Philips Semiconductors

Product data

SCC68681

Dual asynchronous receiver/transmitter (DUART)

2004 Apr 06

4

SYMBOL

NAME AND FUNCTION

TYPE

PIN

SYMBOL

NAME AND FUNCTION

TYPE

DIP40

PLCC44

X1/CLK

36

32

I

Crystal 1: Crystal connection or an external clock input. A crystal of a clock the appropriate

frequency (nominally 3.6864 MHz) must be supplied at all times. For crystal connections see

Figure 8, Clock Timing.

X2

37

33

I

Crystal 2: Crystal connection. See Figure 8. If a crystal is not used it is best to keep this pin not

connected. It must not be grounded.

RxDA

35

31

I

Channel A Receiver Serial Data Input: The least significant bit is received first. ‘Mark’ is HIGH,

‘space’ is LOW.

RxDB

11

10

I

Channel B Receiver Serial Data Input: The least significant bit is received first. ‘Mark’ is HIGH,

‘space’ is LOW.

TxDA

33

30

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

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

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

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). Pin has

IP1

5

4

I

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

IP2

40

36

I

Input 2: General purpose input, or Channel B receiver external clock input (RxCB), or

counter/timer external clock input. When the external clock is used by the receiver, the received

1 to 4

µA of current.

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 the falling edge of the

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 rising edge of the

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 the falling edge of the

44

40

I

Power Supply: +5 V supply input.

GND

22

20

I

Ground.

NC

1, 12,

23, 34

–

–

Not connected.