SYMBOL DESCRIPTION

symbol

pin

Signal Type

Pin Description

D0-D7

RX A-B

RX C-D

TX A-B

TX C-D

CS*A-B

CS*C-D

XTAL1

XTAL2

LOW*

GND

GND

IOR*

5-66

7.29

41.63

17.19

51.53

16.20

50.54

35

36

18

6.23

40.57

52

I/O

I

O

I

I

O

I

O

I

Bi-directional data bus. Eight bit,

three state data bus to

transfer information to or from the CPU. Do is the least

significant bit of the data bus and the first serial data bit to be

received or transmitted.

Serial data input. The serial information (data) received from

serial port to IMP16C554 receive input circuit . A mark (high)

is logic one and a space (low)is logic zero. During the local

loopback mode the RX input is disabled from external

connection and to the TX output internally.

Serial data output. The serial data is transmitted via this pin

with additional start, stop and parity bits. The TX will be held

in mark(high) state during reset, local loopback mode or

when the transmitter is disabled.

Chip select. (active low) A low at this pin enables the

IMP16C554/CPU data transfer operation. Each UART sections

of the IMP16C554 can be accessed independently.

Crystal input 1 or external clock input. A crystal can be

connected to this pin and XTAL2 pin to utilize the internal

oscillator circuit. An external clock can be used to clock

internal

circuit

and

baud

rate

generator

for

custom

transmission rates.

Crystal input 2 or buffered clock output. See XTAL1.

Write strobe.(active low)A low on this pin will transfer the

contents of the CPU data bus to the addressed register.

Signal and power ground.

Read strobe.(active low)A low level on this pin transfers the

contents of the IMP16C554 data bus to the CPU.

2

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© 2002 IMP, Inc.

IMP16C554

IMP16C554