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ST16C454

QUAD UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)

Exar Corporation 

ST16C454

SYMBOL DESCRIPTION

Symbol

-CD A-B

-CD C-D

-CTS A-B

-CTS C-D

-DSR A-B

-DSR C-D

-DTR A-B

-DTR C-D

-RI A-B

-RI C-D

-RTS A-B

-RTS C-D

Rev. 3.31

Pin

9,27

43,61

11,25

45,59

10,26

44,60

12,24

46,58

8,28

42,62

14,22

48,56

Signal

type

Pin Description

I

Carrier Detect (active low) - These inputs are associated with

individual UART channels A through D. A logic 0 on this pin indicates

that a carrier has been detected by the modem for that channel.

I

Clear to Send (active low) - These inputs are associated with

individual UART channels, A through D. A logic 0 on the -CTS pin

indicates the modem or data set is ready to accept transmit data

from the 454. Status can be tested by reading MSR bit-4.

I

Data Set Ready (active low) - These inputs are associated with

individual UART channels, A through D. A logic 0 on this pin

indicates the modem or data set is powered-on and is ready for

data exchange with the UART. This pin has no effect on the

UART’s transmit or receive operation. This pin has no effect on the

UART’s transmit or receive operation.

O

Data Terminal Ready (active low) - These inputs are associated

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

indicates that the 454 is powered-on and ready. This pin can be

controlled via the modem control register. Writing a logic 1 to MCR

bit-0 will set the -DTR output to logic 0, enabling the modem. This

pin will be a logic 1 after writing a logic 0 to MCR bit-0. This pin has

no effect on the UART’s transmit or receive operation.

I

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.

O

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 register (MCR bit-1) will set

this pin to a logic 0 indicating data is available. After a reset this pin

will be set to a logic 1. This pin has no effect on the UART’s transmit

7

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