from Rev. 2513C-09/02 to Rev. 2513D-04/03................................... 314
Changes from Rev. 2513B-09/02 to Rev. 2513C-09/02................................... 315
Changes from Rev. 2513A-05/02 to Rev. 2513B-09/02 ................................... 315
Table of Contents ................................................................................. i
v
2513F–AVR–12/03
vi
ATmega162/V
2513F–AVR–12/03
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