SC68L198A1A_技术文档

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table of Contents

Register Map Detail . . . . . . . . . . . . . . . . . . . . . . . . 364

Reset Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

Device Configuration after Hardware Reset or CRa cmd=x1F 372

Cleared registers: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

Clears Modes for: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

Disables: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

Halts: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

Limitations: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

DC Electrical Specifications

(26C198 and 68C198) . . . . . . . . . . . . . . . . . . . . . . . 373

DC Electrical Specifications

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . 338

Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Absolute Maximum Ratings . . . . . . . . . . . . . . . . . 339

Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Functional Description . . . . . . . . . . . . . . . . . . . . . 340

Conceptual Overview . . . . . . . . . . . . . . . . . . . . . . . 340

Host Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Asynchronous bus cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Synchronous bus cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Timing Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Crystal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Sclk – System Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Baud Rate Generator BRG . . . . . . . . . . . . . . . . . . . . . . . . 341

(26L198 and 68L198) . . . . . . . . . . . . . . . . . . . . . . . 376

AC Electrical Characteristics5 (26L198 and

68L198) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383

DESCRIPTION

BRG Counters (Used for random baud rate generation)

341

The Philips 26C198 Octal UART is a single chip CMOS–LSI

communications device that provides 8 full-duplex asynchronous

channels with significantly deeper 16 byte FIFOs, Automatic

in–band flow control using Xon/Xoff characters defined by the user

and address recognition in the wake up mode. Synchronous bus

interface is used for all communication between host and OCTART.

It is fabricated using Philips 1.0 micron CMOS technology that

combines the benefits of low cost, high density and low power

consumption.

Channel Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Character Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Interrupt Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

Global Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

I/O Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

Detailed Descriptions . . . . . . . . . . . . . . . . . . . . . . . 342

Receiver and Transmitter . . . . . . . . . . . . . . . . . . . 342

Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

Transmitter Status Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

Transmission of ”break” . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

1x and 16x modes, Transmitter . . . . . . . . . . . . . . . . . . . . . 343

Transmitter FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

1x and 16x mode, Receiver . . . . . . . . . . . . . . . . . . . . . . . . . 343

Receiver Status Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

Receiver FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

RxFIFO Status: Status reporting modes . . . . . . . . . . . . . . 344

I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

General Purpose Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Global Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Character Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Xon Xoff Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Multi-drop or Wake up or 9 bit mode . . . . . . . . . . . . . . . . . 345

Character Stripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Interrupt Arbitration and IRQN generation . . . . . . . . . . . . . . . . 345

IACKN Cycle, Update CIR . . . . . . . . . . . . . . . . . . . . . . . . . . 346

Polling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346

Enabling and Activating Interrupt sources . . . . . . . . . . . . . 346

Setting Interrupt Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . 346

Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . 347

Major Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Minor Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

Watch-dog Timer Time–out Mode . . . . . . . . . . . . . . . . . . . 348

Wake Up Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

Xon/Xoff Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

REGISTER DEfiniTIONS . . . . . . . . . . . . . . . . . . . . 351

MR – Mode Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

UCIR – Update CIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

The operating speed of each receiver and transmitter can be

selected independently from one of 22 fixed baud rates, a 16X clock

derived from one of two programmable baud rate counters or one of

three external 16X clocks (1 available at 1x clock rate). The baud

rate generator and counter can operate directly from a crystal or

from seven other external or internal clock inputs. The ability to

independently program the operating speed of the receiver and

transmitter makes the Octal UART particularly attractive for dual

speed full duplex channel applications such as clustered terminal

systems. The receivers and transmitters are buffered with FIFOs of

16 characters to minimize the potential for receiver overrun and to

reduce interrupt overhead. In addition, a handshaking capability and

in–band flow control are provided to disable a remote UART

transmitter when the receiver buffer is full or nearly so.

To minimize interrupt overhead an interrupt arbitration system is

included which reports the context of the interrupting UART via

direct access or through the modification of the interrupt vector. The

context of the interrupt is reported as channel number, type of

device interrupting ( receiver COS etc.) and, for transmitters or

receivers, the fill level of the FIFO.

The Octal UART provides a power down mode in which the

oscillator is stopped but the register contents are maintained. This

results in reduced power consumption of several orders of

magnitudes. The Octal UART is fully TTL compatible when

operating from a single +5V power supply. Operation at 3.3 volts is

maintained with CMOS interface levels.

General Purpose Output Pin Control . . . . . . . . 361

Register Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363

Register Map Summary . . . . . . . . . . . . . . . . . . . . . 363

The device also offered in a version which maintains TTL input and

output levels while operating with a 3.3 volt power supply.

336

1995 May 1

853-1756 15179

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Uses

Statistical Multiplexers

Data Concentrators

• IACKN and DACKN signal pins

• Watch dog timer for each receiver (64 receive clock counts)

Packet–switching networks

Process Control

Building or Plant Control

Laboratory data gathering

ISDN front ends

• Programmable Data Formats:

– 5 to 8 data bits plus parity

– Odd, even force or no parity

– 1, 1.5 or 2 stop bits

Computer Networks

• Flexible baud rate selection for receivers and transmitters:

– 22 fixed rates; 50 – 230.4K baud or 100 to 460.8K baud

Point–of–Sale terminals

Automotive, cab and engine controls

Entertainment systems

MIDDI keyboard control music systems

Theater lighting control

Terminal Servers

– Additional non–standard rates to 500K baud with internal

generators

– Two reload–counters provide additional programmable baud

rate generation

Computer–Printer/Plotter links

– External 1x or 16x clock inputs

– Simplified baud rate selection

• 1 MHz 1x and 16x data rates full duplex all channels.

• Parity, framing and overrun error detection

• False start bit detection

FEATURES

• Single 3.3v power supply

• Eight Philips industry standard full duplex UART channels

• Sixteen byte receiver FIFOs for each UART

• Line break detection and generation

• Programmable channel mode

– Normal(full duplex)

– Diagnostic modes

automatic echo

• Sixteen byte transmit FIFOs for each UART

• In band flow control using programmable Xon/Xoff characters

• Flow control using CTSN RTSN hardware handshaking

• Automatic address detection in multi-drop mode

• Three byte general purpose character recognition

• Fast data bus, 30 ns data bus release time, 125 ns bus cycle time

• Programmable interrupt priorities

local loop back

emote loop back

• Four I/O ports per UART for modem controls, clocks, RTSN, I/O

etc.

– All I/O ports equipped with ”Change of State Detectors”

• Two global inputs and two global outputs for general purpose I/O

• Power down mode

• Automatic identification of highest priority interrupt pending

• Global interrupt and control registers ease setup and interrupt

handling

• On chip crystal oscillator, 2–8 MHz

• Vectored interrupts with programmable interrupt vector formats

– Interrupt vector modified with channel number

– Interrupt vector modified with channel number and channel type

– Interrupt vector not modified

• TTL input levels. Outputs switch between full V and V

CC

SS

• High speed CMOS technology

• 68 pin PLCC

ORDERING CODE

V

CC

= 5V ±10%

PACKAGES

DWG #

1

Commercial

0°C to +70°C

Industrial

-40°C to +85°C

SC26C198A1A

SC68C198A1A

84-Pin Plastic Leaded Chip Carrier (PLCC)

SC26C198C1A

SC68C198C1A

SOT189-3

V

CC

= 3.3V ±10%

1

Commercial

0°C to +70°C

Industrial

-40°C to +85°C

SC26L198A1A

SC68L198A1A

84-Pin Plastic Leaded Chip Carrier (PLCC)

SC26L198C1A

SC68L198C1A

SOT189-3

NOTES:

1. For availability, please contact factory.

337

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

PIN CONFIGURATIONS

11

1

75

12

74

84-Pin PLCC

TOP VIEW

54

32

33

53

PINOUT

Function

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

Function

I/O1d

I/O2d

I/O3d

RxDd

Vss

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

Function

I/O2g

1

V

SS

CC

2

V

I/O1g

3

CEN

W_RN

A2

I/O0g

4

RxDg

TxDg

5

6

A1

TxDd

RESETN

Gin0

Gout0

D0

V

SS

7

A0

X1

X2

8

DACKN

I/O0a

I/O1a

RxDa

RxDb

I/O2a

I/O3a

TxDa

I/O0b

I/O1b

I/O2b

I/O3b

TxDb

I/O0c

Vss

9

TxDf

I/O3f

I/O2f

I/O1f

I/O0f

TxDe

I/O3e

I/O2e

I/O1e

RxDf

RxDe

I/O0e

IRQN

A7

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

D1

D2

D3

V

SS

CC

V

D4

D5

D6

D7

Gin1

I/O3h

I/O2h

I/O1h

I/O0h

Vss

I/O1c

I/O2c

I/O3c

TxDc

RxDc

I/O0d

A6

A5

A4

RxDh

TxDh

I/O3g

A3

IACKN

SCLK

338

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Pin Description

MNEMONIC

SClk

TYPE

DESCRIPTION

I

Host system clock. Used to time operations in the Host Interface and clock internal logic. Must be greater

than twice the frequency of highest X1, Counter/Timer, TxC (1x) or RxC (1x) input frequency.

CEN

I

Chip select: Active low. When asserted, allows I/O access to OCTART registers by host CPU. W_RN signal

indicates direction. (Must not be active in IACKN cycle)

A(7:0)

D(7:0)

I

Address lines (A[6] is NOT used. See ”Host Interface” )

I/O

8–bit bi–directional data bus. Carries command and status information between 26C198 and the host CPU.

Used to convey parallel data for serial I/O between the host CPU and the 26C198

W_RN

DACKN

IRQN

I

Write Read not control: When high indicates that the host CPU will write to a 26C198 register or transmit FIFO.

When low, indicates a read cycle. 0 = Read; 1 = Write

O

I

Data Acknowledge: Active low. When asserted, it signals that the last transfer of the D lines is complete.

Open drain.

Interrupt Request: Active low. When asserted, indicates that the 26C198 requires service for pending

interrupt(s). Open drain.

IACKN

Interrupt Acknowledge: Active low. When asserted, indicates that the host CPU has initiated an interrupt

acknowledge cycle. (Do not use CEN in an IACKN cycle)

TD(a–h)

O

I

Transmit Data: Serial outputs from the 8 UARTs.

RD(a–h)

I/O0(a–d)

I/O1(a–d)

I/O2(a–d)

I/O3(a–d)

Receive Data: Serial inputs to the 8 UARTs

I/O

I

Input/Output 0: Multi–use input or output pin for the UART.

Input/Output 1: Multi–use input or output pin for the UART.

Input/Output 2: Multi–use input or output pin for the UART.

Input/Output 3: Multi–use input or output pin for the UART.

Global general purpose inputs, available to any/all channels.

Global general purpose outputs, available from any channel.

G

(1:0)

IN

0

OUT

O

RESETN

X1/CCLK

X2

I

Master reset: Active Low. Must be asserted at power up and may be asserted at other times to reset and

restart the system. See “Reset Conditions” at end of register map. Minimum width 10 SCLK.

I

O

I

Crystal 1 or Communication Clock: This pin may be connected to one side of a 2–8 MHz crystal. It may

alternatively be driven by an external clock in this frequency range. Standard frequency = 3.6864 MHz

Crystal 2: If a crystal is used, this is the connection to the second terminal. If a clock signal drives X1, this pin

must be left unconnected.

Power Supplies

16 pins total 8 pins for Vss, 8 pins for Vcc

NOTE: Many output pins will have very fast edges, especially when lightly loaded (less than 20 pf.) These edges may move as fast as 1 to 3 ns

fall or rise time. The user must be aware of the possible generation of ringing and reflections on improperly terminated interconnections. See

previous note on Sclk noise under pin assignments.

ABSOLUTE MAXIMUM RATINGS

SYMBOL

PARAMETER

RATING

UNIT

°C

V

T

A

Operating ambient temperature range

Storage temperature range

See Note 3

-65 to +150

-0.5 to +7.0

T

STG

V

CC

Voltage from V to GND

DD

V

SS

Voltage from any pin to GND

-0.5 to V + 0.5

V

CC

PD5

PD3

Power Dissipation at V = 5.0 Volts

1.2

0.5

W

CC

Power Dissipation at V = 3.3 Volts

W

CC

NOTES:

1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and

the functional operation of the device at these or any other conditions above those indicated in the Operation Section of this specification is

not implied.

339

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

BLOCK DIAGRAM

FULL DUPLEX UART CHANNEL

INPUT BUFFERS AND OUTPUT DRIVERS

SD00193

Block Diagram SC26/68C198

As shown in the block diagram, the Octal UART consists of: an

interrupt arbiter, host interface, timing blocks and eight UART

channel blocks. The eight channels blocks operate independently,

interacting only with the timing, host I/F and interrupt blocks.

cycles after CEN is recognized. These four cycles are the C1, C2,

C3, C4 periods shown in the timing diagrams. DACKN always

occurs in the C4 time and occurs approximately 18 ns after the

rising edge of C4.

Addressing of the various functions of the OCTART is through the

address bus A(7:0). The 26C198 is compatible with the SC28L194

Quad UART in software and function. A[7], in a general sense, is

used to separate the data portion of the circuit from the control

portion.

FUNCTIONAL DESCRIPTION

The SC26C198 is composed of several functional blocks:

• Synchronous host interface block

Asynchronous bus cycle

• A timing block consisting of a common baud rate generator

making 22 industry standard baud rates and 2 16–bit counters

used for non–standard baud rate generation

The asynchronous mode requires one bus cycle of the chip select

(CEN) for each read or write to the chip. No more action will occur

on the bus after the C4 time until CEN is returned high.

• 4 identical independent full duplex UART channel blocks

• Interrupt arbitration system evaluating 24 contenders

• I/O port control section and change of state detectors.

Synchronous bus cycle

In the synchronous mode a read or write will be done every four

cycles of the Sclk. CEN does not require cycling but must remain

low to keep the synchronous accesses active. This provides a burst

mode of access to the chip.

In both cases each read or write operation(s) will be completed in

four (4) Sclk cycles. The difference in the two modes is only that the

asynchronous mode will not begin another bus cycle if the CEN

remains active after the four internal Sclk have completed. Internally

the asynchronous cycle will terminate after the four periods of Sclk

regardless of how long CEN is held active

CONCEPTUAL OVERVIEW

Host Interface

The Host interface is comprised of the signal pins CEN, W/RN,

IACKN, DACKN, IRQN Sclk and provides all the control for data

transfer between the external and internal data buses of the host

and the OCTART. The host interface operates in a synchronous

mode with the system (Sclk) which has been designed for a nominal

operating frequency of 33 MHz. The interface operates in either of

two modes; synchronous or asynchronous to the Sclk However

the bus cycle within the OCTART always takes place in four Sclk

In all cases the internal action will terminate at the withdrawal of

CEN. Synchronous CEN cycles shorter than multiples of four Sclk

cycles minus 1 Sclk and asynchronous CEN cycles shorter than four

Sclk cycles may cause short read or write cycles and produce

corrupted data transfers.

340

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Timing Circuits

BRG Timer Input frequency

2 @ 16 @ desired baud rate

_{n +}ǒ

Ǔ _{– 1}

The timing block consists of a crystal oscillator, a fixed baud rate

generator (BRG), a pair of programmable 16 bit register based

counters. A buffer for the System Clock generates internal timing for

processes not directly concerned with serial data flow.

Note: ’n’ may assume values of 0 and 1. In previous Philips data

communications controllers these values were not allowed.

The BRG timer input frequency is controlled by the BRG Timer

control register (BRGTCR)

Crystal Oscillator

The crystal oscillator operates directly from a crystal, tuned between

1.0 and 8.0 MHz, connected across the X1/CCLK and X2 inputs with

a minimum of external components. BRG values listed for the clock

select registers correspond to a 3.6864 MHz crystal frequency. Use

of a 7.3728 MHz crystal will double the Communication Clock

frequencies.

The frequency generated from the above formula will be at a rate 16

times faster than the desired baud rate. The transmitter and

receiver state machines include divide by 16 circuits which provide

the final frequency and provide various timing edges used in the

qualifying the serial data bit stream. Often this division will result in

a non–integer value; 26.3 for example. One may only program

integer numbers to a digital divider. There for 26 would be chosen.

If 26.7 was the result of the division then 27 would be chosen. This

gives a baud rate error of 0.3/26.3 or 0.3/26.7. which yields a

percentage error of 1.14% or 1.12% respectively; well within the

ability of the asynchronous mode of operation.

An external clock in the 100 KHz to 10 MHz frequency range may

be connected to X1/CCLK. If an external clock is used instead of a

crystal, X1/CCLK must be driven and X2 left floating. The X1 clock

serves as the basic timing reference for the baud rate generator

(BRG) and is available to the BRG timers . The X1 oscillator input

may be left unused if the internal BRG is not used and the X1 signal

is not selected for any counter input.

One should be cautious about the assumed benign effects of small

errors since the other receiver or transmitter with which one is

communicating may also have a small error in the precise baud rate.

In a ”clean” communications environment using one start bit, eight

data bits and one stop bit the total difference allowed between the

transmitter and receiver frequency is approximately 4.6%. Less

than eight data bits will increase this percentage.

Sclk – System Clock

A clock frequency, within the limits specified in the electrical

specifications, must be supplied for the system clock Sclk. To

ensure the proper operation of internal controllers, the Sclk

frequency provided, must be strictly greater than twice the frequency

of X1 crystal clock, or any external 1x data clock input. The system

clock serves as the basic timing reference for the host interface and

other internal circuits.

Channel Blocks

There are eight channel blocks, each containing an I/O port control,

a data format control, and a single full duplex UART channel

consisting of a receiver and a transmitter with their associated 16

byte FIFOs. Each block has its own status register, interrupt status

and interrupt mask registers and their interface to the interrupt

arbitration system.

Baud Rate Generator BRG

The baud rate generator operates from the oscillator or external

X1/CCLK clock input and is capable of generating 22 commonly

used data communications baud rates ranging from 50 to 230.4K

baud. These common rates may be doubled (up to 460.8 and 500K

baud) when faster clocks are used on the X1/X2 clock inputs. (See

Receiver and Transmitter Clock Select Register descriptions.) All of

these are available simultaneously for use by any receiver or

transmitter. The clock outputs from the BRG are at 16X the actual

baud rate.

A highly programmable character recognition system is also

included in each block. This system is used for the Xon/Xoff flow

control and the multi-drop (”9 bit mode”) address character

recognition. It may also be used for general purpose character

recognition.

Four I/O pins are provided for each channel. These pins are

configured individually to be inputs or outputs. As inputs they may

be used to bring external data to the bus, as clocks for internal

functions or external control signals. Each I/O pin has a ”Change of

State” detector. The change detectors are used to signal a change

in the signal level at the pin (Either 0 to 1 or 1 to 0). The level

change on these pins must be stable for 25 to 50 Us (two edges of

the 38.4 KHz baud rate clock) before the detectors will signal a valid

change. These are typically used for interface signals from modems

to the OCTART and from there to the host. See the description of

the ”UART channel” under detailed descriptions below.

BRG Counters (Used for random baud rate generation)

The two BRG Timers are programmable 16 bit dividers that are used

for generating miscellaneous clocks. These clocks may be used by

any or all of the receivers and transmitters in the Octart or output on

the general purpose output pin GPO.

Each timer unit has eight different clock sources available to it as

described in the BRG Timer Control Register. (BRGTCR). Note

that the timer run and stop controls are also contained in this

register. The BRG Timers generate a symmetrical square wave

whose half period is equal in time to the division of the selected

BRG Timer clock source by the number loaded to the BRG Timer

Reload Registers ( BRGTRU and BRGTRL). Thus, the output

frequency will be the clock source frequency divided by twice the

value loaded to the BRGTRU and BRGTRL registers. This is the

result of counting down once for the high portion of the output wave

and once for the low portion.

Character Recognition

Character recognition is specific to each of the eight UARTs. Three

programmable characters are provided for the character recognition

for each channel. The three are general purpose in nature and may

be set to only cause an interrupt or to initiate some rather complex

operations specific to ”Multi-drop” address recognition or in–band

Xon/Xoff flow control.

Whenever the these timers are selected via the receiver or

transmitter Clock Select register their output will be configured as a

16x clock for the respective receiver or transmitter. Therefore one

needs to program the timers to generate a clock 16 times faster than

the data rate. The formula for calculating ’n’, the number loaded to

the BRGTRU and BRGTRL registers, is shown below.

Character recognition is accomplished via CAM memory. The

Content Addressable Memory continually examines the incoming

data stream. Upon the recognition of a control character appropriate

bits are set in the Xon/Xoff Interrupt Status Register (XISR) and

Interrupt Status Register (ISR). The setting of these bit(s) will

341

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

initiate any of the automatic sequences or and/or an interrupt that

may have enabled via the MR0 register.

content of the CIR (Current Interrupt Register) as a result of an

interrupt arbitration. In other words they are indirect registers

contained in the Current Interrupt Register (CIR) which the CIR uses

to point to the source and context of the OCTART sub circuit

presently causing an interrupt. The principle purpose of these

”registers” is improving the efficiency of the interrupt service.

The characters of the recognition system are not controlled by the

software or hardware reset. They do not have a pre-defined “reset

value”. They may, however, be loaded by a “Gang White” or “Gang

Load” command as described in the “Xon Xoff Characters”

paragraph.

The global registers and the CIR update procedure are further

described in the Interrupt Arbitration system

Note: Character recognition is further described in the Minor Modes

of Operation.

I/O Ports

Each of the eight UART blocks contains an I/O section of four ports.

These ports function as a general purpose post section which

services the particular UART they are associated with. External

clocks are input and internal clocks are output through these ports.

Each of the four pins has a change of state detector which will signal

a change (0 to 1 or 1 to 0) at the pin. The change of state detectors

are individually enabled and may be set to cause and interrupt.

Interrupt Control

The interrupt system determines when an interrupt should be

asserted thorough an arbitration (or bidding) system. This

arbitration is exercised over the several systems within the OCTART

that may generate an interrupt. These will be referred to as

”interrupt sources”. There are 64 in all. In general the arbitration is

based on the fill level of the receiver FIFO or the empty level of the

transmitter FIFO. The FIFO levels are encoded into a four bit

number which is concatenated to the channel number and source

identification code. All of this is compared (via the bidding or

arbitration process) to a user defined ”threshold”. When ever a

source exceeds the numerical value of the threshold the interrupt

will be generated.

These pins will normally be used for flow control hand–shaking and

the interface to a modem. Their control is further described in I/O

Ports section and the I/OPCR register.

DETAILED DESCRIPTIONS

At the time of interrupt acknowledge (IACKN) the source which has

the highest bid (not necessarily the source that caused the interrupt

to be generated) will be captured in a ”Current Interrupt Register”

(CIR). This register will contain the complete definition of the

interrupting source: channel, type of interrupt (receiver, transmitter,

change of state, etc.), and FIFO fill level. The value of the bits in the

CIR are used to drive the interrupt vector and global registers such

that controlling processor may be steered directly to the proper

service routine. A single read operation to the CIR provides all the

information needed to qualify and quantify the most common

interrupt sources.

RECEIVER AND TRANSMITTER

The Octal UART has eight full-duplex asynchronous

receiver/transmitters. The operating frequency for the receiver and

transmitter can be selected independently from the baud rate

generator, the counter , or from an external input. Registers that are

central to basic full-duplex operation are the mode registers (MR0,

MR1 and MR2), the clock select registers (RxCSR and TxCSR), the

command register (CR), the status register (SR), the transmit

holding register (TxFIFO), and the receive holding register

(RxFIFO).

Transmitter

The interrupt sources for each channel are listed below.

The transmitter accepts parallel data from the CPU and converts it

to a serial bit stream on the TxD output pin. It automatically sends a

start bit followed by the programmed number of data bits, an

optional parity bit, and the programmed number of stop bits. The

least significant bit is sent first. Each character is always ”framed”

by a single start bit and a stop bit that is 9/16 bit time or longer. If a

new character is not available in the TxFIFO, the TxD output

remains high, the ”marking” position, and the TxEMT bit in the SR is

set to 1.

• Transmit FIFO empty level for each channel

• Receive FIFO Fill level for each channel

• Change in break received status for each channel

• Receiver with error for each channel

• Change of state on channel input pins

• Receiver Watch-dog Time out Event

• Xon/Xoff character recognition

Transmitter Status Bits

The SR (Status Register, one per UART) contains two bits that show

the condition of the transmitter FIFO. These bits are TxRDY and

TxEMT. TxRDY means the TxFIFO has space available for one or

more bytes; TxEMT means The TxFIFO is completely empty and

the last stop bit has been completed. TxEMT can not be active

without TxRDY also being active. These two bits will go active upon

initial enabling of the transmitter. They will extinguish on the disable

or reset of the transmitter.

• Address character recognition

Associated with the interrupt system are the interrupt mask register

(IMR) and the interrupt status register (ISR) resident in each UART.

Programming of the IMR selects which of the above sources may

enter the arbitration process. Only the bidders in the ISR whose

associated bit in the IMR is set to one (1) will be permitted to enter

the arbitration process. The ISR can be read by the host CPU to

determine all currently active interrupting conditions. For

convenience the bits of the ISR may be masked by the bits of the

IMR. Whether the ISR is read unmasked or masked is controlled by

the setting of bit 6 in MR1.

Transmission resumes and the TxEMT bit is cleared when the CPU

loads at least one new character into the TxFIFO. The TxRDY will

not extinguish until the TxFIFO is completely full. The TxRDY bit will

always be active when the transmitter is enabled and there is at

lease one open position in the TxFIFO.

Global Registers

The ”Global Registers”, 19 in all, are driven by the interrupt system.

These are not real hardware devices. They are defined by the

The transmitter is disabled by reset or by a bit in the command

register (CR). The transmitter must be explicitly enabled via the CR

before transmission can begin. Note that characters cannot be

342

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

loaded into the TxFIFO while the transmitter is disabled, hence it is

necessary to enable the transmitter and then load the TxFIFO. It is

not possible to load the TxFIFO and then enable the transmission.

user to modify this characteristic so that bidding will not start until

one of four levels (empty, 3/4 empty, 1/2 empty, not full) have been

reached. As will be shown later this feature may be used to make

slight improvements in the interrupt service efficiency. A similar

system exists in the receiver.

Note the difference between transmitter disable and transmitter

reset. The transmitter may by reset by a hardware or software. The

software reset is issued through command 3x of the Command

register (CR). The disable is done by setting the transmitter disable

bit also in the command register. If the transmitter is disabled, it

continues operating until the character currently being transmitted, if

any, is completely sent, including the stop bit. When reset the

transmitter stops immediately, drives the transmitter serial data out

put to a high level and discards any data in the TxFIFO.

Receiver

The receiver accepts serial data on the RxD pin, converts the serial

input to parallel format, checks for start bit, stop bit, parity bit (if

any),framing error or break condition, and presents the assembled

character and its status condition to the CPU via the RxFIFO. Three

status bits are FIFOed with each character received. The RxFIFO is

really 11 bits wide; eight data and 3 status. Unused FIFO bits for

character lengths less than 8 bits are set to zero. It is important to

note that receiver logic considers the entire message to be

contained within the start bit to the stop bit. It is not aware that a

message may contain many characters. The receiver returns to its

idle mode at the end of each stop bit! As described below it

immediately begins to search for another start bit which is normally,

of course, immediately forth coming.

Transmission of ”break”

Transmission of a break character is often needed as a

synchronizing condition in a data stream. The ”break” is defined as

a start bit followed by all zero data bits by a zero parity bit (if parity is

enabled) and a zero in the stop bit position. The forgoing is the

minimum time to define a break. The transmitter can be forced to

send a break (continuous low condition) by issuing a start break

command via the CR. This command does not have any timing

associated with it. Once issued the TxD output will be driven low

(the spacing condition) and remain there until the host issues a

command to ”stop break” via the CR or the transmitter is issued a

software or hardware reset. In normal operation the break is usually

much longer than one character time.

1x and 16x mode, Receiver

The receiver operates in one of two modes; 1x and 16x. Of the two,

the 16x is more robust and the preferred mode. Although the 1x

mode may allow a faster data rate is does not provide for the

alignment of the receiver 1x data clock to that of the transmitter.

This strongly implies that the 1x clock of the remote transmitter is

available to the receiver; the two devices are physically close to

each other.

1x and 16x modes, Transmitter

The transmitter clocking has two modes: 16x and 1x. Data is

always sent at the 1x rate. However the logic of the transmitter may

be operated with a clock that is 16 times faster than the data rate or

at the same rate as the data i.e. 1x. All clocks selected internally

for the transmitter (and the receiver) will be 16x clocks. Only when

an external clock is selected may the transmitter logic and state

machine operate in the 1x mode. The 1x or 16x clocking makes

little difference in transmitter operation. (this is not true in the

receiver) In the 16X clock mode the transmitter will recognize a byte

in the TxFIFO within 1/16 to 2/16 bit time and thus begin

transmission of the start bit; in the 1x mode this delay may be up to

2 bit times.

The 16x mode operates the receiver logic at a rate 16 times faster

than the 1x data rate. This allows for validation of the start bit,

validation of level changes at the receiver serial data input (RxD),

and a stop bit length as short as 9/16 bit time. Of most importance

in the 16x mode is the ability of the receiver logic to align the phase

of the receiver 1x data clock to that of the transmitter with an

accuracy of less than 1/16 bit time.

When the receiver is enabled ( via the CR register) it begins looking

for a high to low (mark to space) transition on the RxD input pin. If a

transition is detected, an internal counter running at 16 times the

data rate is reset to zero. If the RxD remains low and is still low

when the counter reaches a count of 7 the receiver will consider this

a valid start bit and begin assembling the character. If the RxD input

returns to a high state the receiver will reject the previous high to low

(mark to space) transition on the RxD input pin. This action is the

”validation” of the start bit and also establishes the phase of the

receiver 1x clock to that of the transmitter The counter operating at

16x the data rate is the generator for the 1x data rate clock. With

the phase of the receiver 1x clock aligned to the falling of the start

bit (and thus aligned to the transmitter clock) AND with a valid start

bit having been verified the receiver will continue receiving bits by

sampling the RxD input on the rising edge of the 1x clock that is

being generated by the above mentioned counter running 16 times

the data rate. Since the falling edge of the 1x clock was aligned to

falling edge of the start bit then the rising of the clock will be in the

”center” of the bit cell.

Transmitter FIFO

The transmitter buffer memory is a 16 byte by 8 bit ripple FIFO. The

host writes characters to this buffer. This buffer accepts data only

when the transmitter is enabled. The transmitter state machine

reads them out in the order they were received and presents them to

the transmitter shift register for serialization. The transmitter adds

the required start, parity and stop bits as required the MR2 register

programming. The start bit (always one bit time in length) is sent

first followed by the least significant bit (LSB) to the most significant

bit (MSB) of the character, the parity bit (if used) and the required

stop bit(s).

Logic associated with the FIFO encodes the number of empty

positions available in a four bit value. This value is concatenated

with the channel number and type interrupt type identifier and

presented to the interrupt arbitration system. The encoding of the

”positions empty” value is always 1 less than the number of

available positions. Thus, an empty TxFIFO will bid with the value

or 15; when full it will not bid at all; one position empty bids with the

value 0. A full FIFO will not bid since a character written to it will be

lost

This action will continue until a full character has been assembled.

Parity , framing, and stop bit , and break status is then assembled

and the character and its status bits are loaded to the RxFIFO At

this point the receiver has finished its task for that character and will

immediately begin the search for another start bit.

Receiver Status Bits

Normally a TxFIFO will present a bid to the arbitration system when

ever it has one or more empty positions. The MR0[5:4] allow the

There are five (5) status bits that are evaluated with each byte (or

character) received: received break, framing error, parity error,

343

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

overrun error, and change of break. The first three are appended to

each byte and stored in the RxFIFO. The last two are not

necessarily related to the a byte being received or a byte that is in

the RxFIFO. They are however developed by the receiver state

machine

(one or more filled, 1/2 filled, 3/4 filled, full) have been reached. As

will be shown later this feature may be used to make slight

improvements in the interrupt service efficiency. A similar system

exists in the transmitter.

RxFIFO Status: Status reporting modes

. The ”received break” will always be associated with a zero byte in

the RxFIFO. It means that zero character was a break character

and not a zero data byte. The reception of a break condition will

always set the ”change of break” (see below) status bit in the

Interrupt Status Register(ISR).

The description below applies to the upper three bits in the ”Status

Register” These three bits are not ”in the status register”; They are

part of the RxFIFO. The three status bits at the top of the RxFIFO

are presented as the upper three bits of the status register included

in each UART.

The error status of a character , as reported by a read of the SR

(status register upper three bits) can be provided in two ways, as

programmed by the error mode control bit in the mode register:

”Character mode ” or the ”Block Mode”. The block mode may be

further modified (via a CR command) to set the status bits as the

characters enter the FIFO or as they are read from the FIFO.

A framing error occurs when a non zero character was seen and

that character has a zero in the stop bit position.

The parity error indicates that the receiver generated parity was not

the same as that sent by the transmitter.

The overrun error occurs when the RxFIFO is full, the receiver shift

register is full and another start bit is detected. At this moment the

receiver has 17 valid characters and the start bit of the 18th has

been seen. At this point the host has approximately 7/16 bit time to

read a byte from the RxFIFO or the overrun condition will be set and

the 18th character will overrun the 17th and the 19th the 18th and so

on until an open position in the RxFIFO is seen. The meaning of the

overrun is that data has been lost. Data in the RxFIFO remains

valid. The receiver will begin placing characters in the RxFIFO as

soon as a position becomes vacant.

In the ’character’ mode, status is provided on a character by

character basis as the characters are read from the RxFIFO: the

”status” applies only to the character at the top of the RxFIFO – The

next character to be read

In the ’block’ mode, the status provided in the SR for these three bits

is the logical OR of the status for all characters coming to the top of

the RxFIFO, since the last reset error command was issued. In this

mode each of the status bits stored in the RxFIFO are passed

through a latch as they are sequentially read. If any of the

Note: Precaution must be taken when reading an overrun FIFO.

There will be 16 valid characters. Data will begin loading as soon as

the first character is read. The 17 character will have been

characters has an error bit set then that latch will set and remain set

until reset with an ”Reset Error” command from the command

register or a receiver reset. The purpose of this mode is indicating

an error in the data block as opposed to an error in a character

th.

received as valid but it will not be known how many characters were

th.

lost between the two characters of the 16 and 17 reads of the

RxFIFO

The latch used in the block mode to indicate ”problem data” is

usually set as the characters are read out of the RxFIFO. Via a

command in the CR the latch may be configured to set the latch as

the characters are pushed (loaded to) the RxFIFO. This gives the

advantage of indicating ”problem data” 16 characters earlier .

The ”Change of break” means that either a break has been detected

or that the break condition has been cleared. This bit is available in

the ISR. The beginning of a break will be signaled by the break

change bit being set in the ISR AND the received break bit being set

in the SR. At the termination of the break condition only the change

of break in the ISR will be set. After the break condition is detected

the termination of the break will only be recognized when the RxD

input has returned to the high state for two successive edges of the

1x clock; 1/2 to 1 bit time.

In either mode, reading the SR does not affect the RxFIFO. The

RxFIFO is ’popped’ only when the RxFIFO is read. Therefore, the

SR should be read prior to reading the corresponding data

character.

If the RxFIFO is full when a new character is received, that

character is held in the receive shift register until a RxFIFO position

is available. At this time there are 17 valid characters in the

RxFIFO. If an additional character is received while this state exists,

the contents of the RxFIFO are not affected: the character

previously in the shift register is lost and the overrun error status bit,

SR[4], will be set upon receipt of the start bit of the new

(overrunning) character.

The receiver is disabled by reset or via CR commands. A disabled

receiver will not interrupt the host CPU under any circumstance in

the normal mode of operation. If the receiver is in the multi-drop or

special mode, it will be partially enabled and thus may cause an

interrupt. Refer to section on Wake–Up and minor modes and the

register description for MR1 for more information.

Receiver FIFO

I/O ports

The receiver buffer memory is a 16 byte ripple FIFO with three

status bits appended to each data byte. (The FIFO is then 16 11 bit

”words”). The receiver state machine gathers the bits from the

receiver shift register and the status bits from the receiver logic and

writes the assembled byte and status bits to the RxFIFO. Logic

associated with the FIFO encodes the number of filled positions for

presentation to the interrupt arbitration system. The encoding is

always 1 less than the number of filled positions. Thus, a full

RxFIFO will bid with the value or 15; when empty it will not bit at all;

one position occupied bids with the value 0. An empty FIFO will not

bid since no character is available. Normally RxFIFO will present a

bid to the arbitration system when ever it has one or more filled

positions. The MR2[3:2 bits allow the user to modify this

characteristic so that bidding will not start until one of four levels

Each of the eight UARTs includes four I/O ports equipped with

”change of state” detectors. The pins are individually programmable

for an input only function or one of three output functions. These

functions are controlled by the ”I/O Port Configuration Register

(I/OPCR)) They will normally be used for the RTSN–CTSN, DTR

hardware signals, RxD or TxD input or output clocks or switch inputs

as well as data out put from the I/OPIOR register.

It is important to note that the input circuits are always active. That

is the signal on a port, whether it is derived from an internal or

external source is always available to the internal circuits associated

with an input on that port.

The ”Change of State” (COS) detectors are sensitive to both a 1 to 0

or a 0 to 1 transition. The detectors are controlled by the internal

344

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

38.4 KHz baud rate and will signal a change when a transition has

been stable for two rising edges of this clock. Thus a level on the

I/O ports must be stable for 26 s to 52 s. Defining a port as an

output will disable the COS detector at that port. The condition of

the four I/O pins and their COS detectors is available at any time in

the IPR (Input Port Register)

Multi-drop or Wake up or 9 bit mode

This mode is used to address a particular UART among a group

connected to the same serial data source. Normally it is

accomplished by redefining the meaning of the parity bit such that it

indicates a character as address or data. While this method is fully

supported in the SC26C198 it also supports recognition of the

character itself. Upon recognition of its address the receiver will be

enabled and data pushed onto the RxFIFO.

The control of data and COS enable for these ports is through the

I/OPIOR register. This is a read/write register and gives individual

control to the enabling of the change of state detectors and also to

the level driven by I/O pins when programmed to drive the logic level

written to the four lower bits of the I/OPIOR. A read of this register

will indicate the data on the pin at the time of the read and the state

of the enabled COS detectors.

Further the Address recognition has the ability, if so programmed, to

disable (not reset) the receiver when an address is seen that is not

recognized as its own. The particular features of ”Auto Wake and

Auto Doze” are described in the detail descriptions below.

Note: Care should be taken in the programming of the character

recognition registers. Programming x’00, for example, may result in

a break condition being recognized as a control character. This will

be further complicated when binary data is being processed.

General Purpose Pins

In addition to the I/O ports for each UART four other ports are

provided which service the entire chip. Two are dedicated as inputs

Character Stripping

and one as an output. The G 1 and G 0 are the input pins; G 0

OUT

IN

The MR0 register provides for stripping the characters used for

character recognition. Recall that the character recognition may be

conditioned to control several aspects of the communication.

However this system is first a character recognition system. The

status of the various states of this system are reported in the XISR

and ISR registers. The character stripping of this system allows for

the removal of the specified control characters from the data stream:

two for the Xon /Xoff and one for the wake up. Via control in the

MR0 register these characters may be discarded (stripped) from the

data stream when the recognition system “sees” them or they may

be sent on the RxFIFO. Whether they are stripped or not the

recognition will process them according to the action requested: flow

control, wake up, interrupt generation, etc. Care should be

exercised in programming the stripping option if noisy environments

are encountered. If a normal character was corrupted to an Xoff

character turned off the transmitter and it was then stripped, then the

stripping action could make it difficult to determine the cause of

transmitter stopping.

the output. These ports are multiplexed to nearly every functional

unit in the chip. See the registers which describe the multitude of

connections available for these pins. The G

0 pin is highly

OUT

multiplexed output and is controlled by four (4) registers: GPOSR,

GPOR, GPOC and GPOD. The G 0 and G 1 pins are available to

IN

the receivers and transmitters, BRG counters and the G

0 pin.

OUT

Global Registers

The ”Global Registers”, 19 in all, are driven by the interrupt system.

These are not real hardware devices. They are defined by the

content of the CIR (Current Interrupt Register) as a result of an

interrupt arbitration. In other words they are indirect registers

pointed to by the content of the CIR. The list of global register

follows:

GIBCR The byte count of the interrupting FIFO

GICR

GITR

Channel number of the interrupting channel

Type identification of interrupting channel

GRxFIFO Pointer to the interrupting receiver FIFO

GTxFIFO Pointer to the interrupting transmitter FIFO

Interrupt Arbitration and IRQN generation

Interrupt arbitration is the process used to determine that an

interrupt request should be presented to the host. The arbitration is

carried out between the ”Interrupt Threshold” and the ”sources”

whose interrupt bidding is enabled by the IMR. The interrupt

threshold is part of the ICR (Interrupt Control Register) and is a

value programmed by the user. The ”sources” present a value to

the interrupt arbiter. That value is derived from four fields: the

channel number, type of interrupt source, FIFO fill level, and

programmable value. . Only when one or more of these values

exceeds the threshold value in the interrupt control register will the

interrupt request (IRQN) be asserted.

A read of the GRxFIFO will give the content of the RxFIFO that

presently has the highest bid value. The purpose of this system is

to enhance the efficiency of the interrupt system. The global

registers and the CIR update procedure are further described in the

Interrupt Arbitration system

Character Recognition

The character recognition circuits are basically designed to provide

general purpose character recognition. Additional control logic has

been added to allow for Xon/Xoff flow control and for recognition of

the address character in the multi-drop or ”wake–up” mode. This

logic also allows for the generation of an interrupts in either the

general purpose recognition mode or the specific conditions

mentioned above.

Following assertion of the IRQN the host will either assert

IACKN(Interrupt Acknowledge) or will use the command to ”Update

the CIR”. At the time either action is taken the CIR will capture the

value of the source that is prevailing in the arbitration process. (Call

this value the winning bid)

Xon Xoff Characters

The programming of these characters is usually done individually.

However a method has been provided to write to all of registers in

one operation. There are ”Gang Load” and a ”Gang Write”

commands provided in the channel A Command Register. When

these commands are executed all registers are programmed with

the same characters. The ”write” command loads a used defined

character; the ’load” command loads the standard Xon/Xoff

characters. Xon is x’11; Xoff x’13’. Any enabling of the Xon/Xoff

functions will use the contents of the Xon and Xoff character

registers as the basis on which recognition is predicated.

The value in the CIR is the central quantity that results from the

arbitration. It contains the identity of the interrupting channel, the

type of interrupt in that channel (RxD, TxD, COS etc.) the fill levels

of the RxD or TxD FIFOs and , in the case of an RxD interrupt an

indicator of error data or good data. It also drives the Global

Registers associated with the interrupt. Most importantly it drives

the modification of the Interrupt Vector.

The arbitration process is driven by the Sclk. It scans the 10 bits of

the arbitration bus at the Sclk rate developing a value for the CIR

345

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

every 22 Sclk cycles. New arbitration values presented to the

arbitration block during an arbitration cycle will be evaluated in the

next arbitration cycle.

and character count information. Optionally, the global interrupt

registers may be read for particular information about the interrupt

status or use of the global RxD and TxD registers for data transfer

as appropriate. The interrupt context will remain in the CIR until

another update CIR command or an IACKN cycle is initiated by the

host CPU occurs. The CIR loads with x’00 if Update CIR is asserted

when the arbitration circuit has NOT detected arbitration value that

exceeds the threshold value.

For sources other than receiver and transmitters the user may set

the high order bits of an interrupt source’s bid value, thus tailoring

the relative priority of the interrupt sources. The priority of the

receivers and transmitters is controlled by the fill level of their

respective FIFOs. The more filled spaces in the RxFIFO the higher

the bid value; the more empty spaces in the TxFIFO the higher its

priority. Channels whose programmable high order bits are set will

be given interrupt priority higher than those with zeros in their high

order bits , thus allowing increased flexibility. The transmitter and

receiver bid values contain the character counts of the associated

FIFOs as high order bits in the bid value. Thus, as a receiver’s

RxFIFO fills, it bids with a progressively higher priority for interrupt

service. Similarly, as empty space in a transmitter’s TxFIFO

increases, its interrupt arbitration priority increases.

Traditional methods of polling status registers may also be used.

They of course are less efficient but give the most variable and

quickest method of changing the order in which interrupt sources

are evaluated and interrogated.

Enabling and Activating Interrupt sources

An interrupt source becomes enabled when its interrupt capability is

set by writing to the Interrupt Mask Register, IMR. An interrupt

source can never generate an IRQN or have its ”bid” or interrupt

number appear in the CIR unless the source has been enabled by

the appropriate bit in an IMR.

IACKN Cycle, Update CIR

When the host CPU responds to the interrupt, it will usually assert

the IACKN signal low. This will cause the OCTART to generate an

IACKN cycle in which the condition of the interrupting device is

determined. When IACKN asserts, the last valid interrupt number is

captured in the CIR. The value captured presents most of the

important details of the highest priority interrupt at the moment the

IACKN (or the ”Update CIR” command) was asserted.

An interrupt source is active if it is presenting its bid to the interrupt

arbiter for evaluation. Most sources have simple activation

requirements. The watch-dog timer, break received, Xon/Xoff or

Address Recognition and change of state interrupts become active

when the associated events occur and the arbitration value

generated thereby exceeds the threshold value programmed in the

ICR (Interrupt Control Register).

The Octal UART will respond to the IACKN cycle with an interrupt

vector. The interrupt vector may be a fixed value, the content of the

Interrupt Vector Register, or ,when ”Interrupt Vector Modification is

enabled via ICR, it may contain codes for the interrupt type and/or

interrupting channel. This allows the interrupt vector to steer the

interrupt service directly to the proper service routine. The interrupt

value captured in the CIR remains until another IACKN cycle occurs

or until an ”Update CIR” command is given to the OCTART. The

interrupting channel and interrupt type fields of the CIR set the

current ”interrupt context” of the OCTART. The channel component

of the interrupt context allows the use of Global Interrupt Information

registers that appear at fixed positions in the register address map.

For example, a read of the Global RxFIFO will read the channel B

RxFIFO if the CIR interrupt context is channel b receiver. At another

time read of the GRxFIFO may read the channel D RxFIFO (CIR

holds a channel D receiver interrupt) and so on. Global registers

exist to facilitate qualifying the interrupt parameters and for writing to

and reading from FIFOs without explicitly addressing them.

The transmitter and receiver functions have additional controls to

modify the condition upon which the initiation of interrupt ”bidding”

begins: the TxINT and RxINT fields of the MR0 and MR2 registers.

These fields can be used to start bidding or arbitration when the

RxFIFO is not empty, 50% full, 75% full or 100% full. For the

transmitter it is not full, 50% empty, 75% empty and empty.

Example: To increase the probability of transferring the contents of a

nearly full RxFIFO, do not allow it to start bidding until 50% or 75%

full. This will prevent its relatively high priority from winning the

arbitration process at low fill levels. A high threshold level could

accomplish the same thing, but may also mask out low priority

interrupt sources that must be serviced. Note that for fast channels

and/or long interrupt latency times using this feature should be used

with caution since it reduces the time the host CPU has to respond

to the interrupt request before receiver overrun occurs.

Setting Interrupt Priorities

The bid or interrupt number presented to the interrupt arbiter is

composed of character counts, channel codes, fixed and

programmable bit fields. The interrupt values are generated for

various interrupt sources as shown in the table below: The value

represented by the bits 9 to 3 in the table below are compared

against the value represented by the “Threshold. The “Threshold”

,bits 6 to 0 of the ICR (Interrupt Control Register), is aligned such

that bit 6 of the threshold is compared to bit 9 of the interrupt value

generated by any of the sources. When ever the value of the

interrupt source is greater than the threshold the interrupt will be

generated.

The CIR will load with x’00 if IACKN or Update CIR is asserted when

the arbitration circuit is NOT asserting and interrupt. In this

condition there is no arbitration value that exceeds the threshold

value.

Polling

Many users prefer polled to interrupt driven service where there are

a large number of fast data channels and/or the host CPU’s other

interrupt overhead is low. The Octal UART is functional in this

environment.

The most efficient method of polling is the use of the ”update CIR”

command (with the interrupt threshold set to zero) followed by a

read of the CIR. This dummy write cycle will perform the same CIR

capture function that an IACKN falling edge would accomplish in an

interrupt driven system. A subsequent read of the CIR, at the same

address, will give information about an interrupt, if any. If the CIR

contains 0s, no interrupt is awaiting service. If the value is

The channel number arbitrates only against other channels. The

threshold is not used for the channel arbitration. This results in

channel D having the highest arbitration number. The decreasing

order is H to A. If all other parts of an arbitration are equal then the

channel number will determine which channel will dominate in the

arbitration process

non–zero, the fields of the CIR may be decoded for type, channel

.

346

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 1. Interrupt Arbitration Priority

Type

Receiver w/o error

B9

B8

B7

B6

B5

B4

B3

Bits 2:0

Channel No

RxFIFO Byte Count –1

0

1

0

1

0

1

Receiver w/ error

Transmitter

Channel No

000

0

TxFIFO Byte Count –1

Change of Break

Change of State

Xon/Xoff

Programmed Field

RxFIFO Byte Count –1

0

1

0

Address Recognition

Receiver Watch-dog

Threshold

As RxFIFO Above

Bits 6:0 of Interrupt Control Register

Note several characteristics of the above table in bits 6:3. These

bits contain the identification of the bidding source as indicated

below:

the DSR (Data Set Ready) signal from the modem. In this case its

arbitration value should be high. Once the DSR is recognized then

its arbitration value could be reduced or turned off.

x001

x101

xx00

0010

0110

0111

0011

Receiver without error

Receiver with error

Transmitter

There is a single arbiter interrupt number that is not associated with

any of the UART channels. It is the ”Threshold Value” and is

comprised of 7 bits from the Interrupt Control Register, ICR, and

three zeros in the channel field. It is only when one or more of

the enabled interrupt sources generates a arbitration value

larger than the threshold value that the IRQN will be asserted.

When the threshold bidding value is larger than any other bidding

value then the IRQN will be withdrawn. In this condition the CIR will

be loaded with if the IRQN or ”Update CIR” command is asserted.

Because the channels are numbered from 0 to 3 ( A to D) channel 3

will win the bid when all other parts of the bid are equal.

Change of Break

Change of State on I/O Ports

Xon/Xoff Event

Address Recognition

The codes form bits 6:3 drive part of the interrupt vector modification

and the Global Interrupt Type Register. The codes are unique to

each source type and Identify them completely. The channel

numbering progresses from ”a” to ”d” as the binary numbers 000 to

011 and identify the interrupting channel uniquely. As the channels

arbitrate ”d” will have the highest bidding value and ”a” the lowest

Note: Based on this coding for the receiver and transmitter, a

transmitter would not win a bid in the situation where the Count

Field = 0 unless the threshold value is equal or less than

0000011. A single empty slot is left in the TxFIFO or a single

filled slot in the RxFIFO will bid with a value of zero.

Note that the transmitter byte count is off–set from that of the

receiver by one bit. This is to give the receiver more authority in the

arbitration since and over–run receiver corrupts the message but an

under–run transmitter is not harmful. This puts some constraints on

how the threshold value is selected. If a threshold is chosen that

has its MSB set to one then a transmitter can never generate an

interrupt! Of course the counter point to this is the desire to set the

interrupt threshold high so interrupts occur only when a maximum or

near maximum number of characters may be transferred.

MODES OF OPERATION

Major Modes

Four major modes of operation (normal, auto echo, local loop back

and remote loop back) are provided and are controlled by MR2[7:6].

Three of these may be considered diagnostic. See the MR2 register

description.

To give some control over this dilemma control bits have been

provided in the MR0 and MR2 registers of each channel to

individually control when a receiver or transmitter may interrupt. The

use of these bits will prevent a receiver or a transmitter from

entering the arbitration process even though its FIFO fill level is

above that indicated by the threshold value set. The bits in the MR0

and MR2 register are named TxINT (MR0[5:4]) and RxINT

(MR2[3:2])

The normal mode is the usual mode for data I/O operation. Most

reception and transmission will use the normal mode.

In the auto echo mode, the transmitter automatically re-transmits

any character captured by the channel’s receiver. The receiver 1x

clock is used for the transmitter. This mode returns the received

data back to the sending station one bit time delayed from its

departure. Receiver to host communication is normal. Host to

transmitter communication has no meaning.

The watch-dog is included in the table above to show that it affects

the arbitration. It does not have an identity of its own. A barking

watch-dog will prevent any other source type from entering the

arbitration process except enabled receivers. The threshold is

effectively set to zero when any watch-dog times out. The receivers

arbitrate among them selves and the one with the highest fill level

will win the process. Note that the receiver wining the bid may not

be the one that caused the watch-dog to bark.

In the local loop back mode (used for diagnostic purposes) the

transmitter is internally connected to the receiver input. The

transmitter 1x clock used for the receiver. The RxD input pin is

ignored and the transmitter TxD output pin is held high. This

configuration allows the transmitter to send data to the receiver

without any external parameters to affect the transmission of data.

All status bits, interrupt conditions and processor interface operate

normally. It is recommended that this mode be used when

initially verifying processor to UART interface. The

The fields labeled ”Programmed Field” are the contents of the

Bidding Control Registers, BCRs, for these sources. Setting these

bits to high values can elevate the interrupt importance of the

sources they represent to values almost as high as a full receiver.

For example a COS event may be very important when it represents

communication between the transmitter and receiver is entirely

within the UART – it is essentially ”talking to itself”.

347

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

The remote loop back mode (also used for diagnostic purposes) is

similar to auto echo except that the characters are not sent to the

local CPU, nor is the receiver status updated. The received data is

sent directly to the transmitter where it is sent out on the TxD output.

The received data is not sent to the receive FIFO and hence the

host will not normally be participating in any diagnostics.

associated with address recognition, data handling, receiver enables

and disables. In both modes the meaning of the parity bit is

changed. It is often referred to as the A/D bit or the address/data

bit. It is used to indicate whether the byte presently in the receiver

shift register is an ”address” byte or a ”data” byte. ”1” usually means

address; ”0” data.

Its purpose is to allow several receivers connected to the same data

source to be individually addressed. Of course addressing could be

by group also. Normally the ”Master” would send an address byte to

all receivers ”listening” The receiver would then recognize its

address and enable itself receiving the following data stream. Upon

receipt of an address not its own it would then disable itself. As

descried below appropriate status bits are available to describe the

operation.

Minor Modes

The minor modes provide additional features within the major

modes. In general the minor modes provide a reduction in the

control burden and a less stringent interrupt latency time for the host

processor. These modes could be invoked in all of the major

modes.. However it may not be reasonable in many situations.

Watch-dog Timer Time–out Mode

Each receiver in the Octal UART is equipped with a watch-dog timer

that is enabled by the ”Watch-dog Timer Enable Register (WTER).

The watch-dog ”barks” (times out) if 64 counts of the receiver clock

(64 bit times) elapse with no RxFIFO activity. RxFIFO events are a

read of the RxFIFO or GRxFIFO, or the push of a received character

into the RxFIFO. The timer resets when the (G)RxFIFO is read or if

another character is pushed into the RxFIFO. The receiver

watch-dog timer is included to allow detection of the very last

character(s) of a received message that may be waiting in the

RxFIFO, but are too few in number to successfully initiate an

interrupt. The watch-dog timer is enabled for counting if the

channel’s bit in the Watch Dog Timer Control Register (WDTCR) is

set. Note: a read of the GRxFIFO will reset the watch-dog timer of

only the channel specified in the current interrupt context. Other

watch-dogs are unaffected.

Enabling the Wake Up mode

This mode is selected by programming bits MR1[4:3] to ’11’. The

sub modes are controlled by bits 6, 1, 0 in the MR0 register. Bit 6

controls the loading of the address byte to the RxFIFO and MR0[1:0]

determines the sub mode as shown in the following table.

MR0[1:0] = 00 Normal Wake Up Mode (default). Host controls

operation via interrupts and commands written to

the command register (CR).

MR0[1:0] = 01 Auto wake. Enable receiver on address

recognition for this station. Upon recognition of

its assigned address, in the Auto Wake mode,

the local receiver will be enabled and normal

receiver communications with the host will be

established.

MR0[1:0] = 10 Auto Doze. Disable receiver on address

recognition, not for this station. Upon recognition

of an address character that is not its own, in the

Auto Doze mode, the receiver will be disabled

and the address just received either discarded or

pushed to the RxFIFO depending on the

The watch-dog timer may generate an input to the interrupt arbiter if

IMR[6] is set. The status of the Watch-dog timer can be seen as Bit

6 of the Interrupt Status Register, ISR[6]. When a Watch-dog timer

that is programmed to generate an interrupt times out it enters the

arbitration process. It will then only allow receivers to enter the

enter the arbitration. All other sources are bidding sources are

disabled. The receivers arbitrate only amongst themselves.. The

receiver only interrupt mode of the interrupt arbiter continues until

the last watch-dog timer event has been serviced. While in the

receiver only interrupt mode, the control of the interrupt threshold

level is also disabled. The receivers arbitrate only between

themselves. The threshold value is ignored. The receiver with the

programming of MR0[6].

MR0[1:0] = 11 Auto wake and doze. Both modes above. The

programming of MR0[1:0] to 11 will enable both

the auto wake and auto doze features.

The enabling of the wake–up mode executes a partial enabling

of the receiver state machine. Even though the receiver has

been reset the wake up mode will over ride the disable and

reset condition.

most FIFO positions filled will win the bid. Hence the user need not

reduce the bidding threshold level in the ICR to see the interrupt

from a nearly empty RxFIFO that may have caused the watch-dog

time–out.

Normal Wake up (The default configuration)

In the default configuration for this mode of operation, a ’master’

station transmits an address character followed by data characters

for the addressed ’slave’ station. The slave stations, whose

receivers are normally disabled (not reset), examine the received

data stream and interrupts the CPU (by setting RxRDY) only upon

receipt of an address character. The CPU (host) compares the

received address to its station address and enables the receiver if it

wishes to receive the subsequent data characters. Upon receipt of

another address character, the CPU may disable the receiver to

initiate the process again

Note: When any watch-dog times our only the receivers arbitrate.

There is no increase in the probability of receiver being serviced

causing the overrun of another receiver since they will still have

priority based upon received character count.

The interrupt will be cleared automatically upon the push of the next

character received or when the RxFIFO or GRxFIFO is read. The

ICR is unaffected by the watch-dog time–out interrupt and normal

interrupt threshold level sensing resumes after the last watch-dog

timer event has been processed. If other interrupt sources are

active, the IRQN pin may remain low.

. A transmitted character consists of a start bit, the programmed

number of data bits, an address/data (A/D) bit, and the programmed

number of stop bits. The polarity of the transmitted A/D bit is

selected by the CPU by programming bit MR1[2]. MR1[2] = 0

transmits a zero in the A/D bit position which identifies the

corresponding data bits as data. MR1[2] = 1 transmits a one in the

A/D bit position which identifies the corresponding data bits as an

address. The CPU should program the mode register prior to

loading the corresponding data bytes into the TxFIFO.

Wake Up Mode

The SC26C198 provides two modes of this common asynchronous

“party line” protocol: the new automatic mode with 3 sub modes and

the default Host operated mode. The automatic mode has several

sub modes (see below). In the full automatic the internal state

machine devoted to this function will handle all operations

348

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

While in this mode, the receiver continuously looks at the received

data stream, whether it is enabled or disabled. If disabled, it sets

the RxRDY status bit and loads the character into the RxFIFO if the

received A/D bit is a one, but discards the received character if the

received A/D bit is a zero. If the receiver is enabled, all received

characters are transferred to the CPU via the RxFIFO. In either

case, the data bits are loaded into the data FIFO while the A/D bit is

loaded into the status FIFO position normally used for parity error

(SR[5]). Framing error, overrun error, and break detect operate

normally whether or not the receiver is enabled.

In–band flow control is a protocol for controlling a remote transmitter

by embedding special characters within the message stream, itself.

Two characters, Xon and Xoff, which do not represent normal

printable characters take on flow control definitions when the

Xon/Xoff capability is enabled. Flow control characters received

may be used to gate the channel transmitter on and off. This activity

is referred to as Auto–transmitter mode. To protect the channel

receiver from overrun, fixed fill levels (hardware set at 12

characters) of the RxFIFO may be employed to automatically insert

Xon/Xoff characters in the transmitter’s data stream. This mode of

operation is referred to as auto–receiver mode. Commands issued

by the host CPU via the CR can simulate all these conditions.

Automatic operation, Wake Up & Doze

The automatic configuration for this mode uses on-board

comparators to examine incoming address characters. Each UART

channel may be assigned a unique address character. See the

address register map and the description of the Address

Recognition Character Register (ARCR). The device may be

programmed to automatically awaken a sleeping receiver and/or

disable an active receiver based upon address characters received.

The operation of the basic receiver is the same as described above

for the default mode of wake–up operation except that the CPU

need not be interrupted to make a change in the receiver status.

Auto–transmitter mode

When a channel receiver pushes an Xoff character into the RxFIFO,

the channel transmitter will finish transmission of the current

character and then stop transmitting. A transmitter so idled can be

restarted by the receipt of an Xon character by the receiver, or by a

hardware or software reset. The last option results in the loss of the

un–transmitted contents of the TxFIFO. When operating in this

mode the Command Register commands for the transmitter are not

effective.

While idle data may be written to the TxFIFO and it continues to

present its fill level to the interrupt arbiter and maintains the integrity

of its status registers.

Three bits in the Mode Register 0, (MR0), control the address

recognition operation. MR0[6] controls the RxFIFO operation of the

received character; MR0[1:0] controls the wake up mode options. If

MR0[6] is set the address character will be pushed onto the

RxFIFO, otherwise the character will be discarded. (The charter is

stripped from the data stream) The MR0[1:0] bits set the options as

follows: A b’00 in this field, the default or power–on condition, puts

the device in the default (CPU controlled) wake up mode of

operation as described above. The auto–wake mode, enabled if

MR0[0] is set, will cause the dedicated comparators to examine

each address character presented by the receiver. If the received

character matches the reference character in ARCR, the receiver

Use of ’00’ as an Xon/Xoff character is complicated by the Receiver

break operation which pushes a ’00’ character on the RxFIFO. The

Xon/Xoff character detectors do not discriminate this case from an

Xon/Xoff character received through the RxD pin.

Note: To be recognized as an Xon or Xoff character, the receiver

must have room in the RxFIFO to accommodate the character. An

Xon/Xoff character that is received resulting in a receiver overrun

does not effect the transmitter nor is it pushed into the RxFIFO,

regardless of the state of the Xon/Xoff transparency bit, MR0(7).

will be enabled and all subsequent characters will be FIFOed until

another address event occurs or the host CPU disables the receiver

explicitly. The auto doze mode, enabled if MR0[1] is set, will

automatically disable the receiver if an address is received that does

not match the reference character in the ARCR.

Note: Xon /Xoff characters

The Xon/Xoff characters with errors will be accepted as valid. The

user has the option sending or not sending these characters to the

FIFO. Error bits associated with Xon/Xoff will be stored normally to

the receiver FIFO.

The channel’s transmitter may be programmed to automatically

transmit an Xoff character without host CPU intervention when the

RxFIFO fill level exceeds a fixed limit (12). In this mode, it will

conversely transmit an Xon character when the RxFIFO level drops

below a second fixed limit (8). A character from the TxFIFO that has

been loaded into the TxD shift register will continue to transmit.

Character(s) in the TxFIFO that have not been popped are

unaffected by the Xon or Xoff transmission. They will be transmitted

after the Xon/Xoff activity concludes.

The UART channel can present the address recognition event to the

interrupt arbiter for IRQN generation. The IRQN generation may be

masked by setting bit 5 of the Interrupt Mask Register, IMR. The bid

level of an address recognition event is controlled by the Bidding

Control Register, BCRA, of the channel.

Note: To ensure proper operation, the host CPU must clear any

pending Address Recognition interrupt before enabling a disabled

receiver operating in the Special or Wake–up mode. This may be

accomplished via the CR commands to clear the Address Interrupt

or by resetting the receiver.

If the fill level condition that initiates Xon activity negates before the

flow control character can begin transmission, the transmission of

the flow control character will not occur, i.e. either of the following

sequences may be transmitted depending on the timing of the FIFO

level changes with respect to the normal character times:

Xon/Xoff Operation

Receiver Mode

Since the receiving FIFO resources in the Octal UART are limited,

some means of controlling a remote transmitter is desirable in order

to lessen the probability of receiver overrun. The Octal UART

provides two methods of controlling the data flow. A hardware

assisted means of accomplishing control, the so–called out–of–band

flow control, and an in–band flow control method.

Character

Xoff

Character

Xon

Character

Hardware keeps track of Xoff characters sent that are not rescinded

by an Xon. This logic is reset by writing MR0(3) to ’0’. If the user

drops out of Auto–receiver mode while the XISR shows Xon as the

last character sent, the Xon/Xoff logic will not automatically send the

negating Xon.

The out–of–band flow control is implemented through the

CTSN–RTSN signaling via the I/O ports. The operation of these

hardware handshake signals is described in the receiver and

transmitter discussions.

Host mode

When neither the auto–receiver nor auto–transmitter modes are set,

the Xon/Xoff logic is operating in the host mode. In host mode, all

349

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

activity of the Xon/Xoff logic is initiated by commands to the CRx

command forces the transmitter to disable exactly as though an Xoff

character had been received by the RxFIFO. The transmitter will

remain disabled until the chip is reset or the CR(7:3) = 10110 (Xoff

resume) command is given. In particular, reception of an Xon or

disabling or re–enabling the transmitter will NOT cause resumption

of transmission. Redundant CRTXon/off commands, i.e. CRTXon

CRTXon, are harmless, although they waste time. A CRTXon may

be used to cancel a CRTXoff (and vice versa), but both may be

transmitted depending on the timing with the transmit state machine.

The kill CRTX command can be used to cleanly terminate any

CRTX commands pending with the minimum impact on the

transmitter.

Xon or Xoff character is pushed onto the RxFIFO for examination by

the host CPU. The MR0(7) function operates regardless of the

value in MR0(3:2)

Xon/Xoff Interrupts

The Xon/Xoff logic generates interrupts only in response to

recognizing either of the characters in the XonCR or XoffCR (Xon or

Xoff Character Registers). The transmitter activity initiated by the

Xon/Xoff logic or any CR command does not generate an interrupt.

The character comparators operate regardless of the value in

MR0(3:2). Hence the comparators may be used as general purpose

character detectors by setting MR0(3:2)=’00’ and enabling the

Xon/Xoff interrupt in the IMR.

The Octal UART can present the Xon/Xoff recognition event to the

interrupt arbiter for IRQN generation. The IRQN generation may be

masked by setting bit 4 of the Interrupt Mask Register, IMR. The bid

level of an Xon/Xoff recognition event is controlled by the Bidding

Control Register X, BCRX, of the channel. The interrupt status can

be examined in ISR[4]. If cleared, no Xon/Xoff recognition event is

interrupting. If set, an Xon or Xoff recognition event has been

detected. The X Interrupt Status Register, XISR, can be read for

details of the interrupt and to examine other, non–interrupting, status

of the Xon/Xoff logic. Refer to the XISR in the Register

Note: In no case will an Xon/Xoff character transmission be aborted.

Once the character is loaded into the TX Shift Register, transmission

continues until completion or a chip reset is encountered.

The kill CRTX command has no effect in either of the Auto modes.

Mode control

Xon/Xoff mode control is accomplished via the MR0. Bits 3 and 2

reset to zero resulting in all Xon/Xoff processing being disabled. If

MR0[2] is set, the transmitter may be gated by Xon/Xoff characters

received. If MR0[3] is set, the transmitter will transmit Xon and Xoff

when triggered by attainment of fixed fill levels in the channel

RxFIFO. The MR0[7] bit also has an Xon/Xoff function control. If

this bit is set, a received Xon or Xoff character is not pushed into the

Descriptions.

The character recognition function and the associated interrupt

generation is disabled on hardware or software reset

RxFIFO. If cleared, the power–on and reset default, the received

.

350

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

definitions that do not change in normal data handling. This section

is listed in the ”Register Map, Control”.

REGISTER DEFINITIONS

The operation of the Octal UART is programmed by writing control

words into the appropriate registers. Operational feedback is

provided via status registers which can be read by the host CPU.

The Octal UART addressing is loosely divided, by the address bit

A(7), into two parts:

2) That part concerned with the transmission and reception of the bit

streams.

This part concerns the data status, FIFO fill levels, data error

conditions, channel status, data flow control (hand shaking). This

section is listed in the ”Register Map, Data”.

1) That part which is concerned with the configuration of the chip

interface and communication modes.

The Global Configuration Control Register (GCCR) sets the type of

bus cycle, interrupt vector modification and the power up or down

mode.

This part controls the elements of host interface setup, interrupt

arbitration, I/O Port Configuration that part of the UART channel

Table 2. GCCR – Global Configuration Control Register

THIS IS A VERY IMPORTANT REGISTER! IT SHOULD BE THE FIRST REGISTER ADDRESSED DURING INITIALIZATION.

Bit 7

Reserved

Bit 6

Bit 5:3

Reserved

Bit 2:1

Bit 0

Sync bus cycles

IVC, Interrupt Vector Control

Power Down Mode

Reserved

0 – async cycles

1 – Sync,

non–pipe–lined cycle

00 – no interrupt vector

01 – IVR

10 – IVR + channel code

11 – IVR + interrupt type + channel code

0 – Device enabled

1 – Power down

Must be set to 0

Set to 0

GCCR(7): This bit is reserved for future versions of this device. If

not set to zero most internal addressing will be disabled!

transmission/reception activities cease, and all processing for input

change detection, BRG counter/timers and Address/Xon./Xoff

recognition is disabled.

GCCR(6): Bus cycle selection

Controls the operation of the host interface logic. If reset, the power

on/reset default, the host interface can accommodate arbitrarily long

bus I/O cycles. If the bit is set, the Octal UART expects four Sclk

cycle bus I/O operations similar to those produced by an i80386

processor in non–pipelined mode. The major differences in these

modes are observed in the DACKN pin function. In Sync mode, no

negation of CEN is required between cycles.

Note: For maximum power savings it is recommended that all

switching inputs be stopped and all input voltage levels be within 0.5

volt of the Vcc and Vss power supply levels.

To switch from the asynchronous to the synchronous bus cycle

mode, a single write operation to the GCCR, terminated by a

negation of the CEN pin, is required. This cycle may be 4 cycles

long if the setup time of the CEN edge to Sclk can be guaranteed.

The host CPU must ensure that a minimum of two Sclk cycles

elapse before the initiation of the next (synchronous) bus cycle(s).

GCCR(2:1): Interrupt vector configuration

The IVC field controls if and how the assertion of IACKN (the

interrupt acknowledge pin) will form the interrupt vector for the Octal

UART. If b’00, no vector will be presented during an IACKN cycle.

The bus will be driven high (xFF). If the field contains a b’01, the

contents of the IVR, Interrupt Vector Register, will be presented as

the interrupt vector without modification. If IVC = b’10, the channel

code will replace the 3 LSBs of the IVR; if IVC = b’11 then a modified

interrupt type and channel code replace the 5 LSBs of the IVR.

A hardware or software reset is recommended for the unlikely

requirement of returning to the asynchronous bus cycling mode.

MR – Mode Registers

The user must exercise caution when changing the mode of running

receivers, transmitters or BRG counter/timers. The selected mode

will be activated immediately upon selection, even if this occurs

during the reception or transmission of a character. It is also

possible to disrupt internal controllers by changing modes at critical

times, thus rendering later transmission or reception faulty or

impossible. An exception to this policy is switching from auto–echo

or remote loop back modes to normal mode. If the deselection

occurs just after the receiver has sampled the stop bit (in most

cases indicated by the assertion of the channel’s RxRDY bit) and

the transmitter is enabled, the transmitter will remain in auto–echo

mode until the end of the transmission of the stop bit.

Note: The modified type field IVR(4:3) is:

10

11

01

00

Receiver w/o error

Receiver with error

Transmitter

All remaining sources

GCCR(0): Power down control

Controls the power down function. During power down the internal

oscillator is disabled, interrupt arbitration and all data

Table 3. MR0– Mode Register 0

Bit 7

Bit 6

Bit 5:4

TxiNT

Bit 3:2

Bit 1:0

Address Recognition *

transparency

Address Recognition

control

Xon/Xoff * transparency

In–band flow control mode

0 – flow control characters

received are pushed onto

the

RxFIFO

0 – Address characters

received are pushed to

RxFIFO

TxFIFO

interrupt

level

control

00 – empty

01 – 3/4 empty

10 – 1/2 empty

11 – not full

00 – host mode, only the host CPU

may initiate flow control actions

through the CR

01 – Auto Transmitter flow control

10 – Auto Receiver flow control

11 – Auto Receiver and Transmitter

flow control

00 – none

01 – Auto wake

10 – Auto doze

11 – Auto wake and

auto doze

1 – Address characters

received are not pushed

onto the RxFIFO

1 – flow control characters

received are not pushed

onto the RxFIFO

351

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

* If these bits are not 0 the characters will be stripped regardless of

bits (3:2) or (1:0)

character when the RxFIFO has loaded to a depth of 12 characters.

Draining the RxFIFO to a level of 8 or less causes the Transmitter to

emit an Xon character. All transmissions require no host

MR0[7:6] – Control the handling of recognized Xon/Xoff or Address

characters. If set, the character codes are placed on the RxFIFO

along with their status bits just as ordinary characters are. If the

character is not pushed onto the RxFIFO, its received status will be

lost unless the receiver is operating in the block error mode, see

MR1[5] and the general discussion on receiver error handling.

Interrupt processing is not effected by the setting of these bits. See

Character recognition section.

involvement. A setting other than b’00 in this field precludes the use

of the command register to transmit Xon/Xoff characters.

Note: Interrupt generation in Xon/Xoff processing is controlled by the

IMR (Interrupt Mask Register) of the individual channels. The

interrupt may be cleared by a read of the XISR, the Xon/Xoff

Interrupt Status Register. Receipt of a flow control character will

always generate an interrupt if the IMR is so programmed. The

MR0[3:2] bits have effect on the automatic aspects of flow control

only, not the interrupt generation.

MR0[5:4] – Controls the fill level at which a transmitter begins to

present its interrupt number to the interrupt arbitration logic. Use of

a low fill level minimizes the number of interrupts generated and

maximizes the number of transmit characters per interrupt cycle. It

also increases the probability that the transmitter will go idle for lack

of characters in the TxFIFO.

MR0[1:0] – This field controls the operation of the Address

recognition logic. If the device is not operating in the special or

“wake–up” mode, this hardware may be used as a general purpose

character detector by choosing any combination except b’00.

Interrupt generation is controlled by the channel IMR. The interrupt

may be cleared by a read of the XISR, the Xon/Xoff Interrupt Status

Register. See further description in the section on the Wake Up

mode.

MR0[3:2] – Controls the Xon/Xoff processing logic. Auto

Transmitter flow control allows the gating of Transmitter activity by

Xon/Xoff characters received by the Channel’s receiver. Auto

Receiver flow control causes the Transmitter to emit an Xoff

Table 4. MR1 – Mode Register 1

Bit 7

Bit 6

Bit 5

Error Mode

Bit 4:3

Parity Mode

Bit 2

Parity Type

Bit 1:0

Bits per

RxRTS

ISR Read Mode

Control

Character

0 – off

1 – on

0 – ISR unmasked

1 – ISR masked

0 = Character

1 = Block

00 – With Parity

01 – Force parity

10 – No parity

0 = Even

1 = Odd

00 – 5

01 – 6

10 – 7

11 – 8

11 – Special Mode

MR1[7]: Receiver Request to Send Control

on a character by character basis; the status applies only to the

character at. the bottom of the FIFO. In the block mode, the status

provided in the SR for these bits is the accumulation (logical OR) of

the status for all characters coming to the top of the FIFO, since the

last reset error command was issued.

This bit controls the deactivation of the RTSN output (I/O2) by the

receiver. This output is asserted and negated by commands applied

via the command register. MR1[7] = 1 causes RTSN to be

automatically negated upon receipt of a valid start bit if the receiver

FIFO is full or greater. RTSN is reasserted when an the FIFO fill

level falls below full. This constitutes a change from previous

members of Philips (Signets)’ UART families where the RTSN

function triggered on FIFO full. This behavior caused problems with

PC UARTs that could not stop transmission at the proper time. .

The RTSN feature can be used to prevent overrun in the receiver, by

using the RTSN output signal, to control the CTSN input of the

transmitting device.

MR1[4:3]: Parity Mode Select

If ’with parity’ or ’force parity’ is selected, a parity bit is added to the

transmitted character and the receiver performs a parity check on

incoming data. MR1[4:3] = 11 selects the channel to operate in the

special wake up mode.

MR1[2]: Parity Type Select

This bit sets the parity type (odd or even) if the ’with parity’ mode is

programmed by MR1[4:3], and the polarity of the forced parity bit if

the ’force parity’ mode is programmed. It has no effect if the ’no

parity’ mode is programmed. In the special ’wake up’ mode, it

selects the polarity of the A/D bit. The parity bit is used to an

address or data byte in the ’wake up’ mode.

MR1[6]: Interrupt Status Masking

This bit controls the readout mode of the Interrupt Status Register,

ISR. If set, the ISR reads the current status masked by the IMR, i.e.

only interrupt sources enabled in the IMR can ever show a ’1’ in the

ISR. If cleared, the ISR shows the current status of the interrupt

source without regard to the Interrupt Mask setting.

MR1[1:0]: Bits per Character Select

MR1[5]: Error Mode Select

This bit selects the operating mode of the three FIFOed status bits

(FE, PE, received break). In the character mode, status is provided

This field selects the number of data bits per character to be

transmitted and received. This number does not include the start,

parity, or stop bits.

Table 5. MR2 – Mode Register 2

The MR2 register provides basic channel setup control that may need more frequent updating.

Bits 7:6

Channel Mode

Bit 5

Bit 4

Bit 3:2

Bit 1:0

Stop Length

TxRTS Control

CTSN Enable Tx

RxINT

00 = normal

0 = No

1 = Yes

0 = No

1 = Yes

00 = RRDY

01 = Half Full

10 = 3/4 Full

11 = Full

00 = 1.0

01 = 1.5

10 = 2.0

11 = 9/16

01 = Auto echo

10 = Local loop

11 = Remote loop

352

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

MR2[7:6] – Mode Select

appropriate commands issued via the command register. MR2[5] =

1 causes RTSN to be reset automatically one bit time after the

characters in the transmit shift register and in the TxFIFO (if any)

are completely transmitted (includes the programmed number of

stop bits if the transmitter is not enabled). This feature can be used

to automatically terminate the transmission of a message as follows:

The Octal UART can operate in one of four modes: MR2[7:6] = b’00

is the normal mode, with the transmitter and receiver operating

independently.

MR2[7:6] = b’01 places the channel in the automatic echo mode,

which automatically re transmits the received data. The following

conditions are true while in automatic echo mode:

Program auto reset mode: MR2[5]= 1.

Enable transmitter.

Received data is re–clocked and re–transmitted on the TxD

output.

Assert RTSN via command.

Send message.

The receive clock is used for the transmitter.

After the last character of the message is loaded to the TxFIFO,

disable the transmitter. Before disabling the transmitter be sure

the Status Register TxEMT bit is NOT set (i.e., the transmitter is

not underrun). The underrun condition is indicated by the

TxEMT bit in the SR being set. The condition occurs

immediately upon enabling the transmitter and persists until a

character is loaded to the TxFIFO. The Underrun condition will

not be a problem as long as the controlling processor keeps up

with the transmitter data flow. The proper operation of this

feature assumes that the transmitter is busy (not underrun) when

the disable is issued.

The receiver must be enabled, but the transmitter need not be

enabled.

The TxRDY and TxEMT status bits are inactive.

The received parity is checked, but is not regenerated for

transmission,

i.e., transmitted parity bit is as received.

Character framing is checked, but the stop bits are re-transmitted

as received.

A received break is echoed as received until the next valid start

bit is detected

The last character will be transmitted and RTSN will be reset one

bit time after the last stop bit.

. CPU to receiver communication continues normally, but the CPU

to transmitter link is disabled.

NOTE: When the transmitter controls the RTSN pin, the meaning of

the pin is COMPLETELY changed. It has nothing to do with the

normal RTSN/CTSN “handshaking”. It is usually used to mean “end

of message” and to “turn the line around” in simplex

communications.

Two diagnostic modes can also be selected.

MR2[7:6] = b’10 selects local loop back mode. In this mode:

The transmitter output is internally connected to the receiver

input.

The transmit clock is used for the receiver.

The TxD output is held high.

The RxD input is ignored.

The transmitter must be enabled, but the receiver need not be

enabled.

CPU to transmitter and receiver communications continue

normally.

MR2[4] – Clear to Send Control

The state of this bit determines if the CTSN input (I/O0) controls the

operation of the transmitter. If this bit is 0, CTSN has no effect on

the transmitter. If this bit is a 1, the transmitter checks the state of

CTSN each time it is ready to begin sending a character. If it is

asserted (low), the character is transmitted. If it is negated (high),

the TxD output remains in the marking state and the transmission is

delayed until CTSN goes low. Changes in CTSN, while a character

is being transmitted, do not affect the transmission of that character.

This feature can be used to prevent overrun of a remote receiver.

The second diagnostic mode is the remote loop back mode,

selected by MR2[7:6] = b’11. In this mode:

Received data is re–clocked and re–transmitted on the TxD

output.

MR2[3:2] – RxINT control field

Controls when interrupt arbitration for a receiver begins based on

RxFIFO fill level. This field allows interrupt arbitration to begin when

the RxFIFO is full, 3/4 full, 1/2 full or when it contains at least 1

character.

The receive clock is used for the transmitter.

Received data is not sent to the local CPU, and the error status

conditions are inactive.

The received parity is not checked and is not regenerated for

transmission, i.e., the transmitted parity bit is as received.

The receiver must be enabled, but the transmitter need not be

enabled.

Character framing is not checked, and the stop bits are

re-transmitted as received.

A received break is echoed as received until the next valid start

bit is detected.

MR2[1:0] – Stop Bit Length Select

This field programs the length of the stop bit appended to the

transmitted character. Stop bit lengths of 9/16, 1, 1.5 and 2 bits can

be programmed for character lengths of 6, 7, and 8 bits. For a

character length of 5 bits, 1, 1.5 and 2 stop bits can be programmed.

In all cases, the receiver only checks for a mark condition at the

center of the first stop bit position (one bit time after the last data bit,

or after the parity bit if parity is enabled). If an external 1X clock is

used for the transmitter, MR2[1] = 0 selects one stop bit and MR2[1]

= 1 selects two stop bits to be transmitted.

MR2[5] – Transmitter Request to Send Control

This bit controls the deactivation of the RTSN output (I/O2) by the

transmitter. This output is manually asserted and negated by

Table 6. RxCSR and TxCSR – Receiver and Transmitter Clock Select Registers

Both registers consist of single 5 bit field that selects the clock source for the receiver and transmitter, respectively. The unused bits in this

register read b’111. The baud rates shown in the table below are based on the x1 crystal frequency of 3.6864MHz. The baud rates shown

below will vary as the X1 crystal clock varies. For example, if the X1 rate is changed to 7.3728 MHz all the rates below will double.

Bits 7:5

Bits 4:0

Reserved

Transmitter/Receiver Clock select code, (see Clock Mux Table below)

353

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 7. Data Clock Mux

CCLK maximum rate is 8MHz. Data clock rates will follow exactly the ratio of CCLK to 3.6864MHz.

Clock selection,

CCLK = 3.6864 MHz

Clock selection,

CCLK = 3.6864 MHz

Clock Select Code

00000

00001

00010

00011

00100

00101

00110

00111

01000

01001

01010

01011

01100

01101

01110

01111

BRG – 50

10000

10001

10010

10011

10100

10101

10110

10111

11000

11001

11010

11011

11100

11101

11110

11111

BRG – 19.2K

BRG – 28.2K

BRG – 38.4K

BRG – 57.6K

BRG – 115.2K

BRG – 230.4K

BRG – 75

BRG – 150

BRG – 200

BRG – 300

BRG – 450

BRG – 600

BRG – 900

BRG – 1200

BRG – 1800

BRG – 2400

BRG – 3600

BRG – 4800

BRG – 7200

BRG – 9600

BRG – 14.4K

G

0

1

IN

BRG C/T 0

BRG C/T 1

Reserved

I/O2 rcvr, I/O3 xmit –16x

I/O2 rcvr, I/O3 xmit–1x

Reserved

The encoded value of this field can be used to specify a single

command as follows:

Table 8. CR – Command Register

CR is used to write commands to the Octal UART.

00000

00001

00010

No command.

Reserved

Bits 7:3

Bit 2

Bit 1

Bit 0

Reset receiver. Resets the receiver as if a hardware reset

had been applied. The receiver is disabled and the FIFO

pointer is reset to the first location effectively discarding all

unread characters in the FIFO.

Channel

Command

codes see

Lock TxD and

RxFIFO

Enable Tx

Enable Rx

enables

“Command

Register Table”

00011

00100

Reset transmitter. Resets the transmitter as if a hardware

reset had been applied.

CR[2] – Lock TxD and RxFIFO enables

Reset error status. Clears the received break, parity error,

framing error, and overrun error bits in the status register

(SR[7:4]). Used in character mode to clear overrun error

status (although RB, PE and FE bits will also be cleared),

and in block mode to clear all error status after a block of

data has been received.

If set, the transmitter and receiver enable bits, CR[1:0] are not

significant. The enabled/disabled state of a receiver or transmitter

can be changed only if this bit is at zero during the time of the write

to the command register. WRITES TO THE UPPER BITS OF THE

CR WOULD USUALLY HAVE CR[2] AT 1 to maintain the condition

of the receiver and transmitter. The bit provides a mechanism for

writing commands to a channel, via CR[7:3], without the necessity of

keeping track of or reading the current enable status of the receiver

and transmitter.

00101

00110

Reset break change interrupt. Causes the break detect

change bit in the interrupt status register (ISR[2]) to be

cleared to zero.

Start break. Forces the TxD output low (spacing). If the

transmitter is empty, the start of the break condition will be

delayed up to two bit times. If the transmitter is active, the

break begins when transmission of the current character

is completed. If there are characters in the TxFIFO, the

start of break is delayed until those characters, or any

others loaded after it have been transmitted (TxEMT must

be true before break begins). The transmitter must be

enabled to start a break.

CR[1] – Enable Transmitter

A one written to this bit enables operation of the transmitter. The

TxRDY status bit will be asserted. When disabled by writing a zero

to this bit, the command terminates transmitter operation and resets

the TxRDY and TxEMT status bits. However, if a character is being

transmitted or if characters are loaded in the TxFIFO when the

transmitter is disabled, the transmission of the all character(s) is

completed before assuming the inactive state.

00111

Stop break. The TxD line will go high (marking) within two

bit times. TxD will remain high for one bit time before the

next character, if any, is transmitted.

CR[0] – Enable Receiver

01000

01001

Assert RTSN. Causes the RTSN output to be asserted

(low).

Negate RTSN. Causes the RTSN output to be negated

(high).

Note: The two commands above actually reset and

set, respectively, the I/O2 or I/O1 pin associated with

the I/OPIOR register.

Reserved

A one written to this bit enables operation of the receiver. If not in

the special wake up mode, this also forces the receiver into the

search for start bit state. If a zero is written, this command

terminates operation of the receiver immediately – a character being

received will be lost. The command has no effect on the receiver

status bits or any other control registers. If the special wake–up

mode is programmed, the receiver operates even if it is disabled

(see Wake–up Mode).

01010

01011

01100

CR[7:3] – Miscellaneous Commands ( See Table below)

354

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

01101

Block error status mode. Upon reset of the device or an

individual receiver, the block mode of receiver error status

accumulates as each character moves to the bottom of

the RxFIFO, the position from which it will be read. In this

mode of operation, the RxFIFO may contain a character

with non–zero error status for some time. The status will

not reflect the error character’s presence until it is ready to

be popped from the RxFIFO. Command 01101 allows the

error status to be updated as each character is pushed

into the RxFIFO. This allows the earliest detection of a

problem character, but complicates the determination of

exactly which character is causing the error. This mode of

block error accumulation may be exited only by resetting

the chip or the individual receiver.

mechanism to initialize all the Xon Character registers to a

default value with one write. Execution of this command

is immediate and does not effect the timing of subsequent

host I/O operations.

Reserved for channels b-h, for channel a: executes a

Gang Load of Xoff Character Registers. Executing this

command causes a write of the value x’13 to all channel’s

Xoff character registers. This command provides a

mechanism to initialize all the Xoff Character registers to a

default value with one write. Execution of this command

is immediate and does not effect the timing of subsequent

host I/O operations.

Xoff resume command (CRXoffre; not active in

“Auto-Transmit Mode”). A command to cancel a previous

Host Xoff command. Upon receipt, the channel’s

transmitter will transfer a character, if any, from the

TxFIFO and begin transmission.

Host Xoff command (CRXoff). This command allows tight

host CPU control of the flow control of the channel

transmitter. When interrupted for receipt of an Xoff

character by the receiver, the host may stop transmission

of further characters by the channel transmitter by issuing

the Host Xoff command. Any character that has been

transferred to the TxD shift register will complete its

transmission, including the stop bit.

10101

10110

10111

01111

10000

10001

10010

Reserved.

Transmit an Xon Character

Transmit an Xoff Character

Reserved for channels b–h, for channel a: enables a

Gang Write of Xon Character Registers. After this

command is issued, a write to the channel A Xon

Character Register will result in a write to all channel’s

Xon character registers. This command provides a

mechanism to initialize all the Xon Character registers

with one write. A write to channel A Xon Character

Register returns the Octal UART to the individual Xon

write mode.

Reserved for channels b–h, for channel a: enables Gang

Write of Xoff Character Registers. After this command is

issued, a write to the channel A Xoff Character Register

will result in a write to all channel’s Xoff character

registers. This command provides a mechanism to

initialize all the Xoff Character registers with one write. A

write to channel A Xoff Character Register returns the

Octal UART to the individual Xoff write mode.

11000

Cancel Host transmit flow control command. Issuing this

command will cancel a previous transmit command if the

flow control character is not yet loaded into the TxD Shift

Register. If there is no character waiting for transmission

or if its transmission has already begun, then this

command has no effect.

10011

11001–11011

Reserved

11011 Reset Address Recognition Status. This command clears the

interrupt status that was set when an address character

was recognized by a disabled receiver operating in the

special mode.

11100–11101

Note: Gang writing of Xon/Xoff Character Commands: Issuing

command causes the next write to Xon/Xoff Character Register

A to effect a simultaneous write into the other 3 Xon/Xoff

character registers. After the Xon/Xoff Character Register A is

written, the 26C198 returns to individual write mode for the

Xon/Xoff Character Registers. Other intervening reads and

writes are ignored. The device resets to individual write mode.

10100 Reserved for channels b-h, for channel a: executes a Gang

Load of Xon Character Registers. Executing this

Reserved

11110

11111

Resets all UART channel registers. This command

provides a means to zero all the UART channels that are

not reset to x’00 by a reset command or a hardware reset.

Reserved for channels b-h, for channel a: executes a chip

wide reset. Executing this command in channel a is

equivalent to a hardware reset with the RESETN pin.

Executing in channel b-h, has no effect.

command causes a write of the value x’11 to all channel’s

Xon character registers. This command provides a

355

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 9. Command Register Code

Commands x’12, x13, x’14, x’15, x’1f (marked with*) are global and exist only in channel A’s register space.

Channel Command

Code

Channel

Command

Channel Command

Code

Channel

Command

CR[7:3]

00000

00001

00010

00011

00100

00101

00110

00111

01000

01001

01010

01011

01100

01101

01110

01111

Description

NOP

CR[7:3]

10000

10001

10010

10011

10100

10101

10110

10111

11000

11001

11010

11011

11100

11101

11110

11111

Description

Transmit Xon

Reserved

Transmit Xoff

Reset Receiver

Gang Write Xon Character Registers *

Gang Write Xoff Character Registers *

Gang Load Xon Character Registers DC1 *

Gang Load Xoff Character Registers DC3 *

Xoff Resume Command

Host Xoff Command

Reset Transmitter

Reset Error Status

Reset Break Change Interrupt

Begin Transmit Break

End Transmit Break

Assert RTSN (I/O2 or I/O1)

Negate RTSN (I/O2 or I/O1)

Set time–out mode on

Reserved

Cancel Transmit X Char command

Reserved

Reset Address Recognition Status

Reserved

Set time–out mode off

Block Error Status configure

Reserved

Reset All UART channel registers

Reset Device *

Reserved

Table 10. SR – Channel Status Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

TxRDY

Bit 1

RxFULL

Bit 0

RxRDY

Received

Break

Framing Error

Parity

Overrun Error

TxEMT

Error

0 – No

1 – Yes

SR[7] – Received Break

occurs, the character in the receive shift register (and its break

detect, parity error and framing error status, if any) is lost. This bit is

cleared by a reset error status command.

This bit indicates that an all zero character of the programmed

length has been received without a stop bit. Only a single FIFO

position is occupied when a break is received; further entries to the

FIFO are inhibited until the RxD line returns to the marking state for

at least one half bit time (two successive edges of the internal or

external 1x clock). When this bit is set, the change in break bit in

the ISR (ISR[2]) is set. ISR[2] is also set when the end of the break

condition, as defined above, is detected. The break detect circuitry

is capable of detecting breaks that originate in the middle of a

received character. However, if a break begins in the middle of a

character, it must last until the end of the next character in order for

it to be detected.

SR[3] – Transmitter Empty (TxEMT)

This bit is set when the transmitter underruns, i.e., both the TxFIFO

and the transmit shift register are empty.

It is set after transmission of the last stop bit of a character, if no

character is in the TxFIFO awaiting transmission. It is reset when

the TxFIFO is loaded by the CPU, or when the transmitter is

disabled.

SR[2] – Transmitter Ready (TxRDY)

This bit, when set, indicates that the TxFIFO is ready to be loaded

with a character. This bit is cleared when the TxFIFO is loaded by

the CPU and is set when the last character is transferred to the

transmit shift register. TxRDY is reset when the transmitter is

disabled and is set when the transmitter is first enabled, e.g.,

characters loaded in the TxFIFO while the transmitter is disabled will

not be transmitted.

SR[6] – Framing Error (FE)

This bit, when set, indicates that a stop bit was not detected when

the corresponding data character in the FIFO was received. The

stop bit check is made in the middle of the first stop bit position.

SR[5] – Parity Error (PE)

This bit is set when the ’with parity’ or ’force parity’ mode is

programmed and the corresponding character in the FIFO was

received with incorrect parity. In the special ’wake up mode’, the

parity error bit stores the received A/D bit.

SR[1] – RxFIFO Full (RxFULL)

This bit is set when a character is transferred from the receive shift

register to the receive FIFO and the transfer causes the FIFO to

become full, i.e., all sixteen RxFIFO positions are occupied. It is

reset when the CPU reads the RxFIFO and that read leaves one

empty byte position. If a character is waiting in the receive shift

register because the RxFIFO is full, RxFULL is not reset until the

second read of the RxFIFO since the waiting character is

immediately loaded to the RxFIFO.

SR[4] – Overrun Error (OE)

This bit, when set, indicates that one or more characters in the

received data stream have been lost. It is set upon receipt of a new

character when the RxFIFO is full and a character is already in the

receive shift register waiting for an empty FIFO position. When this

356

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

SR[0] – Receiver Ready (RxRDY)

This bit indicates that a character has been received and is waiting

in the RxFIFO to be read by the CPU. It is set when the character is

transferred from the receive shift register to the RxFIFO and reset

when the CPU reads the RxFIFO, and no more characters are in the

RxFIFO.

Table 11. ISR – Interrupt Status Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

I/O Port

change of

state

Receiver

Watch-dog

Time–out

Address

recognition event event

Xon/off

Always 0

Change of

Break State

RxRDY

Receiver has entered Transmitter has entered

arbitration process arbitration process

TxRDY

This register provides the status of all potential interrupt sources for

a UART channel. When generating an interrupt arbitration value,

the contents of this register are masked by the interrupt mask

register (IMR). If a bit in the ISR is a ’1’ and the corresponding bit in

the IMR is also a ’1’, interrupt arbitration for this source will begin. If

the corresponding bit in the IMR is a zero, the state of the bit in the

ISR can have no affect on the IRQN output. Note that the IMR may

or may not mask the reading of the ISR as determined by MR1[6].

If MR1[6] is cleared, the reset and power on default, the ISR is read

without modification. If MR1[6] is set, the a read of the ISR gives a

value of the ISR ANDed with the IMR.

ISR[1] – Receiver Ready

The general function of this bit is to indicate that the RxFIFO has

data available. The particular meaning of this bit is programmed by

MR2[3:2]. If programmed as receiver ready(MR2[3:2] = 00), it

indicates that at least one character has been received and is

waiting in the RxFIFO to be read by the host CPU. It is set when the

character is transferred from the receive shift register to the RxFIFO

and reset when the CPU reads the last character from the RxFIFO.

If MR2[3:2] is programmed as FIFO full, ISR[1] is set when a

character is transferred from the receive holding register to the

RxFIFO and the transfer causes the RxFIFO to become full, i.e. all

sixteen FIFO positions are occupied. It is reset when ever RxFIFO

is not full. If there is a character waiting in the receive shift register

because the FIFO is full, the bit is set again when the waiting

character is transferred into the FIFO.

ISR[7] – Input Change of State

This bit is set when a change of state occurs at the I/O1 or I/O0

input pins. It is reset when the CPU reads the Input Port Register,

IPR.

The other two conditions of these bits, 3/4 and half full operate in a

similar manner. The ISR[1] bit is set when the RxFIFO fill level

meets or exceeds the value; it is reset when the fill level is less.

See the description of the MR2 register.

ISR[6] Watch-dog Time–out

This bit is set when the receiver’s watch-dog timer has counted

more than 64 bit times since the last RxFIFO event. RxFIFO events

are a read of the RxFIFO or GRxFIFO, or the push of a received

character into the FIFO. The interrupt will be cleared automatically

upon the push of the next character received or when the RxFIFO or

GRxFIFO is read. The receiver watch-dog timer is included to allow

detection of the very last characters of a received message that may

be waiting in the RxFIFO, but are too few in number to successfully

initiate an interrupt. Refer to the watch-dog timer description for

details of how the interrupt system works after a watch-dog

time–out.

Note: This bit must be at a one (1) for the receiver to enter the

arbitration process. It is the fact that this bit is zero (0) when the

RxFIFO is empty that stops an empty FIFO from entering the

interrupt arbitration. Also note that the meaning if this bit is not quite

the same as the similar bit in the status register (SR).

ISR[0] – Transmitter Ready

The general function of this bit is to indicate that the TxFIFO has an

at least one empty space for data. The particular meaning of the bit

is controlled by MR0[5:4] indicates the TxFIFO may be loaded with

one or more characters. If MR0[5:4] = 00 (the default condition) this

bit will not set until the TxFIFO is empty – sixteen bytes available. If

the fill level of the TxFIFO is below the trigger level programmed by

the TxINT field of the Mode Register 0, this bit will be set. A one in

this position indicates that at least one character can be sent to the

TxFIFO. It is turned off as the TxFIFO is filled above the level

programmed by MR0[5:4. This bit turns on as the FIFO empties; the

RxFIFO bit turns on as the FIFO fills. This often a point of confusion

in programming interrupt functions for the receiver and transmitter

FIFOs.

ISR[5] – Address Recognition Status Change

This bit is set when a change in receiver state has occurred due to

an Address character being received from an external source and

comparing to the reference address in ARCR. The bit and interrupt

is negated by a write to the CR with command x11011, Reset

Address Recognition Status.

ISR[4] – Xon/Xoff Status Change

This bit is set when an Xon/Xoff character being received from an

external source. The bit is negated by a read of the channel Xon

Interrupt Status Register, XISR.

ISR[3] – Reserved Always reads a 0

Note: This bit must be at a one (1) for the transmitter to enter the

arbitration process. It is the fact that this bit is zero (0) when the

RxFIFO is full that stops a full FIFO from entering the interrupt

arbitration. Also note that the meaning if this bit is not quite the

same as the similar bit in the status register (SR).

ISR[2] – Change in Channel Break Status

This bit, when set, indicates that the receiver has detected the

beginning or the end of a received break. It is reset when the CPU

issues a reset break change interrupt command via the CR.

Table 12. IMR – Interrupt Mask Register

Bit 7

I/O Port change Receiver Watch-dog

of state Time–out

Bit 6

Bit 5

Address

recognition event

Bit 4

Bit 3

Bit 2

Bit 1

RxRDY

interrupt

Bit 0

TxRDY

interrupt

Xon/off event

Set to 0

Change of

Break State

The programming of this register selects which bits in the ISR cause

an interrupt output. If a bit in the ISR is a ’1’ and the corresponding

bit in the IMR is a ’1’, the interrupt source is presented to the internal

interrupt arbitration circuits, eventually resulting in the IRQN output

being asserted (low). If the corresponding bit in the IMR is a zero,

the state of the bit in the ISR has no affect on the IRQN output.

357

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

IMR[7] – Controls if a change of state in the inputs equipped with

IMR[4] – Enables the generation of an interrupt in response to

input change detectors will cause an interrupt.

recognition of an in–band flow control character.

IMR[3] – Reserved

IMR[6] – Controls the generation of an interrupt by the watch-dog

timer event. If set, a count of 64 idle bit times in the receiver will

begin interrupt arbitration.

IMR[2] – Enables the generation of an interrupt when a Break

condition has been detected by the channel receiver.

IMR[1] – Enables the generation of an interrupt when servicing for

the RxFIFO is desired.

IMR[5] – Enables the generation of an interrupt in response to

changes in the Address Recognition circuitry of the Special Mode

(multi-drop or wake–up mode).

IMR[0] – Enables the generation of an interrupt when servicing for

the TxFIFO is desired.

Table 13. RxFIFO Receiver FIFO

This register provides the 3 MSBs of the Interrupt Arbitration number

for a Change of State, COS, interrupt.

Bit[10]

Bit[9]

Bit[8]

Bits [7:0]

Break

Received

Status

Framing

Error

Status

Parity

Error

Status

8 data bits

MSBs =0 for 7,6,5 bit

data

Table 17. BCRx – Bidding Control Register – Xon

The FIFO for the receiver is 11 bits wide and 16 ”words” deep. The

status of each byte received is stored with that byte and is moved

along with the byte as the characters are read from the FIFO. The

upper three bits are presented in the STATUS register and they

change in the status register each time a data byte is read from the

FIFO. Therefor the status register should be read BEFORE the byte

is read from the RxFIFO if one wishes to ascertain the quality of the

byte

Bits 7:3

Reserved

Bits 2:0

MSB of an Xon/Xoff interrupt bid

This register provides the 3 MSBs of the Interrupt Arbitration number

for an Xon/Xoff interrupt.

Table 18. BCRA – Bidding Control Register –

Address

The forgoing applies to the ”character error” mode of status

reporting. See MR1[5] and ”RxFIFO Status” descriptions for ”block

error” status reporting. Briefly ”Block Error” gives the accumulated

error of all bytes received in the RxFIFO since the last “Reset Error”

command was issued. (CR = x’04)

Bits 7:3

Reserved

Bits 2:0

MSB of an address recognition event

interrupt bid

This register provides the 3 MSBs of the Interrupt Arbitration number

for an address recognition event interrupt.

Table 14. TxFIFO – Transmitter FIFO

Bits 7:0

Table 19. XonCR – Xon Character Register

Bits 7:0

8 data bits. MSBs set to 0 for 7, 6, 5 bit data

8 Bits of the Xon Character Recognition

The FIFO for the transmitter is 8 bits wide by 16 bytes deep. For

character lengths less than 8 bits the upper bits will be ignored by

the transmitter state machine and thus are effectively discarded.

An 8 bit character register that contains the compare value for an

Xon character.

Table 15. BCRBRK – Bidding Control Register –

Break Change

Table 20. XoffCR – Xoff Character Register

Bits 7:0

Bits 7:3

Reserved

Bits 2:0

8 Bits of the Xoff Character Recognition

MSB of break change interrupt bid

An 8 bit character register that contains the compare value for an

Xoff character.

This register provides the 3 MSBs of the Interrupt Arbitration number

for a break change interrupt.

Table 21. ARCR – Address Recognition Character

Table 16. BCRCOS – Bidding Control Register –

Change of State

Register

Bits 7:0

Bits 7:3

Reserved

Read as x’0

Bits 2:0

8 Bits of the Multi–Drop Address Character Recognition

MSB of a COS interrupt bid

An 8 bit character register that contains the compare value for the

wake–up address character

358

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 22. XISR – Xon–Xoff Interrupt Status Register

Bits 7:6

Bits 5:4

Bits 3:2

TxD flow status

Bits 1:0

Received X Character

Status

Automatic X Character

transmission status

TxD character status

00 – none

00 – normal

00 – normal TxD data

01 – wait on normal data

10 – Xoff in pending

11 – Xon in pending

01 – Xoff received

10 – Xon received

11 – both received

01 – Xon transmitted

10 – Xoff transmitted

11 – Illegal, does not occur

01 – TxD halt pending

10 – re–enabled

11 – flow disabled

XISR[7:6] – Received X Character Status. This field can be read to

determine if the receiver has encountered an Xon or Xoff character

in the incoming data stream. These bits are maintained until a read

of the XISR. The field is updated by X character reception

regardless of the state of MR0(7, 3:2) or IMR(4). The field can

therefore be used as a character detector for the bit patterns stored

in the Xon and Xoff Character Registers.

Table 23. WDTRCR – Watch-dog Timer Enable

Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

WDT

h

WDT

g

WDT WDT

WDT

d

WDT

c

WDT WDT

b

f

e

a

1 on

0 off

1 on

0 off

1 on

0 off

1 on

0 off

1 on

0 off

1 on

0 off

1 on

0 off

1 on

0 off

XISR[5:4] – Automatic transmission Status. This field indicates the

last flow control character sent in the Auto Receiver flow control

mode. If Auto Receiver mode has not been enabled, this field will

always read b’00. It will likewise reset to b’00 if MR0(3) is reset. If

the Auto Receiver mode is exited while this field reads b’10, it is the

user’s responsibility to transmit an Xon, when appropriate.

This register enables the watch-dog Timer for each of the 8

receivers on the Octal UART.

Table 24. BRGTRU – BRG Timer Reload

Registers, Upper

XISR[3:2] – TxD flow Status. This field tracks the transmitter’s flow

Bits 7:0

status as follows:

00 – normal. The flow control is under host control.

8 MSB of the BRG Timer divisor.

01 – TxD halt pending. After the current character finishes the

transmitter will stop. The status will then change to b’00.

10 – re–enabled. The transmitter had been halted and restarted.

It is sending data characters. After a read of the XISR, it will

return to ”normal” status.

This is the upper byte of the 16 bit value used by the BRG timer in

generating a baud rate clock

Table 25. BRGTRL – BRG Timer Reload

Registers, Lower

11 – disabled. The transmitter is flow controlled.

XISR[1:0] – TxD character Status. This field allows determination of

the type of character being transmitted. If XISR(1:0) is b’01, the

channel is waiting for a data character to transfer from the TxFIFO.

This condition will only occur for a bit time after an Xon or Xoff

character transmission unless the TxFIFO is empty.

Bits 7:0

8 LSB of the BRG Timer divisor.

This is the lower byte of the 16 bit value used by the BRG timer in

generating a baud rate clock.

Table 26. BRGTCR – BRG Timer Control Register (BRGTCR)

Bit 7

Bit 6:4

Bit 3

Bit 2:0

BRGTCR b, Register control

BRGTCR b, Clock selection

BRGTCR a, Register control

BRGTCR a, Clock selection

0 – Resets the timer register and 000 – Sclk / 16

holds it stopped

001 – Sclk / 32

010 – Sclk/ 64

011 – Sclk / 128

100 – X1

holds it stopped.

001 – Sclk / 32

010 – Sclk / 64

011 – Sclk / 128

100 – X1

1 – Allows the timer register to

run.

1 – Allows the timer register to

run.

101 – X1 / 2

110 – I/O1b

101 – X1 / 2

110 – I/O1a

111 – G (1)

111 – G (0)

IN

Start/Stop control and clock select register for the two BRG

counters. The clock selection is for the input to the counters. It is

that clock divided by the number represented by the BRGTU and

BRGTL the will be used as the 16x clock for the receivers and

transmitters. When the BRG timer Clock is selected for the

receiver(s) or transmitter(s) the receivers and transmitters will

consider it as a 16x clock and further device it by 16. In other words

the receivers and transmitters will always be in the 16x ode of

operation when the internal BRG timer is selected for their clock.

Table 27. ICR – Interrupt Control Register

Bit 7

Bits 6:0

Reserved. Set to 0

Upper seven bits of the Arbitration Threshold

This register provides a single 7 bit field called the interrupt

threshold for use by the interrupt arbiter. The field is interpreted as a

single unsigned integer. The interrupt arbiter will not generate an

external interrupt request, by asserting IRQN, unless the value of

the highest priority interrupt exceeds the value of the interrupt

threshold. If the highest bidder in the interrupt arbitration is lower

than the threshold level set by the ICR, the Current Interrupt

Register, CIR, will contain x’00. Refer to the functional description of

359

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

interrupt generation for details on how the various interrupt source

bid values are calculated.

If CIR[7] = 1, then a receiver interrupt is pending and the count is

CIR[5:3], channel is CIR[2:0]

Else If CIR[6] = 1 then a transmitter interrupt is pending and the

count is CIR[5:3], channel is CIR[2:0]

Note: While a watch-dog Timer interrupt is pending, the ICR is not

used and only receiver codes are presented for interrupt arbitration.

This allows receivers with very low count values (perhaps below the

threshold value) to win interrupt arbitration without requiring the user

to explicitly lower the threshold level in the ICR. These bits are the

upper seven (7) bits of the interrupt arbitration system. The lower

three (3) bits represent the channel number.

Else the interrupt is another type, specified in CIR[5:3]

Note: The GIBCR, Global Interrupting Byte Count Register, may be

read to determine an exact character count if 9 or less characters

are indicated in the count field of the CIR.

Table 29. IVR – Interrupt Vector Register

Bits 7:0

UCIR – Update CIR

A command based upon a decode of address x’8C. ( UCIR is not a

register!) A write (the write data is not important; a “don’t care”) to

this ’register’ causes the Current Interrupt Register to be updated

with the value that is winning interrupt arbitration. The register

would be used in systems that poll the interrupt status registers

rather than wait for interrupts. Alternatively, the CIR is normally

updated during an Interrupt Acknowledge Bus cycle in interrupt

driven systems.

8 data bits of the Interrupt Vector (IVR)

The IVR contains the byte that will be placed on the data bus during

an IACKN cycle when the GCCR bits (2:1) are set to binary ‘01’.

This is the unmodified form of the interrupt vector.

Table 30. Modification of the IVR

Bits 7:5

Bits 4:3

Bits 2:0

Always contains

Will be replaced

Replaced with

bits (7:5) of the IVR with current

interrupting channel

Table 28. CIR – Current Interrupt Register

interrupt type if IVC number if IVC field of

field of GCCR > 1 GCCR > 0

Bits 7:6

Bits 5:3

Bits 2:0

Type

Current byte count/type Channel number

The table above indicates how the IVR may be modified by the

interrupting source. The modification of the IVR as it is presented to

the data bus during an IACK cycle is controlled by the setting of the

bits (2:1) in the GCCR (Global Chip Configuration Register)

00 – other

000 – no interrupt

001 – Change of State

010 – Address

000 = a

001 = b

010 = c

011 = d

Recognition

011 – Xon/Xoff status

100 – Not used

101 – Break change

110, 111 do not occur

Table 31. GICR – Global Interrupting Channel

Register

111 = h

Bits 7:3

Bits 2:0

01 – Transmit

11– Receive w/

errors

10 – Receive w/o

errors

Current count code

0 => 9 or less

characters

1 => 10 characters

.

000 = a

001 = b

010 = c

011 = d

Reserved

Channel code

100 = e

000 = a

001 = b

010 = c

011 = d

101 = f

110 = g

111 = h

.

5 => 14 characters

6 => 15 characters

7 => 16

111 = h

A register associated with the interrupting channel as defined in the

CIR. It contains the interrupting channel code for all interrupts.

(See also GIBCR)

Table 32. GIBCR – Global Interrupting Byte Count

Register

The Current Interrupt Register is provided to speed up the

specification of the interrupting condition in the Octal UART. The

CIR is updated at the beginning of an interrupt acknowledge bus

cycle or in response to an Update CIR command. (see immediately

above) Although interrupt arbitration continues in the background,

the current interrupt information remains frozen in the CIR until

another IACKN cycle or Update CIR command occurs. The LSBs of

the CIR provide part of the addressing for various Global Interrupt

registers including the GIBCR, GICR, GITR and the Global RxFIFO

and TxFIFO FIFO. The host CPU need not generate individual

addresses for this information since the interrupt context will remain

stable at the fixed addresses of the Global Interrupt registers until

the CIR is updated. For most interrupting sources, the data

available in the CIR alone will be sufficient to set up a service

routine.

Bits 7:4

Reserved

Bits 3:0

Channel byte count code

0000 = 1 AND RxRDY status set for RxFIFO

0000 = 1 AND TxRDY status set for TxD

0001 = 2

0010 = 3

.

1111 = 16

A register associated with the interrupting channel as defined in the

CIR. Its numerical value equals

the number of bytes minus 1 (count – 1) ready for transfer to the

transmitter or transfer from the receiver. It is undefined for other

types of interrupts

The CIR may be processed as follows:

1995 May 1

360

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 33. Global Interrupting Type Register

Bit 7:6

Receiver Interrupt

Bit 5

Bit 4:3

Bit 2:0

Transmitter Interrupt

Reserved

read b’00

Other types

0x – not receiver

10 – with receive errors

11 – w/o receive errors

0 – not transmitter

1 – transmitter interrupt

000 – not ”other” type

001 – Change of State

010 – Address Recognition

Event

011 – Xon/Xoff status

100 – Not used

101 – Break Change

11x – do not occur

A register associated with the interrupting channel as defined in the

CIR. It contains the type of interrupt code for all interrupts.

Table 35. GTxFIFO – Global TxFIFO Register

Bits 7:0

8 data bits of TxFIFO. MSBs not used for 7, 6, 5 bit data

Table 34. GRxFIFO – Global RxFIFO Register

Bits 7:0

The TxFIFO of the channel indicated in the CIR channel field.

Undefined when the CIR interrupt context is not a transmitter

interrupt. Writing to the GTxFIFO when the current interrupt is not a

transmitter event may result in the characters being transmitted on a

different channel than intended.

8 data bits of RxFIFO. MSBs set to 0 for 7, 6, 5 bit data

The RxFIFO of the channel indicated in the CIR channel field.

Undefined when the CIR interrupt context is not a receiver interrupt.

Global TxFIFO Register

Table 36. IPR – Input Port Register,

Bit 7

Bit 6

Bit 7

Bit 6

Bit 3

I/O3

state

Bit 2

I/O2

state

Bit 1

I/O1

state

Bit 0

I/O0

state

I/O3

change

I/O2

change

I/O1

change

I/O0

change

0 – no change

1 – change

0 – no change

1 – change

0 – no change

1 – change

0 – no change

1 – change

The actual logic level at the I/O pin.

1 = high level; 0 =– low level.

This register may be read to determine the current level of the I/O

pins and examine the output of the change detectors assigned to

each pin. If the change detection is not enabled or if the pin is

configured as an output, the associated change field will read b’0.

Table 37. I/OPIOR – I/O Port Interrupt and Output Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

I/O3 output

OPR[3]

Bit 2

I/O2 output

OPR[2]

Bit 1

I/O1 output

OPR[1]

Bit 0

I/O0 output

OPR[0]

I/O3 enable

I/O2 enable

I/O1 enable

I/O0 enable

0 – disable

1 – enable

0 – disable

1 – enable

0 – disable

1 – enable

0 – disable

1 – enable

I/OPIOR[7:4] bits activate the input change of state detectors. If a

pin is configured as an output, a b’1 value written to a I/O field has

no effect.

I/OPIOR[3:0] bits hold the datum which is the inverse of the datum

driven to its associated I/O pin when the I/OPCR control bits for that

pin are programmed to b’01.

Table 38. I/OPCR – I/O Port Configuration Register

Bits 7:6

Bits 5:4

Bits 3:2

Bits 1:0

I/O3 control

I/O2 control

I/O1 control

I/O0 control

00 – GPI/TxC input

01 – I/OPIOR[3] output

10 – TxC16x output

11 – TxC1x output

00 – GPI/RxC input

01 – I/OPIOR[2]/RTSN *

10 – RxC1x output

11 – RxC16x output

00 – GPI input

01 – I/OPIOR[1]/RTSN *

10 – Reserved

00 – GPI/CTSN input

01 – I/OPIOR[0]output

10 – TxC1x output

11 – RxC1x output

11 – TxC16x output

* If I/OPCR(5:4) is programmed as ’01’ then the RTSN functionality

is assigned to I/O2, otherwise, this function can be implemented on

I/O1. (This allows for a lower pin count package option)

power up or reset. Inputs may be used as RxC, TxC inputs or

CTSN and General Purpose Inputs simultaneously. All inputs are

equipped with change detectors that may be used to generate

interrupts or can be polled, as required.

This register contains 4, 2 bit fields that set the direction and source

for each of the I/O pins associated with the channel. The I/O2

output may be RTSN if MR1[7] is set, or may signal ”end of

transmission” if MR2[5] is set.(Please see the descriptions of these

functions under the MR1 and MR2 register descriptions) If this

control bit is cleared, the pin will use the OPR[2] as a source if

I/OPCR[5:4] is b’01. The b’00 combinations are always inputs. This

register resets to x’0, effectively configuring all I/O pins as inputs on

NOTE: To ensure that CTSN, RTSN and an external RxC are

always available, if I/O2 is not selected as the RTSN output, the

RTSN function is automatically provided on I/O1.

GENERAL PURPOSE OUTPUT PIN CONTROL

The following four registers control the function of the G

0 pin.

OUT

These output pins have a unique control matrix which includes a

361

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

clocking mechanism that will allow the pin to change synchronously

with an internal or external stimulus. See diagram below.

Table 41. GPOC – General Purpose Output Clk

Register

This controls the clock source for GPOR that will clock and/or toggle

the data from the selected GPOD source. When code b’00 is

selected, no clock will be provided, thereby preventing any change

through the D port.

Table 39. GPOSR – General Purpose Output

Select Register

GPOSR selects the signal or data source for the G

0 pin. The Tx

OUT

and Rx clock selection is straight forward. The selection of the

Bits 7:6

Clk Sel

Bits 5:4

Clk Sel

Bits 3:2

Clk Sel

Bits 1:0

Clk Sel

GPOR allows a more flexible timing control of when the G

changes.

0 pin

OUT

GPOR(3)

GPOR(2)

GPOR(1)

GPOR(0)

Bits 7:4

Reserved

Bits 3:0

00 = none

Global General Purpose Output 0 Selection

01 = G

10 = G

0

1

01 = G

10 = G

0

1

01 = G

10 = G

0

1

01 = G

10 = G

0

1

IN

0000 – 0111 reserved

1000 = TxC1x a

IN

11 = reserved

11 = reserved 11 = I/O3c

11 = I/O3a

1001 = TxC16x a

1010 = RxC16x a

1011 = TxC16x b

1100 = GGPOR(3)

1101 = GGPOR(2)

1110 = GGPOR(1)

1111 = GGPOR(0)

Table 42. GPOD – General Purpose Output Data

Register

This register selects the data that will be presented to the GPOR “D”

input. Note that selection b’10 selects the inverted GPOR data as

the input. In this case, the GPOR output will toggle synchronously

with the clock selected in the GPOC.

Table 40. GPOR – General Purpose Output

Bits 7:6

Data Sel

Bits 5:4

Data Sel

Bits 3:2

Data Sel

Bits 1:0

Data Sel

Register

This register is a read/write register. Its contents may be altered by

a GPOR Write or by the GPOC and GPOD registers shown below.

The GPOD and GPOC may be programmed to cause the individual

bits of the GPOR to change synchronously with internal or external

events. The cells of this register may be thought of as a “Two Port

flip-flop”; one port is controlled by a D input and clock, the other by a

data load strobe. A read of the GPOR always returns its current

value regardless of the port from which it was loaded.

GPOR(3)

GPOR(2)

GPOR(1)

GPOR(0)

00 = ’1’

01 = ’0’

00 = ’1’

01 = ’0’

00 = ’1’

01 = ’0’

00 = ’1’

01 = ’0’

10 = GPOR3N 10 = GPOR2N 10 = GPOR1N 10 = GPOR0N

11 = reserved

11 = reserved 11 = I/O3d

11 = I/O3b

Bits 7:4

Bit 3

Bit 2

Bit 1

Bit 0

Reserved

GPOR(3)

GPOR(2)

GPOR(1)

GPOR(0)

GPOD

GPOR

GPOSR

DATA BUS

GPOR R/W

4:1 MULTIPLEX

“1”

DATA IN/OUT

TxC1Xa

TxC16Xa

RxC16Xa

TxC16Xb

DATA READ/WRITE

“0”

GPORON

1/O3b

GPO PIN

D INPUT

GPOR(0)

GPOR(1)

GPOR(2)

GPOR(3)

QN

4:1 MULTIPLEX

NONE

D CLOCK

G

IN

0

8:1 MULTIPLEX

G

IN

1

1/O3a

SD00526

Figure 1. General Purpose Pin Control Logic

362

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART B that apply to the total chip configuration. The ”Register

Map Detail” shows the use of every address in the 8 bit address

space.

REGISTER MAPS

The registers of the SC26C198 are partitioned into two groups:

those used in controlling data channels and those used in handling

the actual data flow and status. Below is shown the general

configuration of all the register addressed. The ”Register Map

Summary” shows the configuration of the lower four bits of the

address that is the same for the individual UARTs. It also shows the

addresses for the several in the address space of UART A and

NOTE: The register maps for channels A and B (UARTs A and B)

contain some control registers that configure the entire chip. These

are denoted by a ♣ symbol.

REGISTER MAP SUMMARY

Table 43. Summary Register Map, Control

Address (hex) ccc = channel

0ccc 0000 (x00)

0ccc 0001 (x01)

0ccc 0010 (x02)

0ccc 0011 (x03)

0ccc 0100 (x04)

0ccc 0110 (x06)

0ccc 0111 (x07)

0ccc 1000 (x08)

0ccc 1001 (x09)

0ccc 1010 (x0A)

0ccc 1100 (x0C)

0000 1101 (x0D)

0ccc 1110 (x0E)

0000 1111 (x0F)

0001 1011 (x1B)

0001 1101 (x1D)

0001 1111 (x1F)

Register Name

Mode Register 0 MR0a

Acronym

MR0

Read / Write

R/W

Page

22

32

28

29

24

Mode Register 1 MR1a

MR1

R/W

I/O Port Configuration Reg a I/OPCRa

Bid Control, Break Change

Bid Control, Change of State

Bid Control, Xon/Xoff

IOPCR

BCRBRK

BCRCOS

BCRX

R/W

Bid Control, Address recognition

Xon Character Register

BCRA

R/W

XonCR

XoffCR

ARCR

R/W

Xoff Character Register

R/W

Address Recognition Character

Receiver Clock Select Register

♣ Test Register

R/W

RxCSR

R/W

Reserved, set to 0

TxCSR

Transmitter Clock Select Register

♣ Global Chip Configuration Register

♣ Interrupt Control Register

♣ Watch-dog Timer Run Control

♣ Interrupt Vector Register

R/W

24

21

GCCR

ICR

WDTRCR

IVR

29

363

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 44. Summary Register Map, Data

Address (hex) ccc = Channel

1ccc 0000 (x80)

1ccc 0001 (x81)

1ccc 0010 (x82)

1ccc 0011 (x83)

1ccc 0100 (x84)

1000 0100 (x84)

1ccc 0101 (x85)

1ccc 0110 (x86)

1000 0111 (x87)

1000 1011 (x8B)

1000 1100 (x8C)

1001 1101 (x8D)

1000 1110 (x8E)

1000 1111 (x8F)

1000 0100 (x94)

1001 0111 (x97)

1001 1011 (x9B)

1000 1100 (x9C)

1001 1100 (x9C)

1001 1101 (x9D)

1001 1111 (x9F)

Register Name

Acronym

MR2

Read/Write

Page

23

26

25

27

28

32

29

32

29

33

30

29

32

21

29

33

30

31

29

32

Mode Register 2

Status Register

R/W

R

SR

Command Register

CR

W

Interrupt Status Register

Interrupt Mask Register

Transmitter FIFO Register

Receiver FIFO Reg

ISR

R

IMR

W

TxFIFO

RxFIFO

IPR

W

R

Input Port Reg

R

♣ BRG Timer Reg Upper a

I/O Port Interrupt and Output

Xon/Xoff Interrupt Status Reg

♣ GP Out Select Reg

BRGTRUa

I/OPIOR

XISR

W

R/W

R

GPOSR

GPOC

UCIR

R/W

W

♣ GP Out Clk Reg

♣ Update Current Interrupt Reg

♣ Current Interrupt Reg

♣ BRG Timer Reg Upper b

♣ Global Receive FIFO Reg

♣ Global Transmit FIFO Reg

♣ Global Chip Configuration Reg

♣ BRG Timer Reg Lower a

♣ GP Output Reg

CIR

R

BRGTRUb

GRxFIFO

GTxFIFO

GCCR

BGRTRLa

GPOR

GPOD

BRGTCR

GICR

W

R

W

R/W

W

R/W

W

♣ GP Out Data Reg

♣ BRG Timer Control Reg

♣ Global Interrupt Channel Reg

♣ BRG Timer Reg Lower b

♣ Global Interrupt Byte Count

♣ Global Interrupt Type Register

R

BRGTRLb

GIBCR

GITR

W

R

REGISTER MAP DETAIL

Table 45. Register Map, Control

NOTE: The register maps for channels A and B (UARTs A and B) contain some control registers that configure the entire chip. These are

denoted by a ♣ symbol

UART A

A(7:0)

Read

Mode Register 0 MR0a

Mode Register 1 MR1a

I/O Port Configuration Reg a I/OPCRa

BCRBRKa

Write

Mode Register 0 MR0a

Mode Register 1 MR1a

I/O Port Configuration Reg a I/OPCRa

BCRBRKa

0000 0000 (x00)

0000 0001 (x01)

0000 0010 (x02)

0000 0011 (x03)

0000 0100 (x04)

0000 0101 (x05)

0000 0110 (x06)

0000 0111 (x07)

0000 1000 (x08)

0000 1001 (x09)

0000 1010 (x0A)

0000 1011 (x0B)

0000 1100 (x0C)

0000 1101 (x0D)

0000 1110 (x0E)

0000 1111 (x0F)

BCRCOSa

Reserved

BCRXa

BCRAa

Xon Character Reg a (XonCRa)

Xoff Character Reg a (XoffCRa)

Address Recognition Character a (ARCRa)

Reserved

Xon Character Reg a (XonCRa)

Xoff Character Reg a (XoffCRa)

Address Recognition Character a (ARCRa)

Reserved

Receiver Clock Select Register a (RxCSRa)

♣ Test Register

Receiver Clock Select Register a (RxCSRa)

Test Register

Xmit Clock Select Register a TxCSRa)

♣ Global Chip Configuration Reg(GCCR)

Xmit Clock Select Register a TxCSRa)

Global Chip Configuration Reg GCCR)

364

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART B

A(7:0)

Read

Write

Mode Register 0 MR0b

0001 0000 (x10)

0001 0001 (x11)

0001 0010 (x12)

0001 0011 (x13)

0001 0100 (x14)

0001 0101 (x15)

0001 0110 (x16)

0001 0111 (x17)

0001 1000 (x18)

0001 1001 (x19)

0001 1010 (x1A)

0001 1011 (x1B)

0001 1100 (x1C)

0001 1101 (x1D)

0001 1110 (x1E)

0001 1111 (x1F)

Mode Register 0 MR0b

Mode Register 1 MR1b

I/O Port Configuration Reg b I/OPCRb

BCRBRKb

I/O Port Configuration Reg b I/OPCRb

BCRBRKb

BCRCOSb

Reserved

BCRXb

BCRAb

Xon Character Reg b (XonCRb)

Xoff Character Reg b (XoffCRb)

Address Recognition Character b (ARCRb)

♣ Interrupt Control Register (ICR)

Receiver Clock Select Register b (RxCSRb)

♣ Watch-dog Timer Run Control (WDTRCR)

Xmit Clock Select Register b (TxCSRb)

♣ Interrupt Vector Register (IVR)

Xon Character Reg b (XonCRb)

Xoff Character Reg b (XoffCRb)

Address Recognition Character b (ARCRb)

Interrupt Control Register (ICR)

Receiver Clock Select Register b (RxCSRb)

Watch-dog Timer Run Control (WDTRCR)

Xmit Clock Select Register b (TxCSRb)

Interrupt Vector Register (IVR)

UART C

A(7:0)

Read

Mode Register 0 MR0c

Mode Register 1

Write

Mode Register 0 MR0c

Mode Register 1 MR1c

I/O Port Configuration Reg c I/OPCRc

BCRBRKc

0010 0000 (x20)

0010 0001 (x21)

0010 0010 (x22)

0010 0011 (x23)

0010 0100 (x24)

0010 0101 (x25)

0010 0110 (x26)

0010 0111 (x27)

0010 1000 (x28)

0010 1001 (x29)

0010 1010 (x2A)

0010 1011 (x2B)

0010 1100 (x2C)

0010 1101 (x2D)

0010 1110 (x2E)

0010 1111 (x2F)

I/O Port Configuration Reg c I/OPCRc

BCRBRKc

BCRCOSc

Reserved

BCRXc

BCRAc

Xon Character Reg c (XonCRc)

Xoff Character Reg c (XoffCRc)

Address Recognition Character c (ARCRc)

Reserved

Xon Character Reg c (XonCRc)

Xoff Character Reg c (XoffCRc)

Address Recognition Character c (ARCRc)

Reserved

Receiver Clock Select Register c (RxCSRc)

Reserved

Receiver Clock Select Register c (RxCSRc)

Reserved

Xmit Clock Select Register c (TxCSRc)

Reserved

Xmit Clock Select Register c (TxCSRc)

Reserved

365

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART D

A(7:0)

Read

Write

Mode Register 0 MR0d

Mode Register 1 MR1d

I/O Port Configuration Reg d I/OPCRd

BCRBRKd

0011 0000 (x30)

0011 0001 (x31)

0011 0010 (x32)

0011 0011 (x33)

0011 0100 (x34)

0011 0101 (x35)

0011 0110 (x36)

0011 0111 (x37)

0011 1000 (x38)

0011 1001 (x39)

0011 1010 (x3A)

0011 1011 (x3B)

0011 1100 (x3C)

0011 1101 (x3D)

0011 1110 (x3E)

0011 1111 (x3F)

Mode Register 0 MR0d

Mode Register 1 MR1d

I/O Port Configuration Reg d I/OPCRd

BCRBRKd

BCRCOSd

Reserved

BCRXd

BCRAd

Xon Character Reg d (XonCRd)

Xoff Character Reg d (XoffCRd)

Address Recognition Character d (ARCRd)

Reserved

Xon Character Reg d (XonCRd)

Xoff Character Reg d (XoffCRd)

Address Recognition Character d (ARCRd)

Reserved

Receiver Clock Select Register d (RxCSRd)

Reserved

Receiver Clock Select Register d (RxCSRd)

Reserved

Xmit Clock Select Register d (TxCSRd)

Reserved

Xmit Clock Select Register d (TxCSRd)

Reserved

A(7:0)

Read

Write

UART E

01000000 (x40)

01000001 (x41)

01000010 (x42)

01000011 (x43)

01000100 (x44)

01000101 (x45)

01000110 (x46)

01000111 (x47)

01001000 (x48)

01001001 (x49)

01001010 (x4A)

01001011 (x4B)

01001100 (x4C)

01001101 (x4D)

01001110 (x4E)

01001111 (x4F)

Mode Register 0 MR0e

Mode Register 1 MR1e

I/OPort Configuration Reg e I/OPCRe

BCRBRKe

Mode Register 0 MR0e

Mode Register 1 MR1e

I/OPort Configuration Reg e I/OPCRe

BCRBRKe

BCRCOSe

Reserved

BCRXe

BCRAe

Xon Character Reg e (XonCRe)

Xoff Character Reg e (XoffCRe)

Address Recognition Char e (ARCRe)

Reserved

Xon Character Reg e (XonCRe)

Xoff Character Reg e (XoffCRe)

Address Recognition Char e (ARCRe)

Reserved

Receiver Clock Select Register e (RxCSRe)

Reserved

Receiver Clock Select Register e (RxCSRe)

Reserved

Xmit Clock Select Register e (TxCSRe)

Reserved

Xmit Clock Select Register e (TxCSRe)

Reserved

366

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART F

01010000 (x50)

01010001 (x51)

01010010 (x52)

01010011 (x53)

01010100 (x54)

01010101 (x55)

01010110 (x56)

01010111 (x57)

01011000 (x58)

01011001 (x59)

01011010 (x5A)

01011011 (x5B)

01011100 (x5C)

01011101 (x5D)

01011110 (x5E)

01011111 (x5F)

Mode Register 0 MR0f

Mode Register 1 MR1f

I/OPort Configuration Reg f I/OPCRf

BCRBRKf

Mode Register 0 MR0f

Mode Register 1 MR1f

I/OPort Configuration Reg f I/OPCRf

BCRBRKf

BCRCOSf

Reserved

BCRXf

BCRAf

Xon Character Reg f (XonCRf)

Xoff Character Reg f (XoffCRf)

Address Recognition Char f (ARCRf)

Reserved

Xon Character Reg f (XonCRf)

Xoff Character Reg f (XoffCRf)

Address Recognition Char f (ARCRf)

Reserved

Receiver Clock Select Register f (RxCSRf)

Reserved

Receiver Clock Select Register f (RxCSRf)

Reserved

Xmit Clock Select Register f (TxCSRf)

Reserved

Xmit Clock Select Register f (TxCSRf)

Reserved

A(7:0)

Read

Write

UART G

01100000 (x60)

01100001 (x61)

01100010 (x62)

01100011 (x63)

01100100 (x64)

01100101 (x65)

01100110 (x66)

01100111 (x67)

01101000 (x68)

01101001 (x69)

01101010 (x6A)

01101011 (x6B)

01101100 (x6C)

01101101 (x6D)

01101110 (x6E)

01101111 (x6F)

Mode Register 0 MR0g

Mode Register 1 MR1g

I/OPort Configuration Reg g I/OPCRg

BCRBRKg

Mode Register 0 MR0g

Mode Register 1 MR1g

I/OPort Configuration Reg g I/OPCRg

BCRBRKg

BCRCOSg

Reserved

BCRXg

BCRAg

Xon Character Reg g (XonCRg)

Xoff Character Reg g (XoffCRg)

Address Recognition Char g (ARCRg)

Reserved

Xon Character Reg g (XonCRg)

Xoff Character Reg g (XoffCRg)

Address Recognition Char g (ARCRg)

Reserved

Receiver Clock Select Register g (RxCSRg)

Reserved

Receiver Clock Select Register g (RxCSRg)

Reserved

Xmit Clock Select Register g (TxCSRg)

Reserved

Xmit Clock Select Register g (TxCSRg)

Reserved

367

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART H

01110000 (x70)

01110001 (x71)

01110010 (x72)

01110011 (x73)

01110100 (x74)

01110101 (x75)

01110110 (x76)

01110111 (x77)

01111000 (x78)

01111001 (x79)

01111010 (x7A)

01111011 (x7B)

01111100 (x7C)

01111101 (x7D)

01111110 (x7E)

01111111 (x7F)

Mode Register 0 MR0h

Mode Register 1 MR1h

I/OPort Configuration Reg h I/OPCRh

BCRBRKh

Mode Register 0 MR0h

Mode Register 1 MR1h

I/OPort Configuration Reg h I/OPCRh

BCRBRKh

BCRCOSh

Reserved

BCRXh

BCRAh

Xon Character Reg h (XonCRh)

Xoff Character Reg h (XoffCRh)

Address Recognition Char h (ARCRh)

Reserved

Xon Character Reg h (XonCRh)

Xoff Character Reg h (XoffCRh)

Address Recognition Char h (ARCRh)

Reserved

Receiver Clock Select Register h (RxCSRh)

Reserved

Receiver Clock Select Register h (RxCSRh)

Reserved

Xmit Clock Select Register h (TxCSRh)

Reserved

Xmit Clock Select Register h (TxCSRh)

Reserved

368

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Table 46. Register Map, Data

UART A

A(7:0)

Read

Write

1000 0000 (x80)

1000 0001 (x81)

1000 0010 (x82)

1000 0011 (x83)

1000 0100 (x84)

1000 0101 (x85)

1000 0110 (x86)

1000 0111 (x87)

1000 1011 (x8B)

1000 1100 (x8C)

1000 1101 (x8D)

1000 1110 (x8E)

1000 1111 (x8F)

Mode Register a (MR2a)

Status Register a (SRa)

Mode Register a (MR2a)

Command Register a (CRa)

Interrupt Mask Register a (IMRa)

Transmitter FIFO Reg a (TxFIFOa)

♣ BRG Timer Reg Upper a (BRGTRUa)

Reserved

Interrupt Status Register a (ISRa)

Receiver FIFO Reg a (RxFIFOa)

Reserved

Input Port Reg a (IPRa)

I/O Port Interrupt and Output a I/OPIORa)

Xon/Xoff Interrupt Status Reg a (XISRa)

♣ GP Out Select Reg (GPOSR)

♣ GP Out Clk Reg (GPOC)

♣ Current Interrupt Reg (CIR)

Reserved

I/O Port Interrupt and Output a (I/OPIORa)

Reserved

GP Out Select Reg (GPOSR)

GP Out Clk Reg (GPOC)

♣ Update CIR

♣ BRG Timer Reg Upper b (BRGTRUb)

♣ Global Transmit FIFO Reg (GTxFIFO)

♣ Global Chip Configuration Reg (GCCR)

♣ Global Receive FIFO Reg (GRxFIFO)

♣ Global Chip Configuration Reg (GCCR)

UART B

A(7:0)

Read

Mode Register b (MR2b)

Status Register b (SRb)

Interrupt Status Register b (ISRb)

Receiver FIFO Reg b (RxFIFOb)

Reserved

Write

Mode Register b (MR2b)

Command Register b (CRb)

Interrupt Mask Register b (IMRb)

Transmitter FIFO Reg b (TxFIFOb)

♣ BRG Timer Reg Lower a (BRGTRLa)

Reserved

1001 0000 (x90)

1001 0001 (x91)

1001 0010 (x92)

1001 0011 (x93)

1001 0100 (x94)

1001 0101 (x95)

1001 0110 (x96)

1001 0111 (x97)

1001 1010 (x9A)

1001 1011 (x9B)

1001 1100 (x9C)

1001 1101 (x9D)

1001 1110 (x9E)

1001 1111 (x9F)

Input Port Reg b (IPRb)

I/O Port Interrupt and Output b (I/OPIORb)

Xon/Xoff Interrupt Status Reg b (XISRb)

♣ GP Output Reg (GPOR)

Reserved

I/O Port Interrupt and Output b (I/OPIORb)

Reserved

♣ GP Output Reg (GPOR)

Reserved

♣ GP Out Data Reg (GPOD)

Reserved

♣ GP Out Data Reg (GPOD)

♣ BRG Timer Control Reg (BRGCTCR)

Reserved

♣ Global Interrupt Channel Reg (GICR)

Reserved

♣ BRG Timer Reg Lower b (BRGTRLb)

Reserved

♣ Global Interrupt Byte Count (GIBCR)

Reserved

♣ Global Interrupt Type Register (GITR)

Reserved

369

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

UART C

A(7:0)

Read

Write

Mode Register c (MR2c)

Command Register c (CRc)

Interrupt Mask Register c (IMRc)

Transmitter FIFO Reg c (TxFIFOc)

Reserved

1010 0000 (xA0)

1010 0001 (xA1)

1010 0010 (xA2)

1010 0011 (xA3)

1010 0100 (xA4)

1010 0101 (xA5)

1010 0110 (xA6)

1010 0111 (xA7)

1010 1000 (xA8)

1010 1001 (xA9)

1010 1010 (xAA)

1010 1011 (xAB)

1010 1100 (xAC)

1010 1101 (xAD)

1010 1110 (xAE)

1010 1111 (xAF)

Mode Register c (MR2c)

Status Register c (SRc)

Interrupt Status Register c (ISRc)

Receiver FIFO Reg c (RxFIFOc)

Input Port Reg c (IPRc)

I/O Port Interrupt and Output c (I/OPIORc)

Xon/Xoff Interrupt Status Reg c (XISRc)

Reserved

I/O Port Interrupt and Output c (I/OPIORc)

Reserved

UART D

A(7:0)

Read

Mode Register d (MR2d)

Status Register d (SRd)

Interrupt Status Register d (ISRd)

Receiver FIFO Reg d (RxFIFOd)

Input Port Reg d (IPRd)

I/O Port Interrupt and Output d (I/OPIORd)

Xon/Xoff Interrupt Status Reg d (XISRd)

Reserved

Write

Mode Register d (MR2d)

Command Register d (CRd)

Interrupt Mask Register d (IMRd)

Transmitter FIFO Reg d (TxFIFOd)

Reserved

1011 0000 (xB0)

1011 0001 (xB1)

1011 0010 (xB2)

1011 0011 (xB3)

1011 0100 (xB4)

1011 0101 (xB5)

1011 0110 (xB6)

1011 0111 (xB7)

1011 1000 (xBB)

1011 1001 (xB9)

1011 1010 (xBA)

1011 1011 (xBB)

1011 1100 (xBC)

1011 1101 (xBD)

1011 1110 (xBE)

1011 1111 (xBF)

I/O Port Interrupt and Output d (I/OPIORd)

Reserved

370

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

A(7:0)

Read

Write

UART E

11000000 (xC0)

11000001 (xC1)

11000010 (xC2)

11000011 (xC3)

11000100 (xC4)

11000101 (xC5)

11000110 (xC6)

11000111 (xC7)

11001000 (xC8)

11001001 (xC9)

11001010 (xCA)

11001011 (xCB)

11001100 (xCC)

11001101 (xCD)

11001110 (xCE)

11001111 (xCF)

Mode Register e (MR2e)

Status Register e (SRe)

Interrupt Status Register e (ISRe)

Receiver FIFO Reg e (RxFIFOe)

Input Port Reg e (IPRe)

I/O Port Interrupt and Output e (I/OPIORe)

Xon/XoffInterrupt Status Reg e (XISRe)

Reserved

Mode Register e (MR2e)

Command Register e (CRe)

Interrupt Mask Register e (IMRe)

Transmitter FIFO Reg e (TxFIFOe)

Reserved

I/O Port Interrupt and Output e (I/OPIORe)

Reserved

UART F

11010000 (xD0)

11010001 (xD1)

11010010 (xD2)

11010011 (xD3)

11010100 (xD4)

11010101 (xD5)

11010110 (xD6)

11010111 (xD7)

11011000 (xD8)

11011001 (xD9)

11011010 (xDA)

11011011 (xDB)

11011100 (xDC)

11011101 (xDD)

11011110 (xDE)

11011111 (xDF)

Mode Register f (MR2f)

Status Register f (SRf)

Interrupt Status Register f (ISRf)

Receiver FIFO Reg f (RxFIFOf)

Input Port Reg f (IPRf)

I/O Port Interrupt and Output f (I/OPIORf)

Xon/XoffInterrupt Status Reg f (XISRf)

Reserved

Mode Register f (MR2f)

Command Register f (CRf)

Interrupt Mask Register f (IMRf)

Transmitter FIFO Reg f (TxFIFOf)

Reserved

I/O Port Interrupt and Output f (I/OPIORf)

Reserved

371

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

A(7:0)

Read

Write

UART G

11100000 (xE0)

11100001 (xE1)

11100010 (xE2)

11100011 (xE3)

11100100 (xE4)

11100101 (xE5)

11100110 (xE6)

11100111 (xE7)

11101000 (xE8)

11101001 (xE9)

11101010 (xEA)

11101011 (xEB)

11101100 (xEC)

11101101 (xED)

11101110 (xEE)

11101111 (xEF)

Mode Register g (MR2g)

Status Register g (SRg)

Interrupt Status Register g (ISRg)

Receiver FIFO Reg g (RxFIFOg)

Input Port Reg g (IPRg)

I/O Port Interrupt and Output g (I/OPIORg)

Xon/XoffInterrupt Status Reg g (XISRg)

Reserved

Mode Register g (MR2g)

Command Register g (CRg)

Interrupt Mask Register g (IMRg)

Transmitter FIFO Reg g (TxFIFOg)

Reserved

I/O Port Interrupt and Output g (I/OPIORg)

Reserved

UART H

11110000 (xF0)

11110001 (xF1)

11110010 (xF2)

11110011 (xF3)

11110100 (xF4)

11110101 (xF5)

11110110 (xF6)

11110111 (xF7)

11111000 (xF8)

11111001 (xF9)

11111010 (xFA)

11111011 (xFB)

11111100 (xFC)

11111101 (xFD)

11111110 (xFE)

11111111 (xFF)

Mode Register h (MR2h)

Status Register h (SRh)

Interrupt Status Register h (ISRh)

Receiver FIFO Reg h (RxFIFOh)

Input Port Reg h (IPRh)

I/O Port Interrupt and Output h (I/OPIORh)

Xon/XoffInterrupt Status Reg h (XISRh)

Reserved

Mode Register h (MR2h)

Command Register h (CRh)

Interrupt Mask Register h (IMRh)

Transmitter FIFO Reg h (TxFIFOh)

Reserved

I/O Port Interrupt and Output h (I/OPIORh)

Reserved

BRG Counter/Timer Registers

RESET CONDITIONS

Clears Modes for:

Device Configuration after Hardware Reset or CRa

cmd=x1F

Power down

Test modes

Cleared registers:

Input Port Changed bits

Gang write to Xon or Xoff

Xon/Xoff/Address detection

Receiver error status

Channel Status Registers (SR)

Channel Interrupt Status Registers (ISR)

Channel Interrupt Mask Registers (IMR)

Channel Interrupt Xon Status Register (XISR)

Interrupt Control Register (ICR)

Disables:

Transmitters

Receivers

Interrupts, current and future

Global Configuration Control Register (GCCR)

Hence the device enters the asynchronous bus cycling mode.

Current Interrupt Register (CIR)

BRG Timer Run Control Register (BRGTCR)

Watch-dog Timer Run Control Register (WDTRCR)

Channel Input/Output Port Configuration Registers (I/OPCR)

Hence all I/O pins have direction = Input after reset

Halts:

BRG Counters

Bus cycle in progress (hardware RESET only)

372

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

The user must allow a minimum of 6 SClk cycles to elapse after

a reset (RESETN pin or CRa initiated) of the device terminates

before initiating a new bus cycle.

Limitations:

Minimum RESETN pin pulse width is 10 SClk cycles after Vcc

reaches operational range

DC ELECTRICAL SPECIFICATIONS (26C198 and 68C198)

V

CC

= 5.0V ±10%, 0° to 70°C

LIMITS

SYMBOL

PARAMETER

TEST CONDITIONS

UNIT

MIN

TYP

MAX

V

Input low voltage

V

0.8

V

IL

SS

V

Input high voltage (except X1/CLK)

Input high voltage (X1/CLK)

2.0

V

CC

IH

V

IH

0.8 V

V

CC

V

Output low voltage (except OD outputs)

Output high voltage (except OD outputs)

I

= 7.0mA

= -400µA

= -100µA

0.4

OL

I

0.8V

0.9V

V

OH

CC

I

V

Open drain low voltage

I

= 14.0mA

0.4

10

V

OL

I

Input current low, I/O pins

Input current high, I/O pins

V

IN

= 0

IL

-10

-5

µA

I

IH

V

= V

IN CC

I

Input leakage current

V

= 0 to V

CC

5

I

IN

I

X1/CLK input low current

X1/CLK input high current

V =GND,X2=Open

IN

V =V , X2=Open

IN CC

IKX1

IHX1

-100

+100

I

Output off current high, 3-state data bus

Output off current low, 3-state data bus

V

= V

OZH

IN CC

-10

10

µA

= 0

OZL

IN

I

Open-drain output low current in off state

Open drain output high current in off state

V

IN

V

IN

= V

ODL

CC

I

ODH

Power supply current

Operating mode

Power down mode (no clocks operating)

TTL Input levels

CMOS input levels

200

75

25

mA

µA

I

CC

373

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

5

AC ELECTRICAL CHARACTERISTICS (26C198 and 68C198)

LIMITS

UNIT

SYMBOL

FIGURE

PARAMETER

MIN

TYP

MAX

RESET TIMING

t

RESET pulse width

10

Sclk

RES

BUS TIMING

t

A0-A7 setup time before Sclk C3 rising edge

A0-A7 hold time after Sclk C3 rising edge

CEN setup time before Sclk C1 high (ASYNC)

CEN setup time before Sclk C2 high (SYNC)

CEN hold time after Sclk C3 high (SYNC)

10

18

5

3

ns

AS

AH

t

12

t

ns

CS

CH

5

15

25

1.5 Sclk

ns

t

1

CEN hold time after Sclk C4 high (ASYNC)

t

CEN high after C4 end. To terminate cycle (SYNC)

W-Rn setup time before Sclk C2 rising edge

W-Rn hold time after Sclk C3 rising edge

18

Sclk

ns

STP

t

5

RWS

RWH

t

20

1.5 Sclk

25

ns

t

Read cycle Data valid after Sclk C3 falling edge

Read cycle data bus floating after CEN high (ASYNC)

Read cycle data bus floating after C4 end (SYNC)

Write cycle data setup time before Sclk C4 rising edge

Write cycle data hold time after Sclk C4 rising edge

High time between CEN low (ASYNC)

37

35

ns

DD

20

t

ns

DF

20

t

25

30

12

15

ns

DS

t

18

DH

t

10

RWD

I/O PORT PIN TIMING

t

I/O input setup time before Sclk C3 falling edge (Read IPR)

I/O input hold time after Sclk C4 rising edge (Read IPR)

20

18

ns

PS

PH

t

I/O output valid from:

Write Sclk C4 rising edge (write to I/OPIOR)

t

50

43

ns

PD

INTERRUPT TIMING

IRQN from:

Internal interrupt source active bid

Software reset to IRQN inactive

Write IMR (clear IMR bit after C4 end)

22

20

Sclk

ns

t

IR

3

50

37

t

Interrupt vector valid after C3 falling edge, IACKN cycle

25

ns

DD

2

Tx / Rx CLOCK TIMING, External

t

RxC high or low time

ns

MHz

ns

RX

RxC frequency (16 X)

(1 X)

0

16

1

f

RX

t

f

TxC high or low time

20

TX

RF

TxC frequency (16 X)

(1 X)

0

16

1

MHz

ns

t

Tx / Rx clock rise and fall times

20

TRANSMITTER TIMING

t

TxD output delay from TxC low

100

20

ns

TXD

TCS

TxC output delay from TxD output data

-20

RECEIVER TIMING

t

RxD data setup time to RxC high (data)

RxD data hold time from RxC high (data)

RxD data setup time to RxC high (Start Bit)

30

ns

RXS

RXH

TsSTRT

Sclk TIMING

Tsclkl

17 / 32

16X clk

3

Min low time at Vil (0.8V)

Min high time at Vih (2.0V)

Sclk frequency

11

ns

Tsclkh

Fsclk

33

MHz

ns

T/RFsclk

Sclk rise/fall time (0.8 to 2.0Volts)

3 / 3

374

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

AC ELECTRICAL CHARACTERISTICS (26C198 and 68C198) (Continued)

LIMITS

UNIT

SYMBOL

FIGURE

PARAMETER

MIN

TYP

MAX

2

X1 / X2 COMMUNICATION CRYSTAL CLOCK

Fx1

X1 clock frequency

X1 Low / High time

X1 Rise / Fall time

0

3.6864

8.0

MHz

ns

X1 L / H

T/RFx1

20

10/10

8

ns

COUNTER / TIMER BAUD RATE CLOCK (EXTERNAL CLOCK INPUT)

FC/T

Clock frequency

0

MHz

ns

TC/TLH

C/T high and low time

30

TC/TO

Delay C/T clock external to output pin

60

ns

4

DACKN TIMING

DAKdly

DACK low from Sclk C4 rising edge

DACK high from CEN high (ASYNC)

DACK high from C4 end rising edge (SYNC)

25

40

ns

DAKdlya

DAKdlys

28

I/O PORT External Clock

Tgpirtx

GPI to Rx/Tx clock out

TBD

ns

RxD setup to I/OP rising edge 1X mode

I/OP falling edge to TxD out 1X mode

Gout TIMING

GPOtdd

GPO valid after write to GPOR

TBD

ns

NOTES:

1. The ASYNC pulse width low must include 4 rising edges plus the setup & hold times. For those applications where the control processor

has no knowledge of the Sclk period, this will imply a CEN period of 5 Sclk rising edges.

2. Production test will use rise and fall time less than 7ns. Specified rise and fall times are guaranteed by design.

3. Sclk is required for proper bus timing. Sclk must always be faster than twice the fastest 1X data clock.

4. The meaning of DACKN is that data will be valid before the end of the C4 time.

5. All voltage measurements are relative to gnd. Input and output levels are those shown in “DC Electrical Specifications”. For testing, inputs

switch between 0.2 and 2.8V; outputs are measured between 0.8 and 2.0V.

375

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

DC ELECTRICAL SPECIFICATIONS (26L198 and 68L198)

V

CC

= 3.3 V ±10%, 0° to 70°C

LIMITS

UNIT

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

V

Input low voltage

V

0.7

V

IL

SS

V

Input high voltage (except X1/CLK)

Input high voltage (X1/CLK)

2.0

V

CC

IH

V

IH

0.8 V

V

CC

V

Output low voltage (except OD outputs)

Output high voltage (except OD outputs)

I

= 5.0mA

= -400µA

= -100µA

0.4

OL

I

0.8V

0.9V

V

OH

CC

I

V

Open drain low voltage

I

= 10.0mA

0.4

5

V

OL

I

Input current low, I/O pins

Input current high, I/O pins

V

IN

= 0

IL

-5

µA

I

IH

V

= V

IN CC

I

Input leakage current

V

= 0 to V

CC

5

I

IN

I

X1/CLK input low current

X1/CLK input high current

V =GND,X2=Open

IN

V =V , X2=Open

IN CC

IKX1

IHX1

-50

-5

+50

I

Output off current high, 3-state data bus

Output off current low, 3-state data bus

V

= V

OZH

IN CC

5

µA

I

V

IN

= 0

OZL

I

Open-drain output low current in off state

Open drain output high current in off state

V

= V

ODL

IN

CC

-5

I

ODH

Power supply current

Operating mode

Power down mode (no clocks operating)

TTL Input levels

CMOS input levels

22

12

1

35

20

30

mA

µA

I

CC

376

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

5

AC ELECTRICAL CHARACTERISTICS (26L198 and 68L198)

LIMITS

UNIT

SYMBOL

FIGURE

PARAMETER

MIN

TYP

MAX

RESET TIMING

t

RESET pulse width

10

Sclk

RES

BUS TIMING

t

A0-A7 setup time before Sclk C3 rising edge

A0-A7 hold time after Sclk C3 rising edge

CEN setup time before Sclk C1 high (ASYNC)

CEN setup time before Sclk C2 high (SYNC)

CEN hold time after Sclk C3 high (SYNC)

25

40

7

3

ns

AS

AH

t

12

t

ns

CS

CH

7

35

50

7

1.5 Sclk

t

1

CEN hold time after Sclk C4 high (ASYNC)

t

W-Rn setup time before Sclk C2 rising edge

W-Rn hold time after Sclk C3 rising edge

ns

RWS

t

35

1.5 Sclk

34

RWH

t

Read cycle Data valid after Sclk C3 falling edge

Read cycle data bus floating after CEN high (ASYNC)

Read cycle data bus floating after C4 end (SYNC)

Write cycle data setup time before Sclk C4 rising edge

Write cycle data hold time after Sclk C4 rising edge

High time between CEN low (ASYNC)

50

35

DD

26

t

DF

ns

19

t

30

35

15

13

ns

DS

t

21

DH

t

.5 Sclk

RWD

I/O PORT PIN TIMING

t

I/O input setup time before Sclk C3 falling edge (Read IPR)

I/O input hold time after Sclk C4 rising edge (Read IPR)

20

18

ns

PS

PH

t

I/O output valid from:

Write Sclk C4 rising edge (write to I/OPIOR)

t

80

ns

PD

INTERRUPT TIMING

IRQN from:

Internal interrupt source active bid

Software reset to IRQN inactive

Write IMR (clear IMR bit after C4 end)

22

25

33

34

43

120

75

Sclk

ns

t

IR

t

Interrupt vector valid after C3 falling edge, IACKN cycle

50

ns

DD

2

Tx / Rx CLOCK TIMING, External

t

RxC high or low time

RxC frequency

ns

MHz

ns

RX

(16 X)

(1 X)

0

8

1

6

f

RX

t

TX

TxC high or low time

TxC frequency

25

(16 X)

(1 X)

0

8

1

6

f

MHz

ns

TX

t

RF

Tx / Rx clock rise and fall times

20

TRANSMITTER TIMING

t

TxD output delay from TxC low

100

20

ns

TXD

TCS

TxC output delay from TxD output data

-20

RECEIVER TIMING

t

RxD data setup time to RxC high (data)

RxD data hold time from RxC high (data)

35

ns

RXS

RXH

17

32

TsSTRT

RxD data setup time to RxC high (Start Bit)

16X clk

3

Sclk TIMING

Tsclkl

Min low time at Vil (0.8V)

Min high time at Vih (2.0V)

Sclk frequency

20

ns

Tsclkh

Fsclk

0.1

17

MHz

ns

T/RFsclk

Sclk rise/fall time (0.8 to 2.0Volts)

5 / 5

377

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

AC ELECTRICAL CHARACTERISTICS (Continued)

LIMITS

UNIT

SYMBOL

FIGURE

PARAMETER

MIN

TYP

MAX

2

X1 / X2 COMMUNICATION CRYSTAL CLOCK

Fx1

X1 clock frequency

X1 Low / High time

X1 Rise / Fall time

0

3.6864

8.0

MHz

ns

X1 L / H

T/RFx1

25

10 / 10

8

ns

COUNTER / TIMER BAUD RATE CLOCK (EXTERNAL CLOCK INPUT)

FC/T

Clock frequency

0

MHz

ns

TC/TLH

C/T high and low time

25

TC/TO

Delay C/T clock external to output pin

125

ns

4

DACKN TIMING

DAKdly

DACK low from Sclk C4 rising edge

DACK high from CEN high (ASYNC)

DACK high from C4 end rising edge (SYNC)

42

45

ns

DAKdlya

DAKdlys

23

32

I/O PORT External Clock

Tgpirtx

GPI to Rx/Tx clock out

80

ns

RxD setup to I/OP rising edge 1X mode

I/OP falling edge to TxD out 1X mode

35

100

G

TIMING

OUT

GPOtdd

GPO valid after write to GPOR

100

ns

NOTES:

1. The ASYNC pulse width low must include 4 rising edges plus the setup & hold times. For those applications where the control processor

has no knowledge of the Sclk period, this will imply a CEN period of 5 Sclk rising edges.

2. Production test will use rise and fall time less than 7ns. Specified rise and fall times are guaranteed by design.

3. Sclk is required for proper bus timing. Sclk must always be faster than twice the fastest 1X data clock.

4. The meaning of DACKN is that data will be valid before the end of the C4 time.

5. All voltage measurements are relative to gnd. Input and output levels are those shown in “DC Electrical Specifications”. For testing, inputs

switch between 0.2 and 2.8V; outputs are measured between 0.8 and 2.0V.

6. Some values not tested, but guaranteed by design.

378

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

t

CH

C1

C2

C3

C4

SCLK

CEN

t

RWD

W_RN

t

RWH

ADDRESS

INVALID

VALID

INVALID

VALID

INVALID

DATA

DACKN

t

AH

AS

t

RWS

CS

t

DS

DAK

DLY

C4

CEN HIGH

t

DH

SD00194

Figure 2. Basic Write Cycle, ASYNC

t

CS

C1

C2

C3

C4

SCLK

CEN

t

STP

t

CH

W_RN

t

RWH

ADDRESS

INVALID

VALID

INVALID

VALID

INVALID

DATA

DACKN

t

AH

AS

t

RWS

DS

DAK

DLY

C4

DLY

C4 END

t

DH

SD00195

Figure 3. Basic Write Cycle, SYNC

379

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

t

CH

C1

C2

C3

C4

SCLK

CEN

t

RWD

t

W_RN

RWH

ADDRESS

INVALID

VALID

INVALID

DATA=00

VALID

INVALID

DATA

DACKN

t

AH

t

AS

CS

t

RWS

t

DF

t

DD

DAK

DLY

C4

DAK

DLY

CEN

SD00196

Figure 4. Basic Read Cycle, ASYNC

t

CS

C1

C2

C3

C4

SCLK

CEN

t

STP

t

CH

W_RN

t

RWH

ADDRESS

INVALID

VALID

INVALID

DATA=00

VALID

INVALID

DATA

DACKN

t

AH

t

AS

t

DF

t

RWS

t

DD

DAK

C4 END

DLY

C4

DLY

SD00197

Figure 5. Basic Read Cycle, SYNC

380

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

C1

C2

C3

C4

SCLK

IACKN

CEN

W_RN

DON’T CARE

INVALID

DON’T CARE

INVALID

ADDRESS

INVALID

VALID

INVALID

DATA

DACKN

t

AH

t

AS

t

CS

t

RWS

t

DF

t

DD

NOTE: CEN must not be active during an IACKN cycle. If CEN is active, IACKN will be ignored

and a normal read or write will be executed according to W_RN. In the synchronous

mode, extended IACKN signal will start another IACKN. (This may not be desired, but

is allowed.)

C4

DAK

DLY

DAK

DLY

CEN

HIGH

SD00525

Figure 6. Basic IACKN Cycle, ASYNC/SYNC

+5V

T/R f

X1

1K required for

TTL gate.

X1 L/H

X1

X2

f

X1

NC

C1 = C2 = 24pF FOR C = 20PF

L

C1 and C2 should be chosen according to the

crystal manufacturer’s specification.

C1 and C2 values will include any parasitic

capacitance of the wiring.

26C94

X1

X2

22

STANDARD

BRG

BAUD

3pF

RATES

C1

50 KOHMs

TO

150 KOHMs

38.4kHz CLOCK

TO I/O CHANGE-OF-STATE DETECTORS

C2

3.6864MHz

4pF

To

MUX

remainder

of circuit

÷ 2

NOTES:

C1 and C2 should be based on manufacturer’s specification.

X1 and X2 parasitic capacitance IS 1-2pF AND 3-5pF, respectively.

GAIN: at 4MHz 8 to 14db; at 8MHz 2 to 6db

PHASE: at 4MHz 272° to 276°; at 8MHz 272° to 276°

The above figures for 5V operation. Operation at 3V is to be determined.

TYPICAL CRYSTAL SPECIFICATION

2 – 4MHZ

FREQUENCY:

LOAD CAPACITANCE (C ):

12 – 32pF

L

TYPE OF OPERATION:

PARALLEL RESONANT, FUNDAMENTAL MODE

SD00198

Figure 7. X1/X2 Communication Crystal Clock

381

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

T/RF

SCLK

t

SCLKL

t

SCLKH

f

SCLK

SD00199

Figure 8. SCLK Timing

T/RF

SCLK

TC/TL

TC/TH

FC/T

TC/TO

SD00200

Figure 9. Counter/Timer Baud Rate Clock, External

T/RF

Trx

Ttx

TC/TH

Frx

Ftx

TC/TO

SD00201

Figure 10. Tx/Rx Clock Timing, External

1X DATA CLOCK

t

RXH

RxD

t

RXS

t

TXD

TxD

SD00202

Figure 11. Transmitter and Receiver Timing

Note: CEN must not be active during an IACKN cycle. If CEN is

active IACKN will be ignored and a normal read or write will be

executed according to W_RN.

In the synchronous mode extended IACKN signal cycle will start

another IACKN. (This may not be desired but is allowed)

382

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

GRxFIFO, 360

GTxFIFO, 360

INDEX

Numbers

1x and 16x modes, Receiver, 342

1x and 16x modes, Transmitter, 342

H

Host Interface, 339

Host interface, 339

A

I

Address Recognition Character Register, 357

ARCR, 357

I/O Port Configuration Register, 360

I/O Port Interrupt and Output Register, 360

I/O ports, 343

Asynchronous bus cycle, 339

I/OPCR, 343, 360

I/OPIOR, 360

IACKN, 341

IACKNCycle, 345

ICR, 358

IMR, 341, 356

INDEX, 381

B

Baud Rate Generator , 340

BCRA, 357

BCRBRK, 357

BCRCOS, 357

BCRx, 357

Input Port Register, 360

Interrupt Arbitration, 344

Interrupt Control, 341

Interrupt Mask Register, 356

Interrupt sources, Enabling, 345

Interrupt Status Register, 356

Interrupt Vector Register, 359

Interrupts, Xon/Xoff, 349

IOPIOR register, 344

IPR , 360

Bidding Control Register – Address, 357

Bidding Control Register – Break Change, 357

Bidding Control Register – Change of State, 357

Bidding Control Register – Xon, 357

Block diagram, 339

Break, transmission of, 342

BRG Timer Control Register, 358

BRG Timer Reload Registers, Lower, 358

BRG Timer Reload Registers, Upper, 358

BRGCTCR , 358

ISR, 341, 356

IVR, 359

BRGTRL, 358

BRGTRU, 358

M

C

Minor Modes, 347

Mode control, Xon/Xoff, 349

Mode Register 1, 351

Mode Register 2, 351

Mode Registers, Initialization, 350

Modes of Operation, 346

MR0 , 350

MR1, 351

MR2, 351

Multidrop mode, 344

CEN, 339

Channel Blocks, 340

Channel Status Register, 355

Character Recognition, 340

CharacterStripping, 344

CIR, 359

Clock Register, Rx & Tx, 352

Command Register, 353

COMMAND REGISTER TABLE, 355

CR , 353

Crystal oscillator, 340

Current Interrupt Register, 359

O

Overrun error, 343

D

P

Description, 335

Parity error, 343

Pin Description, 338

Pinout, 337

DESCRIPTION, over all, 339

F

Polling, 345

Framing error, 343

R

G

Receiver, 342

Receiver FIFO, 343, 357

Receiver Status Bits, 342

REGISTER DESCRIPTIONS, 350

Register Map, 362

GCCR, 350

General Purpose Pins, 344

GIBCR, 359

GICR, 359

Register Map, Control, 362, 363

Register Map, Data, 363, 368

Reset Conditons, 371

RxCSR , 352

GITR, 360

Global Configuration Control Register (GCCR), 350

Global Interrupting Byte Count Register, 359

Global Interrupting Channel Register, 359

Global Registers, 341, 344

Global RxFIFO Register, 360

Global TxFIFO Register, 360

GPOC , 361

RxFIFO, 357

S

Sclk, 339

GPOD, 361

SR , 355

GPOR, 361

GPOSR, 361

Synchronous bus cycle, 339

System Clock, 340

383

1995 May 1

Philips Semiconductors

Product specification

Octal UART with TTL compatibility at 3.3V

and 5V supply voltages

SC26C198 SC68C198

SC26L198 SC68L198

Wake up mode, 344

T

Wake Up modes, 347

Wake up. Default, 347

Watch–dog Timer , 347

Watch–dog Timer Enable Register, 358

WDTRCR, 358

Timing Circuits, 340

Transmitter, 341

Transmitter FIFO, 342, 357

Tx, Status Bits , 341

TxCSR , 352

TxEMT, 341

TxFIFO, 357

TxRDY, 341

X

XISR, 358

Xoff Character Register, 357

XoffCR, 357

U

Xon /Xoff characters , 348

Xon Character Register, 357

Xon–Xoff Interrupt Status Register, 358

Xon/Xoff modes, 348

Xon/Xoff Operation, 348

XonCR , 357

UCIR, 359

Update CIR, 345, 359

W

Wake Up Mode, 347

384

1995 May 1


型号：	SC68L198A1A
厂家：	NXP
描述：	Octal UART with TTL compatibility at 3.3V and 5V supply voltages 八通道UART，具有在3.3V和5V电源电压TTL兼容
文件：	总49页 (文件大小：355K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

SC68L198A1A [NXP]

相关型号：

SI9130DB

SI9135LG-T1

SI9135LG-T1-E3

SI9135_11

SI9136_11

SI9130CG-T1-E3

SI9130LG-T1-E3

SI9130_11

SI9137

SI9137DB

SI9137LG

SI9122E