AT89LP52-20AU [ATMEL]
8-bit Microcontroller with 8K Bytes In-System Programmable Flash; 8位微控制器具有8K字节的系统内可编程闪存
| 型号： | AT89LP52-20AU |
| 厂家： | 
ATMEL |
| 描述： | 8-bit Microcontroller with 8K Bytes In-System Programmable Flash |
| 文件： | 总113页 (文件大小：4202K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Features
• 8-bit Microcontroller Compatible with 8051 Products
• Enhanced 8051 Architecture
– Single Clock Cycle per Byte Fetch
– 12 Clock per Machine Cycle Compatibility Mode
– Up to 20 MIPS Throughput at 20 MHz Clock Frequency
– Fully Static Operation: 0 Hz to 20 MHz
– On-chip 2-cycle Hardware Multiplier
– 256 x 8 Internal RAM
– External Data/Program Memory Interface
– Dual Data Pointers
– 4-level Interrupt Priority
8-bit
Microcontroller
with 8K Bytes
In-System
Programmable
Flash
• Nonvolatile Program and Data Memory
– 4K/8K Bytes of In-System Programmable (ISP) Flash Program Memory
– 256 Bytes of Flash Data Memory
– 256-byte User Signature Array
– Endurance: 10,000 Write/Erase Cycles
– Serial Interface for Program Downloading
– 64-byte Fast Page Programming Mode
– 3-level Program Memory Lock for Software Security
– In-Application Programming of Program Memory
• Peripheral Features
– Three 16-bit Timer/Counters with Clock Out Modes
– Enhanced UART
AT89LP51
AT89LP52
Preliminary
• Automatic Address Recognition
• Framing Error Detection
• SPI and TWI Emulation Modes
– Programmable Watchdog Timer with Software Reset and Prescaler
• Special Microcontroller Features
– Brown-out Detection and Power-on Reset with Power-off Flag
– Selectable Polarity External Reset Pin
– Low Power Idle and Power-down Modes
– Interrupt Recovery from Power-down Mode
– Internal 1.8432 MHz Auxiliary Oscillator
• I/O and Packages
– Up to 36 Programmable I/O Lines
– Green (Pb/Halide-free) Packages
• 40-lead PDIP
• 44-lead TQFP/PLCC
• 44-pad VQFN/MLF
– Configurable Port Modes (per 8-bit port)
• Quasi-bidirectional (80C51 Style)
• Input-only (Tristate)
• Push-pull CMOS Output
• Open-drain
• Operating Conditions
– 2.4V to 5.5V VCC Voltage Range
– -40° C to 85°C Temperature Range
– 0 to 20 MHz @ 2.4V–5.5V
– 0 to 25 MHz @ 4.5V–5.5V
3709B–MICRO–12/10
1. Pin Configurations
1.1
40-lead PDIP
(T2) P1.0
(T2 EX) P1.1
P1.2
1
2
3
4
5
6
7
8
9
40 VCC
39 P0.0 (AD0)
38 P0.1 (AD1)
37 P0.2 (AD2)
36 P0.3 (AD3)
35 P0.4 (AD4)
34 P0.5 (AD5)
33 P0.6 (AD6)
32 P0.7 (AD7)
31 POL
P1.3
P1.4
(MOSI) P1.5
(MISO) P1.6
(SCK) P1.7
RST
(RXD) P3.0 10
(TXD) P3.1 11
(INT0) P3.2 12
(INT1) P3.3 13
(T0) P3.4 14
(T1) P3.5 15
(WR) P3.6 16
(RD) P3.7 17
(XTAL2) P4.1 18
(XTAL1) P4.0 19
GND 20
30 P4.2 (ALE)
29 P4.3 (PSEN)
28 P2.7 (A15)
27 P2.6 (A14)
26 P2.5 (A13)
25 P2.4 (A12)
24 P2.3 (A11)
23 P2.2 (A10)
22 P2.1 (A9)
21 P2.0 (A8)
1.2
44-lead TQFP
(MOSI) P1.5
(MISO) P1.6
(SCK) P1.7
RST
1
2
3
4
5
6
7
8
9
33 P0.4 (AD4)
32 P0.5 (AD5)
31 P0.6 (AD6)
30 P0.7 (AD7)
29 POL
(RXD) P3.0
*NC
28 *NC
(TXD) P3.1
(INT0) P3.2
(INT1) P3.3
27 P4.4 (ALE)
26 P4.5 (PSEN)
25 P2.7 (A15)
24 P2.6 (A14)
23 P2.5 (A13)
(T0) P3.4 10
(T1) P3.5 11
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AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
1.3
44-lead PLCC
(MOSI) P1.5
(MISO) P1.6
(SCK) P1.7
7
8
9
39 P0.4 (AD4)
38 P0.5 (AD5)
37 P0.6 (AD6)
36 P0.7 (AD7)
35 POL
RST 10
(RXD) P3.0 11
*NC 12
34 *NC
(TXD) P3.1 13
(INT0) P3.2 14
(INT1) P3.3 15
(T0) P3.4 16
(T1) P3.5 17
33 P4.4 (ALE)
32 P4.5 (PSEN)
31 P2.7 (A15)
30 P2.6 (A14)
29 P2.5 (A13)
1.4
44-pad VQFN/QFN/MLF
MOSI/P1.5
1
33
32
31
30
29
28
27
26
25
24
23
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
POL
MISO/P1.6
SCK/P1.7
RST
2
3
4
RXD/P3.0
*NC
5
6
*NC
TXD/P3.1
INT0/P3.2
INT1/P3.3
T0/P3.4
T1/P3.5
7
P4.4/ALE
P4.5/PSEN
P2.7/A15
P2.6/A14
P2.5/A13
8
9
10
11
NOTE:
Bottom pad
should be
soldered to ground
3
3709B–MICRO–12/10
1.5
Pin Description
Table 1-1.
AT89LP51/52 Pin Description
Pin Number
PLCC PDIP
TQFP
VQFN
Symbol
Type
Description
I/O
I/O
P1.5: I/O Port 1 bit 5.
MOSI: SPI master-out/slave-in. In UART SPI mode this pin is an output. During In-
System Programming, this pin is an input.
1
7
8
6
1
P1.5
I/O
I/O
P1.6: I/O Port 1 bit 6.
MISO: SPI master-in/slave-out. In UART SPI mode this pin is an input. During In-
System Programming, this pin is an output.
2
3
4
7
2
3
4
P1.6
P1.7
I/O
I/O
P1.7: I/O Port 1 bit 7.
SCK: SPI Clock. In UART SPI mode this pin is an output. During In-System
Programming, this pin is an input.
9
8
RST: External Reset input (Reset polarity depends on POL pin. See “External Reset”
on page 32.). The RST pin can output a pulse when the internal Watchdog reset is
active.
I/O
10
9
RST
I/O
I
P3.0: I/O Port 3 bit 0.
RXD: Serial Port Receiver Input.
5
6
7
11
12
13
10
5
6
7
P3.0
NC
Not internally connected
I/O
O
P3.1: I/O Port 3 bit 1.
TXD: Serial Port Transmitter Output.
11
12
13
14
P3.1
P3.2
P3.3
P3.4
I/O
I
P3.2: I/O Port 3 bit 2.
INT0: External Interrupt 0 Input or Timer 0 Gate Input.
8
9
14
15
16
8
9
I/O
I
P3.3: I/O Port 3 bit 3.
INT1: External Interrupt 1 Input or Timer 1 Gate Input
I/O
I/O
P3.4: I/O Port 3 bit 4.
T1: Timer/Counter 0 External input or output.
10
10
I/O
I/O
P3.5: I/O Port 3 bit 5.
T1: Timer/Counter 1 External input or output.
11
12
13
17
18
19
15
16
17
1
P3.5
P3.6
P3.7
I/O
O
P3.6: I/O Port 3 bit 6.
WR: External memory interface Write Strobe (active-low).
12
13
I/O
O
P3.7: I/O Port 3 bit 7.
RD: External memory interface Read Strobe (active-low).
I/O
O
P4.7: I/O Port 4 bit 7.
XTAL2: Output from inverting oscillator amplifier. It may be used as a port pin if the
internal RC oscillator or external clock is selected as the clock source.
14
15
20
21
18
14
15
P4.7
P4.6: I/O Port 4 bit 6.
I/O
I
XTAL1: Input to the inverting oscillator amplifier and internal clock generation circuits.
It may be used as a port pin if the internal RC oscillator is selected as the clock
source.
19
20
P4.6
GND
16
17
22
23
16
17
I
Ground
NC
Not internally connected
I/O
O
P2.0: I/O Port 2 bit 0.
A8: External memory interface Address bit 8.
18
19
20
24
25
26
21
22
23
18
19
20
P2.0
P2.1
P2.1
I/O
O
P2.1: I/O Port 2 bit 1.
A9: External memory interface Address bit 9.
I/O
O
P2.2: I/O Port 2 bit 2.
A10: External memory interface Address bit 10.
4
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table 1-1.
AT89LP51/52 Pin Description
Pin Number
PLCC PDIP
TQFP
VQFN
Symbol
Type
Description
I/O
O
P2.3: I/O Port 2 bit 3.
A11: External memory interface Address bit 11.
21
27
28
29
30
31
32
33
24
21
P2.3
I/O
O
P2.4: I/O Port 2 bit 5.
A12: External memory interface Address bit 12.
22
23
24
25
26
27
25
26
27
28
29
30
22
23
24
25
26
27
P2.4
P2.5
P2.6
P2.7
P4.5
P4.4
I/O
O
P2.5: I/O Port 2 bit 5.
A13: External memory interface Address bit 13.
I/O
O
P2.6: I/O Port 2 bit 6.
A14: External memory interface Address bit 14.
I/O
O
P2.7: I/O Port 2 bit 7.
A15: External memory interface Address bit 15.
I/O
O
P4.5: I/O Port 4 bit 5.
PSEN: External memory interface Program Store Enable (active-low).
I/O
O
P4.4: I/O Port 4 bit 4.
ALE: External memory interface Address Latch Enable.
28
34
35
28
NC
I
Not internally connected
29
31
32
29
POL
P0.7
POL: Reset polarity (See “External Reset” on page 32.)
I/O
I/O
P0.7: I/O Port 0 bit 7.
AD7: External memory interface Address/Data bit 7.
30
31
32
33
34
35
36
37
36
37
38
39
40
41
42
43
30
31
32
33
34
35
36
37
I/O
I/O
P0.6: I/O Port 0 bit 6.
AD6: External memory interface Address/Data bit 6.
33
34
35
36
37
38
P0.6
P0.5
P0.4
P0.3
P0.2
P0.1
I/O
I/O
P0.5: I/O Port 0 bit 5.
AD5: External memory interface Address/Data bit 5.
I/O
I/O
P0.4: I/O Port 0 bit 4.
AD4: External memory interface Address/Data bit 4.
I/O
I/O
P0.3: I/O Port 0 bit 3.
AD3: External memory interface Address/Data bit 3.
I/O
I/O
P0.2: I/O Port 0 bit 2.
AD2: External memory interface Address/Data bit 2.
I/O
I/O
P0.1: I/O Port 0 bit 1.
AD1: External memory interface Address/Data bit 1.
I/O
I/O
P0.0: I/O Port 0 bit 0.
AD0: External memory interface Address/Data bit 0.
39
40
P0.0
VDD
38
44
1
38
I
Supply Voltage
39
39
NC
Not internally connected
I/O
I/O
P1.0: I/O Port 1 bit 0.
T2: Timer 2 External Input or Clock Output.
40
41
2
3
1
2
40
41
P1.0
P1.1
I/O
I
P1.1: I/O Port 1 bit 1.
T2EX: Timer 2 External Capture/Reload Input.
42
43
44
4
5
6
3
4
5
42
43
44
P1.2
P1.3
P1.4
I/O
I/O
I/O
P1.2: I/O Port 1 bit 2.
P1.3: I/O Port 1 bit 3.
P1.4: I/O Port 1 bit 4.
5
3709B–MICRO–12/10
2. Overview
The AT89LP51/52 is a low-power, high-performance CMOS 8-bit microcontroller with 4K/8K
bytes of In-System Programmable Flash program memory and 256 bytes of Flash data memory.
The device is manufactured using Atmel's high-density nonvolatile memory technology and is
compatible with the industry-standard 80C52 instruction set.
The AT89LP51/52 is built around an enhanced CPU core that can fetch a single byte from mem-
ory every clock cycle. In the classic 8051 architecture, each fetch requires 6 clock cycles, forcing
instructions to execute in 12, 24 or 48 clock cycles. In the AT89LP51/52 CPU, instructions need
only 1 to 4 clock cycles providing 6 to 12 times more throughput than the standard 8051. Sev-
enty percent of instructions need only as many clock cycles as they have bytes to execute, and
most of the remaining instructions require only one additional clock. The enhanced CPU core is
capable of 20 MIPS throughput whereas the classic 8051 CPU can deliver only 4 MIPS at the
same current consumption. Conversely, at the same throughput as the classic 8051, the new
CPU core runs at a much lower speed and thereby greatly reducing power consumption and
EMI. The AT89LP51/52 also includes a compatibility mode that will enable classic 12 clock per
machine cycle operation for true timing compatibility with AT89S51/52.
The AT89LP51/52 provides the following standard features: 4K/8K bytes of In-System
Programmable Flash program memory, 256 bytes of Flash data memory, 256 bytes of RAM, up
to 36 I/O lines, three 16-bit timer/counters, a programmable watchdog timer, a full-duplex serial
port, an on-chip crystal oscillator, an internal 1.8432 MHz auxiliary oscillator, and a four-level,
six-vector interrupt system. A block diagram is shown in Figure 2-1.
All three timer/counters of the AT89LP51/52, Timer 0, Timer 1 and Timer 2, can be configured to
toggle a port pin on overflow for clock/waveform generation. Unlike AT89S51, Timer 2 is also
present on AT89LP51.
The enhanced full-duplex UART of the AT89LP51/52 includes Framing Error Detection and
Automatic Address Recognition. In addition, enhancements to Mode 0 allow hardware acceler-
ated emulation of a Serial Peripheral Interface (SPI) or a Two-Wire Interface (TWI).
The Watchdog Timer of the AT89LP51/52 includes a 7-bit prescaler, a software reset command
and an overflow flag. The watchdog can be configured to output a reset pulse on the external
Reset pin.
Each 8-bit I/O port of the AT89LP51/52 can be independently configured in one of four operating
modes. In quasi-bidirectional mode, the port operates as in the classic 8051. In input-only mode,
the port is tristated. Push-pull output mode provides full CMOS drivers and open-drain mode
provides just a pull-down. Unlike other 8051s, this allows Port 0 to operate with on-chip pull-ups
if desired.
6
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
2.1
Block Diagram
Figure 2-1. AT89LP51/52 Block Diagram
4K/8K Bytes
Flash Code
256 Bytes
Flash Data
256 Bytes
RAM
XRAM
Interface
8051 Single Cycle CPU
with 12-cycle Compatibility
Port 0
Configurable I/O
UART
Port 1
Configurable I/O
16-bit Timer 0
16-bit Timer 1
Port 2
Configurable I/O
16-bit Timer 2
Port 3
Configurable I/O
Watchdog
Timer
Port 4
Configurable I/O
POR
BOD
Crystal or
Resonator
RC Auxiliary
Oscillator
Configurable
Oscillator
2.2
Comparison to AT89S51/52
The AT89LP51/52 is part of a family of devices with enhanced features that are fully binary com-
patible with the 8051 instruction set. The AT89LP51/52 has two modes of operations,
Compatibility mode and Fast mode. In Compatibility mode the instruction timing, peripheral
behavior, SFR addresses, bit assignments and pin functions are identical to Atmel's existing
AT89S51/52 product. Additional enhancements are transparent to the user and can be used if
desired. Fast mode allows greater performance, but with some differences in behavior. The
major enhancements from the AT89S51/52 are outlined in the following paragraphs and may be
useful to users migrating to the AT89LP51/52 from older devices. A summary of the differences
between Compatibility and Fast modes is given in Table 2-1 on page 9. See also the Application
note “Migrating from AT89S52 to AT89LP52.”
2.2.1
Instruction Execution
In Compatibility mode the AT89LP51/52 CPU uses the six-state machine cycle of the standard
8051 where instruction bytes are fetched every three system clock cycles. Execution times in
this mode are identical to AT89S51/52. For greater performance the user can enable Fast mode
7
3709B–MICRO–12/10
by disabling the Compatibility fuse. In Fast mode the CPU fetches one code byte from memory
every clock cycle instead of every three clock cycles. This greatly increases the throughput of
the CPU. Each standard instruction executes in only 1 to 4 clock cycles. See “Instruction Set
Summary” on page 75 for more details. Any software delay loops or instruction-based timing
operations may need to be retuned to achieve the desired results in Fast mode.
2.2.2
System Clock
By default in Compatibility mode the system clock frequency is divided by 2 from the externally
supplied XTAL1 frequency for compatibility with standard 8051s (12 clocks per machine cycle).
The System Clock Divider can scale the system clock versus the oscillator source (See Section
6.4 on page 30). The divide-by-2 can be disabled to operate in X2 mode (6 clocks per machine
cycle) or the clock may be further divided to reduce the operating frequency. In Fast mode the
clock divider defaults to divide by 1.
The system clock source is selectable between the crystal oscillator, an externally driven clock
and an internal 1.8432 MHz auxiliary oscillator.
2.2.3
Reset
The RST pin of the AT89LP51/52 has selectable polarity using the POL pin (formerly EA). When
POL is high the RST pin is active high with a pull-down resistor and when POL is low the RST
pin is active low with a pull-up resistor. For existing AT89S51/52 sockets where EA is tied to
VDD, replacing AT89S51/52 with AT89LP51/52 will maintain the active high reset. Note that
forcing external execution by tying EA low is not supported.
The AT89LP51/52 includes an on-chip Power-On Reset and Brown-out Detector circuit that
ensures that the device is reset from system power up. In most cases a RC startup circuit is not
required on the RST pin, reducing system cost, and the RST pin may be left unconnected if a
board-level reset is not present.
2.2.4
Timer/Counters
A common prescaler is available to divide the time base for Timer 0, Timer 1, Timer 2 and the
WDT. The TPS3-0 bits in the CLKREG SFR control the prescaler (Table 6-2 on page 30). In
Compatibility mode TPS3-0 defaults to 0101B, which causes the timers to count once every
machine cycle. The counting rate can be adjusted linearly from the system clock rate to 1/16 of
the system clock rate by changing TPS3-0. In Fast mode TPS3-0 defaults to 0000B, or the system
clock rate. TPS does not affect Timer 2 in Clock Out or Baud Generator modes.
In Compatibility mode the sampling of the external Timer/Counter pins: T0, T1, T2 and T2EX;
and the external interrupt pins, INT0 and INT1, is also controlled by the prescaler. In Fast mode
these pins are always sampled at the system clock rate.
Both Timer 0 and Timer 1 can toggle their respective counter pins, T0 and T1, when they over-
flow by setting the output enable bits in TCONB.
The Watchdog Timer includes a 7-bit prescaler for longer timeout periods than the AT89S51/52.
Note that in Fast Mode the WDIDLE and DISRTO bits are located in WDTCON and not in
AUXR.
2.2.5
Interrupt Handling
With the addition of the IPH register, the AT89LP51/52 provides four levels of interrupt priority
for greater flexibility in handling multiple interrupts. Also, Fast mode allows for faster interrupt
response due to the shorter instruction execution times.
8
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
2.2.6
Serial Port
The timer prescaler increases the range of achievable baud rates when using Timer 1 to gener-
ate the baud rate in UART Modes 1 or 3, including an increase in the maximum baud rate
available in Compatibility mode. Additional features include automatic address recognition and
framing error detection.
The shift register mode (Mode 0) has been enhanced with more control of the polarity, phase
and frequency of the clock and full-duplex operation. This allows emulation of master serial
pheriperal (SPI) and two-wire (TWI) interfaces.
2.2.7
I/O Ports
The P0, P1, P2 and P3 I/O ports of the AT89LP51/52 may be configured in four different modes.
The default setting depends on the Tristate-Port User Fuse. When the fuse is set all the I/O ports
revert to input-only (tristated) mode at power-up or reset. When the fuse is not active, ports P1,
P2 and P3 start in quasi-bidirectional mode and P0 starts in open-drain mode. P4 always oper-
ates in quasi-bidirectional mode. P0 can be configured to have internal pull-ups by placing it in
quasi-bidirectional or output modes. This can reduce system cost by removing the need for
external pull-ups on Port 0.
The P4.4–P4.7 pins are additional I/Os that replace the normally dedicated ALE, PSEN, XTAL1
and XTAL2 pins of the AT89S51/52. These pins can be used as additional I/Os depending on
the configuration of the clock and external memory.
2.2.8
2.2.9
Security
The AT89LP51/52 does not support the extenal access pin (EA). Therefore it is not possible to
execute from external program memory in address range 0000H–1FFFH. When the third Lockbit
is enabled (Lock Mode 4) external program execution is disabled for all addresses above
1FFFH. This differs from AT89S51/52 where Lock Mode 4 prevents EA from being sampled low,
but may still allow external execution at addresses outside the 8K internal space.
Programming
The AT89LP51/52 supports a richer command set for In-System Programming (ISP). Existing
AT89S51/52 programmers should be able to program the AT89LP51/52 in byte mode. In page
mode the AT89LP51/52 only supports programming of a half-page of 64 bytes and therefore
requires an extra address byte as compared to AT89S51/52. Furthermore the device signature
is located at addresses 0000H, 0001H and 0003H instead of 0000H, 0100H and 0200H.
Table 2-1.
Feature
Compatibility Mode versus Fast Mode Summary
Compatibility
Fast
Instruction Fetch in System Clocks
3
1
Instruction Execution Time in System Clocks
Default System Clock Divisor
6, 12, 18 or 24
1, 2, 3, 4 or 5
2
1
Default Timer Prescaler Divisor
6
Prescaler Rate
12
1
System Clock
2
Pin Sampling Rate (INT0, INT1, T0, T1, T2, T2EX)
Minimum RST input pulse in System Clocks
WDIDLE and DISRTO bit locations
AUXR
WDTCON
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3709B–MICRO–12/10
3. Memory Organization
The AT89LP51/52 uses a Harvard Architecture with separate address spaces for program and
data memory. The program memory has a regular linear address space with support for 64K
bytes of directly addressable application code. The data memory has 256 bytes of internal RAM
and 128 bytes of Special Function Register I/O space. The AT89LP51/52 supports up to 64K
bytes of external data memory, with portions of the external data memory space implemented on
chip as nonvolatile Flash data memory. External program memory is supported for addresses
above 8K. The memory address spaces of the AT89LP51/52 are listed in Table 3-1.
Table 3-1.
Name
DATA
AT89LP51/52 Memory Address Spaces
Description
Range
00H–7FH
Directly addressable internal RAM
Indirectly addressable internal RAM and stack space
Directly addressable I/O register space
On-chip nonvolatile Flash data memory
External data memory
IDATA
00H–FFH
SFR
80H–FFH
FDATA
XDATA
0000H–00FFH
0100H–FFFFH
0000H–0FFFH (AT89LP51)
0000H–1FFFH (AT89LP52)
CODE
On-chip nonvolatile Flash program memory
2000H–FFFFH (AT89LP51)
1000H–FFFFH (AT89LP52)
XCODE
External program memory
SIG
On-chip nonvolatile Flash signature array
0000H–01FFH
3.1
Program Memory
The AT89LP51/52 contains 4K/8K bytes of on-chip In-System Programmable Flash memory for
program storage, plus support for up to 60K/56K bytes of external program memory. The Flash
memory has an endurance of at least 10,000 write/erase cycles and a minimum data retention
time of 10 years. The reset and interrupt vectors are located within the first 83 bytes of program
memory (refer to Table 9-1 on page 37). Constant tables can be allocated within the entire 64K
program memory address space for access by the MOVC instruction. A map of the
AT89LP51/52 program memory is shown in Figure 3-1.
Figure 3-1. Program Memory Map
AT89LP51
AT89LP52
01FF
0100
01FF
0100
User Signature Array
User Signature Array
SIGEN=1
007F
0000
007F
0000
Atmel Signature Array
Atmel Signature Array
FFFF
FFFF
External Program
Memory
External Program
Memory
(XCODE: 60KB)
(XCODE: 56KB)
SIGEN=0
2000
1FFF
1000
0FFF
Internal Program
Memory
(CODE: 8KB)
Internal Program
Memory
(CODE: 4KB)
0000
0000
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3.1.1
External Program Memory Interface
The AT89LP51/52 uses the standard 8051 external program memory interface with the upper
address on Port 2, the lower address and data in/out multiplexed on Port 0, and the ALE and
PSEN strobes. Program memory addresses are always 16-bits wide, even though the actual
amount of program memory used may be less than 64K byes. External program execution sacri-
fices two full 8-bit ports, P0 and P2, to the function of addressing the program memory.
Figure 3-2 shows a hardware configuration for accessing up to 64K bytes of external ROM using
a 16-bit linear address. Port 0 serves as a multiplexed address/data bus to the ROM. The
Address Latch Enable strobe (ALE) is used to latch the lower address byte into an external reg-
ister so that Port 0 can be freed for data input/output. Port 2 provides the upper address byte
throughout the operation. PSEN strobes the external memory.
Figure 3-3 shows the timing of the external program memory interface. ALE is emitted at a con-
stant rate of 1/3 of the system clock with a 1/3 duty cycle. PSEN is emitted at a similar rate, but
with 50% duty cycle. The new address changes in the middle of the ALE pulse for latching on
the falling edge and is tristated at the falling edge of PSEN. The instruction data is sampled from
P0 and latched internally during the high phase of the clock prior to the rising edge of PSEN.
This timing applies to both Compatibility and Fast modes. In Compatibility mode there is no dif-
ference in instruction timing between internal and external execution.
Figure 3-2. Executing from External Program Memory
AT89LP
EXTERNAL
PROGRAM
MEMORY
INSTR.
P1
P0
ALE
LATCH
ADDR
OE
P2
P3
PSEN
Figure 3-3. External Program Memory Fetches
CLK
ALE
PSEN
DATA
DATA
DATA
SAMPLED
SAMPLED
SAMPLED
PCL
OUT
PCL
OUT
PCL
OUT
P0
P2
FLOAT
PCH OUT
PCH OUT
PCH OUT
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3709B–MICRO–12/10
In order for Fast mode to fetch externally, two wait states must be inserted for every clock cycle,
increasing the instruction execution time by a factor of 3. However, due to other optimizations,
external Fast mode instructions may still be 1/4 to 1/2 faster than their Compatibility mode equiv-
alents. Note that if ALE is allowed to toggle in Fast mode, there is a possibility that when the
CPU jumps from internal to external execution a short pulse may occur on ALE as shown in Fig-
ure 3-4. The setup time from the address to the falling edge of ALE remains the same. However,
this behavior can be avoided by setting the DISALE bit prior to any jump above the 8K border.
Figure 3-4. Internal/External Program Memory Boundary (Fast Mode)
CLK
SHORT
PULSE
ALE
DISALE=0
ALE
DISALE=1
INTERNAL EXECUTION
EXTERNAL EXECUTION
DATA
PSEN
P0
SAMPLED
P0 SFR OUT
P2 SFR OUT
PCL OUT
PCL OUT
FLOAT
PCH OUT
PCH OUT
P2
3.1.2
SIG
In addition to the 64K code space, the AT89LP51/52 also supports a 256-byte User Signature
Array and a 128-byte Atmel Signature Array that are accessible by the CPU. The Atmel Signa-
ture Array is initialized with the Device ID in the factory. The User Signature Array is available for
user identification codes or constant parameter data. Data stored in the signature array is not
secure. Security bits will disable writes to the array; however, reads by an external device pro-
grammer are always allowed.
In order to read from the signature arrays, the SIGEN bit (AUXR1.3) must be set (See Table 5-3
on page 27). While SIGEN is one, MOVC A,@A+DPTR will access the signature arrays. The
User Signature Array is mapped from addresses 0100h to 01FFh and the Atmel Signature Array
is mapped from addresses 0000h to 007Fh. SIGEN must be cleared before using MOVC to
access the code memory. The User Signature Array may also be modified by the In-Application
Programming interface. When IAP = 1 and SIGEN = 1, MOVX @DPTR instructions will access
the array (See Section 3.4 on page 22).
3.2
Internal Data Memory
The AT89LP51/52 contains 256 bytes of general SRAM data memory plus 128 bytes of I/O
memory mapped into a single 8-bit address space. Access to the internal data memory does not
require any configuration. The internal data memory has three address spaces: DATA, IDATA
and SFR; as shown in Figure 3-5. Some portions of external data memory are also implemented
internally. See “External Data Memory” below for more information.
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Figure 3-5. Internal Data Memory Map
FFH
FFH
IDATA
SFR
ACCESSIBLE
UPPER
ACCESSIBLE
BY DIRECT
ADDRESSING
BY INDIRECT
ADDRESSING
ONLY
128
80H
7FH
80H
DATA/IDATA
ACCESSIBLE
BY DIRECT
AND INDIRECT
ADDRESSING
SPECIAL
PORTS
FUNCTION
STATUS AND
REGISTERS
CONTROL BITS
LOWER
128
TIMERS
REGISTERS
STACK POINTER
ACCUMULATOR
(ETC.)
0
3.2.1
DATA
The first 128 bytes of RAM are directly addressable by an 8-bit address (00H–7FH) included in
the instruction. The lowest 32 bytes of DATA memory are grouped into 4 banks of 8 registers
each. The RS0 and RS1 bits (PSW.3 and PSW.4) select which register bank is in use. Instruc-
tions using register addressing will only access the currently specified bank. The lower 128 bit
addresses are also mapped into DATA addresses 20H—2FH.
3.2.2
3.2.3
IDATA
SFR
The full 256 byte internal RAM can be indirectly addressed using the 8-bit pointers R0 and R1.
The first 128 bytes of IDATA include the DATA space. The hardware stack is also located in the
IDATA space.
The upper 128 direct addresses (80H–FFH) access the I/O registers. I/O registers on AT89LP
devices are referred to as Special Function Registers. The SFRs can only be accessed through
direct addressing. All SFR locations are not implemented. See Section 4. for a listed of available
SFRs.
3.3
External Data Memory
AT89LP microcontrollers support a 16-bit external memory address space for up to 64K bytes of
external data memory (XDATA). The external memory space is accessed with the MOVX
instructions. Some internal data memory resources are mapped into portions of the external
address space as shown in Figure 3-6. These memory spaces may require configuration before
the CPU can access them. The AT89LP51/52 includes 256 bytes of nonvolatile Flash data
memory (FDATA).
3.3.1
XDATA
The external data memory space can accommodate up to 64KB of external memory. The
AT89LP51/52 uses the standard 8051 external data memory interface with the upper address
byte on Port 2, the lower address byte and data in/out multiplexed on Port 0, and the ALE, RD
and WR strobes. XDATA can be accessed with both 16-bit (MOVX @DPTR) and 8-bit (MOVX
@Ri) addresses. See Section 3.3.3 on page 17 for more details of the external memory
interface.
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3709B–MICRO–12/10
Some internal data memory spaces are mapped into portions of the XDATA address space. In
this case the lower address ranges will access internal resources instead of external memory.
Addresses above the range implemented internally will default to XDATA. The AT89LP51/52
supports up to 63.75K or 56K bytes of external memory when using the internally mapped mem-
ories. Setting the EXRAM bit (AUXR.1) to one will force all MOVX instructions to access the
entire 64KB XDATA regardless of their address (See “AUXR – Auxiliary Control Register” on
page 19).
Figure 3-6. External Data Memory Map
FFFF
FFFF
FFFF
External Data
(XDATA: 56KB)
External Data
(XDATA: 64KB)
External Data
(XDATA: 63.75KB)
2000
1FFF
Flash Program
(CODE: 8KB)
0100
00FF
Flash Data
(FDATA: 256)
0000
EXRAM = 1 or
DMEN = 0
IAP = 0
EXRAM = 0
DMEN = 1
IAP = 0
EXRAM = 0
DMEN = x
IAP = 1
3.3.2
FDATA
The Flash Data Memory is a portion of the external memory space implemented as an internal
nonvolatile data memory. Flash Data Memory is enabled by setting the DMEN bit (MEMCON.3)
to one. When IAP = 0 and DMEN = 1, the Flash Data Memory is mapped into the FDATA space,
at the bottom of the external memory address space, from 0000H to 00FFH. (See Figure 3-6).
MOVX instructions to this address range will access the internal nonvolatile memory. FDATA is
not accessible while DMEN = 0. FDATA can be accessed only by 16-bit (MOVX @DPTR)
addresses. MOVX @Ri instructions to the FDATA address range will access external memory.
Addresses above the FDATA range are mapped to XDATA.
3.3.2.1
Write Protocol
The FDATA address space accesses an internal nonvolatile data memory. This address space
can be read just like EDATA by issuing a MOVX A,@DPTR; however, writes to FDATA require a
more complex protocol and take several milliseconds to complete.
For internal execution the AT89LP51/52 uses an idle-while-write architecture where the CPU is
placed in an idle state while the write occurs. When the write completes, the CPU will continue
executing with the instruction after the MOVX @DPTR,A instruction that started the write. All
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AT89LP51/52 - Preliminary
peripherals will continue to function during the write cycle; however, interrupts will not be ser-
viced until the write completes.
For external execution the AT89LP51/52 uses an execute-while-write architecture where the
CPU continues to operate while the write occurs. The software should poll the state of the BUSY
flag to determine when the write completes. Interrupts must be disabled during the write
sequence as the CPU will not be able to vector to the internal interrupt table and care should be
taken that the application does not jump to an internal address until the write completes.
To enable write access to the nonvolatile data memory, the MWEN bit (MEMCON.4) must be set
to one. When MWEN = 1 and DMEN = 1, MOVX @DPTR,A may be used to write to FDATA.
FDATA uses flash memory with a page-based programming model. Flash data memory differs
from traditional EEPROM data memory in the method of writing data. EEPROM generally can
update a single byte with any value. Flash memory splits programming into write and erase
operations. A Flash write can only program zeroes, i.e change ones into zeroes ( 1 →0 ). Any
ones in the write data are ignored. A Flash erase sets an entire page of data to ones so that all
bytes become FFH. Therefore after an erase, each byte in the page can only be written once
with any possible value. Bytes can be overwritten without an erase as long as only ones are
changed into zeroes. However, if even a single bit needs updating from zero to one ( 0 →1 );
then the contents of the page must first be saved, the entire page must be erased and the zero
bits in all bytes (old and new data combined) must be written. Avoiding unnecessary page
erases greatly improves the endurance of the memory..
The AT89LP51/52 includes 2 data pages of 128 bytes each. One or more bytes in a page may
be written at one time. The AT89LP51/52 includes a temporary page buffer of 64 bytes, or half of
a page. Because the page buffer is 64 bytes long, the maximum number of bytes written at one
time is 64. Therefore, two write cycles are required to fill the entire 128-byte page, one for the
low half page (00H–3FH) and one for the high half page (40H–7FH) as shown in Figure 3-7.
Figure 3-7. Page Programming Structure
00
3F
Page Buffer
Data Memory
Low Half Page
High Half Page
00
3F 40
7F
The LDPG bit (MEMCON.5) allows multiple data bytes to be loaded to the temporary page buf-
fer. While LDPG = 1, MOVX @DPTR,A instructions will load data to the page buffer, but will not
start a write sequence. Note that a previously loaded byte must not be reloaded prior to the write
sequence. To write the half page into the memory, LDPG must first be cleared and then a
MOVX @DPTR,A with the final data byte is issued. The address of the final MOVX determines
which half page will be written. If a MOVX @DPTR,A instruction is issued while LDPG = 0 with-
out loading any previous bytes, only a single byte will be written. The page buffer is reset after
each write operation. Figures 3-8 and Figure 3-9 on page 16 show the difference between byte
writes and page writes.
15
3709B–MICRO–12/10
Figure 3-8. FDATA Byte Write
DMEN
MWEN
LDPG
IDLE
t
t
WC
WC
MOVX
Figure 3-9. FDATA Page Write
DMEN
MWEN
LDPG
IDLE
t
WC
MOVX
The auto-erase bit AERS (MEMCON.6) can be set to one to perform a page erase automatically
at the beginning of any write sequence. The page erase will erase the entire page, i.e. both the
low and high half pages. However, the write operation paired with the auto-erase can only pro-
gram one of the half pages. A second write cycle without auto-erase is required to update the
other half page.
Frequently just a few bytes within a page must be updated while maintaining the state of the
other bytes. There are two options for handling this situation that allow the Flash Data memory
to emulate a traditional EEPROM memory. The simplest method is to copy the entire page into a
buffer allocated in RAM, modify the desired byte locations in the RAM buffer, and then load and
write back first the low half page (with auto-erase) and then the high half page to the Flash mem-
ory. This option requires that at least one page size of RAM is available as a temporary buffer.
The second option is to store only one half page in RAM. The unmodified bytes of the other page
are loaded directly into the Flash memory’s temporary load buffer before loading the updated
values of the modified bytes. For example, if just the low half page needs modification, the user
must first store the high half page to RAM, followed by reading and loading the unaffected bytes
of the low half page into the page buffer. Then the modified bytes of the low half page are stored
to the page buffer before starting the auto-erase sequence. The stored value of the high half
page must be written without auto-erase after the programming of the low half page completes.
This method reduces the amount of RAM required; however, more software overhead is needed
because the read-and-load-back routine must skip those bytes in the page that need to be
updated in order to prevent those locations in the buffer from being loaded with the previous
data, as this will block the new data from being loaded correctly.
A write sequence will not occur if the Brown-out Detector is active. If a write currently in progress
is interrupted by the BOD due to a low voltage condition, the ERR flag will be set.
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Table 3-2.
MEMCON – Memory Control Register
MEMCON = 96H
Reset Value = 0000 0XXXB
Not Bit Addressable
IAP
AERS
LDPG
5
MWEN
4
DMEN
3
ERR
2
BUSY
WRTINH
0
Bit
Symbol
IAP
7
6
1
Function
In-Application Programming Enable. When IAP = 1 and the IAP Fuse is enabled, programming of the CODE/SIG space
is enabled and MOVX @DPTR instructions will access CODE/SIG instead of EDATA or FDATA. Clear IAP to disable
programming of CODE/SIG and allow access to EDATA and FDATA.
AERS
LDPG
MWEN
DMEN
ERR
Auto-Erase Enable. Set to perform an auto-erase of a Flash memory page (CODE, SIG or FDATA) during the next write
sequence. Clear to perform write without erase.
Load Page Enable. Set to this bit to load multiple bytes to the temporary page buffer. Byte locations may not be loaded
more than once before a write. LDPG must be cleared before writing.
Memory Write Enable. Set to enable programming of a nonvolatile memory location (CODE, SIG or FDATA). Clear to
disable programming of all nonvolatile memories.
Data Memory Enable. Set to enable nonvolatile data memory and map it into the FDATA space. Clear to disable
nonvolatile data memory.
Error Flag. Set by hardware if an error occurred during the last programming sequence due to a brownout condition (low
voltage on VDD). Must be cleared by software.
BUSY
Busy Flag.
WRTINH
Write Inhibit Flag. Cleared by hardware when the voltage on VDD has fallen below the minimum programming voltage.
Set by hardware when the voltage on VDD is above the minimum programming voltage.
3.3.3
External Data Memory Interface
The AT89LP51/52 uses the standard 8051 external data memory interface with the upper
address on Port 2, the lower address and data in/out multiplexed on Port 0, and the ALE, RD
and WR strobes. The interface may be used in two different configurations depending on which
type of MOVX instruction is used to access XDATA.
Figure 3-10 shows a hardware configuration for accessing up to 64K bytes of external RAM
using a 16-bit linear address. Port 0 serves as a multiplexed address/data bus to the RAM. The
Address Latch Enable strobe (ALE) is used to latch the lower address byte into an external reg-
ister so that Port 0 can be freed for data input/output. Port 2 provides the upper address byte
throughout the operation. The MOVX @DPTR instructions use Linear Address mode.
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3709B–MICRO–12/10
Figure 3-10. External Data Memory 16-bit Linear Address Mode
EXTERNAL
DATA
AT89LP
MEMORY
P0
P1
DATA
ALE
P2
LATCH
ADDR
P3
RD
WR
WE OE
Figure 3-11 shows a hardware configuration for accessing 256-byte blocks of external RAM
using an 8-bit paged address. Port 0 serves as a multiplexed address/data bus to the RAM. The
ALE strobe is used to latch the address byte into an external register so that Port 0 can be freed
for data input/output. The Port 2 I/O lines (or other ports) can provide control lines to page the
memory; however, this operation is not handled automatically by hardware. The software appli-
cation must change the Port 2 register when appropriate to access different pages. The
MOVX @Ri instructions use Paged Address mode.
Figure 3-11. External Data Memory 8-bit Paged Address Mode
EXTERNAL
DATA
AT89LP
MEMORY
P0
P1
DATA
ALE
LATCH
ADDR
P3 P2
RD
I/O
PAGE
BITS
WR
WE OE
Note that prior to using the external memory interface, WR (P3.6) and RD (P3.7) must be config-
ured as outputs. See Section 10.1 “Port Configuration” on page 40. P0 and P2 are configured
automatically to push-pull output mode when outputting address or data and P0 is automatically
tristated when inputting data regardless of the port configuration. The Port 0 configuration will
determine the idle state of Port 0 when not accessing the external memory.
Figure 3-12 and Figure 3-13 show examples of external data memory write and read cycles,
respectively. The address on P0 and P2 is stable at the falling edge of ALE. The idle state of
ALE is controlled by DISALE (AUXR.0). When DISALE = 0 the ALE toggles at a constant rate
when not accessing external memory. When DISALE = 1 the ALE is weakly pulled high. DISALE
must be one in order to use P4.4 as a general-purpose I/O. The WS bits in AUXR can extended
the RD and WR strobes by 1, 2 or 3 cycles as shown in Figures 3-16, 3-17 and 3-18. If a longer
strobe is required, the application can scale the system clock with the clock divider to meet the
requirements (See Section 6.4 on page 30).
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AT89LP51/52 - Preliminary
Table 3-3.
AUXR – Auxiliary Control Register
AUXR = 8EH
Reset Value = xxx0 0000B
Not Bit Addressable
DISRTO(1)
WS1(2)
–
–
6
–
5
WDIDLE(1)
4
WS0
EXRAM
1
DISALE
Bit
7
3
2
0
Symbol
Function
WDT Disable during Idle(1). When WDIDLE = 0 the WDT continues to count in Idle mode. When WDIDLE = 1 the WDT
halts counting in Idle mode.
WDIDLE
Disable Reset Output(1). When DISTRO = 0 the reset pin is driven to the same level as POL when the WDT resets.
When DISRTO = 1 the reset pin is input only.
DISRTO
WS[1-0]
Wait State Select. Determines the number of wait states inserted into external memory accesses.
WS1(2)
WS0
Wait States
RD / WR Strobe Width
ALE to RD / WR Setup
0
0
1
1
0
1
0
1
0
1
2
3
1 x tCYC (Fast); 3 x tCYC (Compatibility)
2 x tCYC (Fast); 15 x tCYC (Compatibility)
2 x tCYC (Fast)
1 x tCYC (Fast); 1.5 x tCYC (Compatibility)
1 x tCYC (Fast); 1.5 x tCYC (Compatibility)
2 x tCYC (Fast)
3 x tCYC (Fast)
2 x tCYC (Fast)
External RAM Enable. When EXRAM = 0, MOVX instructions can access the internally mapped portions of the address
space. Accesses to addresses above internally mapped memory will access external memory. Set EXRAM = 1 to
bypass the internal memory and map the entire address space to external memory.
EXRAM
ALE Disable. When DISALE = 0 the ALE pulse is active at 1/3 of the system clock frequency in Compatibility mode and
1/2 of the system clock frequency in Fast mode. When DISALES = 1 the ALE is inactive (high) unless an external
memory access occurs. DISALE must be set to use P4.4 as a general I/O.
DISALE
Notes: 1. AUXR.4 and AUXR.3 function as WDIDLE and DISRTO only in Compatibility mode. In Fast mode these bits are located in
WDTCON.
2. WS1 is only available in Fast mode. WS1 is forced to 0 in Compatibility mode.
Figure 3-12. Fast Mode External Data Memory Write Cycle (WS = 00B)
S1
S2
S3
S4
CLK
ALE
WR
P0
P0 SFR
P2 SFR
DPL or Ri OUT
DATA OUT
P0 SFR
P2 SFR
DPH or P2 OUT
P2
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3709B–MICRO–12/10
Figure 3-13. Fast Mode External Data Memory Read Cycle (WS = 00B)
S1
S2
S3
S4
CLK
ALE
RD
P0
DATA SAMPLED
P0 SFR
P2 SFR
DPL or Ri OUT
P0 SFR
P2 SFR
FLOAT
DPH or P2 OUT
P2
Figure 3-14. Compatibility Mode External Data Memory Write Cycle (WS0 = 0)
S4
S5
S6
S1
S2
S3
S4
S5
CLK
ALE
WR
P0
DPL or Ri
OUT
PCL or
P0 SFR
P0 SFR
DATA OUT
PCH or
P2 SFR
PCH or
P2 SFR
DPH or P2 OUT
P2
Figure 3-15. Compatibility Mode External Data Memory Read Cycle (WS0 = 0)
S4
S5
S6
S1
S2
S3
S4
S5
CLK
ALE
RD
P0
DATA SAMPLED
FLOAT
PCL or
P0 SFR
DPL or Ri
OUT
P0 SFR
PCH or
P2 SFR
PCH or
P2 SFR
DPH or P2 OUT
P2
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Figure 3-16. MOVX with One Wait State (WS = 01B)
S1
S2
S3
W1
S4
CLK
ALE
P2
P2 SFR
P0 SFR
P0 SFR
DPH or P2 OUT
P2 SFR
P0 SFR
P0 SFR
WR
P0
DPL OUT
DPL OUT
DATA OUT
RD
P0
FLOAT
Figure 3-17. MOVX with Two Wait States (WS = 10B)
S1
S2
S3
W1
W2
S4
CLK
ALE
P2
P2 SFR
P0 SFR
P0 SFR
DPH or P2 OUT
P2 SFR
P0 SFR
P0 SFR
WR
P0
DPL OUT
DPL OUT
DATA OUT
RD
P0
FLOAT
Figure 3-18. MOVX with Three Wait States (WS = 11B)
S1
S2
S3
W1
W2
W3
S4
CLK
ALE
P2
P2 SFR
P0 SFR
P0 SFR
DPH or P2 OUT
P2 SFR
P0 SFR
P0 SFR
WR
P0
DPL OUT
DPL OUT
DATA OUT
RD
P0
FLOAT
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3709B–MICRO–12/10
3.4
In-Application Programming (IAP)
The AT89LP51/52 supports In-Application Programming (IAP), allowing the program memory to
be modified during execution. IAP can be used to modify the user application on the fly or to use
program memory for nonvolatile data storage. The same page structure write protocol for
FDATA also applies to IAP (See Section 3.3.2.1 “Write Protocol” on page 14). The CPU is
always placed in idle while modifying the program memory. When the write completes, the CPU
will continue executing with the instruction after the MOVX @DPTR,A instruction that started the
write.
To enable access to the program memory, the IAP bit (MEMCON.7) must be set to one and the
IAP User Fuse must be enabled. The IAP User Fuse can disable all IAP operations. When this
fuse is disabled, the IAP bit will be forced to 0. While IAP is enabled, all MOVX @DPTR instruc-
tions will access the CODE space instead of EDATA/FDATA/XDATA. IAP also allows
reprogramming of the User Signature Array when SIGEN = 1. The IAP access settings are sum-
marized in Table 3-4 and Table 3-5.
Table 3-4.
IAP
IAP Access Settings for AT89LP52
SIGEN
DMEN
MOVX @DPTR
MOVC @DPTR
CODE (0000–1FFFH)
XCODE (2000–FFFFH)
0
0
0
XDATA (0000–FFFFH)
FDATA (0000–00FFH)
XDATA (0100–FFFFH)
CODE (0000–1FFFH)
XCODE (2000–FFFFH)
0
0
0
0
1
1
1
0
1
XDATA (0000–FFFFH)
SIG (0000–01FFH)
SIG (0000–01FFH)
FDATA (0000–00FFH)
XDATA (0100–FFFFH)
CODE (0000–1FFFH)
XDATA (2000–FFFFH)
CODE (0000–1FFFH)
XCODE (2000–FFFFH)
1
1
0
1
X
X
SIG (0000–01FFH)
XDATA (2000–FFFFH)
SIG (0000–01FFH)
Table 3-5.
IAP
IAP Access Settings for AT89LP51
SIGEN
DMEN
MOVX @DPTR
MOVC @DPTR
CODE (0000–0FFFH)
XCODE (1000–FFFFH)
0
0
0
XDATA (0000–FFFFH)
FDATA (0000–00FFH)
XDATA (0100–FFFFH)
CODE (0000–0FFFH)
XCODE (1000–FFFFH)
0
0
0
0
1
1
1
0
1
XDATA (0000–FFFFH)
SIG (0000–01FFH)
SIG (0000–01FFH)
FDATA (0000–00FFH)
XDATA (0100–FFFFH)
CODE (0000–0FFFH)
XDATA (1000–FFFFH)
CODE (0000–0FFFH)
XCODE (1000–FFFFH)
1
1
0
1
X
X
SIG (0000–01FFH)
XDATA (1000–FFFFH)
SIG (0000–01FFH)
Note:
When In-Application programming is not required, it is recommended that the IAP User Fuse be
disabled.
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AT89LP51/52 - Preliminary
4. Special Function Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is shown in
Table 4-1.
Note that not all of the addresses are occupied, and unoccupied addresses may not be imple-
mented on the chip. Read accesses to these addresses will in general return random data, and
write accesses will have an indeterminate effect. User software should not write to these unlisted
locations, since they may be used in future products to invoke new features.
Table 4-1.
AT89LP51/52 SFR Map and Reset Values
8
9
A
B
C
D
E
F
0F8H
0F0H
0E8H
0E0H
0D8H
0FFH
0F7H
0EFH
0E7H
0DFH
0D7H
0CFH
0C7H
0BFH
0B7H
0AFH
0A7H
9FH
B
0000 0000
ACC
0000 0000
PSW
0000 0000
0D0H
0C8H
T2CON
0000 0000
T2MOD
0000 0000
RCAP2L
0000 000
RCAP2H
0000 0000
TL2
0000 000
TH2
0000 0000
P4
1111 1111
PMOD
0C0H
0B8H
0B0H
(2)
IP
SADEN
0000 0000
xx00 0000
P3
1111 1111
IPH
xx00 0000
IE
SADDR
0000 0000
0A8H
0x00 0000
0A0H
P2
1111 1111
AUXR1
0000 00x0
WDTRST
(write-only)
WDTCON
0000 0xx0
SCON
0000 0000
SBUF
xxxx xxxx
98H
90H
88H
80H
P1
1111 1111
TCONB
000x xxxx
MEMCON
0000 00xx
97H
TCON
0000 0000
TMOD
0000 0000
TL0
0000 0000
TL1
0000 0000
TH0
0000 0000
TH1
0000 0000
AUXR
0000 0000
CLKREG
8FH
(3)
P0
1111 1111
SP
0000 0111
DP0L
0000 0000
DP0H
0000 0000
DP1L
0000 0000
DP1H
0000 0000
PCON
000x 0000
87H
0
1
2
3
4
5
6
7
Notes: 1. All SFRs in the left-most column are bit-addressable.
2. Reset value is 0101 0101B when Tristate-Port Fuse is enabled and 0000 0011B when disabled.
3. Reset value is 0101 0010B when Compatibility mode is enabled and 0000 0000B when disabled.
23
3709B–MICRO–12/10
5. Enhanced CPU
The AT89LP51/52 uses an enhanced 8051 CPU that runs at 6 to 12 times the speed of standard
8051 devices (or 3 to 6 times the speed of X2 8051 devices). The increase in performance is
due to two factors. First, the CPU fetches one instruction byte from the code memory every clock
cycle. Second, the CPU uses a simple two-stage pipeline to fetch and execute instructions in
parallel. This basic pipelining concept allows the CPU to obtain up to 1 MIPS per MHz. The
AT89LP51/52 also has a Compatibility mode that preserves the 12-clock machine cycle of stan-
dard 8051s like the AT89S51/52.
5.1
Fast Mode
Fast (Single-Cycle) mode must be enabled by clearing the Compatibility User Fuse. (See “User
Configuration Fuses” on page 86.) In this mode one instruction byte is fetched every system
clock cycle. The 8051 instruction set allows for instructions of variable length from 1 to 3 bytes.
In a single-clock-per-byte-fetch system this means each instruction takes at least as many
clocks as it has bytes to execute. The majority of instructions in the AT89LP51/52 follow this
rule: the instruction execution time in system clock cycles equals the number of bytes per
instruction, with a few exceptions. Branches and Calls require an additional cycle to compute the
target address and some other complex instructions require multiple cycles. See “Instruction Set
Summary” on page 75. for more detailed information on individual instructions.
Example of Fast mode instructions are shown in Figure 5-1. Note that Fast mode instructions
take three times as long to execute if they are fetched from external program memory.
Figure 5-1. Instruction Execution Sequences in Fast Mode
CLK
READ NEXT
OPCODE
S1
(A) 1-byte, 1-cycle instruction, e.g. INC A
READ OPERAND
READ NEXT OPCODE
S1
S2
(B) 2-byte, 2-cycle instruction, e.g. ADD A, #data
READ NEXT OPCODE
S1
S2
(C) 1-byte, 2-cycle instruction, e.g. INC DPTR
READ NEXT
OPCODE
S1
S2
S3
S4
ADDR
DATA
ACCESS EXTERNAL
MEMORY
(D) MOVX (1-byte, 4-cycle)
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AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
5.2
Compatibility Mode
Compatibility (12-Clock) mode is enabled by default from the factory or by setting the Compati-
bility User Fuse. In Compatibility mode instruction bytes are fetched every three system clock
cycles and the CPU operates with 6-state machine cycles and a divide-by-2 system clock for 12
oscillator periods per machine cycle. Standard instructions execute in1, 2 or 4 machine cycles.
Instruction timing in this mode is compatible with standard 8051s such as the AT89S51/52.
Compatibility mode can be used to preserve the execution profiles of legacy applications. For a
summary of differences between Fast and Compatibility modes see Table 2-1 on page 9. Exam-
ples of Compatibility mode instructions are shown in Figure 5-2.
Figure 5-2. Instruction Execution Sequences in Compatibility Mode
S1
S2
S3
S4
S5
S6
S1
S2
S3
S4
S5
S6
S1
CLKK
ALE
REAADD OOPPCCOODDEE
REAADD NNEEXXTT
OPCODE
(DDIISSCCAARRDD))
REAADD NNEEXXTT OOPPCCOODDEE AAGGAAIINN
S1
S2
S3
S4
S5
S6
(A) 1-byte, 1-cycle instruction, e.g., INC AA
READ OPCODE
REAADD 22NNDD
BYYTTEE
RREEAADD NNEEXXTT OOPPCCOODDEE
REAADD NNEEXXTT
S1
S2
S3
S4
S5
S6
(B) 2-byte, 1-cycle instruction, e.g., ADD A, #dataa
REAADD OOPPCCOODDEE
REAADD NNEEXXTT
OPCODE ((DDIISSCCAARRDD))
OPCODE AGAINN
S1
(C) 1-byte, 2-cycle instruction, e..gg..,, IINNCC DDPPTTR
READ READ NEXT
S2
S3
S4
S5
S6
S1
S2
S3
S3
S4
S5
S6
NO
NO READ NEXT
FEETTCCHH
OPCODE OPCODE (DISCARD) FETCH
(MOVX)
NO
ALE
OPCODE
AGAINN
S1
(D) MOVX (1-byte, 2-cycle)
S2
S3
S4
S5
S6
S1
S2
S4
S5
S6
AADDDDRR
DDAATA
ACCESS EXTERNAL MEMOORY
5.3
Enhanced Dual Data Pointers
The AT89LP51/52 provides two 16-bit data pointers: DPTR0 formed by the register pair DPOL
and DPOH (82H an 83H), and DPTR1 formed by the register pair DP1L and DP1H (84H and
85H). The data pointers are used by several instructions to access the program or data memo-
ries. The Data Pointer Configuration Register (AUXR1) controls operation of the dual data
pointers (Table 5-3 on page 27). The DPS bit in AUXR1 selects which data pointer is currently
referenced by instructions including the DPTR operand. Each data pointer may be accessed at
its respective SFR addresses regardless of the DPS value. The AT89LP51/52 provides two
methods for fast context switching of the data pointers:
25
3709B–MICRO–12/10
• Bit 2 of AUXR1 is hard-wired as a logic 0. The DPS bit may be toggled (to switch data
pointers) simply by incrementing the AUXR1 register, without altering other bits in the register
unintentionally. This is the preferred method when only a single data pointer will be used at
one time.
EX:
INC AUXR1 ; Toggle DPS
• In some cases, both data pointers must be used simultaneously. To prevent frequent toggling
of DPS, the AT89LP51/52 supports a prefix notation for selecting the opposite data pointer
per instruction. All DPTR instructions, with the exception of JMP @A+DPTR, when prefixed
with an 0A5H opcode will use the inverse value of DPS (DPS) to select the data pointer.
Some assemblers may support this operation by using the /DPTR operand. For example, the
following code performs a block copy within EDATA:
MOV AUXR1, #00H
MOV DPTR, #SRC
MOV /DPTR, #DST
MOV R7, #BLKSIZE
COPY: MOVX A, @DPTR
INC DPTR
; DPS = 0
; load source address to dptr0
; load destination address to dptr1
; number of bytes to copy
; read source (dptr0)
; next src (dptr0+1)
MOVX @/DPTR, A
INC /DPTR
; write destination (dptr1)
; next dst (dptr1+1)
DJNZ R7, COPY
For assemblers that do not support this notation, the 0A5H prefix must be declared in-line:
EX: DB 0A5H
INC DPTR
A summary of data pointer instructions with fast context switching is listed inTable 5-1.
Table 5-1. Data Pointer Instructions
; equivalent to INC /DPTR
Operation
DPS = 1
Instruction
DPS = 0
JMP @A+DPTR
JMP @A+DPTR0
MOV DPTR0, #data16
MOV DPTR1, #data16
INC DPTR0
JMP @A+DPTR1
MOV DPTR1, #data16
MOV DPTR0, #data16
INC DPTR1
MOV DPTR, #data16
MOV /DPTR, #data16
INC DPTR
INC /DPTR
INC DPTR1
INC DPTR0
MOVC A,@A+DPTR
MOVC A,@A+/DPTR
MOVX A,@DPTR
MOVX A,@/DPTR
MOVX @DPTR, A
MOVX @/DPTR, A
MOVC A,@A+DPTR0
MOVC A,@A+DPTR1
MOVX A,@DPTR0
MOVX A,@DPTR1
MOVX @DPTR0, A
MOVX @DPTR1, A
MOVC A,@A+DPTR1
MOVC A,@A+DPTR0
MOVX A,@DPTR1
MOVX A,@DPTR0
MOVX @DPTR1, A
MOVX @DPTR0, A
5.3.1
Data Pointer Update
The Dual Data Pointers on the AT89LP51/52 include two features that control how the data
pointers are updated. The data pointer decrement bits, DPD1 and DPD0 in AUXR1, configure
the INC DPTR instruction to act as DEC DPTR. The resulting operation will depend on DPS as
shown in Table 5-2. These bits also control the direction of auto-updates during MOVC and
MOVX.
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AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table 5-2.
Data Pointer Decrement Behavior
Equivalent Operation for INC DPTR and INC /DPTR
DPS = 0 DPS = 1
DPD1
DPD0
INC DPTR
INC DPTR0
DEC DPTR0
INC DPTR0
DEC DPTR0
INC /DPTR
INC DPTR1
INC DPTR1
DEC DPTR1
DEC DPTR1
INC DPTR
INC DPTR1
INC DPTR1
DEC DPTR1
DEC DPTR1
INC /DPTR
INC DPTR0
DEC DPTR0
INC DPTR0
DEC DPTR0
0
0
1
1
0
1
0
1
Table 5-3.
AUXR1 – Data Pointer Configuration Register
AUXR1 = A2H
Reset Value = 0000 00X0B
Not Bit Addressable
DPU1
DPU0
6
DPD1
5
DPD0
4
SIGEN
0
2
–
1
DPS
Bit
7
3
0
Symbol
Function
DPU1
Data Pointer 1 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR1 will also update
DPTR1 based on DPD1. If DPD1 = 0 the operation is post-increment and if DPD1 = 1 the operation is post-decrement.
When DPU1 = 0, DPTR1 is not updated.
DPU0
DPD1
DPD0
Data Pointer 0 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR0 will also update
DPTR0 based on DPD0. If DPD0 = 0 the operation is post-increment and if DPD0 = 1 the operation is post-decrement.
When DPU0 = 0, DPTR0 is not updated.
Data Pointer 1 Decrement. When set, INC DPTR instructions targeted to DPTR1 will decrement DPTR1. When cleared,
INC DPTR instructions will increment DPTR1. DPD1 also determines the direction of auto-update for DPTR1 when
DPU1 = 1.
Data Pointer 0 Decrement. When set, INC DPTR instructions targeted to DPTR0 will decrement DPTR0. When cleared,
INC DPTR instructions will increment DPTR0. DPD0 also determines the direction of auto-update for DPTR0 when
DPU0 = 1.
SIGEN
DPS
Signature Enable. When SIGEN = 1 all MOVC @DPTR instructions and all IAP accesses will target the signature array
memory. When SIGEN = 0, all MOVC and IAP accesses target CODE memory.
Data Pointer Select. DPS selects the active data pointer for instructions that reference DPTR. When DPS = 0, DPTR will
target DPTR0 and /DPTR will target DPTR1. When DPS = 1, DPTR will target DPTR1 and /DPTR will target DPTR0.
The data pointer update bits, DPU1 and DPU0, allow MOVX @DPTR and MOVC @DPTR
instructions to update the selected data pointer automatically in a post-increment or post-decre-
ment fashion. The direction of update depends on the DPD1 and DPD0 bits as shown in Table
5-4. These bits can be used to make block copy routines more efficient.
Table 5-4.
Data Pointer Auto-Update
Update Operation for MOVX and MOVC (DPU1 = 1 & DPU0 = 1)
DPS = 0 DPS = 1
DPD1
DPD0
DPTR
/DPTR
DPTR
/DPTR
0
0
1
1
0
1
0
1
DPTR0++
DPTR0--
DPTR0++
DPTR0--
DPTR1++
DPTR1++
DPTR1--
DPTR1--
DPTR1++
DPTR1++
DPTR1--
DPTR1--
DPTR0++
DPTR0--
DPTR0++
DPTR0--
27
3709B–MICRO–12/10
6. System Clock
The system clock is generated directly from one of three selectable clock sources. The three
sources are the on-chip crystal oscillator, external clock source, and internal RC oscillator. A dia-
gram of the clock subsystem is shown in Figure 6-1. The on-chip crystal oscillator may also be
configured for low or high power operation. The clock source is selected by the Clock Source
User Fuses as shown in Table 6-1. See “User Configuration Fuses” on page 86. By default, in
Fast mode no internal clock division is used to generate the CPU clock from the system clock. In
Compatibility mode the default is to divide the oscillator output by two. The system clock divider
may be used to prescale the system clock with other values. The choice of clock source also
affects the start-up time after a POR, BOD or Power-down event (See “Reset” on page 31 or
“Power-down Mode” on page 34)
Figure 6-1. Clock Subsystem Diagram
CLOCK FUSES
INTERNAL
1.8432MHz
CLKIRC
0
1
2
3
CLKEXT
CLKXTAL
OSC
5-BIT
CLOCK
DIVIDER
XTAL1
TPS3-0
XTAL2
0
1 2 3 4 5
CDV2-0
Timer 0
Timer 1
Timer 2
Watchdog
4-BIT
PRESCALER
SYSTEM CLOCK
(CLKSYS
)
Table 6-1.
Clock Source Settings
Clock Source
Fuse 1
Clock Source
Fuse 0
Selected Clock Source
1
1
0
0
1
0
1
0
High Power Crystal Oscillator (f > 12 MHz)
Low Power Crystal Oscillator (f ≤12 MHz)
External Clock on XTAL1
Internal 1.8432 MHz Auxiliary Oscillator
6.1
Crystal Oscillator
When enabled, the internal inverting oscillator amplifier is connected between XTAL1 and
XTAL2 for connection to an external quartz crystal or ceramic resonator. The oscillator may
operate in either high-power or low-power mode. Low-speed mode is intended for crystals of 12
MHz or less and consumes less power than the higher speed mode. The configuration as shown
in Figure 6-2 applies for both high and low power oscillators. Note that in some cases, external
capacitors C1 and C2 may NOT be required due to the on-chip capacitance of the XTAL1 and
XTAL2 inputs (approximately 10 pF each). When using the crystal oscillator, P4.6 and P4.7 will
have their inputs and outputs disabled. Also, XTAL2 in crystal oscillator mode should not be
used to directly drive a board-level clock without a buffer.
28
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
An optional 5 MΩon-chip resistor can be connected between XTAL1 and GND. This resistor can
improve the startup characteristics of the oscillator especially at higher frequencies. The resistor
can be enabled/disabled with the R1 User Fuse (See “User Configuration Fuses” on page 86.)
Figure 6-2. Crystal Oscillator Connections
C2
~10 pF
C1
R1
~10 pF
~5 MΩ
Note:
1. C1, C2 = 5 pF 5pF for Crystals
= 5 pF 5pF for Ceramic Resonators
6.2
External Clock Source
The external clock option disables the oscillator amplifier and allows XTAL1 to be driven directly
by an external clock source as shown in Figure 6-3. XTAL2 may be left unconnected, used as
general purpose I/O P4.7, or configured to output a divided version of the system clock.
Figure 6-3. External Clock Drive Configuration
NC GPIO
XTAL2 (P4.7)
EXTERNAL
OSCILLATOR
SIGNAL
XTAL1 (P4.6)
GND
6.3
Internal RC Oscillator
The AT89LP51/52 has an Internal Auxiliary oscillator tuned to 1.8432 MHz 2.0%. When
enabled as the clock source, XTAL1 and XTAL2 may be used as P4.6 and P4.7 respectively.
29
3709B–MICRO–12/10
6.4
System Clock Divider
The CDV2-0 bits in CLKREG allow the system clock to be divided down from the selected clock
source by powers of 2. The clock divider provides users with a greater frequency range when
using the Internal Oscillator. For example, to achieve a 230.4 kHz system frequency when using
the RC oscillator, CDV2-0 should be set to 011B for divide-by-8 operation. The divider can also
be used to reduce power consumption by decreasing the operational frequency during non-criti-
cal periods. The resulting system frequency is given by the following equation:
fOSC
fSYS = ------------
2CDV
where fOSC is the frequency of the selected clock source. The clock divider will prescale the clock
for the CPU and all peripherals. The value of CDV may be changed at any time without interrupt-
ing normal execution. Changes to CDV are synchronized such that the system clock will not
pass through intermediate frequencies. When CDV is updated, the new frequency will take
affect within a maximum period of 32 x tOSC
.
In Compatibility mode the divider defaults to divide-by-2 and and in Fast mode it defaults to no
division.
Table 6-2.
CLKREG – Clock Control Register
CLKREG = 8FH
Reset Value = 0?0? 00?0B
Not Bit Addressable
TPS3
TPS2
TPS1
TPS0
CDV2
3
CDV1
2
CDV0
1
—
0
Bit
7
6
5
4
Symbol
Function
TPS[3-0]
Timer Prescaler. The Timer Prescaler selects the time base for Timer 0, Timer 1, Timer 2 and the Watchdog Timer. The
prescaler is implemented as a 4-bit binary down counter. When the counter reaches zero it is reloaded with the value
stored in the TPS bits to give a division ratio between 1 and 16. By default the timers will count every clock cycle in Fast
mode (TPS = 0000B) and every six cycles in Compatibility mode (TPS = 0101B).
System Clock Division. Determines the frequency of the system clock relative to the oscillator clock source.
CDIV2
CDIV1
CDIV0
System Clock Frequency
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/1
fOSC/2
fOSC/4
CDV[2-0]
f
OSC/8
fOSC/16
fOSC/32
Reserved
Reserved
Note:
The reset value of CLKREG is 0000000B in Fast mode and 01010010B in Compatibility mode.
30
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AT89LP51/52 - Preliminary
7. Reset
During reset, all I/O Registers are set to their initial values, the port pins are set to their default
mode, and the program starts execution from the Reset Vector, 0000H. The AT89LP51/52 has
five sources of reset: power-on reset, brown-out reset, external reset, watchdog reset, and soft-
ware reset.
7.1
Power-on Reset
A Power-on Reset (POR) is generated by an on-chip detection circuit. The detection level VPOR
is nominally 1.4V. The POR is activated whenever VDD is below the detection level. The POR cir-
cuit can be used to trigger the start-up reset or to detect a major supply voltage failure. The POR
circuit ensures that the device is reset from power-on. A power-on sequence is shown in Figure
7-1. When VDD reaches the Power-on Reset threshold voltage VPOR, an initialization sequence
lasting tPOR is started. When the initialization sequence completes, the start-up timer determines
how long the device is kept in POR after VDD rise. The start-up timer does not begin counting
until after VDD reaches the Brown-out Detector (BOD) threshold voltage VBOD. The POR signal is
activated again, without any delay, when VDD falls below the POR threshold level. A Power-on
Reset (i.e. a cold reset) will set the POF flag in PCON. The internally generated reset can be
extended beyond the power-on period by holding the RST pin active longer than the time-out.
Figure 7-1. Power-on Reset Sequence
V
BOD
V
VDD
POR
t
SUT
t
Time-out
POR
(POL Tied to VCC)
POL
RST
(RST Tied to GND)
Internal
Reset
V
RST
(RST Controlled Externally)
IL
Internal
Reset
t
RHD
Note:
tPOR is approximately 143 µs 5%.
The start-up timer delay is user-configurable with the Start-up Time User Fuses and depends on
the clock source (Table 7-1). The Start-Up Time fuses also control the length of the start-up time
after a Brown-out Reset or when waking up from Power-down during internally timed mode. The
start-up delay should be selected to provide enough settling time for VDD and the selected clock
source. The device operating environment (supply voltage, frequency, temperature, etc.) must
meet the minimum system requirements before the device exits reset and starts normal opera-
tion. The RST pin may be held active externally until these conditions are met.
31
3709B–MICRO–12/10
Table 7-1.
SUT Fuse 1
Start-up Timer Settings
SUT Fuse 0
Clock Source
tSUT ( 5ꢀ) µs
16
Internal RC/External Clock
Crystal Oscillator
0
0
1
1
0
1024
Internal RC/External Clock
Crystal Oscillator
512
1
0
1
2048
Internal RC/External Clock
Crystal Oscillator
1024
4096
Internal RC/External Clock
Crystal Oscillator
4096
16384
7.2
Brown-out Reset
The AT89LP51/52 has an on-chip Brown-out Detection (BOD) circuit for monitoring the VDD level
during operation by comparing it to a fixed trigger level. The trigger level VBOD for the BOD is
nominally 2.0V. The purpose of the BOD is to ensure that if VDD fails or dips while executing at
speed, the system will gracefully enter reset without the possibility of errors induced by incorrect
execution. A BOD sequence is shown in Figure 7-2. When VDD decreases to a value below the
trigger level VBOD, the internal reset is immediately activated. When VDD increases above the
trigger level plus about 200 mV of hysteresis, the start-up timer releases the internal reset after
the specified time-out period has expired (Table 7-1).
Figure 7-2. Brown-out Detector Reset
V
BOD
VDD
V
POR
t
SUT
Time-out
Internal
Reset
The AT89LP51/52 allows for a wide VDD operating range. The on-chip BOD may not be suffi-
cient to prevent incorrect execution if VBOD is lower than the minimum required VDD range, such
as when a 5.0V supply is coupled with high frequency operation. In such cases an external
Brown-out Reset circuit connected to the RST pin may be required.
7.3
External Reset
The RST pin of the AT89LP51/52 can function as either an active-low reset input or as an active-
high reset input. The polarity of the RST pin is selectable using the POL pin (formerly EA). When
POL is high the RST pin is active high with an on-chip pull-down resistor tied to GND. When
POL is low the RST pin is active low with an on-chip pull-up resistor tied to VDD. The RST pin
structure is shown in Figure 7-3. In Compatibility mode the reset pin is sampled every six clock
cycles and must be held active for at least twelve clock cycles to trigger the internal reset. In
Fast mode the reset pin is sampled every clock cycle and must be held active for at least two
clock cycles to trigger the internal reset.
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The AT89LP51/52 includes an on-chip Power-On Reset and Brown-out Detector circuit that
ensures that the device is reset from system power up. In most cases a RC startup circuit is not
required on the RST pin, reducing system cost, and the RST pin may be left unconnected if a
board-level reset is not present.
Note:
RST also serves as the In-System Programming (ISP) enable. ISP is enabled when the external
reset pin is held active. When ISP is disabled by fuse, ISP may only be entered by pulling RST
active during power-up. If this behavior is necessary, it is recommended to use an active-low reset
so that ISP can be entered by shorting RST to GND at power-up.
Figure 7-3. Reset Pin Structure
V
CC
V
CC
POL = 1
POL = 0
DISRTO
WDT Reset
Internal Reset
DISRTO
RST
RST
Internal Reset
WDT Reset
7.4
7.5
Watchdog Reset
When the Watchdog times out, it will generate a reset pulse lasting 49 clock cycles. By default
this pulse is also output on the RST pin. To disable the RST output the DISRTO bit in AUXR
(Compatibility mode) or WDTCON (Fast mode) must be set to one. Watchdog reset will set the
WDTOVF flag in WDTCON. To prevent a Watchdog reset, the watchdog reset sequence
1EH/E1H must be written to WDTRST before the Watchdog times out. See “Programmable
Watchdog Timer” on page 73. for details on the operation of the Watchdog.
Software Reset
The CPU may generate a 49-clock cycle reset pulse by writing the software reset sequence
5AH/A5H to the WDRST register. A software reset will set the SWRST bit in WDTCON. See
“Software Reset” on page 73 for more information on software reset. Writing any sequences
other than 5AH/A5H or 1EH/E1H to WDTRST will generate an immediate reset and set both
WDTOVF and SWRST to flag an error. Software reset will also drive the RST pin active unless
DISRTO is set.
8. Power Saving Modes
The AT89LP51/52 supports two different power-reducing modes: Idle and Power-down. These
modes are accessed through the PCON register. Additional steps may be required to achieve
the lowest possible power consumption while using these modes.
8.1
Idle Mode
Setting the IDL bit in PCON enters idle mode. Idle mode halts the internal CPU clock. The CPU
state is preserved in its entirety, including the RAM, stack pointer, program counter, program
status word, and accumulator. The Port pins hold the logic states they had at the time that Idle
was activated. Idle mode leaves the peripherals running in order to allow them to wake up the
33
3709B–MICRO–12/10
CPU when an interrupt is generated. The timer and UART peripherals continue to function dur-
ing Idle. If these functions are not needed during idle, they should be explicitly disabled by
clearing the appropriate control bits in their respective SFRs. The watchdog may be selectively
enabled or disabled during Idle by setting/clearing the WDIDLE bit. The Brown-out Detector is
always active during Idle. Any enabled interrupt source or reset may terminate Idle mode. When
exiting Idle mode with an interrupt, the interrupt will immediately be serviced, and following RETI
the next instruction to be executed will be the one following the instruction that put the device
into Idle.
The power consumption during Idle mode can be further reduced by prescaling down the system
clock using the System Clock Divider (Section 6.4 on page 30). Be aware that the clock divider
will affect all peripheral functions and baud rates may need to be adjusted to maintain their rate
with the new clock frequency.
.
Table 8-1.
PCON – Power Control Register
PCON = 87H
Reset Value = 000X 0000B
Not Bit Addressable
SMOD1
SMOD0
PWDEX
5
POF
4
GF1
3
GF0
2
PD
1
IDL
0
Bit
7
6
Symbol
SMOD1
SMOD0
Function
Double Baud Rate bit. Doubles the baud rate of the UART in Modes 1, 2, or 3.
Frame Error Select. When SMOD0 = 1, SCON.7 is SM0. When SMOD0 = 1, SCON.7 is FE. Note that FE will be set after
a frame error regardless of the state of SMOD0.
PWDEX
POF
Power-down Exit Mode. When PWDEX = 0, wake up from Power-down is externally controlled. When PWDEX = 1, wake
up from Power-down is internally timed.
Power Off Flag. POF is set to “1” during power up (i.e. cold reset). It can be set or reset under software control and is not
affected by RST or BOD (i.e. warm resets).
GF1, GF0
PD
General-purpose Flags
Power-down bit. Setting this bit activates power-down operation. The PD bit is cleared automatically by hardware when
waking up from power-down.
IDL
Idle Mode bit. Setting this bit activates Idle mode operation. The IDL bit is cleared automatically by hardware when
waking up from idle
8.2
Power-down Mode
Setting the Power-down (PD) bit in PCON enters Power-down mode. Power-down mode stops
the oscillator, disables the BOD and powers down the Flash memory in order to minimize power
consumption. Only the power-on circuitry will continue to draw power during Power-down. Dur-
ing Power-down, the power supply voltage may be reduced to the RAM keep-alive voltage. The
RAM contents will be retained, but the SFR contents are not guaranteed once VDD has been
reduced. Power-down may be exited by external reset, power-on reset, or certain enabled
interrupts.
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8.2.1
Interrupt Recovery from Power-down
Two external interrupt sources may be configured to terminate Power-down mode: external
interrupts INT0 (P3.2) and INT1 (P3.3). To wake up by external interrupt INT0 or INT1, that inter-
rupt must be enabled by setting EX0 or EX1 in IE and must be configured for level-sensitive
operation by clearing IT0 or IT1.
When terminating Power-down by an interrupt, two different wake-up modes are available.
When PWDEX in PCON is one, the wake-up period is internally timed as shown in Figure 8-1. At
the falling edge on the interrupt pin, Power-down is exited, the oscillator is restarted, and an
internal timer begins counting. The internal clock will not be allowed to propagate to the CPU
until after the timer has timed out. After the time-out period the interrupt service routine will
begin. The time-out period is controlled by the Start-up Timer Fuses (see Table 7-1 on page 32).
The interrupt pin need not remain low for the entire time-out period.
Figure 8-1. Interrupt Recovery from Power-down (PWDEX = 1)
PWD
XTAL1
t
SUT
INT1
Internal
Clock
When PWDEX = “0”, the wake-up period is controlled externally by the interrupt. Again, at the
falling edge on the interrupt pin, power-down is exited and the oscillator is restarted. However,
the internal clock will not propagate until the rising edge of the interrupt pin as shown in Figure 8-
2. The interrupt pin should be held low long enough for the selected clock source to stabilize.
After the rising edge on the pin the interrupt service routine will be executed.
Figure 8-2. Interrupt Recovery from Power-down (PWDEX = 0)
PWD
XTAL1
INT1
Internal
Clock
8.2.2
Reset Recovery from Power-down
The wake-up from Power-down through an external reset is similar to the interrupt with
PWDEX = “1”. At the rising edge of RST, Power-down is exited, the oscillator is restarted, and
an internal timer begins counting as shown in Figure 8-3. The internal clock will not be allowed to
propagate to the CPU until after the timer has timed out. The time-out period is controlled by the
Start-up Timer Fuses. (See Table 7-1 on page 32). If RST returns low before the time-out, a two
clock cycle internal reset is generated when the internal clock restarts. Otherwise, the device will
remain in reset until RST is brought low.
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3709B–MICRO–12/10
Figure 8-3. Reset Recovery from Power-down (POL = 1)
PWD
XTAL1
t
SUT
RST
Internal
Clock
Internal
Reset
8.3
Reducing Power Consumption
Several possibilities need consideration when trying to reduce the power consumption in an
8051-based system. Generally, Idle or Power-down mode should be used as often as possible.
All unneeded functions should be disabled. The System Clock Divider can scale down the oper-
ating frequency during periods of low demand. The ALE output can be disabled by setting
DISALE in AUXR, thereby also reducing EMI.
9. Interrupts
The AT89LP51/52 provides 6 interrupt sources: two external interrupts, three timer interrupts,
and a serial port interrupt. These interrupts and the system reset each have a separate program
vector at the start of the program memory space. Each interrupt source can be individually
enabled or disabled by setting or clearing a bit in the interrupt enable register IE. The IE register
also contains a global disable bit, EA, which disables all interrupts.
Each interrupt source can be individually programmed to one of four priority levels by setting or
clearing bits in the interrupt priority registers IP and IPH. IP holds the low order priority bits and
IPH holds the high priority bits for each interrupt. An interrupt service routine in progress can be
interrupted by a higher priority interrupt, but not by another interrupt of the same or lower priority.
The highest priority interrupt cannot be interrupted by any other interrupt source. If two requests
of different priority levels are pending at the end of an instruction, the request of higher priority
level is serviced. If requests of the same priority level are pending at the end of an instruction, an
internal polling sequence determines which request is serviced. The polling sequence is based
on the vector address; an interrupt with a lower vector address has higher priority than an inter-
rupt with a higher vector address. Note that the polling sequence is only used to resolve pending
requests of the same priority level.
The External Interrupts INT0 and INT1 can each be either level-activated or edge-activated,
depending on bits IT0 and IT1 in Register TCON. The flags that actually generate these inter-
rupts are the IE0 and IE1 bits in TCON. When the service routine is vectored to, hardware clears
the flag that generated an external interrupt only if the interrupt was edge-activated. If the inter-
rupt was level activated, then the external requesting source (rather than the on-chip hardware)
controls the request flag.
The Timer 0 and Timer 1 Interrupts are generated by TF0 and TF1, which are set by a rollover in
their respective Timer/Counter registers (except for Timer 0 in Mode 3). When a timer interrupt is
generated, the on-chip hardware clears the flag that generated it when the service routine is
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vectored to. The Timer 2 Interrupt is generated by a logic OR of bits TF2 and EXF2 in register
T2CON. Neither of these flags is cleared by hardware when the CPU vectors to the service rou-
tine. The service routine normally must determine whether TF2 or EXF2 generated the interrupt
and that bit must be cleared by software.
The Serial Port Interrupt is generated by the logic OR of RI and TI in SCON. Neither of these
flags is cleared by hardware when the CPU vectors to the service routine. The service routine
normally must determine whether RI or TI generated the interrupt and that bit must be cleared by
software.
All of the bits that generate interrupts can be set or cleared by software, with the same result as
though they had been set or cleared by hardware. That is, interrupts can be generated and
pending interrupts can be canceled in software.
Table 9-1.
Interrupt Vector Addresses
Source
Interrupt
Vector Address
0000H
System Reset
RST or POR or BOD
External Interrupt 0
Timer 0 Overflow
External Interrupt 1
Timer 1 Overflow
Serial Port Interrupt
Timer 2 Interrupt
IE0
0003H
TF0
000BH
IE1
0013H
TF1
001BH
RI or TI
TF2 or EXF2
0023H
002BH
9.1
Interrupt Response Time
The interrupt flags may be set by their hardware in any clock cycle. The interrupt controller polls
the flags in the last clock cycle of the instruction in progress. If one of the flags was set in the
preceding cycle, the polling cycle will find it and the interrupt system will generate an LCALL to
the appropriate service routine as the next instruction, provided that the interrupt is not blocked
by any of the following conditions: an interrupt of equal or higher priority level is already in prog-
ress; the instruction in progress is RETI or any write to the IE, IP or IPH registers; the CPU is
currently forced into idle by an IAP or FDATA write. Each of these conditions will block the gen-
eration of the LCALL to the interrupt service routine. The second condition ensures that if the
instruction in progress is RETI or any access to IE, IP or IPH, then at least one more instruction
will be executed before any interrupt is vectored to. The polling cycle is repeated at the last cycle
of each instruction, and the values polled are the values that were present at the previous clock
cycle. If an active interrupt flag is not being serviced because of one of the above conditions and
is no longer active when the blocking condition is removed, the denied interrupt will not be ser-
viced. In other words, the fact that the interrupt flag was once active but not serviced is not
remembered. Every polling cycle is new.
If a request is active and conditions are met for it to be acknowledged, a hardware subroutine
call to the requested service routine will be the next instruction executed. The call itself takes
four cycles. Thus, a minimum of five complete clock cycles elapsed between activation of an
interrupt request and the beginning of execution of the first instruction of the service routine. A
longer response time results if the request is blocked by one of the previously listed conditions. If
an interrupt of equal or higher priority level is already in progress, the additional wait time
depends on the nature of the other interrupt's service routine. If the instruction in progress is not
in its final clock cycle, the additional wait time cannot be more than 4 cycles, since the longest
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3709B–MICRO–12/10
instruction is 5 cycles long. If the instruction in progress is RETI, the additional wait time cannot
be more than 9 cycles (a maximum of 4 more cycles to complete the instruction in progress, plus
a maximum of 5 cycles to complete the next instruction). Thus, in a single-interrupt system, the
response time is always more than 5 clock cycles and less than 14 clock cycles. See Figure 9-1
and Figure 9-2.
Figure 9-1. Minimum Interrupt Response Time (Fast Mode)
Clock Cycles
INT0
1
5
IE0
Ack.
Instruction
Cur. Instr.
LCALL
1st ISR Instr.
Figure 9-2. Maximum Interrupt Response Time (Fast Mode)
Clock Cycles
INT0
1
5
10
14
Ack.
IE0
Instruction
RETI
MOVX @/DPTR, A
LCALL
1st ISR Instr.
Figure 9-3. Minimum Interrupt Response Time (Compatibility Mode)
1
14
Clock Cycles
INT0
Ack.
IE0
Instruction
LCALL
ISR
Figure 9-4. Maximum Interrupt Response Time (Compatibility Mode)
1
13
37
49
Clock Cycles
INT0
Ack.
IE0
Instruction
RETI
MUL AB
LCALL
ISR
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Table 9-2.
IE = A8H
IE – Interrupt Enable Register
Reset Value = 0000 0000B
Bit Addressable
EA
–
6
ET2
5
ES
ET1
3
EX1
2
ET0
1
EX0
0
Bit
Symbol
EA
7
4
Function
Global enable/disable. All interrupts are disabled when EA = 0. When EA = 1, each interrupt source is enabled/disabled by setting
/clearing its own enable bit.
ET2
ES
Timer 2 Interrupt Enable
Serial Port Interrupt Enable
Timer 1 Interrupt Enable
External Interrupt 1 Enable
Timer 0 Interrupt Enable
External Interrupt 0 Enable
ET1
EX1
ET0
EX0
Table 9-3.
IP – Interrupt Priority Register
IP = B8H
Reset Value = 0000 0000B
Bit Addressable
PT2
5
PS
PT1
3
PX1
2
PT0
1
PX0
0
–
–
6
Bit
7
4
Symbol
PT2
Function
Timer 2 Interrupt Priority Low
Serial Port Interrupt Priority Low
Timer 1 Interrupt Priority Low
External Interrupt 1 Priority Low
Timer 0 Interrupt Priority Low
External Interrupt 0 Priority Low
PS
PT1
PX1
PT0
PX0
Table 9-4.
IPH – Interrupt Priority High Register
IPH = B7H
Reset Value = 0000 0000B
Not Bit Addressable
PT2H
5
PSH
PT1H
3
PX1H
2
PT0H
1
PX0H
0
–
–
6
Bit
7
4
Symbol
PT2H
PSH
Function
Timer 2 Interrupt Priority High
Serial Port Interrupt Priority High
Timer 1 Interrupt Priority High
External Interrupt 1 Priority High
Timer 0 Interrupt Priority High
External Interrupt 0 Priority High
PT1H
PX1H
PT0H
PX0H
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3709B–MICRO–12/10
10. I/O Ports
The AT89LP51/52 can be configured for between 32 and 36 I/O pins. The exact number of I/O
pins available depends on the clock, external memory and package type as shown in Table 10-
1.
Table 10-1. I/O Pin Configurations
Number of I/O
Clock Source
External Program Access
External Data Access
Pins
14
16
31
34
15
17
32
35
16
18
33
36
Yes (RD+WR)
Yes (PSEN+ALE+P0+P2)
No
External Crystal or
Resonator
Yes (ALE+RD+WR+P0)
No
No
Yes (RD+WR)
Yes (PSEN+ALE+P0+P2)
No
External Clock
Yes (ALE+RD+WR+P0)
No
No
Yes (RD+WR)
Yes (PSEN+ALE+P0+P2)
No
Yes (ALE+RD+WR+P0)
No
Internal RC
Oscillator
No
10.1 Port Configuration
Each 8-bit port on the AT89LP51/52 may be configured in one of four modes: quasi-bidirectional
(standard 8051 port outputs), push-pull output, open-drain output, or input-only. Port modes may
be assigned in software on a port-by-port basis as shown in Table 10-2 using the PMOD register
listed in Table 10-3. The Tristate-Port User Fuse determines the default state of the port pins.
When the fuse is enabled, all port pins default to input-only mode after reset. When the fuse is
disabled, all port pins on P1, P2 and P3 default to quasi-bidirectional mode after reset and are
weakly pulled high. P0 is set to Open-drain mode. P4 always operates in quasi-bidirectional
mode.
Each port pin also has a Schmitt-triggered input for improved input noise rejection. During
Power-down all the Schmitt-triggered inputs are disabled with the exception of P3.2 (INT0), P3.3
(INT1), RST, P4.6 (XTAL1) and P4.7 (XTAL2). Therefore, P3.2, P3.3, P4.6 and P4.7 should not
be left floating during Power-down.
.
Table 10-2. Configuration Modes for Port x
PxM0
PxM1
Port Mode
0
0
1
1
0
1
0
1
Quasi-bidirectional
Push-pull Output
Input Only (High Impedance)
Open-Drain Output
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.
Table 10-3. PMOD – Port Mode Register
PMOD = C1H
Reset Value = 0000 0011B
Not Bit Addressable
P3M1
7
P3M0
6
P2M1
5
P2M0
4
P1M1
3
P1M0
2
P0M1
1
P0M0
0
Bit
Symbol
P3M1-0
P2M1-0
P1M1-0
P0M1-0
Function
Port 3 Configuration Mode
Port 2 Configuration Mode
Port 1 Configuration Mode
Port 0 Configuration Mode
10.1.1
Quasi-bidirectional Output
Port pins in quasi-bidirectional output mode function similar to standard 8051 port pins. A Quasi-
bidirectional port can be used both as an input and output without the need to reconfigure the
port. This is possible because when the port outputs a logic high, it is weakly driven, allowing an
external device to pull the pin low. When the pin is driven low, it is driven strongly and able to
sink a large current. There are three pull-up transistors in the quasi-bidirectional output that
serve different purposes.
One of these pull-ups, called the “very weak” pull-up, is turned on whenever the port latch for the
pin contains a logic “1”. This very weak pull-up sources a very small current that will pull the pin
high if it is left floating. When the pin is pulled low externally this pull-up will always source some
current.
A second pull-up, called the “weak” pull-up, is turned on when the port latch for the pin contains
a logic “1” and the pin itself is also at a logic “1” level. This pull-up provides the primary source
current for a quasi-bidirectional pin that is outputting a “1”. If this pin is pulled low by an external
device, this weak pull-up turns off, and only the very weak pull-up remains on. In order to pull the
pin low under these conditions, the external device has to sink enough current to overpower the
weak pull-up and pull the port pin below its input threshold voltage.
The third pull-up is referred to as the “strong” pull-up. This pull-up is used to speed up low-to-
high transitions on a quasi-bidirectional port pin when the port latch changes from a logic “0” to a
logic “1”. When this occurs, the strong pull-up turns on for one CPU clock, quickly pulling the port
pin high. The quasi-bidirectional port configuration is shown in Figure 10-1.
10.1.2
Input-only Mode
The input only port configuration is shown in Figure 10-2. The output drivers are tristated. The
input includes a Schmitt-triggered input for improved input noise rejection. The input circuitry of
P3.2, P3.3, P4.6 and P4.7 is not disabled during Power-down (see Figure 10-3) and therefore
these pins should not be left floating during Power-down when configured in this mode.
Input-only mode can reduce power consumption for low-level inputs over quasi-bidirectional
mode because the “very weak” pull-up is turned off and only very small leakage current in the
sub microamp range is present.
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3709B–MICRO–12/10
Figure 10-1. Quasi-bidirectional Output
V
CC
V
CC
V
CC
1 Clock Delay
(D Flip-Flop)
Very
Weak
Strong
Weak
Port
Pin
From Port
Register
Input
Data
PWD
Figure 10-2. Input Only
Port
Pin
Input
Data
PWD
Figure 10-3. Input Circuit for P3.2, P3.3, P4.6 and P4.7
Input
Data
Port
Pin
10.1.3
Open-drain Output
The open-drain output configuration turns off all pull-ups and only drives the pull-down transistor
of the port pin when the port latch contains a logic “0”. To be used as a logic output, a port con-
figured in this manner must have an external pull-up, typically a resistor tied to VDD. The pull-
down for this mode is the same as for the quasi-bidirectional mode. The open-drain port configu-
ration is shown in Figure 10-4. The input circuitry of P3.2, P3.3, P4.6 and P4.7 is not disabled
during Power-down (see Figure 10-3) and therefore these pins should not be left floating during
Power-down when configured in this mode.
Figure 10-4. Open-Drain Output
Port
Pin
From Port
Register
Input
Data
PWD
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10.1.4
Push-pull Output
The push-pull output configuration has the same pull-down structure as both the open-drain and
the quasi-bidirectional output modes, but provides a continuous strong pull-up when the port
latch contains a logic “1”. The push-pull mode may be used when more source current is needed
from a port output. The push-pull port configuration is shown in Figure 10-5.
Figure 10-5. Push-pull Output
VCC
Port
Pin
From Port
Register
Input
Data
PWD
10.2 Port Read-Modify-Write
A read from a port will read either the state of the pins or the state of the port register depending
on which instruction is used. Simple read instructions will always access the port pins directly.
Read-modify-write instructions, which read a value, possibly modify it, and then write it back, will
always access the port register. This includes bit write instructions such as CLR or SETB as they
actually read the entire port, modify a single bit, then write the data back to the entire port. See
Table 10-4 for a complete list of Read-Modify-Write instruction which may access the ports.
Table 10-4. Port Read-Modify-Write Instructions
Mnemonic
ANL
Instruction
Example
Logical AND
ANL P1, A
ORL P1, A
XRL P1, A
JBC P3.0, LABEL
CPL P3.1
ORL
Logical OR
XRL
Logical EX-OR
JBC
Jump if bit set and clear bit
Complement bit
CPL
INC
Increment
INC P1
DEC
Decrement
DEC P3
DJNZ
Decrement and jump if not zero
Move carry to bit Y of Port X
Clear bit Y of Port X
Set bit Y of Port X
DJNZ P3, LABEL
MOV P1.0, C
CLR P1.1
MOV PX.Y, C
CLR PX.Y
SETB PX.Y
SETB P3.2
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10.3 Port Alternate Functions
Most general-purpose digital I/O pins of the AT89LP51/52 share functionality with the various
I/Os needed for the peripheral units. Table 10-6 lists the alternate functions of the port pins.
Alternate functions are connected to the pins in a logic AND fashion. In order to enable the
alternate function on a port pin, that pin must have a “1” in its corresponding port register bit,
otherwise the input/output will always be “0”. However, alternate functions may be temporarily
forced to “0” by clearing the associated port bit, provided that the pin is not in input-only mode.
Furthermore, each pin must be configured for the correct input/output mode as required by its
peripheral before it may be used as such. Table 10-5 shows how to configure a generic pin for
use with an alternate function. If two or more port pins on the same 8-bit require difference direc-
tions, the port must be configured for bidirectional operation.
Table 10-5. Pin Function Configurations for Port x Pin y
PxM0
PxM1
Px.y
I/O Mode
0
0
1
1
0
1
0
1
1
1
X
1
bidirectional (internal pull-up)
output
input
bidirectional (external pull-up)
Table 10-6. Port Pin Alternate Functions
Configuration Bits
Alternate
Function
Port Pin
PxM0
PxM1
Notes
Address and data on Port 0 are
automatically configured as output
or input regardless of P0M0 and
P0M1.
P0.0–P0.7
N/A
AD0–AD7
P1.0
P1.1
P1.5
P1.6
P1.7
P1M0
P1M0
P1M0
P1M0
P1M0
P1M1
P1M1
P1M1
P1M1
P1M1
T2
T2 Clock out toggles P1.0 directly
T2EX
MOSI
MISO
SCK
Address on Port 2 is automatically
configured as output regardless of
P2M0 and P2M1.
P2.0–P2.7
N/A
A8–A15
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
P3M0
P3M0
P3M0
P3M0
P3M0
P3M0
P3M0
P3M0
P3M1
P3M1
P3M1
P3M1
P3M1
P3M1
P3M1
P3M1
RXD
TXD
INT0
INT1
T0
T0 Clock out toggles P3.4 directly
T1 Clock out toggles P3.5 directly
T1
WR
RD
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11. Timer 0 and Timer 1
The AT89LP51/52 has two 16-bit Timer/Counters, Timer 0 and Timer 1, with the following
features:
• Two independent 16-bit timer/counters with 8-bit reload registers
• UART baud rate generation using Timer 1
• Output pin toggle on timer overflow
• Split timer mode allows for three separate timers (2 8-bit, 1 16-bit)
• Gated modes allow timers to run/halt based on an external input
Timer 0 and Timer 1 have similar modes of operation. As timers, the timer registers normally
increase every clock cycle. Thus, the registers count clock cycles. The timer rate can be pres-
caled by a value between 1 and 16 using the Timer Prescaler (see Table 6-2 on page 30). Both
Timers share the same prescaler. In Compatibility mode CDV defaults to 2, so a clock cycle con-
sists of two oscillator periods,and the prescaler defaults to 6 making the count rate equal to 1/12
of the oscillator frequency. By default in Fast mode CDV = 0 and TPS = 0 so the count rate is
equal to the oscillator frequency.
As counters, the timer registers are incremented in response to a 1-to-0 transition at the corre-
sponding input pins, T0 or T1. In Fast mode the external input is sampled every clock cycle.
When the samples show a high in one cycle and a low in the next cycle, the count is incre-
mented. The new count value appears in the register during the cycle following the one in which
the transition was detected. Since 2 clock cycles are required to recognize a 1-to-0 transition,
the maximum count rate is 1/2 of the system frequency. There are no restrictions on the duty
cycle of the input signal, but it should be held for at least one full clock cycle to ensure that a
given level is sampled at least once before it changes.
In Compatibility mode the counter input sampling is controlled by the prescaler. Since TPS
defaults to 6 in this mode, the pins are sampled every six system clocks. Therefore the input sig-
nal should be held for at least six clock cycles to ensure that a given level is sampled at least
once before it changes.
Furthermore, the Timer or Counter functions for Timer 0 and Timer 1 have four operating modes:
13-bit timer, 16-bit timer, 8-bit auto-reload timer, and split timer. The control bits C/T in the Spe-
cial Function Register TMOD select the Timer or Counter function. The bit pairs (M1, M0) in
TMOD select the operating modes.
Table 11-1. Timer 0/1 Register Summary
Name
TCON
TMOD
TL0
Address
88H
Purpose
Bit-Addressable
Control
Y
N
N
N
N
N
N
89H
Mode
8AH
Timer 0 low-byte
Timer 1 low-byte
Timer 0 high-byte
Timer 1 high-byte
Mode
TL1
8BH
TH0
8CH
8DH
91H
TH1
TCONB
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3709B–MICRO–12/10
11.1 Mode 0 – 13-bit Timer/Counter
Both Timers in Mode 0 are 8-bit Counters with a divide-by-32 prescaler. Figure 11-1 shows the
Mode 0 operation as it applies to Timer 1. As the count rolls over from all “1”s to all “0”s, it sets
the Timer interrupt flag TF1. The counter input is enabled to the Timer when TR1 = 1 and either
GATE1 = 0 or INT1 = 1. Setting GATE1 = 1 allows the Timer to be controlled by external input
INT1, to facilitate pulse width measurements. TR1 is a control bit in the Special Function Regis-
ter TCON. GATE1 is in TMOD. The 13-bit register consists of all 8 bits of TH1 and the lower 5
bits of TL1. The upper 3 bits of TL1 are indeterminate and should be ignored. Setting the run flag
(TR1) does not clear the registers.
8192
System Frequency
-------------------------------------------------
× (TPS + 1)
Mode 0:
Time-out Period =
Figure 11-1. Timer/Counter 1 Mode 0: 13-bit Counter
OSC
÷CDV
÷TPS
C/T = 0
C/T = 1
TL1
(5 Bits)
TH1
(8 Bits)
Interrupt
TF1
T1 Pin
Control
TR1
GATE1
INT1 Pin
Mode 0 operation is the same for Timer 0 as for Timer 1, except that TR0, TF0, GATE0 and
INT0 replace the corresponding Timer 1 signals in Figure 11-1. There are two different C/T bits,
one for Timer 1 (TMOD.6) and one for Timer 0 (TMOD.2).
11.2 Mode 1 – 16-bit Timer/Counter
In Mode 1 the Timers are configured for 16-bit operation. The Timer register is run with all 16 bits
and the clock is applied to the combined high and low timer registers (TH1/TL1). As clock pulses
are received, the timer counts up: 0000H, 0001H, 0002H, etc. An overflow occurs on the
FFFFH-to-0000H transition, upon which the overflow flag bit in TCON is set. See Figure 11-2.
Mode 1 operation is the same for Timer/Counter 0.
65536
System Frequency
-------------------------------------------------
× (TPS + 1)
Mode 1:
Time-out Period =
Figure 11-2. Timer/Counter 1 Mode 1: 16-bit Counter
÷CDV
÷TPS
OSC
C/T = 0
C/T =1
TL1
(8 Bits)
TH1
(8 Bits)
Interrupt
TF1
T1 Pin
Control
TR1
GATE1
INT1 Pin
46
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
11.3 Mode 2 – 8-bit Auto-Reload Timer/Counter
Mode 2 configures the Timer register as an 8-bit Counter (TL1) with automatic reload, as shown
in Figure 11-3. Overflow from TL1 not only sets TF1, but also reloads TL1 with the contents of
TH1, which is preset by software. The reload leaves TH1 unchanged. Mode 2 operation is the
same for Timer/Counter 0.
(256 – TH0)
-------------------------------------------------
× (TPS + 1)
Mode 2:
Time-out Period =
System Frequency
Figure 11-3. Timer/Counter 1 Mode 2: 8-bit Auto-Reload
OSC
÷CDV
÷TPS
C/T = 0
C/T = 1
TL1
(8 Bits)
TF1
Interrupt
Control
T1 Pin
Reload
TR1
TH1
(8 Bits)
GATE1
INT0 Pin
11.4 Mode 3 – 8-bit Split Timer
Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0. Timer 0 in
Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on Timer 0 is
shown in Figure 11-4. TL0 uses the Timer 0 control bits: C/T, GATE0, TR0, INT0, and TF0. TH0
is locked into a timer function (counting clock cycles) and takes over the use of TR1 and TF1
from Timer 1. Thus, TH0 now controls the Timer 1 interrupt. While Timer 0 is in Mode 3, Timer 1
will still obey its settings in TMOD but cannot generate an interrupt.
Mode 3 is for applications requiring an extra 8-bit timer or counter. With Timer 0 in Mode 3, the
AT89LP51/52 can appear to have four Timer/Counters. When Timer 0 is in Mode 3, Timer 1 can
be turned on and off by switching it out of and into its own Mode 3. In this case, Timer 1 can still
be used by the serial port as a baud rate generator or in any application not requiring an
interrupt.
Figure 11-4. Timer/Counter 0 Mode 3: Two 8-bit Counters
OSC
÷CDV
÷TPS
C/T = 0
C/T =1
Interrupt
(8 Bits)
T0 Pin
Control
GATE0
INT0 Pin
÷CDV
OSC
÷TPS
Interrupt
(8 Bits)
Control
47
3709B–MICRO–12/10
.
Table 11-2. TCON – Timer/Counter Control Register
TCON = 88H
Reset Value = 0000 0000B
Bit Addressable
TF1
7
TR1
6
TF0
5
TR0
4
IE1
3
IT1
2
IE0
1
IT0
0
Bit
Symbol
TF1
Function
Timer 1 overflow flag. Set by hardware on Timer/Counter overflow. Cleared by hardware when the processor vectors
to interrupt routine.
TR1
Timer 1 run control bit. Set/cleared by software to turn Timer/Counter on/off.
Timer 0 overflow flag. Set by hardware on Timer/Counter overflow. Cleared by hardware when the processor vectors
to interrupt routine.
TF0
TR0
IE1
IT1
IE0
IT0
Timer 0 run control bit. Set/cleared by software to turn Timer/Counter on/off.
Interrupt 1 edge flag. Set by hardware when external interrupt edge detected. Cleared when interrupt processed.
Interrupt 1 type control bit. Set/cleared by software to specify falling edge/low level triggered external interrupts.
Interrupt 0 edge flag. Set by hardware when external interrupt edge detected. Cleared when interrupt processed.
Interrupt 0 type control bit. Set/cleared by software to specify falling edge/low level triggered external interrupts.
Table 11-3. TCONB – Timer/Counter Control Register B
TCONB = 91H
Reset Value = 0000 0000B
Not Bit Addressable
T1OE
7
T0OE
6
SPEN
–
4
–
3
–
2
–
1
–
0
Bit
5
Symbol
T1OE
Function
Timer 1 Output Enable. Configures Timer 1 to toggle T1 (P3.5) upon overflow.
Timer 0 Output Enable. Configures Timer 0 to toggle T0 (P3.4) upon overflow.
Enables SPI mode for UART mode 0
T0OE
SPEN
11.5 Clock Output (Pin Toggle Mode)
On the AT89LP51/52, Timer 0 and Timer 1 may be independently configured to toggle their
respective counter pins, T0 and T1, on overflow by setting the T0OE or T1OE bits in TCONB.
The C/Tx bits must be set to “0” when in toggle mode and the T0 (P3.4) and T1 (P3.5) pins must
be configured in an output mode. The Timer Overflow Flags and Interrupts will continue to func-
tion while in toggle mode and Timer 1 may still generate the baud rate for the UART. The timer
GATE function also works in toggle mode, allowing the output to be halted by an external input.
Toggle mode can be used with Timer Mode 2 to output a 50% duty cycle clock with 8-bit pro-
grammable frequency. Tx is toggled at every Timer x overflow with the pulse width determined
by the value of THx. An example waveform is given in Figure 11-5. The following formula gives
the output frequency for Timer 0 in Mode 2.
System Frequency
2 × (256 – TH0)
1
------------------------------------------------- --------------------
Mode 2:
f
=
×
out
TPS + 1
48
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Figure 11-5. Timer 0/1 Toggle Mode 2 Waveform
FFh
THx
Tx
Table 11-4. TMOD – Timer/Counter Mode Control Register
TMOD Address = 089H
Reset Value = 0000 0000B
Not Bit Addressable
GATE1
7
C/T1
6
T1M1
5
T1M0
4
GATE0
3
C/T0
2
T0M0
1
T0M1
0
Bit
Symbol
Function
Timer 1 Gating Control. When set, Timer/Counter 1 is enabled only while INT1 pin is high and TR1 control pin is set.
When cleared, Timer 1 is enabled whenever TR1 control bit is set.
GATE1
C/T1
Timer or Counter Selector 1. Cleared for Timer operation (input from internal system clock). Set for Counter operation
(input from T1 input pin). C/T1 must be zero when using Timer 1 in Clock Out mode.
T1M1
T1M0
Timer 1 Operating Mode
Mode
T1M1
T1M0
Operation
0
1
0
0
0
1
13-bit Timer Mode. 8-bit Timer/Counter TH1 with TL1 as 5-bit prescaler.
16-bit Timer Mode. TH1 and TL1 are cascaded to form a 16-bit Timer/Counter.
8-bit Auto Reload Mode. TH1 holds a value which is reloaded into 8-bit Timer/Counter
TL1 each time it overflows.
2
3
1
1
0
1
Timer/Counter 1 is stopped
Timer 0 Gating Control. When set, Timer/Counter 0 is enabled only while INT0 pin is high and TR0 control pin is set.
When cleared, Timer 0 is enabled whenever TR0 control bit is set.
GATE0
C/T0
Timer or Counter Selector 0. Cleared for Timer operation (input from internal system clock). Set for Counter operation
(input from T0 input pin). C/T0 must be zero when using Timer 0 in Clock Out mode.
T0M1
T0M0
Timer 0 Operating Mode
Mode
T0M1
T0M0
Operation
0
1
0
0
0
1
13-bit Timer Mode. 8-bit Timer/Counter TH0 with TL0 as 5-bit prescaler.
16-bit Timer Mode. TH0 and TL0 are cascaded to form a 16-bit Timer/Counter.
8-bit Auto Reload Mode. TH0 holds a value which is reloaded into 8-bit Timer/Counter
TL0 each time it overflows.
2
3
1
1
0
1
Split Timer Mode. TL0 is an 8-bit Timer/Counter controlled by the standard Timer 0
control bits. TH0 is an 8-bit timer only controlled by Timer 1 control bits.
49
3709B–MICRO–12/10
12. Timer 2
The AT89LP51/52 includes a 16-bit Timer/Counter 2 with the following features:
• 16-bit timer/counter with one 16-bit reload/capture register
• One external reload/capture input
• Up/Down counting mode with external direction control
• UART baud rate generation
• Output-pin toggle on timer overflow
• Dual slope symmetric operating modes
• Timer 2 is included in AT89LP51, unlike AT89S51.
Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The
type of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has three operating modes:
capture, auto-reload (up or down counting), and baud rate generator. The modes are selected
by bits in T2CON and T2MOD, as shown in Table 12-3. Timer 2 also serves as the time base for
the Compare/Capture Array (See Section 13. “External Interrupts” on page 56).
Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the register is incre-
mented every clock cycle. Since a clock cycle consists of one oscillator period, the count rate is
equal to the oscillator frequency. The timer rate can be prescaled by a value between 1 and 16
using the Timer Prescaler (see Table 6-2 on page 30).
In the Counter function, the register is incremented in response to a 1-to-0 transition at its corre-
sponding external input pin, T2. In this function, the external input is sampled every clock cycle.
When the samples show a high in one cycle and a low in the next cycle, the count is incre-
mented. The new count value appears in the register during the cycle following the one in which
the transition was detected. Since two clock cycles are required to recognize a 1-to-0 transition,
the maximum count rate is 1/2 of the oscillator frequency. To ensure that a given level is sam-
pled at least once before it changes, the level should be held for at least one full clock cycle.
Table 12-1. Timer 2 Operating Modes
RCLK + TCLK CP/RL2
DCEN
T2OE
TR2
1
MODE
0
0
0
1
X
X
0
0
0
1
0
0
0
X
1
X
16-bit Auto-reload
16-bit Auto-reload Up-Down
16-bit Capture
1
1
X
X
X
X
1
X
X
X
1
Baud Rate Generator
Frequency Generator
(Off)
1
0
The following definitions for Timer 2 are used in the subsequent paragraphs:
Table 12-2. Timer 2 Definitions
Symbol
MIN
Definition
0000H
MAX
FFFFH
BOTTOM
16-bit value of {RCAP2H,RCAP2L}
50
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3709B–MICRO–12/10
AT89LP51/52 - Preliminary
12.1 Timer 2 Registers
Control and status bits for Timer 2 are contained in registers T2CON (see Table 12-3) and
T2MOD (see Table 12-4). The register pair {TH2, TL2} at addresses 0CDH and 0CCH are the
16-bit timer register for Timer 2. The register pair {RCAP2H, RCAP2L} at addresses 0CBH and
0CAH are the 16-bit Capture/Reload register for Timer 2 in capture and auto-reload modes.
Table 12-3. T2CON – Timer/Counter 2 Control Register
T2CON Address = 0C8H
Bit Addressable
TF2
Reset Value = 0000 0000B
EXF2
6
RCLK
5
TCLK
4
EXEN2
3
TR2
2
C/T2
1
CP/RL2
0
Bit
7
Symbol
TF2
Function
Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set when either
RCLK = 1 or TCLK = 1.
Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and EXEN2 = 1.
When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the Timer 2 interrupt routine. EXF2 must be
cleared by software. EXF2 does not cause an interrupt in up/down counter mode (DCEN = 1) or dual-slope mode.
EXF2
Receive clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock in serial port
Modes 1 and 3. RCLK = 0 causes Timer 1 overflows to be used for the receive clock.
RCLK
TCLK
Transmit clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock in serial port
Modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.
Timer 2 external enable. When set, allows a capture or reload to occur as a result of a negative transition on T2EX if
Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to ignore events at T2EX.
EXEN2
TR2
Start/Stop control for Timer 2. TR2 = 1 starts the timer.
Timer or counter select for Timer 2. C/T2 = 0 for timer function. C/T2 = 1 for external event counter (falling edge
triggered).
C/T2
Capture/Reload select. CP/RL2 = 1 causes captures to occur on negative transitions at T2EX if EXEN2 = 1. CP/RL2 = 0
causes automatic reloads to occur when Timer 2 overflows or negative transitions occur at T2EX when EXEN2 = 1. When
either RCLK or TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow.
CP/RL2
Table 12-4. T2MOD – Timer 2 Mode Control Register
T2MOD Address = 0C9H
Reset Value = 0000 0000B
Not Bit Addressable
–
7
–
6
–
5
–
4
–
3
–
2
T2OE
1
DCEN
0
Bit
Symbol
T2OE
Function
Timer 2 Output Enable. When T2OE = 1 and C/T2 = 0, the T2 pin will toggle after every Timer 2 overflow.
DCEN
Timer 2 Down Count Enable. When Timer 2 operates in Auto-Reload mode and EXEN2 = 1, setting DCEN = 1 will cause
Timer 2 to count up or down depending on the state of T2EX.
51
3709B–MICRO–12/10
12.2 Capture Mode
In the Capture mode, Timer 2 is a fixed 16-bit timer or counter that counts up from MIN to MAX.
An overflow from MAX to MIN sets bit TF2 in T2CON. If EXEN2 = 1, a 1-to-0 transition at exter-
nal input T2EX also causes the current value in TH2 and TL2 to be captured into RCAP2H and
RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in T2CON to be set.
The EXF2 and TF2 bits can generate an interrupt. Capture mode is illustrated in Figure 12-1.
The Timer 2 overflow rate in Capture mode is given by the following equation:
65536
System Frequency
-------------------------------------------------
Capture Mode:
Time-out Period =
× (TPS + 1)
Figure 12-1. Timer 2 Diagram: Capture Mode
OSC
÷CDV
÷TPS
C/T2 = 0
TL2
TH2
TF2
OVERFLOW
TR2
CAPTURE
C/T2 = 1
T2 PIN
RCAP2L RCAP2H
EXF2
TRANSITION
DETECTOR
TIMER 2
INTERRUPT
T2EX PIN
EXEN2
12.3 Auto-Reload Mode
Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload
mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR
T2MOD (see Table 12-4). Upon reset, the DCEN bit is set to 0 so that timer 2 will default to
count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the
T2EX pin. A summary of the Auto-Reload behaviors is listed in Table 12-5.
Table 12-5. Summary of Auto-Reload Modes
DCEN
T2EX
Direction
Up
Behavior
0
1
1
X
0
1
BOTTOM →MAX reload to BOTTOM
MAX →BOTTOM underflow to MAX
BOTTOM →MAX overflow to BOTTOM
Down
Up
12.3.1
Up Counter
Figure 12-2 shows Timer 2 automatically counting up when DCEN = 0. In this mode Timer 2
counts up to MAX and then sets the TF2 bit upon overflow. The overflow also causes the timer
registers to be reloaded with BOTTOM, the 16-bit value in RCAP2H and RCAP2L. If EXEN2 = 1,
a 16-bit reload can be triggered either by an overflow or by a 1-to-0 transition at external input
T2EX. This transition also sets the EXF2 bit. Both the TF2 and EXF2 bits can generate an inter-
rupt. The Timer 2 overflow rate for this mode is given in the following equation:
Auto-Reload Mode:
65536 – {RCAP2H,RCAP2L}
------------------------------------------------------------------------------
Time-out Period =
× (TPS + 1)
System Frequency
DCEN = 0
52
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Figure 12-2. Timer 2 Diagram: Auto-Reload Mode (DCEN = 0)
OSC
÷CDV
÷TPS
TL2
TH2
Figure 12-3. Timer 2 Waveform: Auto-Reload Mode (DCEN = 0)
TF2 Set
MAX
BOTTOM
MIN
12.3.2
Up or Down Counter
Setting DCEN = 1 enables Timer 2 to count up or down, as shown in Figure 12-5. In this mode,
the T2EX pin controls the direction of the count (if EXEN2 = 1). A logic 1 at T2EX makes Timer 2
count up. When T2CM1-0 = 00B, the timer will overflow at MAX and set the TF2 bit. This overflow
also causes BOTTOM, the 16-bit value in RCAP2H and RCAP2L, to be reloaded into the timer
registers, TH2 and TL2, respectively. A logic 0 at T2EX makes Timer 2 count down. The timer
underflows when TH2 and TL2 equal BOTTOM, the 16-bit value stored in RCAP2H and
RCAP2L. The underflow sets the TF2 bit and causes MAX to be reloaded into the timer regis-
ters. The EXF2 bit toggles whenever Timer 2 overflows or underflows and can be used as a 17th
bit of resolution. In this operating mode, EXF2 does not flag an interrupt.
The behavior of Timer 2 when DCEN is enabled is shown in Figure 12-4.
Figure 12-4. Timer 2 Waveform: Auto-Reload Mode (DCEN = 1)
TF2 Set
MAX
BOTTOM
MIN
T2EX
EXF2
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3709B–MICRO–12/10
Figure 12-5. Timer 2 Diagram: Auto-Reload Mode (DCEN = 1)
÷TPS
The timer overflow/underflow rate for up-down counting mode is the same as for up counting
mode, provided that the count direction does not change. Changes to the count direction may
result in longer or shorter periods between time-outs.
12.4 Baud Rate Generator
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON (Table
12-3). Note that the baud rates for transmit and receive can be different if Timer 2 is used for the
receiver or transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK
puts Timer 2 into its baud rate generator mode, as shown in Figure 12-6.
The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2
causes the Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and
RCAP2L, which are preset by software.
The baud rates in UART Modes 1 and 3 are determined by Timer 2’s overflow rate according to
the following equation.
Timer 2 Overflow Rate
Modes 1 and 3 Baud Rates = -----------------------------------------------------------
16
The Timer can be configured for either timer or counter operation. In most applications, it is con-
figured for timer operation (CP/T2 = 0). The baud rate formulas are given below.
Modes 1, 3
Baud Rate
System Frequency
16 × (TPS + 1) × [65536 – (RCAP2H,RCAP2L)]
= --------------------------------------------------------------------------------------------------------------------------------
where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit unsigned
integer.
Timer 2 as a baud rate generator is shown in Figure 12-6. This figure is valid only if RCLK or
TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an inter-
rupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a
reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a baud rate gen-
erator, T2EX can be used as an extra external interrupt. Also note that the Baud Rate and
Frequency Generator modes may be used simultaneously.
54
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Figure 12-6. Timer 2 in Baud Rate Generator Mode
TIMER 1 OVERFLOW
2
÷
"0"
"0"
"1"
SMOD1
RCLK
OSC
÷CDV
C/T2 = 0
"1"
"1"
TL2
TH2
Rx
CLOCK
16
÷
TR2
C/T2 = 1
"0"
T2 PIN
TCLK
RCAP2L RCAP2H
Tx
CLOCK
EXEN2
TRANSITION
DETECTOR
16
÷
TIMER 2
INTERRUPT
T2EX PIN
EXF2
12.5 Frequency Generator (Programmable Clock Out)
Timer 2 can generate a 50% duty cycle clock on T2 (P1.0), as shown in Figure 13.. This pin,
besides being a regular I/O pin, has two alternate functions. It can be programmed to input the
external clock for Timer/Counter 2 or to toggle its output at every timer overflow. To configure
the Timer/Counter 2 as a clock generator, bit C/T2 (T2CON.1) must be cleared and bit T2OE
(T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer. The clock-out frequency
depends on the system frequency and the reload value of Timer 2 capture registers (RCAP2H,
RCAP2L), as shown in the following equation.
System Frequency
Clock Out Frequency = -------------------------------------------------------------------------------------------
2 × [65536 – (RCAP2H,RCAP2L)]
In the frequency generator mode, Timer 2 roll-overs will not generate an interrupt. This behavior
is similar to when Timer 2 is used as a baud-rate generator. It is possible to use Timer 2 as a
baud-rate generator and a clock generator simultaneously. Note, however, that the baud-rate
and clock-out frequencies cannot be determined independently from one another since they
both use RCAP2H and RCAP2L.
Figure 12-7. Timer 2 in Clock-out Mode
OSC
÷CDV
TL2
TH2
TR2
RCAP2L RCAP2H
C/T2
T2OE
T2 PIN
÷2
TIMER 2
INTERRUPT
T2EX PIN
EXF2
TRANSITION
DETECTOR
EXEN2
55
3709B–MICRO–12/10
13. External Interrupts
The INT0 (P3.2) and INT1 (P3.3) pins of the AT89LP51/52 may be used as external interrupt
sources. The external interrupts can be programmed to be level-activated or transition-activated
by setting or clearing bit IT1 or IT0 in Register TCON. If ITx = 0, external interrupt x is triggered
by a detected low at the INTx pin. If ITx = 1, external interrupt x is edge-triggered. In this mode if
successive samples of the INTx pin show a high in one cycle and a low in the next cycle, inter-
rupt request flag IEx in TCON is set. Flag bit IEx then requests the interrupt. Since the external
interrupt pins are sampled once each clock cycle, an input high or low should hold for at least 2
system periods to ensure sampling. If the external interrupt is transition-activated, the external
source has to hold the request pin high for at least two clock cycles, and then hold it low for at
least two clock cycles to ensure that the transition is seen so that interrupt request flag IEx will
be set. IEx will be automatically cleared by the CPU when the service routine is called if gener-
ated in edge-triggered mode. If the external interrupt is level-activated, the external source has
to hold the request active until the requested interrupt is actually generated. Then the external
source must deactivate the request before the interrupt service routine is completed, or else
another interrupt will be generated. Both INT0 and INT1 may wake up the device from the
Power-down state.
14. Serial Interface (UART)
The serial interface on the AT89LP51/52 implements a Universal Asynchronous
Receiver/Transmitter (UART). The UART has the following features:
• Full-duplex Operation
• 8 or 9 Data Bits
• Framing Error Detection
• Multiprocessor Communication Mode with Automatic Address Recognition
• Baud Rate Generator Using Timer 1 or Timer 2
• Interrupt on Receive Buffer Full or Transmission Complete
• Synchronous SPI or TWI Master Emulation
The serial interface is full-duplex, which means it can transmit and receive simultaneously. It is
also receive-buffered, which means it can begin receiving a second byte before a previously
received byte has been read from the receive register. (However, if the first byte still has not
been read when reception of the second byte is complete, one of the bytes will be lost.) The
serial port receive and transmit registers are both accessed at the Special Function Register
SBUF. Writing to SBUF loads the transmit register, and reading SBUF accesses a physically
separate receive register. The serial port can operate in the following four modes.
• Mode 0: Serial data enters and exits through RXD. TXD outputs the shift clock. Eight data
bits are transmitted/received, with the LSB first. The baud rate is programmable to 1/6 or 1/3
the system frequency in Compatibility mode, 1/4 or 1/2 the system frequency in Fast mode,
or variable based on Time 1.
• Mode 1: 10 bits are transmitted (through TXD) or received (through RXD): a start bit (0),
8 data bits (LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in the Special
Function Register SCON. The baud rate is variable based on Timer 1 or Timer 2.
• Mode 2: 11 bits are transmitted (through TXD) or received (through RXD): a start bit (0),
8 data bits (LSB first), a programmable 9th data bit, and a stop bit (1). On transmit, the 9th
data bit (TB8 in SCON) can be assigned the value of “0” or “1”. For example, the parity bit
(P, in the PSW) can be moved into TB8. On receive, the 9th data bit goes into RB8 in the
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AT89LP51/52 - Preliminary
Special Function Register SCON, while the stop bit is ignored. The baud rate is
programmable to either 1/16 or 1/32 the system frequency.
• Mode 3: 11 bits are transmitted (through TXD) or received (through RXD): a start bit (0),
8 data bits (LSB first), a programmable 9th data bit, and a stop bit (1). In fact, Mode 3 is the
same as Mode 2 in all respects except the baud rate, which is variable based on Timer 1 or
Timer 2 in Mode 3.
In all four modes, transmission is initiated by any instruction that uses SBUF as a destination
register. Reception is initiated in Mode 0 by the condition RI = 0 and REN = 1. Reception is initi-
ated in the other modes by the incoming start bit if REN = 1.
Table 14-1. SCON – Serial Port Control Register
SCON Address = 98H
Bit Addressable
SM0/FE
Reset Value = 0000 0000B
SM1
SM2
REN
4
TB8
RB8
T1
1
RI
0
Bit
7
6
5
3
2
(SMOD0 = 0/1)(1)
Symbol
FE
Function
Framing error bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not cleared by valid
frames and must be cleared by software. The SMOD0 bit must be set to enable access to the FE bit. FE will be set
regardless of the state of SMOD0.
SM0
Serial Port Mode Bit 0, (SMOD0 must = 0 to access bit SM0)
Serial Port Mode Bit 1
SM0
SM1
Mode
Description
shift register
8-bit UART
9-bit UART
9-bit UART
Baud Rate (Compat.)(2)
fSYS/3 or fSYS/6 or Timer 1
variable (Timer 1 or Timer 2)
Baud Rate (Fast)(2)
fSYS/2 or fSYS/4 or Timer 1
variable (Timer 1 or Timer 2)
fSYS/32 or fSYS/16
0
0
1
1
0
1
0
1
0
1
2
3
SM1
SM2
f
SYS/32 or fSYS/16
variable (Timer 1 or Timer 2)
variable (Timer 1 or Timer 2)
Enables the Automatic Address Recognition feature in Modes 2 or 3. If SM2 = 1 then Rl will not be set unless the received
9th data bit (RB8) is 1, indicating an address, and the received byte is a Given or Broadcast Address. In Mode 1, if SM2 =
1 then Rl will not be activated unless a valid stop bit was received, and the received byte is a Given or Broadcast Address.
In Mode 0, SM2 determines the idle state of the shift clock such that the clock is the inverse of SM2, i.e. when SM2 = 0
the clock idles high and when SM2 = 1 the clock idles low.
REN
Enables serial reception. Set by software to enable reception. Clear by software to disable reception.
The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired. In Mode 0, setting TB8
enables Timer 1 as the shift clock generator.
TB8
In Modes 2 and 3, the 9th data bit that was received. In Mode 1, if SM2 = 0, RB8 is the stop bit that was received. In Mode
0, RB8 is not used.
RB8
TI
Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of the stop bit in the
other modes, in any serial transmission. Must be cleared by software.
Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through the stop bit time in the
other modes, in any serial reception (except see SM2). Must be cleared by software.
RI
Notes: 1. SMOD0 is located at PCON.6.
2. fSYS = system frequency. The baud rate depends on SMOD1 (PCON.7).
57
3709B–MICRO–12/10
14.1 Multiprocessor Communications
Modes 2 and 3 have a special provision for multiprocessor communications. In these modes,
9 data bits are received, followed by a stop bit. The 9th bit goes into RB8. Then comes a stop bit.
The port can be programmed such that when the stop bit is received, the serial port interrupt is
activated only if RB8 = 1. This feature is enabled by setting bit SM2 in SCON.
The following example shows how to use the serial interrupt for multiprocessor communications.
When the master processor must transmit a block of data to one of several slaves, it first sends
out an address byte that identifies the target slave. An address byte differs from a data byte in
that the 9th bit is “1” in an address byte and “0” in a data byte. With SM2 = 1, no slave is
interrupted by a data byte. An address byte, however, interrupts all slaves. Each slave can
examine the received byte and see if it is being addressed. The addressed slave clears its SM2
bit and prepares to receive the data bytes that follows. The slaves that are not addressed set
their SM2 bits and ignore the data bytes. See “Automatic Address Recognition” on page 60.
The SM2 bit can be used to check the validity of the stop bit in Mode 1. In a Mode 1 reception, if
SM2 = 1, the receive interrupt is not activated unless a valid stop bit is received.
14.2 Baud Rates
The baud rate in Mode 0 depends on the value of the SMOD1 bit in Special Function Register
PCON.7. If SMOD1 = 0 (the value on reset) and TB8 = 0, the baud rate is 1/4 of the system fre-
quency in Fast mode. If SMOD1 = 1 and TB8 = 0, the baud rate is 1/2 of the system frequency,
as shown in the following equation:
SMOD1
Mode 0 Baud Rate
TB8 = 0
2
--------------------
=
× System Frequency
4
:In Compatibility mode the baud rate is 1/6 of the system frequency, scaling to 1/3 when
SMOD1 = 1.
SMOD1
Mode 0 Baud Rate
TB8 = 0
2
--------------------
=
× System Frequency
6
The baud rate in Mode 2 also depends on the value of the SMOD1 bit. If SMOD1 = 0, the baud
rate is 1/32 of the system frequency. If SMOD1 = 1, the baud rate is 1/16 of the system fre-
quency, as shown in the following equation:
SMOD1
2
--------------------
Mode 2 Baud Rate =
× System Frequency
32
14.2.1
Using Timer 1 to Generate Baud Rates
Setting TB8 = 1 in Mode 0 enables Timer 1 as the baud rate generator. When Timer 1 is the
baud rate generator for Mode 0, the baud rates are determined by the Timer 1 overflow rate and
the value of SMOD1 according to the following equation:
SMOD1
Mode 0 Baud Rate
TB8 = 1
2
--------------------
=
× (Timer 1 Overflow Rate)
4
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AT89LP51/52 - Preliminary
The Timer 1 overflow rate normally determines the baud rates in Modes 1 and 3. When Timer 1
is the baud rate generator, the baud rates are determined by the Timer 1 overflow rate and the
value of SMOD1 according to the following equation:
SMOD1
Modes 1, 3
Baud Rate
2
--------------------
=
× (Timer 1 Overflow Rate)
32
The Timer 1 interrupt should be disabled in this application. The Timer itself can be configured
for either timer or counter operation in any of its 3 running modes. In the most typical applica-
tions, it is configured for timer operation in auto-reload mode (high nibble of TMOD = 0010B). In
this case, the baud rate is given by the following formula:
SMOD1
Modes 1, 3
Baud Rate
2
System Frequency
1
-------------------- ------------------------------------------------- --------------------
=
×
×
32
[256 – (TH1)]
TPS + 1
Table 14-2 lists commonly used baud rates and how they can be obtained from Timer 1.
Table 14-2. Commonly Used Baud Rates Generated by Timer 1
Timer 1
TPS
Baud Rate
fOSC (MHz)
12
CDV
0
SMOD1
C/T
X
X
0
Mode
Reload Value
X
Mode 0 Max: 6 MHz
1
1
1
1
0
0
0
0
0
1
0
1
0
0
0
0
0
0
0
X
X
2
2
2
2
2
1
1
1
1
2
2
2
2
2
2
2
1
0
0
0
0
0
0
0
0
0
0
0
5
5
5
5
5
5
5
5
Mode 2 Max: 750K
12
0
X
Modes 1, 3 Max: 750K
12
0
F4H
19.2K
9.6K
4.8K
2.4K
1.2K
137.5
110
11.059
11.059
11.059
11.059
11.059
11.986
6
0
0
DCH
DCH
B8H
0
0
0
0
0
0
70H
0
0
FEE0H
F55CH
F2AFH
F2AFH
FDH
0
0
0
0
110
12
0
0
19.2K
9.6K
4.8K
2.4K
1.2K
137.5
110
11.059
11.059
11.059
11.059
11.059
11.986
6
1
0
1
0
FDH
1
0
FAH
1
0
F4H
1
0
E8H
1
0
1DH
1
0
72H
110
12
1
0
FEEBH
14.2.2
Using Timer 2 to Generate Baud Rates
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON. Under
these conditions, the baud rates for transmit and receive can be simultaneously different by
using Timer 1 for transmit and Timer 2 for receive, or vice versa. The baud rate generator mode
59
3709B–MICRO–12/10
is similar to the auto-reload mode, in that a rollover causes the Timer 2 registers to be reloaded
with the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. In this
case, the baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate according to
the following equation:
Modes 1 and 3
Baud Rate
1
System Frequency
------ ---------------------------------------------------------------------------------
=
×
16 [65536 – (RCAP2H,RCAP2L)]
Table 14-3 lists commonly used baud rates and how they can be obtained from Timer 2.
Table 14-3. Commonly Used Baud Rates Generated by Timer 2
Timer 2
Baud Rate
Max: 750K
19.2K
9.6K
fOSC (MHz)
12
CDV
0
CP/RL2
C/T2
0
TCLK or RCLK
Reload Value
FFFFH
FFDCH
FFB8H
FF70H
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
11.059
11.059
11.059
11.059
11.059
11.986
6
0
0
0
0
4.8K
0
0
2.4K
0
0
FEE0H
FDC0H
EAB8H
F2AFH
E55EH
FFEEH
FFDCH
FFB8H
FF70H
1.2K
0
0
137.5
110
0
0
0
0
110
12
0
0
19.2K
9.6K
11.059
11.059
11.059
11.059
11.059
11.986
12
1
0
1
0
4.8K
1
0
2.4K
1
0
1.2K
1
0
FEE0H
F55CH
F2AFH
137.5
110
1
0
1
0
14.3 Framing Error Detection
In addition to all of its usual modes, the UART can perform framing error detection by looking for
missing stop bits, and automatic address recognition. When used for framing error detect, the
UART looks for missing stop bits in the communication. A missing bit will set the FE bit in the
SCON register. The FE bit shares the SCON.7 bit with SM0 and the function of SCON.7 is deter-
mined by PCON.6 (SMOD0). If SMOD0 is set then SCON.7 functions as FE. SCON.7 functions
as SM0 when SMOD0 is cleared. When used as FE, SCON.7 can only be cleared by software.
The FE bit will be set by a framing error regardless of the state of SMOD0.
14.4 Automatic Address Recognition
Automatic Address Recognition is a feature which allows the UART to recognize certain
addresses in the serial bit stream by using hardware to make the comparisons. This feature
saves a great deal of software overhead by eliminating the need for the software to examine
every serial address which passes by the serial port. This feature is enabled by setting the SM2
bit in SCON for Modes 1, 2 or 3. In the 9-bit UART modes, Mode 2 and Mode 3, the Receive
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AT89LP51/52 - Preliminary
Interrupt flag (RI) will be automatically set when the received byte contains either the “Given”
address or the “Broadcast” address. The 9-bit mode requires that the 9th information bit be a “1”
to indicate that the received information is an address and not data.
In Mode 1 (8-bit) the RI flag will be set if SM2 is enabled and the information received has a valid
stop bit following the 8th address bits and the information is either a Given or Broadcast
address. Automatic Address Recognition is not available during Mode 0.
Using the Automatic Address Recognition feature allows a master to selectively communicate
with one or more slaves by invoking the given slave address or addresses. All of the slaves may
be contacted by using the Broadcast address. Two special Function Registers are used to
define the slave’s address, SADDR, and the address mask, SADEN. SADEN is used to define
which bits in the SADDR are to be used and which bits are “don’t care”. The SADEN mask can
be logically ANDed with the SADDR to create the “Given” address which the master will use for
addressing each of the slaves. Use of the Given address allows multiple slaves to be recognized
while excluding others. The following examples show the versatility of this scheme:
Slave 0
SADDR = 1100 0000
SADEN = 1111 1101
Given = 1100 00X0
Slave 1
SADDR = 1100 0000
SADEN = 1111 1110
Given = 1100 000X
In the previous example, SADDR is the same and the SADEN data is used to differentiate
between the two slaves. Slave 0 requires a “0” in bit 0 and it ignores bit 1. Slave 1 requires a “0”
in bit 1 and bit 0 is ignored. A unique address for slave 0 would be 1100 0010 since slave 1
requires a “0” in bit 1. A unique address for slave 1 would be 1100 0001 since a “1” in bit 0 will
exclude slave 0. Both slaves can be selected at the same time by an address which has bit 0 = 0
(for slave 0) and bit 1 = 0 (for slave 1). Thus, both could be addressed with 1100 0000.
In a more complex system, the following could be used to select slaves 1 and 2 while excluding
slave 0:
Slave 0
Slave 1
Slave 2
SADDR = 1100 0000
SADEN = 1111 1001
Given = 1100 0XX0
SADDR = 1110 0000
SADEN = 1111 1010
Given = 1110 0X0X
SADDR = 1110 0000
SADEN = 1111 1100
Given = 1110 00XX
In the above example, the differentiation among the 3 slaves is in the lower 3 address bits. Slave
0 requires that bit 0 = 0 and it can be uniquely addressed by 1110 0110. Slave 1 requires that
bit 1 = 0 and it can be uniquely addressed by 1110 and 0101. Slave 2 requires that bit 2 = 0 and
its unique address is 1110 0011. To select Slaves 0 and 1 and exclude Slave 2, use address
1110 0100, since it is necessary to make bit 2 = 1 to exclude slave 2.
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3709B–MICRO–12/10
The Broadcast Address for each slave is created by taking the logic OR of SADDR and SADEN.
Zeros in this result are trended as don’t cares. In most cases, interpreting the don’t cares as
ones, the broadcast address will be FF hexadecimal.
Upon reset SADDR (SFR address 0A9H) and SADEN (SFR address 0B9H) are loaded with
“0”s. This produces a given address of all “don’t cares” as well as a Broadcast address of all
“don’t cares”. This effectively disables the Automatic Addressing mode and allows the microcon-
troller to use standard 80C51-type UART drivers which do not make use of this feature.
14.5 More About Mode 0
In Mode 0, the UART is configured as either a two wire half-duplex or three wire full-duplex syn-
chronous serial interface. In two-wire mode serial data enters and exits through RXD and TXD
outputs the shift clock. In three-wire mode serial data enters through MISO, exits through MOSI
and SCK outputs the shift clock. Eight data bits are transmitted/received, with the LSB first. Fig-
ure 14-3 and Figure 14-5 on page 67 show simplified functional diagrams of the serial port in
Mode 0 and associated timing. The baud rate is programmable to 1/2 or 1/4 the system fre-
quency by setting/clearing the SMOD1 bit in Fast mode, or 1/3 or 1/6 the system frequency in
Compatibility mode. However, changing SMOD1 has an effect on the relationship between the
clock and data as described below. The baud rate can also be generated by Timer 1 by setting
TB8. Table 14-4 lists the baud rate options for Mode 0.
Table 14-4. Mode 0 Baud Rates
TB8
0
SMOD1
Baud Rate (Fast)
SYS/4
Baud Rate (Compatibility)
fSYS/6
0
1
0
1
f
0
fSYS/2
fSYS/3
1
(Timer 1 Overflow) / 4
(Timer 1 Overflow) / 2
(Timer 1 Overflow) / 4
(Timer 1 Overflow) / 2
1
14.5.1
Two-Wire (Half-Duplex) Mode
Transmission is initiated by any instruction that uses SBUF as a destination register. The “write
to SBUF” signal also loads a “1” into the 9th position of the transmit shift register and tells the TX
Control Block to begin a transmission. The internal timing is such that one full bit slot may elapse
between “write to SBUF” and activation of SEND.
SEND transfers the output of the shift register to the alternate output function line of P3.0, and
also transfers Shift Clock to the alternate output function line of P3.1. As data bits shift out to the
right, “0”s come in from the left. When the MSB of the data byte is at the output position of the
shift register, the “1” that was initially loaded into the 9th position is just to the left of the MSB,
and all positions to the left of that contain “0”s. This condition flags the TX Control block to do
one last shift, then deactivate SEND and set TI.
Reception is initiated by the condition REN = 1 and RI = 0. At the next clock cycle, the RX Con-
trol unit writes the bits 11111110B to the receive shift register and activates RECEIVE in the
next clock phase. RECEIVE enables Shift Clock to the alternate output function line of P3.1. As
data bits come in from the right, “1”s shift out to the left. When the “0” that was initially loaded
into the right-most position arrives at the left-most position in the shift register, it flags the RX
Control block to do one last shift and load SBUF. Then RECEIVE is cleared and RI is set.
The relationship between the shift clock and data is determined by the combination of the SM2
and SMOD1 bits as listed in Table 14-5 and shown in Figure . The SM2 bit determines the idle
62
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AT89LP51/52 - Preliminary
state of the clock when not currently transmitting/receiving. The SMOD1 bit determines if the
output data is stable for both edges of the clock, or just one.
Table 14-5. Mode 0 Clock and Data Modes
SM2
SMOD1
Clock Idle
High
Data Changes
While clock is high
Negative edge of clock
While clock is low
Data Sampled
0
0
1
1
0
1
0
1
Positive edge of clock
Positive edge of clock
Negative edge of clock
Positive edge of clock
High
Low
Low
Negative edge of clock
In Two-Wire configuration Mode 0 may be used as a hardware accelerator for software emula-
tion of serial interfaces such as a half-duplex Serial Peripheral Interface (SPI) master in mode
(0,0) or (1,1) or a Two-Wire Interface (TWI) in master mode. An example of Mode 0 emulating a
TWI master device is shown in Figure 14-2. In this example, the start, stop, and acknowledge
are handled in software while the byte transmission is done in hardware. Falling/rising edges on
TXD are created by setting/clearing SM2. Rising/falling edges on RXD are forced by set-
ting/clearing the P3.0 register bit. SM2 and P3.0 must be 1 while the byte is being transferred.
Figure 14-1. Mode 0 Waveforms (Two-Wire)
SMOD1 = 0
SM2 = 0
TXD
0
1
2
3
4
5
6
7
RXD (TX)
0
0
0
0
1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
6
6
7
7
7
7
RXD (RX)
SMOD1 = 1
TXD
RXD (TX)
RXD (RX)
SM2 = 0
0
1
2
3
4
5
6
7
SMOD1 = 0
SM2 = 1
TXD
0
1
2
3
4
5
6
7
RXD (TX)
RXD (RX)
SMOD1 = 1
TXD
RXD (TX)
RXD (RX)
SM2 = 1
0
1
2
3
4
5
6
7
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3709B–MICRO–12/10
Figure 14-2. UART Mode 0 TWI Emulation (SMOD1 = 1)
(SCL) TXD
0
1
2
3
4
5
6
7
ACK
(SDA) RXD
SM2
P3.0
Sample ACK
Write to SBUF
TI
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AT89LP51/52 - Preliminary
Figure 14-3. Serial Port Mode 0 (Two-Wire)
INTERNAL BUS
TIMER 1
OVERFLOW
“1“
f
sys
1
0
TB8
÷2
÷2
0
1
SMOD1
SM2
INTERNAL BUS
WRITE TO SBUF
SEND
SHIFT
RXD (DATA OUT)
TXD (SHIFT CLOCK)
TI
WRITE TO SCON (CLEAR RI)
RI
RECEIVE
SHIFT
RXD (DATA IN)
TXD (SHIFT CLOCK)
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3709B–MICRO–12/10
Mode 0 transfers data LSB first whereas SPI or TWI are generally MSB first. Emulation of these
interfaces may require bit reversal of the transferred data bytes. The following code example
reverses the bits in the accumulator:
EX:
REVRS: RLC
XCH A, R6
RRC
MOV R7, #8
A
; C << msb (ACC)
; msb (ACC) >> B
A
XCH A, R6
DJNZ R7, REVRS
14.5.2
Three-Wire (Full-Duplex) Mode
Three-Wire Mode is similar to Two-Wire except that the shift data input and data output are sep-
arated for full-duplex operation. Three-Wire Mode is enabled by setting the SPEN bit in TCONB.
Transmission is initiated by any instruction that uses SBUF as a destination register. The “write
to SBUF” signal also loads a “1” into the 9th position of the transmit shift register and tells the TX
Control Block to begin a transmission. The internal timing is such that one full bit slot may elapse
between “write to SBUF” and activation of SEND.
SEND transfers the output of the shift register to the alternate output function line of P1.5, and
also transfers Shift Clock to the alternate output function line of P1.7. As data bits shift out to the
right, “0”s come in from the left. When the MSB of the data byte is at the output position of the
shift register, the “1” that was initially loaded into the 9th position is just to the left of the MSB,
and all positions to the left of that contain “0”s. This condition flags the TX Control block to do
one last shift, then deactivate SEND and set TI.
Reception occurs simultaneously with transmission if REN = 1. Data is input from P1.6. When
REN = 1 any write to SBUF causes the RX Control unit to write the bits 11111110B to the
receive shift register and activates RECEIVE in the next clock phase. As data bits come in from
the right, “1”s shift out to the left. When the “0” that was initially loaded into the right-most posi-
tion arrives at the left-most position in the shift register, it flags the RX Control block to do one
last shift and load SBUF. Then RECEIVE is cleared and RI is set. When REN = 0, the receiver is
not enabled. When a transmission occurs, SBUF will not be updated and RI will not be set even
though serial data is received on P1.6.
The relationship between the shift clock and data is identical to Two-Wire mode as listed in
Table 14-5 and shown in Figure . Three-Wire mode uses different I/Os from Two-Wire mode and
can be connected to SPI slave devices as shownin Figure 14-4. It is possible to time share the
UART hardware between SPI devices connected on P1 and UART devices on P3 with the
caveat that any asynchronous receptions on the RXD pin will be ignored while the UART is in
Mode 0.
Figure 14-4. SPI Connections for UART Mode 0
Master
Slave
MSB
LSB
MSB
LSB
MISO
MOSI
MISO
MOSI
8-Bit Shift Register
8-Bit Shift Register
AT89LP52
SS
GPIO
SCK
SCK
Clock
Generator
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AT89LP51/52 - Preliminary
Figure 14-5. Serial Port Mode 0 (Three-Wire)
INTERNAL BUS
TIMER 1
OVERFLOW
“1“
f
sys
1
0
MOSI
TB8
P1.5 ALT
OUTPUT
FUNCTION
÷2
÷2
0
1
TI
SMOD1
SCK
SERIAL
PORT
INTERRUPT
P1.7 ALT
OUTPUT
FUNCTION
SM2
MISO
P1.6 ALT
OUTPUT
FUNCTION
INTERNAL BUS
WRITE TO SBUF
SEND
SHIFT
MOSI
(DATA OUT)
SCK (SHIFT CLOCK)
(DATA IN)
MISO
TI
RI
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3709B–MICRO–12/10
14.6 More About Mode 1
Ten bits are transmitted (through TXD), or received (through RXD): a start bit (0), 8 data bits
(LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in SCON. In the
AT89LP51/52, the baud rate is determined either by the Timer 1 overflow rate, the TImer 2 over-
flow rate, or both. In this case one timer is for transmit and the other is for receive. Figure 14-6
shows a simplified functional diagram of the serial port in Mode 1 and associated timings for
transmit and receive.
Transmission is initiated by any instruction that uses SBUF as a destination register. The “write
to SBUF” signal also loads a “1” into the 9th bit position of the transmit shift register and flags the
TX Control unit that a transmission is requested. Transmission actually commences at S1P1 of
the machine cycle following the next rollover in the divide-by-16 counter. Thus, the bit times are
synchronized to the divide-by-16 counter, not to the “write to SBUF” signal.
The transmission begins when SEND is activated, which puts the start bit at TXD. One bit time
later, DATA is activated, which enables the output bit of the transmit shift register to TXD. The
first shift pulse occurs one bit time after that.
As data bits shift out to the right, “0”s are clocked in from the left. When the MSB of the data byte
is at the output position of the shift register, the “1” that was initially loaded into the 9th position is
just to the left of the MSB, and all positions to the left of that contain “0”s. This condition flags the
TX Control unit to do one last shift, then deactivate SEND and set TI. This occurs at the tenth
divide-by-16 rollover after “write to SBUF.”
Reception is initiated by a 1-to-0 transition detected at RXD. For this purpose, RXD is sampled
at a rate of 16 times the established baud rate. When a transition is detected, the divide-by-16
counter is immediately reset, and 1FFH is written into the input shift register. Resetting the
divide-by-16 counter aligns its roll-overs with the boundaries of the incoming bit times.
The 16 states of the counter divide each bit time into 16ths. At the 7th, 8th, and 9th counter
states of each bit time, the bit detector samples the value of RXD. The value accepted is the
value that was seen in at least 2 of the 3 samples. This is done to reject noise. In order to reject
false bits, if the value accepted during the first bit time is not 0, the receive circuits are reset and
the unit continues looking for another 1-to-0 transition. If the start bit is valid, it is shifted into the
input shift register, and reception of the rest of the frame proceeds.
As data bits come in from the right, “1”s shift out to the left. When the start bit arrives at the left-
most position in the shift register, (which is a 9-bit register in Mode 1), it flags the RX Control
block to do one last shift, load SBUF and RB8, and set RI. The signal to load SBUF and RB8
and to set RI is generated if, and only if, the following conditions are met at the time the final shift
pulse is generated.
RI = 0 and
Either SM2 = 0, or the received stop bit = 1
If either of these two conditions is not met, the received frame is irretrievably lost. If both condi-
tions are met, the stop bit goes into RB8, the 8 data bits go into SBUF, and RI is activated. At
this time, whether or not the above conditions are met, the unit continues looking for a 1-to-0
transition in RXD.
68
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Figure 14-6. Serial Port Mode 1
TIMER 1
OVERFLOW
TIMER 2
OVERFLOW
INTERNAL BUS
“1”
WRITE
TO
÷2
SBUF
S
Q
D
SBUF
“0”
“1”
CL
TXD
SMOD1
ZERO DETECTOR
“0”
“1”
“1”
SHIFT
DATA
START
TX CONTROL
TCLK
RCLK
÷16
RX CLOCK
SEND
TTII
SERIAL
PORT
INTERRUPT
“0”
÷16
SAMPLE
1-TO-0
LOAD
RX CLOCK
RI
SBUF
START
TRANSITION
RX CONTROL
DETECTOR
SHIFT
1FFH
BIT
DETECTOR
INPUT SHIFT REG.
(9 BITS)
RXD
SHIFT
LOAD
SBUF
SBUF
READ
SBUF
INTERNAL BUS
TX
CLOCK
WRITE TO SBUF
SEND
DATA
SHIFT
D0
D1
D2
D3
D4
D5
D6
D7
TXD
TI
STOP BIT
START BIT
÷16 RESET
RX
CLOCK
RXD
START BIT
D0
D1
D2
D3
D4
D5
D6
D7
STOP BIT
BIT DETECTOR SAMPLE TIMES
SHIFT
RI
69
3709B–MICRO–12/10
14.7 More About Modes 2 and 3
Eleven bits are transmitted (through TXD), or received (through RXD): a start bit (0), 8 data bits
(LSB first), a programmable 9th data bit, and a stop bit (1). On transmit, the 9th data bit (TB8)
can be assigned the value of “0” or “1”. On receive, the 9th data bit goes into RB8 in SCON. The
baud rate is programmable to either 1/16 or 1/32 of the oscillator frequency in Mode 2. Mode 3
may have a variable baud rate generated from either Timer 1 or Timer 2, depending on the state
of RCLK and TCLK.
Figures 14-7 and 14-8 show a functional diagram of the serial port in Modes 2 and 3. The
receive portion is exactly the same as in Mode 1. The transmit portion differs from Mode 1 only
in the 9th bit of the transmit shift register.
Transmission is initiated by any instruction that uses SBUF as a destination register. The “write
to SBUF” signal also loads TB8 into the 9th bit position of the transmit shift register and flags the
TX Control unit that a transmission is requested. Transmission commences at S1P1 of the
machine cycle following the next rollover in the divide-by-16 counter. Thus, the bit times are syn-
chronized to the divide-by-16 counter, not to the “write to SBUF” signal.
The transmission begins when SEND is activated, which puts the start bit at TXD. One bit time
later, DATA is activated, which enables the output bit of the transmit shift register to TXD. The
first shift pulse occurs one bit time after that. The first shift clocks a “1” (the stop bit) into the 9th
bit position of the shift register. Thereafter, only “0”s are clocked in. Thus, as data bits shift out to
the right, “0”s are clocked in from the left. When TB8 is at the output position of the shift register,
then the stop bit is just to the left of TB8, and all positions to the left of that contain “0”s. This con-
dition flags the TX Control unit to do one last shift, then deactivate SEND and set TI. This occurs
at the 11th divide-by-16 rollover after “write to SBUF.”
Reception is initiated by a 1-to-0 transition detected at RXD. For this purpose, RXD is sampled
at a rate of 16 times the established baud rate. When a transition is detected, the divide-by-16
counter is immediately reset, and 1FFH is written to the input shift register.
At the 7th, 8th and 9th counter states of each bit time, the bit detector samples the value of RXD.
The value accepted is the value that was seen in at least 2 of the 3 samples. If the value
accepted during the first bit time is not 0, the receive circuits are reset and the unit continues
looking for another 1-to-0 transition. If the start bit proves valid, it is shifted into the input shift
register, and reception of the rest of the frame proceeds.
As data bits come in from the right, “1”s shift out to the left. When the start bit arrives at the left-
most position in the shift register (which in Modes 2 and 3 is a 9-bit register), it flags the RX Con-
trol block to do one last shift, load SBUF and RB8, and set RI. The signal to load SBUF and RB8
and to set RI is generated if, and only if, the following conditions are met at the time the final shift
pulse is generated:
RI = 0, and
Either SM2 = 0 or the received 9th data bit = 1
If either of these conditions is not met, the received frame is irretrievably lost, and RI is not set. If
both conditions are met, the received 9th data bit goes into RB8, and the first 8 data bits go into
SBUF. One bit time later, whether the above conditions were met or not, the unit continues look-
ing for a 1-to-0 transition at the RXD input.
Note that the value of the received stop bit is irrelevant to SBUF, RB8, or RI.
70
AT89LP51/52 - Preliminary
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AT89LP51/52 - Preliminary
Figure 14-7. Serial Port Mode 2
INTERNAL BUS
CPU CLOCK
SMOD1 1
SMOD1 0
INTERNAL BUS
71
3709B–MICRO–12/10
Figure 14-8. Serial Port Mode 3
TIMER 2
OVERFLOW
TIMER 1
OVERFLOW
INTERNAL BUS
TB8
WRITE
TO
SBUF
÷2
S
Q
D
SBUF
“0”
“1”
TXD
CL
SMOD1
ZERO DETECTOR
“0”
“1”
“1”
STOP BIT
SHIFT
DATA
START
TX CONTROL
TCLK
RCLK
÷16
RX CLOCK
SEND
TI
SERIAL
PORT
“0”
INTERRUPT
÷16
SAMPLE
1-TO-0
LOAD
SBUF
SHIFT
RX CLOCK
RI
START
TRANSITION
DETECTOR
RX CONTROL
1FFH
BIT
DETECTOR
INPUT SHIFT REG.
(9 BITS)
RXD
SHIFT
LOAD
SBUF
SBUF
READ
SBUF
INTERNAL BUS
TX
CLOCK
WRITE TO SBUF
SEND
DATA
SHIFT
D0
D1
D2
D3
D4
D5
D6
D7
TB8
TXD
TI
STOP BIT
START BIT
STOP BIT GEN
÷16 RESET
START BIT
RX
CLOCK
RXD
D0
D1
D2
D3
D4
D5
D6
D7
RB8
STOP
BIT
BIT DETECTOR SAMPLE TIMES
SHIFT
RI
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AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
15. Programmable Watchdog Timer
The programmable Watchdog Timer (WDT) protects the system from incorrect execution by trig-
gering a system reset when it times out after the software has failed to feed the timer prior to the
timer overflow. By Default the WDT counts CPU clock cycles. The prescaler bits, PS0, PS1 and
PS2 in SFR WDTCON are used to set the period of the Watchdog Timer from 16K to 2048K
clock cycles. The Timer Prescaler can also be used to lengthen the time-out period (see Table
6-2 on page 30) The WDT is disabled by Reset and during Power-down mode. When the WDT
times out without being serviced, an internal RST pulse is generated to reset the CPU. See
Table 15-1 for the available WDT period selections.
Table 15-1. Watchdog Timer Time-out Period Selection
WDT Prescaler Bits
Period(1)
PS2
0
PS1
PS0
(Clock Cycles)
0
0
16K
0
0
1
32K
0
1
0
64K
0
1
1
128K
1
0
0
256K
1
0
1
512K
1
1
0
1024K
2048K
1
1
1
Note:
1. The WDT time-out period is dependent on the system clock frequency.
(PS + 14)
2
-------------------------------------------------
Time-out Period =
× (TPS + 1)
System Frequency
The Watchdog Timer consists of a 14-bit timer with 7-bit programmable prescaler. Writing the
sequence 1EH/E1H to the WDTRST register enables the timer. When the WDT is enabled, the
WDTEN bit in WDTCON will be set to “1”. To prevent the WDT from generating a reset when if
overflows, the watchdog feed sequence must be written to WDTRST before the end of the time-
out period. To feed the watchdog, two write instructions must be sequentially executed success-
fully. Between the two write instructions, SFR reads are allowed, but writes are not allowed. The
instructions should move 1EH to the WDTRST register and then 1EH to the WDTRST register.
An incorrect feed or enable sequence will cause an immediate watchdog reset. The program
sequence to feed or enable the watchdog timer is as follows:
MOV WDTRST, #01Eh
MOV WDTRST, #0E1h
15.1 Software Reset
A Software Reset of the AT89LP51/52 is accomplished by writing the software reset sequence
5AH/A5H to the WDTRST SFR. The WDT does not need to be enabled to generate the software
reset. A normal software reset will set the SWRST flag in WDTCON. However, if at any time an
incorrect sequence is written to WDTRST (i.e. anything other than 1EH/E1H or 5AH/A5H), a
software reset will immediately be generated and both the SWRST and WDTOVF flags will be
set. In this manner an intentional software reset may be distinguished from a software error-gen-
erated reset. The program sequence to generate a software reset is as follows:
73
3709B–MICRO–12/10
MOV WDTRST, #05Ah
MOV WDTRST, #0A5h
Table 15-2. WDTCON – Watchdog Control Register
WDTCON Address = A7H
Not Bit Addressable
Reset Value = 0000 0XX0B
PS2
PS1
PS0
WDIDLE(1)
4
DISRTO(1)
SWRST
WDTOVF
1
WDTEN
0
Bit
7
6
5
3
2
Symbol
Function
PS2
PS1
PS0
Prescaler bits for the watchdog timer (WDT). When all three bits are cleared to 0, the watchdog timer has a nominal
period of 16K clock cycles. When all three bits are set to 1, the nominal period is 2048K clock cycles.
WDT Disable during Idle(1). When WDIDLE = 0 the WDT continues to count in Idle mode. When WDIDLE = 1 the WDT
halts counting in Idle mode.
WDIDLE
DISRTO
SWRST
WDTOVF
WDTEN
Disable Reset Output(1). When DISTRO = 0 the reset pin is driven to the same level as POL when the WDT resets.
When DISRTO = 1 the reset pin is input only.
Software Reset Flag. Set when a software reset is generated by writing the sequence 5AH/A5H to WDTRST. Also set
when an incorrect sequence is written to WDTRST. Must be cleared by software.
Watchdog Overflow Flag. Set when a WDT rest is generated by the WDT timer overflow. Also set when an incorrect
sequence is written to WDTRST. Must be cleared by software.
Watchdog Enable Flag. This bit is READ-ONLY and reflects the status of the WDT (whether it is running or not). The
WDT is disabled after any reset and must be re-enabled by writing 1EH/E1H to WDTRST
Note:
1. WDTCON.4 and WDTCON.3 function as WDIDLE and DISRTO only in Fast mode. In Compatibility mode these bits are in
AUXR. (See Table 3-3 on page 19)
Table 15-3. WDTRST – Watchdog Reset Register
WDTCON Address = A6H
(Write-Only)
Not Bit Addressable
–
7
–
6
–
5
–
4
–
3
–
2
–
1
–
0
Bit
The WDT is enabled by writing the sequence 1EH/E1H to the WDTRST SFR. The current status may be checked by reading
the WDTEN bit in WDTCON. To prevent the WDT from resetting the device, the same sequence 1EH/E1H must be written to
WDTRST before the time-out interval expires. A software reset is generated by writing the sequence 5AH/A5H to WDTRST.
74
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
16. Instruction Set Summary
The AT89LP51/52 is fully binary compatible with the 8051 instruction set. In Compatibility mode
the AT89LP51/52 has identical execution time with AT89S51/52 and other standard 8051s. The
difference between the AT89LP51/52 in Fast mode and the standard 8051 is the number of
cycles required to execute an instruction. Fast mode instructions may take 1 to 5 clock cycles to
complete. The execution times of most instructions may be computed using Table 16-1. Note
that for the purposes of this table, a clock cycle is one period of the output of the system clock
divider. For Fast mode the divider defaults to 1, so the clock cycle equals the oscillator period.
For Compatibility mode the divider defaults to 2, so the clock cycle is twice the oscillator period,
or conversely the clock count is half the number of oscillator periods.
Table 16-1. Instruction Execution Times and Exceptions(1)
Generic Instruction Types
Fast Mode Cycle Count Formula
Most arithmetic, logical, bit and transfer instructions
# bytes
Branches and Calls
# bytes + 1
Single Byte Indirect (i.e. ADD A, @Ri, etc.)
2
4
RET, RETI
MOVC
MOVX
MUL
3
4(3)
2
DIV
4
INC DPTR
2
Clock Cycles
Compatibility
Arithmetic
ADD A, Rn
ADD A, direct
ADD A, @Ri
ADD A, #data
ADDC A, Rn
ADDC A, direct
ADDC A, @Ri
ADDC A, #data
SUBB A, Rn
SUBB A, direct
SUBB A, @Ri
SUBB A, #data
INC Rn
Bytes
Fast
1
Hex Code
28-2F
25
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
2
2
26-27
24
2
1
38-3F
35
2
2
36-37
34
2
1
98-9F
95
2
2
96-97
94
2
1
08-0F
05
INC direct
2
INC @Ri
2
06-07
04
INC A
2
DEC Rn
1
18-1F
15
DEC direct
2
75
3709B–MICRO–12/10
Table 16-1. Instruction Execution Times and Exceptions(1) (Continued)
DEC @Ri
DEC A
1
2
1
2
1
1
1
6
6
2
2
2
3
2
4
1
16-17
14
INC DPTR
INC /DPTR(2)
MUL AB
DIV AB
12
18
24
24
6
A3
A5 A3
A4
84
DA A
D4
Clock Cycles
Logical
Bytes
Compatibility
Fast
1
Hex Code
E4
CLR A
1
1
1
2
1
2
2
3
1
2
1
2
2
3
1
2
1
2
2
3
1
1
1
1
1
6
6
CPL A
1
F4
ANL A, Rn
ANL A, direct
ANL A, @Ri
ANL A, #data
ANL direct, A
ANL direct, #data
ORL A, Rn
ORL A, direct
ORL A, @Ri
ORL A, #data
ORL direct, A
ORL direct, #data
XRL A, Rn
XRL A, direct
XRL A, @Ri
XRL A, #data
XRL direct, A
XRL direct, #data
RL A
6
1
58-5F
55
6
2
6
2
56-57
54
6
2
6
2
52
12
6
3
53
1
48-4F
45
6
2
6
2
46-47
44
6
2
6
2
42
12
6
3
43
1
68-6F
65
6
2
6
2
66-67
64
6
2
6
2
62
12
6
3
63
1
23
RLC A
6
1
33
RR A
6
1
03
RRC A
6
1
13
SWAP A
6
1
C4
Clock Cycles
Data Transfer
MOV A, Rn
Bytes
Compatibility
Fast
Hex Code
E8-EF
E5
1
2
1
6
6
6
1
2
2
MOV A, direct
MOV A, @Ri
E6-E7
76
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table 16-1. Instruction Execution Times and Exceptions(1) (Continued)
MOV A, #data
2
1
2
2
2
2
3
2
3
1
2
2
3
4
1
2
1
1
1
2
1
1
2
2
2
1
2
1
1
6
6
2
1
74
F8-FF
A8-AF
78-7F
F5
MOV Rn, A
MOV Rn, direct
MOV Rn, #data
MOV direct, A
12
6
2
2
6
2
MOV direct, Rn
MOV direct, direct
MOV direct, @Ri
MOV direct, #data
MOV @Ri, A
12
12
12
12
6
2
88-8F
85
3
2
86-87
75
3
1
F6-F7
A6-A7
76-77
90
MOV @Ri, direct
MOV @Ri, #data
MOV DPTR, #data16
MOV /DPTR, #data16(2)
MOVC A, @A+DPTR
MOVC A, @A+/DPTR(2)
MOVC A, @A+PC
MOVX A, @Ri
12
6
2
2
12
–
3
4
A5 90
93
12
–
3
4
A5 93
83
12
12
12(3)
18(3)
12
12(3)
18(3)
12
12
6
3
2
E2-E3
E0
MOVX A, @DPTR
MOVX A, @/DPTR(2)
MOVX @Ri, A
4(3)
5(3)
2
A5 E0
F2-F3
F0
MOVX @DPTR, A
MOVX @/DPTR, A(2)
PUSH direct
4(3)
5(3)
2
A5 F0
C0
POP direct
2
D0
XCH A, Rn
1
C8-CF
C5
XCH A, direct
6
2
XCH A, @Ri
6
2
C6-C7
D6-D7
XCHD A, @Ri
6
2
Clock Cycles
Bit Operations
CLR C
Bytes
Compatibility
Fast
1
Hex Code
1
2
1
2
1
2
2
2
6
6
C3
C2
D3
D2
B3
B2
82
CLR bit
2
SETB C
6
1
SETB bit
CPL C
6
2
6
1
CPL bit
6
2
ANL C, bit
ANL C, bit
12
12
2
2
B0
77
3709B–MICRO–12/10
Table 16-1. Instruction Execution Times and Exceptions(1) (Continued)
ORL C, bit
ORL C, /bit
MOV C, bit
MOV bit, C
2
2
2
2
12
12
6
2
2
2
2
72
A0
A2
92
12
Clock Cycles
Branching
JC rel
Bytes
Compatibility
Fast
3
Hex Code
2
2
3
3
3
2
2
2
12
12
12
12
12
12
12
12
40
50
20
30
10
60
70
80
JNC rel
3
JB bit, rel
JNB bit, rel
JBC bit, rel
JZ rel
4
4
4
3
JNZ rel
3
SJMP rel
3
11,31,51,71,91,
B1,D1,F1
ACALL addr11
2
12
3
LCALL addr16
RET
3
1
1
12
12
12
4
4
4
12
22
32
RETI
01,21,41,61,81,
AJMP addr11
2
12
3
A1,C1,E1
LJMP addr16
3
1
2
3
3
3
3
3
3
2
3
1
12
12
12
12
12
12
12
18
18
12
12
6
4
2
3
4
4
4
4
4
4
3
4
1
02
73
JMP @A+DPTR
JMP @A+PC(2)
CJNE A, direct, rel
CJNE A, #data, rel
CJNE Rn, #data, rel
CJNE @Ri, #data, rel
CJNE A, @R0, rel(2)
CJNE A, @R1, rel(2)
DJNZ Rn, rel
A5 73
B5
B4
B8-BF
B6-B7
A5 B6
A5 B7
D8-DF
D5
DJNZ direct, rel
NOP
00
Notes: 1. A clock cycle is one period of the output of the system clock divider. For Fast mode the divider
defaults to 1, so the clock cycle equals the oscillator period. For Compatibility mode the divider
defaults to 2, so the clock cycle is twice the oscillator period, or conversely the clock count is
half the number of oscillator periods.
2. This escaped instruction is an extension to the instruction set.
3. This is the minimum time for MOVX with no wait states. In Compatibility mode an additional 24
clocks are added for the wait state. In Fast mode, 1 clock is added for each wait state (0–3).
78
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AT89LP51/52 - Preliminary
17. Programming the Flash Memory
The Atmel AT89LP51/52 microcontroller features 8K bytes of on-chip In-System Programmable
Flash program memory and 256bytes of nonvolatile Flash data memory. In-System Program-
ming allows programming and reprogramming of the microcontroller positioned inside the end
system. Using a simple 3-wire SPI interface, the programmer communicates serially with the
AT89LP51/52 microcontroller, reprogramming all nonvolatile memories on the chip. In-System
Programming eliminates the need for physical removal of the chips from the system. This will
save time and money, both during development in the lab, and when updating the software or
parameters in the field. The programming interface of the AT89LP51/52 includes the following
features:
• Three-wire serial SPI Programming Interface or 11-pin Parallel Interface
• Selectable Polarity Reset Entry into Programming
• User Signature Array
• Flexible Page Programming
• Row Erase Capability
• Page Write with Auto-Erase Commands
• Programming Status Register
For more detailed information on In-System Programming, refer to the Application Note entitled
“AT89LP In-System Programming Specification”.
17.1 Physical Interface
The AT89LP51/52 provides a standard programming command set with two physical interfaces:
a bit-serial and a byte-parallel interface. Normal Flash programming utilizes the Serial Peripheral
Interface (SPI) pins of an AT89LP51/52 microcontroller. The SPI is a full-duplex synchronous
serial interface consisting of three wires: Serial Clock (SCK), Master-In/Slave-out (MISO), and
Master-out/Slave-in (MOSI)). When programming an AT89LP51/52 device, the programmer
always operates as the SPI master, and the target system always operates as the SPI slave. To
enter or remain in Programming mode the device’s reset line (RST) must be held active. With
the addition of VDD and GND, an AT89LP51/52 microcontroller can be programmed with a min-
imum of seven connections as shown in Figure 17-1.
Figure 17-1. In-System Programming Device Connections
AT89LP51/52
Serial Clock
Serial Out
Serial In
P1.7/SCK
P1.6/MISO
P1.5/MOSI
VDD
POL
GND or VDD
RST
RST
GND
79
3709B–MICRO–12/10
The Parallel interface is a special mode of the serial interface, i.e. the serial interface is used to
enable the parallel interface. After enabling the interface serially over P1.7/SCK and P1.5/MOSI,
P1.5 is reconfigured as an active-low output enable (OE) for data on Port 0. When OE = 1, com-
mand, address and write data bytes are input on Port 0 and sampled at the rising edge of SCK.
When OE = 0, read data bytes are output on Port 0 and should be sampled on the falling edge of
SCK. The P1.7/SCK and RST pins continue to function in the same manner. With the addition of
VDD and GND, the parallel interface requires a minimum of fourteen connections as shown in
Figure 17-2. Note that a connection to P1.6/MISO is not required for using the parallel interface.
Figure 17-2. Parallel Programming Device Connections
AT89LP51/52
Clock
RST
P1.7/SCK
RST
VDD
OE
P1.5/MOSI
POL
GND or VDD
8
P0.7-0
Data In/Out
GND
The Programming Interface is the only means of externally programming the AT89LP51/52
microcontroller. The Interface can be used to program the device both in-system and in a stand-
alone serial programmer. The Interface does not require any clock other than SCK and is not
limited by the system clock frequency. During Programming the system clock source of the tar-
get device can operate normally.
When designing a system where In-System Programming will be used, the following observa-
tions must be considered for correct operation:
• The ISP interface uses the SPI clock mode 0 (CPOL = 0, CPHA = 0) exclusively with a
maximum frequency of 5 MHz.
• The AT89LP51/52 will enter programming mode only when its reset line (RST) is active. To
simplify this operation, it is recommended that the target reset can be controlled by the In-
System programmer. To avoid problems, the In-System programmer should be able to keep
the entire target system reset for the duration of the programming cycle. The target system
should never attempt to drive the three SPI lines while reset is active.
• The ISP Enable Fuse must be set to allow programming during any reset period. If the ISP
Fuse is disabled, ISP may only be entered at POR. To enter programming the RST pin must
be driven active prior to the end of Power-On Reset (POR). After POR has completed the
device will remain in ISP mode until RST is brought inactive. Once the initial ISP session has
ended, the power to the target device must be cycled OFF and ON to enter another session.
Note that if this method is required, an active-low reset polarity is recommended.
• For standalone programmers, an active-low reset polarity is recommended (POL = 0). RST
may then be tied directly to GND to ensure correct entry into Programming mode regardless
of the device settings.
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17.2 Memory Organization
The AT89LP51/52 offers 8K bytes of In-System Programmable (ISP) nonvolatile Flash code
memory and 256 bytes of nonvolatile Flash data memory. In addition, the device contains a 256-
byte User Signature Array and a 128-byte read-only Atmel Signature Array. The memory organi-
zation is shown in Table 17-1 and Figure 17-3. The memory is divided into pages of 128 bytes
each. A single read or write command may only access half a page (64 bytes) in the memory;
however, write with auto-erase commands will erase an entire 128-byte page even though they
can only write one half page. Each memory type resides in its own address space and is
accessed by commands specific to that memory. However, all memory types share the same
page size.
User configuration fuses are mapped as a row in the memory, with each byte representing one
fuse. From a programming standpoint, fuses are treated the same as normal code bytes except
they are not affected by Chip Erase. Fuses can be enabled at any time by writing 00h to the
appropriate locations in the fuse row. However, to disable a fuse, i.e. set it to FFh, the entire
fuse row must be erased and then reprogrammed. The programmer should read the state of all
the fuses into a temporary location, modify those fuses which need to be disabled, then issue a
Fuse Write with Auto-Erase command using the temporary data. Lock bits are treated in a simi-
lar manner to fuses except they may only be erased (unlocked) by Chip Erase.
Table 17-1. AT89LP51/52 Memory Organization
Memory
Capacity
Page Size
# Pages
Address Range
4096 bytes
8192 bytes
32
64
0000H – 0FFFH
0000H – 1FFFH
CODE
128 bytes
DATA
256 bytes
256 bytes
128 bytes
128 bytes
128 bytes
128 bytes
2
2
1
0000H – 00FFH
0000H – 00FFH
0000H – 007FH
User Signature
Atmel Signature
Figure 17-3. AT89LP52 Memory Organization
00
3F
Page Buffer
Page 0 Low
User Fuse Row
User Signature Array
Atmel Signature Array
Data Memory
Page 1 Low
Page 0 Low
Page 1 High
Page 0 High
Page 0 Low
Page 0 High
Page 1 Low
Page 0 Low
Page 1 High
Page 0 High
1FFF
Page 63 Low
Page 63 High
Page 62 Low
Page 62 High
Code Memory
Page 1 Low
Page 0 Low
Page 1 High
Page 1 High
0000
00
3F 40
7F
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3709B–MICRO–12/10
17.3 Command Format
Programming commands consist of an opcode byte, two address bytes, and zero or more data
bytes. Figure 17-4 on page 82 shows a simplified flow chart of a command sequence.
A sample command packet is shown in Figure 17-5 on page 83. The SS pin defines the packet
frame. SS must be brought low before the first byte in a command is sent and brought back high
after the final byte in the command has been sent. The command is not complete until SS
returns high. Command bytes are issued serially on MOSI. Data output bytes are received seri-
ally on MISO. Packets of variable length are supported by returning SS high when the final
required byte has been transmitted. In some cases command bytes have a don’t care value.
Don’t care bytes in the middle of a packet must be transmitted. Don’t care bytes at the end of a
packet may be ignored.
Page oriented instructions always include a full 16-bit address. The higher order bits select the
page and the lower order bits select the byte within that page. The AT89LP51/52 allocates 6 bits
for byte address, 1 bit for low/high half page selection and 9 bits for page address. The half page
to be accessed is always fixed by the page address and half select as transmitted. The byte
address specifies the starting address for the first data byte. After each data byte has been
transmitted, the byte address is incremented to point to the next data byte. This allows a page
command to linearly sweep the bytes within a page. If the byte address is incremented past the
last byte in the half page, the byte address will roll over to the first byte in the same half page.
While loading bytes into the page buffer, overwriting previously loaded bytes will result in data
corruption.
For a summary of available commands, see Table 17-2 on page 84.
Figure 17-4. Command Sequence Flow Chart
Input Opcode
Input Address
High Byte
Input Address
Low Byte
Input/Output
Data
Address +1
no
Byte Mode or
Count == 64
yes
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Figure 17-5. ISP Command Packet (Serial Byte)
SCK
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
7
6
6
5
5
4
3
2
2
1
1
0
0
MOSI
MISO
Opcode
X
Address High
Address Low
Data In
X
X
4 3
Data Out
Figure 17-6. ISP Command Packet (Serial Page)
SCK
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
7
7
6
6
5
4
3
2
1
1
0
0
7
7
6
6
5
4
3
2
1
1
0
0
MOSI
MISO
Opcode
X
Address High
Address Low
Data In 0
Data In 63
X
X
5
4
3
2
5 4 3 2
Data Out 0
Data Out 63
Figure 17-7. ISP Command Packet (Parallel Byte)
SCK
WRITE
OE
Opcode
Opcode
Address High
Address High
Address Low
READ
Data In
P0
OE
P0
Address Low
Data Out
Figure 17-8. ISP Command Packet (Parallel Page)
SCK
WRITE
OE
Opcode
Opcode
Address High
Address High
Address Low
READ
Data In 0
Data In 63
P0
OE
P0
Address Low
Data Out 0
Out 62
Data Out 63
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Table 17-2. Programming Command Summary
Command
Opcode
Addr High
Addr Low
Data 0
Data 1–63
xxxx xxxx
Program Enable(1)
1010 1100
0101 0011
xxxx xxxx
–
(0110 1001)(2)
Parallel Enable(3)
1010 1100
1010 1100
0110 0000
0100 0000
0010 0000
0101 0000
0111 0000
0011 0000
1100 0000
1010 0000
1101 0000
1101 0010
1011 0000
0100 0001
0010 0001
0101 0001
0111 0001
0011 0001
1010 1100
0010 0100
0100 0100
0101 0100
0011 0100
0100 0010
0010 0010
0101 0010
0111 0010
0011 0010
0010 1000
0011 1000
0011 0101
100x xxxx
xxxx xxxx
000a aaaa
000a aaaa
000a aaaa
000a aaaa
000a aaaa
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
1110 00BB
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
xxxx xxxx
asbb bbbb
asbb bbbb
as00 0000
as00 0000
as00 0000
asbb bbbb
asbb bbbb
as00 0000
as00 0000
as00 0000
00bb bbbb
00bb bbbb
0000 0000
0000 0000
0000 0000
xxxx xxxx
xxxx xxxx
00bb bbbb
0000 0000
0000 0000
asbb bbbb
asbb bbbb
as00 0000
as00 0000
as00 0000
0sbb bbbb
0s00 0000
xxxx xxxx
xxxx xxxx
Status Out
Data In
–
Chip Erase
–
Read Status
–
Write Code Byte
–
Read Code Byte
Data Out
Byte 0
–
Write Code Page
Bytes 1–63
Write Code Page with Auto-Erase
Read Code Page
Byte 0
Bytes 1–63
Byte 0
Bytes 1–63
Write Data Byte
Data In
–
Read Data Byte
Data Out
Byte 0
–
Write Data Page
Bytes 1–63
Write Data Page with Auto-Erase
Read Data Page
Byte 0
Bytes 1–63
Byte 0
Bytes 1–63
Write User Fuse(5)
Fuse In(4)
Fuse Out(4)
Fuse 0(4)
Fuse 0(4)
Fuse 0(4)
xxxx xxxx
xxxL LLxx
Data In(4)
Byte 0(4)
Byte 0(4)
Data In
–
Read User Fuse(5)
–
Write User Fuses(5)
Bytes 1–63
Write User Fuses with Auto-Erase(5)
Read User Fuses(5)
Fuses 1–63(4)
Fuses 1–63(4)
Write Lock Mode(6)
–
Read Lock Mode(6)
–
Write Lock Bit(6)
–
Bytes 1–63(4)
Bytes 1–63(4)
–
Write Lock Bits(6)
Read Lock Bits(6)
Write User Signature Byte
Read User Signature Byte
Write User Signature Page
Write User Signature Page with Auto-Erase
Read User Signature Page
Read Atmel Signature Byte(7)
Read Atmel Signature Page(7)
Data Out
Byte 0
–
Byte 1–63
Byte 1–63
Byte 1–63
–
Byte 0
Byte 0
Data Out
Byte 0
Byte 1–63
Notes: 1. Program Enable must be the first command issued after entering into programming mode.
2. 0110 1001B is returned on MISO when Program Enable was successful.
3. Parallel Enable switches the interface from serial to parallel format until RST goes inactive.
4. Each byte address selects one fuse or lock bit. Data bytes must be 00h or FFh.
5. See Table 17-5 on page 86 for Fuse definitions.
6. See Table 17-4 on page 86 for Lock Bit definitions.
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7. Atmel Signature Bytes:
Address:
AT89LP51:
AT89LP52:
0000H
0001H
54H
0002H
05H
1EH
1EH
54H
06H
8. Symbol Key:
a:
s:
b:
x:
Page Address Bit
Half Page Select Bit
Byte Address Bit
Don’t Care Bit
17.4 Status Register
The current state of the memory may be accessed by reading the status register. The status reg-
ister is shown in Table 17-3.
Table 17-3. Status Register
–
6
–
5
–
4
LOAD
3
SUCCESS
WRTINH
1
BUSY
–
Bit
7
2
0
Symbol
Function
Load flag. Cleared low by the load page buffer command and set high by the next memory write. This flag signals that
the page buffer was previously loaded with data by the load page buffer command.
LOAD
Success flag. Cleared low at the start of a programming cycle and will only be set high if the programming cycle
completes without interruption from the brownout detector.
SUCCESS
Write Inhibit flag. Cleared low by the brownout detector (BOD) whenever programming is inhibited due to VDD falling
below the minimum required programming voltage. If a BOD episode occurs during programming, the SUCCESS flag
will remain low after the cycle is complete.
WRTINH
BUSY
Busy flag. Cleared low whenever the memory is busy programming or if write is currently inhibited.
17.5 DATA Polling
The AT89LP51/52 implements DATA polling to indicate the end of a programming cycle. While
the device is busy, any attempted read of the last byte written will return the data byte with the
MSB complemented. Once the programming cycle has completed, the true value will be acces-
sible. During Erase the data is assumed to be FFH and DATA polling will return 7FH. When
writing multiple bytes in a page, the DATA value will be the last data byte loaded before pro-
gramming begins, not the written byte with the highest physical address within the page.
17.6 Flash Security
The AT89LP51/52 provides three Lock Bits for Flash Code and Data Memory security. Lock bits
can be left unprogrammed (FFh) or programmed (00h) to obtain the protection levels listed in
Table 17-4. Lock bits can only be erased (set to FFh) by Chip Erase. Lock bit mode 2 disables
programming of all memory spaces, including the User Signature Array and User Configuration
Fuses. User fuses must be programmed before enabling Lock bit mode 2 or 3. Lock bit mode 3
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3709B–MICRO–12/10
implements mode 2 and also blocks reads from the code and data memories; however, reads of
the User Signature Array, Atmel Signature Array, and User Configuration Fuses are still allowed.
The Lock Bits will not disable FDATA or IAP programming initiated by the application software.
Table 17-4. Lock Bit Protection Modes
Program Lock Bits (by address)
Mode
00h
FFh
00h
00h
01h
FFh
FFh
00h
02h
FFh
FFh
FFh
Protection Mode
1
2
3
No program lock features
Further programming of the Flash is disabled
Further programming of the Flash is disabled and verify (read) is also disabled
Further programming of the Flash is disabled and verify (read) is also disabled;
External execution above 4K/8K is disabled
4
00h
00h
00h
17.7 User Configuration Fuses
The AT89LP51/52 includes 10 user fuses for configuration of the device. Each fuse is accessed
at a separate address in the User Fuse Row as listed in Table 17-5. Fuses are cleared by pro-
gramming 00h to their locations. Programming FFh to a fuse location will cause that fuse to
maintain its previous state. To set a fuse (set to FFh) the fuse row must be erased and then
reprogrammed using the Fuse Write with Auto-erase command. The default state for all fuses is
FFh.
Table 17-5. User Configuration Fuse Definitions
Address
Fuse Name
Description
Selects source for the system clock:
CS1
FFh
FFh
00h
00h
CS0
FFh
00h
FFh
00h
Selected Source
High Speed Crystal Oscillator (XTAL)
Low Speed Crystal Oscillator (XTAL)
External Clock on XTAL1 (XCLK)
Internal Auxiliary Oscillator (IRC)
00 – 01h
Clock Source – CS[0:1](2)
Selects time-out delay for the POR/BOD/PWD wake-up period:
SUT1
00h
SUT0
00h
Selected Time-out
1 ms (XTAL); 16 µs (XCLK/IRC)
2 ms (XTAL); 512 µs (XCLK/IRC)
4 ms (XTAL); 1 ms (XCLK/IRC)
16 ms (XTAL); 4 ms (XCLK/IRC)
02 – 03h
Start-up Time – SUT[0:1]
00h
FFh
00h
FFh
FFh
FFh
FFh: CPU functions in 12-clock Compatibility mode
00h: CPU functions is single-cycle Fast mode
04h
05h
06H
Compatibility Mode
ISP Enable(3)
FFh: In-System Programming Enabled
00h: In-System Programming Disabled (Enabled at POR only)
FFh: Programming of User Signature Disabled
00h: Programming of User Signature Enabled
User Signature Programming
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Table 17-5. User Configuration Fuse Definitions
Address
Fuse Name
Description
FFh: I/O Ports start in input-only mode (tristated) after reset
00h: I/O Ports start in quasi-bidirectional mode after reset
07H
Tristate Ports
FFh: In-Application Programming Disabled
00h: In-Application Programming Enabled
08H
In-Application Programming
R1 Enable
FFh: 5 MΩ resistor on XTAL1 Disabled
00h: 5 MΩ resistor on XTAL1 Enabled
09H
Notes: 1. The default state for all fuses is FFh.
2. Changes to these fuses will only take effect after a device POR.
3. Changes to these fuses will only take effect after the ISP session terminates by bringing RST inactive.
17.8 User Signature
The User Signature Array contains 256 bytes of non-volatile memory in two 128-byte pages. The
User Signature is available for serial numbers, firmware revision information, date codes or other
user parameters. The User Signature Array may only be written by an external device when the
User Signature Programming Fuse is enabled. When the fuse is enabled, Chip Erase will also
erase the first page of the array. When the fuse is disabled, the array is not affected by write or
erase commands. Programming of the Signature Array can also be disabled by the Lock Bits.
However, reading the signature is always allowed and the array should not be used to store
security sensitive information. The User Signature Array may be modified during execution
through the In-Application Programming interface, regardless of the state of the User Signature
Programming fuse or Lock Bits, provided that the IAP Fuse is enabled. Note that the address of
the User Signature Array, as seen by the IAP interface, equals the User Signature address plus
256 (0100H–01FFH instead of 0000H–00FFH).
17.9 Programming Interface Timing
This section details general system timing sequences and constraints for entering or exiting In-
System Programming as well as parameters related to the Serial Peripheral Interface during
ISP. The general timing parameters for the following waveform figures are listed in section “Tim-
ing Parameters” on page 91.
17.9.1
Power-up Sequence
Execute this sequence to enter programming mode immediately after power-up. In the RST pin
is disabled or if the ISP Fuse is disabled, this is the only method to enter programming (see
“External Reset” on page 32).
1. Apply power between VDD and GND pins. RST should remain low.
2. Wait at least tPWRUP. and drive RST high if active-high otherwise keep low.
3. Wait at least tSUT for the internal Power-on Reset to complete. The value of tSUT will
depend on the current settings of the device.
4. Start programming session.
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Figure 17-9. Serial Programming Power-up Sequence
VDD
tPWRUP
RST
tPOR + tSUT
RST
SCK
MISO
MOSI
HIGH Z
HIGH Z
17.9.2
Power-down Sequence
Execute this sequence to power-down the device after programming.
1. Drive SCK low.
2. Wait at least tSSD and Tristate MOSI.
3. Wait at least tRHZ and drive RST low.
4. Wait at least tSSZ and tristate SCK.
5. Wait no more than tPWRDN and power off VDD.
Figure 17-10. Serial Programming Power-down Sequence
V
DD
t
PWRDN
RST
SCK
t
t
t
SSZ
SSD
RHZ
MISO
MOSI
HIGH Z
HIGH Z
17.9.3
ISP Start Sequence
Execute this sequence to exit CPU execution mode and enter ISP mode when the device has
passed Power-On Reset and is already operational.
1. Drive RST high.
2. Wait tRLZ + tSTL
.
3. Drive SCK low.
4. Start programming session.
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Figure 17-11. In-System Programming (ISP) Start Sequence
VDD
XTAL1
RST
tRLZ
tSTL
tZSS
tSSE
SCK
MISO
MOSI
HIGH Z
HIGH Z
17.9.4
ISP Exit Sequence
Execute this sequence to exit ISP mode and resume CPU execution mode.
1. Drive SCK low.
1. Wait at least tSSD
.
2. Tristate MOSI.
3. Wait at least tRHZ and bring RST low.
4. Wait tSSZ and tristate SCK.
Figure 17-12. In-System Programming (ISP) Exit Sequence
VDD
XTAL1
RST
tSSD
tRHZ
tSSZ
SCK
MISO
MOSI
HIGH Z
HIGH Z
Note:
The waveforms on this page are not to scale.
17.9.5
Serial Peripheral Interface
The Serial Peripheral Interface (SPI) is a byte-oriented full-duplex synchronous serial communi-
cation channel. During In-System Programming, the programmer always acts as the SPI master
and the target device always acts as the SPI slave. The target device receives serial data on
MOSI and outputs serial data on MISO. The Programming Interface implements a standard
SPI Port with a fixed data order and For In-System Programming, bytes are transferred MSB
first as shown in Figure 17-13. The SCK phase and polarity follow SPI clock mode 0 (CPOL = 0,
CPHA = 0) where bits are sampled on the rising edge of SCK and output on the falling edge of
SCK. For more detailed timing information see Figure 17-14.
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3709B–MICRO–12/10
Figure 17-13. ISP Byte Sequence
SCK
MOSI
MISO
7
7
6
6
5
4
4
3
3
2
2
1
1
0
0
5
Data Sampled
Figure 17-14. Serial Programming Interface Timing
RST
t
t
t
t
SR
t
SSD
SCK
SSE
SF
t
t
SHSL
SLSH
SCK
t
t
t
SOH
SOX
SOV
MISO
MOSI
t
t
SIH
SIS
Figure 17-15. Parallel Programming Interface Timing
RST
t
t
t
t
SR
t
SSD
SCK
SSE
SF
t
t
SHSL
SLSH
SCK
OE
P0
t
POV
t
t
PIH
PIS
t
t
POH
t
POE
POX
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17.9.6
Timing Parameters
The timing parameters for Figure 17-9, Figure 17-10, Figure 17-11, Figure 17-12, Figure 17-14
and Figure 17-15 are shown in Table .
Table 17-6. Programming Interface Timing Parameters
Symbol
tCLCL
tPWRUP
tPOR
tPWRDN
tRLZ
Parameter
Min
0
Max
Units
ns
µs
µs
µs
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
ms
ms
System Clock Cycle Time
Power On to SS High Time
Power-on Reset Time
SS Tristate to Power Off
RST Low to I/O Tristate
RST Low Settling Time
RST High to SS Tristate
Serial Clock Cycle Time
Clock High Time
60
10
100
1
tCLCL
100
0
2 tCLCL
tSTL
tRHZ
tSCK
tSHSL
tSLSH
tSR
2 tCLCL
200(1)
75
Clock Low Time
50
Rise Time
25
25
tSF
Fall Time
tSIS
Serial Input Setup Time
Serial Input Hold Time
Serial Output Hold Time
Serial Output Valid Time
Parallel Input Setup Time
Parallel Input Hold Time
Parallel Output Hold Time
Parallel Output Valid Time
Serial Output Enable Time
Serial Output Disable Time
Parallel Output Enable Time
Parallel Output Disable Time
RST Active Lead Time
RST Inactive Lag Time
SCK Setup to SS Low
SCK Hold after SS High
Write Cycle Time
10
10
tSIH
tSOH
tSOV
tPIS
10
35
10
10
tPIH
tPOH
tPOV
tSOE
tSOX
tPOE
tPOX
tSSE
tSSD
tZSS
10
35
10
25
10
25
tSLSH
tSLSH
25
tSSZ
25
tWR
2.5
5
tAWR
Write Cycle with Auto-Erase Time
tERS
Chip Erase Cycle Time
7.5
Note:
1. tSCK is independent of tCLCL.
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18. Electrical Characteristics
18.1 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 any
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 ................................... -40°C to +85°C
Storage Temperature..................................... -65°C to +150°C
Voltage on Any Pin with Respect to Ground......-0.7V to +5.5V
Maximum Operating Voltage ............................................ 5.5V
Total DC Output Current ........................................... 150.0 mA
18.2 DC Characteristics
TA = -40°C to 85°C, VDD = 2.4V to 5.5V (unless otherwise noted)
Symbol
VIL
Parameter
Condition
Min
-0.5
Max
0.2 VDD - 0.1
VDD + 0.5
0.5
Units
Input Low-voltage
Input High-voltage
Output Low-voltage(1)
V
V
V
V
V
V
VIH
0.2 VDD + 0.9
VOL
IOL = 10 mA, VDD = 2.4V, TA = 85°C
IOH = -80 µA, VDD = 3V 10%
2.4
Output High-voltage
With Weak Pull-ups Enabled
VOH
I
OH = -30 µA
0.75 VDD
0.9 VDD
0.9 VDD
0.75 VDD
IOH = -12 µA
IOH = -10 mA, TA = 85°C
IOH = -5 mA, TA = 85°C
VIN = 0.45V
Output High-voltage
With Strong Pull-ups Enabled
VOH1
IIL
Logic 0 Input Current
Logic 1 to 0 Transition Current
Input Leakage Current
Reset Pull-up Resistor
Pin Capacitance
-50
-750
10
150
10
7
µA
µA
µA
kΩ
pF
ITL
VIN = 2V, VDD = 5V 10%
0 < VIN < VDD
ILI
RRST
CIO
50
Test Freq. = 1 MHz, TA = 25°C
Active Mode, 12 MHz, VDD = 5.5V
Idle Mode, 12 MHz, VDD = 5.5V
Active Mode, 12 MHz, VDD = 5.5V
Idle Mode, 12 MHz, VDD = 5.5V
VDD = 5.5V
mA
mA
mA
mA
µA
µA
Power Supply Current
(Fast Mode)
3
5
Power Supply Current
(Compatibility Mode)
ICC
3
5
Power-down Mode(2)
VDD = 3V
2
Notes: 1. Under steady state (non-transient) conditions, IOL must be externally limited as follows:
Maximum IOL per port pin: 10 mA
Maximum total IOL for all output pins: 100 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 conditions.
2. Minimum VDD for Power-down is 2V.
3. All characteristics contained in this datasheet are based on simulation and characterization of other microcontrollers manu-
factured in the same process technology. These values are preliminary values representing design targets, and will be
updated after characterization of actual silicon.
92
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
18.3 Typical Characteristics
The following charts show typical behavior. These figures are not tested during manufacturing.
All current consumption measurements are performed with all I/O pins configured as quasi-bidi-
rectional (with internal pull-ups). A square wave generator with rail-to-rail output is used as an
external clock source for consumption versus frequency measurements.
18.3.1
Supply Current (Internal Oscillator)
Figure 18-1. Active Supply Current vs. Vcc (1.8432 MHz Internal Oscillator)
Active Supply Current vs.Vcc
1.8432 MHz Internal Oscillator
1.25
85C
-40C
25C
Compatibility Mode
1.00
0.75
0.50
0.25
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vcc (V)
3.0
85C
-40C
25C
Fast Mode
2.5
2.0
1.5
1.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vcc (V)
93
3709B–MICRO–12/10
Figure 18-2. Idle Supply Current vs. Vcc (1.8432 MHz Internal Oscillator)
Idle Supply Current vs.Vcc
1.8432 MHz Internal Oscillator
0.75
85C
-40C
25C
Compatibility Mode
0.50
0.25
0.00
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vcc (V)
0.75
85C
-40C
25C
Fast Mode
0.50
0.25
0.00
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vcc (V)
Note:
All characteristics contained in this datasheet are based on simulation and characterization of
other microcontrollers manufactured in the same process technology. These values are prelimi-
nary values representing design targets, and will be updated after characterization of actual
silicon.
94
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
18.3.2
Supply Current (External Clock)
Figure 18-3. Active Supply Current vs. Frequency
Active Supply Current vs. Frequency
External Clock Source
8
7
6
5
4
3
2
1
0
5.5V
5.0V
4.5V
3.6V
3.0V
2.4V
Compatibility Mode
0
5
10
15
20
25
Frequency (MHz)
20
18
16
14
12
10
8
5.5V
5.0V
4.5V
3.6V
3.0V
2.4V
Fast Mode
6
4
2
0
0
5
10
15
20
25
Frequency (MHz)
20
18
16
14
12
10
8
5V Compat.
3V Compat.
5V Fast
3V Fast
6
4
2
0
0
5
10
15
20
25
MIPS
95
3709B–MICRO–12/10
Figure 18-4. Idle Supply Current vs. Frequency
Idle Supply Current vs. Frequency
External Clock Source
3.0
2.5
2.0
1.5
1.0
0.5
0.0
5.5V
5.0V
4.5V
3.6V
3.0V
2.4V
Compatibility Mode
0
5
10
15
20
25
Frequency (MHz)
6
5
4
3
2
1
0
5.5V
5.0V
4.5V
3.6V
3.0V
2.4V
Fast Mode
0
5
10
15
20
25
Frequency (MHz)
18.4 Clock Characteristics
The values shown in this table are valid for TA = -40°C to 85°C and VDD = 2.4 to 5.5V, unless otherwise noted.
Figure 18-5. External Clock Drive Waveform
96
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table 18-1. External Clock Parameters
VDD = 2.4V to 5.5V
VDD = 4.5V to 5.5V
Symbol
1/tCLCL
tCLCL
Parameter
Min
0
Max
Min
0
Max
Units
MHz
ns
Oscillator Frequency(1)
20
25
Clock Period
50
40
12
12
tCHCX
tCLCX
External Clock High Time
External Clock Low Time
External Clock Rise Time
External Clock Fall Time
ns
ns
tCLCH
5
5
ns
tCHCL
ns
Note:
1. No wait state (single-cycle) fetch speed for Fast Mode
Table 18-2.
Symbol
Clock Characteristics
Parameter
Condition
Min
0
Max
12
Units
MHz
MHz
MHz
MHz
Low Power Oscillator
High Power Oscillator
TA = 25°C; VDD = 5.0V
fXTAL
Crystal Oscillator Frequency
Internal Oscillator Frequency
0
24
1.824
1.751
1.862
1.935
fRC
VDD = 2.4 to 5.5V
18.5 Reset Characteristics
The values shown in this table are valid for TA = -40°C to 85°C and VDD = 2.4 to 5.5V, unless otherwise noted.
Table 18-3.
Symbol
RRST
Reset Characteristics
Parameter
Condition
Min
50
Max
150
1.6
Units
kΩ
V
Reset Pull-up Resistor
VPOR
Power-On Reset Threshold
Brown-Out Detector Threshold
Brown-Out Detector Hysteresis
Power-On Reset Delay
Watchdog Reset Pulse Width
1.3
VBOD
1.9
2.2
V
VBH
200
300
150
mV
µs
tPOR
135
tWDTRST
49tCLCL
ns
97
3709B–MICRO–12/10
18.6 External Memory Characteristics
The values shown in this table are valid for TA = -40°C to 85°C and VDD = 2.4 to 5.5V, unless otherwise noted. Under oper-
ating conditions, load capacitance for Port 0, ALE and PSEN = 100 pF; load capacitance for all other outputs = 80 pF.
Parameters refer to Figure 18-6, Figure 18-7 and Figure 18-8.
Table 18-4. External Program and Data Memory Characteristics
Compatibility Mode(1)
Fast Mode(1)
Symbol
1/tCLCL
tLHLL
Parameter
Min
0
Max
Min
Max
Units
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Oscillator Frequency
24
0
24
ALE Pulse Width
tCLCL - d
tCLCL - d(4)
0.5tCLCL - d(2)
0.5tCLCL - d(3)
tAVLL
Address Valid to ALE Low
Address Hold after ALE Low
ALE Low to Valid Instruction In
ALE Low to PSEN Low
PSEN Pulse WIdth
0.5tCLCL - d(2)
0.5tCLCL - d(3)
tLLAX
tLLIV
2tCLCL - d
2tCLCL - d
tLLPL
0.5tCLCL - d(2)
1.5tCLCL - d(2)
0.5tCLCL - d(2)
1.5tCLCL - d(2)
tPLPH
tPLIV
PSEN Low to Valid Instruction In
Input Instruction Hold after PSEN
Input Instruction Float after PSEN
PSEN to Address Valid
Address to Valid Instruction In
PSEN Low to Address Float
RD Pulse Width(5)
1.5tCLCL - d(2)
1.5tCLCL - d(2)
tPXIX
0
0
tPXIZ
0.5tCLCL - d(2)
0.5tCLCL - d(2)
tPXAV
tAVIV
0.5tCLCL - d(2)
0.5tCLCL - d(2)
2.5tCLCL - d(2)
10
2.5tCLCL - d(2)
10
tPLAZ
tRLRH
tWLWH
tRLDV
tRHDX
tRHDZ
tLLDV
tAVDV
tLLWL
tAVWL
tQVWX
tQVWH
tWHQX
tRLAZ
tWHAX
tWHLH
3tCLCL - d
3tCLCL - d
tCLCL - d
tCLCL - d
WR Pulse Width(5)
RD Low to Valid Data In
Data Hold after RD
2.5tCLCL - d
tCLCL - d
0
0
Data Float after RD
tCLCL - d
4tCLCL - d
tCLCL - d
2tCLCL - d
ALE Low to Valid Data In
Address to Valid Data In
ALE Low to RD or WR Low
Address to RD or WR Low
Data Valid to WR Transition
Data Valid to WR High
Data Hold after WR
4.5tCLCL - d(2)
1.5tCLCL + d
2.5tCLCL - d(2)
tCLCL + d
1.5tCLCL - d
2tCLCL - d(2)
1tCLCL - d(2)
4tCLCL - d(2)
1tCLCL - d(3)
tCLCL - d
1.5tCLCL - d(2)
0.5tCLCL - d(2)
1.5tCLCL - d(2)
0.5tCLCL - d(3)
RD Low to Address Float
Address Hold after RD or WR High
RD or WR High to ALE High
-1tCLCL + d(2)
-0.5tCLCL + d(2)
1tCLCL - d(3)
0.5tCLCL - d
0.5tCLCL - d(3)
tCLCL - d
0.5tCLCL + d
Notes: 1. Compatibility Mode timing for MOVX also applies to Fast Mode during exeternal execution of MOVX.
2. This assumes 50% clock duty cycle. The half period depends on the clock high value tCHCX (high duty cycle).
3. This assumes 50% clock duty cycle. The half period depends on the clock low value tCLCX (low duty cycle).
4. In some cases parameter tLHLL may have a minimum of 0.5tCLCL during Fast mode external execution with DISALE = 0.
5. The strobe pulse width may be lengthened by 1, 2 or 3 additional tCLCL using wait states.
98
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Figure 18-6. External Program Memory Read Cycle
tLHLL
ALE
tPLPH
tAVLL
tLLIV
tPLIV
tLLPL
PSEN
tPXAV
tPLAZ
tPXIZ
tPXIX
tLLAX
A0 - A7
INSTR IN
A0 - A7
PORT 0
PORT 2
tAVIV
A8 - A15
A8 - A15
Figure 18-7. External Data Memory Read Cycle
tLHLL
ALE
tLLDV
tLLWL
tWHLH
tRLRH
RD
tRLAZ
tRLDV
tRHDX
DATA IN
tRHDZ
tAVLL
tLLAX
PORT 0
PORT 2
A0 - A7
tAVWL
tAVDV
A8 - A15 FROM DPH OR P2.0 - P2.7
tWHAX
P2
P2
Figure 18-8. External Data Memory Write Cycle
tLHLL
ALE
tLLWL
tWLWH
tWHLH
WR
tQVWX
tWHQX
tAVLL
tLLAX
PORT 0
PORT 2
A0 - A7
DATA OUT
tQVWH
tAVWL
A8 - A15 FROM DPH OR P2.0 - P2.7
tWHAX
P2
P2
99
3709B–MICRO–12/10
18.7 Serial Port Timing: Shift Register Mode
The values in this table are valid for VDD = 2.4V to 5.5V and Load Capacitance = 80 pF.
SMOD1 = 0
SMOD1 = 1
Symbol
tXLXL
Parameter
Min
4tCLCL -15
3tCLCL -15
tCLCL -15
0
Max
Min
Max
Units
µs
Serial Port Clock Cycle Time
2tCLCL -15
tCLCL -15
tCLCL -15
0
tQVXH
tXHQX
tXHDX
tXHDV
Output Data Setup to Clock Rising Edge
Output Data Hold after Clock Rising Edge
Input Data Hold after Clock Rising Edge
Input Data Valid to Clock Rising Edge
ns
ns
ns
15
15
ns
Figure 18-9. Shift Register Mode Timing Waveform
SMOD1 = 0
Clock
Write to SBUF
Output Data
0
1
2
3
4
5
6
7
Clear RI
Valid
Valid
Valid
Valid
Valid
Valid
Valid
Valid
Input Data
SMOD1 = 1
Clock
Write to SBUF
Output Data
0
1
2
3
4
5
6
7
Clear RI
Valid
Valid
Valid
Valid
Valid
Valid
Valid
Valid
Input Data
18.8 Test Conditions
18.8.1
AC Testing Input/Output Waveform(1)
Note:
1. AC Inputs during testing are driven at VDD - 0.5V for a logic “1” and 0.45V for a logic “0”. Timing measurements are made at
IH min. for a logic “1” and VIL max. for a logic “0”.
V
100
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
18.8.2
Float Waveform(1)
Note:
1. For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to
float when 100 mV change from the loaded VOH/VOL level occurs.
18.8.3
ICC Test Condition, Active Mode, All Other Pins are Disconnected
VDD
VDD
ICC
VDD
RST
GND
POL
(NC)
XTAL2
CLOCK SIGNAL
XTAL1
GND
18.8.4
ICC Test Condition, Idle Mode, All Other Pins are Disconnected
VDD
VDD
ICC
VDD
RST
POL
GND
(NC)
XTAL2
CLOCK SIGNAL
XTAL1
GND
18.8.5
Clock Signal Waveform for ICC Tests in Active and Idle Modes, tCLCH = tCHCL = 5 ns
VCC - 0.5V
0.7 VCC
tCHCX
0.2 VCC - 0.1V
tCLCH
0.45V
tCHCL
tCHCX
tCLCL
101
3709B–MICRO–12/10
18.8.6
ICC Test Condition, Power-down Mode, All Other Pins are Disconnected, VDD = 2V to 5.5V
VDD
VDD
ICC
VDD
RST
POL
GND
(NC)
XTAL2
XTAL1
GND
102
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
19. Ordering Information
19.1 Green Package Option (Pb/Halide-free)
Speed
(MHz)
Power
Supply
Ordering Code
Package
Operation Range
AT89LP51-20AU
AT89LP51-20PU
44A
40P6
44J
44M1
Industrial
(-40°C to 85° C)
20
20
2.4V to 5.5V
2.4V to 5.5V
AT89LP51-20JU
AT89LP51-20MU
AT89LP52-20AU
AT89LP52-20PU
44A
40P6
44J
44M1
Industrial
(-40°C to 85° C)
AT89LP52-20JU
AT89LP52-20MU
Package Types
44A
44-lead, Thin Plastic Quad Flat Package (TQFP)
40-lead, 0.600” Wide, Plastic Dual Inline Package (PDIP)
44-lead, Plastic J-leaded Chip Carrier (PLCC)
40P6
44J
44M1
44-pad, 7 x 7 x 1.0 mm Body, Plastic Very Thin Quad Flat No Lead Package (VQFN/MLF)
103
3709B–MICRO–12/10
20. Packaging Information
20.1 44A – TQFP
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
104
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
20.2 40P6 – PDIP
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
105
3709B–MICRO–12/10
20.3 44J – PLCC
1.14(0.045) X 45˚
PIN NO. 1
1.14(0.045) X 45˚
0.318(0.0125)
0.191(0.0075)
IDENTIFIER
D2/E2
E1
E
B1
B
e
A2
A1
D1
D
A
0.51(0.020)MAX
45˚ MAX (3X)
COMMON DIMENSIONS
(Unit of Measure = mm)
MIN
4.191
MAX
4.572
3.048
–
NOM
NOTE
SYMBOL
A
–
A1
A2
D
2.286
–
0.508
–
17.399
16.510
17.399
16.510
–
17.653
D1
E
–
16.662 Note 2
17.653
–
Notes:
1. This package conforms to JEDEC reference MS-018, Variation AC.
2. Dimensions D1 and E1 do not include mold protrusion.
Allowable protrusion is .010"(0.254 mm) per side. Dimension D1
and E1 include mold mismatch and are measured at the extreme
material condition at the upper or lower parting line.
E1
–
16.662 Note 2
16.002
D2/E2 14.986
–
B
0.660
0.330
–
–
0.813
3. Lead coplanarity is 0.004" (0.102 mm) maximum.
B1
e
0.533
1.270 TYP
10/04/01
DRAWING NO. REV.
44J
TITLE
2325 Orchard Parkway
San Jose, CA 95131
44J, 44-lead, Plastic J-leaded Chip Carrier (PLCC)
B
R
106
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
20.4 44M1 – VQFN/MLF
D
Marked Pin# 1 ID
E
SEATING PLANE
A1
TOP VIEW
A3
A
K
L
Pin #1 Corner
SIDE VIEW
D2
Pin #1
Triangle
Option A
COMMON DIMENSIONS
(Unit of Measure = mm)
1
2
3
MIN
0.80
–
MAX
1.00
0.05
NOM
0.90
NOTE
SYMBOL
A
E2
Option B
Option C
A1
A3
b
0.02
Pin #1
Chamfer
(C 0.30)
0.20 REF
0.23
0.18
6.90
5.00
6.90
0.30
7.10
5.40
7.10
D
7.00
D2
E
5.20
K
Pin #1
Notch
(0.20 R)
e
b
7.00
E2
e
5.00
5.20
0.50 BSC
0.64
5.40
BOTTOM VIEW
L
0.59
0.20
0.69
0.41
Note: JEDEC Standard MO-220, Fig. 1 (SAW Singulation) VKKD-3.
K
0.26
9/26/08
GPC
ZWS
DRAWING NO.
TITLE
REV.
44M1, 44-pad, 7 x 7 x 1.0 mm Body, Lead
Pitch 0.50 mm, 5.20 mm Exposed Pad,Thermally
Enhanced Plastic Very Thin Quad Flat No
Lead Package (VQFN)
Package Drawing Contact:
packagedrawings@atmel.com
44M1
H
107
3709B–MICRO–12/10
21. Revision History
Revision No.
History
Revision A – Sept. 2010
•
Initial Release
•
•
•
Added AT89LP51 device
Revision B – Dec. 2010
Updated Device IDs
Lowered Minimum Operating Voltage to 2.4V
108
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table of Contents
Features..................................................................................................... 1
Pin Configurations ................................................................................... 2
1
1.1
1.2
40-lead PDIP .....................................................................................................2
44-lead TQFP ....................................................................................................2
.................................................................................................................... 3
1.3
1.4
1.5
44-lead PLCC ....................................................................................................3
44-pad VQFN/QFN/MLF ....................................................................................3
Pin Description ..................................................................................................4
2
3
Overview ................................................................................................... 6
2.1
2.2
Block Diagram ...................................................................................................7
Comparison to AT89S51/52 ..............................................................................7
Memory Organization ............................................................................ 10
3.1
3.2
3.3
3.4
Program Memory .............................................................................................10
Internal Data Memory ......................................................................................12
External Data Memory .....................................................................................13
In-Application Programming (IAP) ...................................................................22
4
5
Special Function Registers ................................................................... 23
Enhanced CPU ....................................................................................... 24
5.1
5.2
5.3
Fast Mode ........................................................................................................24
Compatibility Mode ..........................................................................................25
Enhanced Dual Data Pointers .........................................................................25
6
7
System Clock ......................................................................................... 28
6.1
6.2
6.3
6.4
Crystal Oscillator .............................................................................................28
External Clock Source .....................................................................................29
Internal RC Oscillator ......................................................................................29
System Clock Divider ......................................................................................30
Reset ....................................................................................................... 31
7.1
7.2
7.3
7.4
7.5
Power-on Reset ...............................................................................................31
Brown-out Reset ..............................................................................................32
External Reset .................................................................................................32
Watchdog Reset ..............................................................................................33
Software Reset ................................................................................................33
i
3709B–MICRO–12/10
Table of Contents (Continued)
8
Power Saving Modes ............................................................................. 33
8.1
8.2
8.3
Idle Mode .........................................................................................................33
Power-down Mode ...........................................................................................34
Reducing Power Consumption ........................................................................36
9
Interrupts ................................................................................................ 36
9.1
Interrupt Response Time .................................................................................37
10 I/O Ports .................................................................................................. 40
10.1
10.2
10.3
Port Configuration ............................................................................................40
Port Read-Modify-Write ...................................................................................43
Port Alternate Functions ..................................................................................44
11 Timer 0 and Timer 1 ............................................................................... 45
11.1
11.2
11.3
11.4
11.5
Mode 0 – 13-bit Timer/Counter ........................................................................46
Mode 1 – 16-bit Timer/Counter ........................................................................46
Mode 2 – 8-bit Auto-Reload Timer/Counter .....................................................47
Mode 3 – 8-bit Split Timer ...............................................................................47
Clock Output (Pin Toggle Mode) .....................................................................48
12 Timer 2 .................................................................................................... 50
12.1
12.2
12.3
12.4
12.5
Timer 2 Registers ............................................................................................51
Capture Mode ..................................................................................................52
Auto-Reload Mode ...........................................................................................52
Baud Rate Generator ......................................................................................54
Frequency Generator (Programmable Clock Out) ...........................................55
13 External Interrupts ................................................................................. 56
14 Serial Interface (UART) .......................................................................... 56
14.1
14.2
14.3
14.4
14.5
14.6
14.7
Multiprocessor Communications .....................................................................58
Baud Rates ......................................................................................................58
Framing Error Detection ..................................................................................60
Automatic Address Recognition ......................................................................60
More About Mode 0 .........................................................................................62
More About Mode 1 .........................................................................................68
More About Modes 2 and 3 .............................................................................70
ii
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
AT89LP51/52 - Preliminary
Table of Contents (Continued)
15 Programmable Watchdog Timer ........................................................... 73
15.1
Software Reset ................................................................................................73
16 Instruction Set Summary ...................................................................... 75
17 Programming the Flash Memory .......................................................... 79
17.1
17.2
17.3
17.4
17.5
17.6
17.7
17.8
17.9
Physical Interface ............................................................................................79
Memory Organization ......................................................................................81
Command Format ............................................................................................82
Status Register ................................................................................................85
DATA Polling ...................................................................................................85
Flash Security ..................................................................................................85
User Configuration Fuses ................................................................................86
User Signature .................................................................................................87
Programming Interface Timing ........................................................................87
18 Electrical Characteristics ...................................................................... 92
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
Absolute Maximum Ratings* ...........................................................................92
DC Characteristics ...........................................................................................92
Typical Characteristics ....................................................................................93
Clock Characteristics .......................................................................................96
Reset Characteristics ......................................................................................97
External Memory Characteristics .....................................................................98
Serial Port Timing: Shift Register Mode ........................................................100
Test Conditions ..............................................................................................100
19 Ordering Information ........................................................................... 103
19.1
Green Package Option (Pb/Halide-free) ........................................................103
20 Packaging Information ........................................................................ 104
20.1
20.2
20.3
20.4
44A – TQFP ...................................................................................................104
40P6 – PDIP ..................................................................................................105
44J – PLCC ...................................................................................................106
44M1 – VQFN/MLF .......................................................................................107
21 Revision History ................................................................................... 108
iii
3709B–MICRO–12/10
iv
AT89LP51/52 - Preliminary
3709B–MICRO–12/10
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