ST68C554 datasheet(10/40 Pages) EXAR

10 / 40 page

ST16C554/554D/68C554

Rev. 3.10

Symbol

Signal

Pin Description

type

SYMBOL DESCRIPTION

-RI A-B

8,28

63,19

-RI C-D

42,62

30,50

Ring Indicator (active low) - These inputs are associated

with individual UART channels, A through D. A logic 0 on

this pin indicates the modem has received a ringing signal

from the telephone line. A logic 1 transition on this input pin

will generate an interrupt.

-RTS A-B

14,22

5,13

-RTS C-D

48,56

36,44

Request to Send (active low) - These outputs are associated

with individual UART channels, A through D. A logic 0 on the

-RTS pin indicates the transmitter has data ready and

waiting to send. Writing a logic 1 in the modem control

data is available. After a reset this pin will be set to a logic

1. This pin has no effect on the UARTs transmit or receive

operation.

RX A-B

7,29

62,20

RX C-D

41,63

29,51

Receive Data Input RX A-D. - These inputs are associated

with individual serial channel data to the ST16C554D. The

RX signal will be a logic 1 during reset, idle (no data), or

when the transmitter is disabled. During the local loopback

mode, the RX input pin is disabled and TX data is internally

connected to the UART RX Input, internally.

TX A-B

17,19

8,10

TX C-D

51,53

39,41

Transmit Data - These outputs are associated with indi-

vidual serial transmit channel data from the 554D. The TX

signal will be a logic 1 during reset, idle (no data), or when

the transmitter is disabled. During the local loopback mode,

the TX input pin is disabled and TX data is internally

connected to the UART RX Input.

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