Philips Semiconductors

Product data

SCC2681

Dual asynchronous receiver/transmitter (DUART)

2004 Apr 06

4

SYMBOL

NAME AND FUNCTION

TYPE

PIN

SYMBOL

NAME AND FUNCTION

TYPE

DIP28

DIP40

PLCC44

X2

37

33

24

I

Crystal 2: Crystal connection. See Figure 7. If a crystal is not used it is best to keep

this pin not connected although it must not be grounded.

RxDA

35

31

22

I

Channel A Receiver Serial Data Input: The least significant bit is received first. “Mark”

is HIGH, “space” is LOW.

RxDB

11

10

7

I

Channel B Receive Serial Data Input: The least significant bit is received first. “Mark”

is HIGH, “space” is LOW.

TxDA

33

30

21

O

Channel A Transmitter Serial Data Output: The least significant bit is transmitted

first. This output is held in the “mark” condition when the transmitter is disabled, idle or

when operating in local loopback mode. “Mark” is HIGH, “space” is LOW.

TxDB

13

11

8

O

Channel B Transmitter Serial Data Output: The least significant bit is transmitted

first. This output is held in the “mark” condition when the transmitter is disabled, idle or

when operating in local loopback mode. “Mark” is HIGH, “space” is LOW.

OP0

32

29

20

O

Output 0: General purpose output or Channel A request to send (RTSAN,

active-LOW). Can be deactivated automatically on receive or transmit.

OP1

14

12

9

O

Output 1: General purpose output or Channel B request to send (RTSBN,

active-LOW). Can be deactivated automatically on receive or transmit.

OP2

31

28

–

O

Output 2: General purpose output or Channel A transmitter 1

× or 16× clock output, or

Channel A receiver 1

× clock output.

OP3

15

13

–

O

Output 3: General purpose output or open-drain, active-LOW counter/timer interrupt

output or Channel B transmitter 1

× clock output, or Channel B receiver 1× clock output.

OP4

30

27

–

O

Output 4: General purpose output or Channel A open-drain, active-LOW,

RxRDYA/FFULLA interrupt output.

OP5

16

14

–

O

Output 5: General purpose output or Channel B open-drain, active-LOW,

RxRDYB/FFULLB interrupt output.

OP6

29

26

–

O

Output 6: General purpose output or Channel A open-drain, active-LOW, TxRDYA

interrupt output.

OP7

17

15

–

O

Output 7: General purpose output or Channel B open-drain, active-LOW, TxRDYB

interrupt output.

IP0

8

7

–

I

Input 0: General purpose input or Channel A clear to send active-LOW input (CTSAN).

IP1

5

4

–

I

Input 1: General purpose input or Channel B clear to send active-LOW input (CTSBN).

IP2

40

36

27

I

Input 2: General purpose input or counter/timer external clock input. Pin has an internal

IP3

3

2

–

I

Input 3: General purpose input or Channel A transmitter external clock input (TxCA).

When the external clock is used by the transmitter, the transmitted data is clocked on

of current.

IP4

43

39

–

I

Input 4: General purpose input or Channel A receiver external clock input (RxCA).

When the external clock is used by the receiver, the received data is sampled on the

current.

IP5

42

38

–

I

Input 5: General purpose input or Channel B transmitter external clock input (TxCB).

When the external clock is used by the transmitter, the transmitted data is clocked on

of current.

IP6

41

37

–

I

Input 6: General purpose input or Channel B receiver external clock input (RxCB).

When the external clock is used by the receiver, the received data is sampled on the

current.

44

40

28

I

Power Supply: +5V supply input.

GND

22

20

14

I

Ground

n.c.

1, 12,

34, 23

–

–

–

Not connected.