ST16C554D datasheet(3/39 Pages) EXAR

3 / 39 page

ST16C554/554D

REV. 4.0.1

2.97V TO 5.5V QUAD UART WITH 16-BYTE FIFO

PIN DESCRIPTIONS

Pin Description

NAME

64-LQFP

PIN #

68-PLCC

PIN#

TYPE

DESCRIPTION

DATA BUS INTERFACE

Address data lines [2:0]. These 3 address lines select one of the internal regis-

ters in UART channel A-D during a data bus transaction.

I/O

Data bus lines [7:0] (bidirectional).

IOR#

(VCC)

When 16/68# pin is HIGH, the Intel bus interface is selected and this input

becomes read strobe (active low). The falling edge instigates an internal read

cycle and retrieves the data byte from an internal register pointed by the address

lines [A2:A0], puts the data byte on the data bus to allow the host processor to

read it on the rising edge.

When 16/68# pin is LOW, the Motorola bus interface is selected and this input is

not used and should be connected to VCC.

IOW#

(R/W#)

When 16/68# pin is HIGH, it selects Intel bus interface and this input becomes

write strobe (active low). The falling edge instigates the internal write cycle and

the rising edge transfers the data byte on the data bus to an internal register

pointed by the address lines.

When 16/68# pin is LOW, the Motorola bus interface is selected and this input

becomes read (HIGH) and write (LOW) signal.

CSA#

(CS#)

When 16/68# pin is HIGH, this input is chip select A (active low) to enable chan-

nel A in the device.

When 16/68# pin is LOW, this input becomes the chip select (active low) for the

Motorola bus interface.

CSB#

(A3)

When 16/68# pin is HIGH, this input is chip select B (active low) to enable chan-

nel B in the device.

When 16/68# pin is LOW, this input becomes address line A3 which is used for

channel selection in the Motorola bus interface.

CSC#

(A4)

When 16/68# pin is HIGH, this input is chip select C (active low) to enable chan-

nel C in the device.

When 16/68# pin is LOW, this input becomes address line A4 which is used for

channel selection in the Motorola bus interface.

CSD#

(VCC)

When 16/68# pin is HIGH, this input is chip select D (active low) to enable chan-

nel D in the device.

When 16/68# pin is LOW, this input is not used and should be connected VCC.

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