ST16C552AIJ68 datasheet(3/39 Pages) EXAR

3 / 39 page

ST16C552/552A

Rev. 3.40

SYMBOL DESCRIPTION

Symbol

Signal Type

Pin Description

Address-0 Select Bit - Internal registers address selection.

Address-1 Select Bit - Internal registers address selection.

Address-2 Select Bit - Internal registers address selection.

-ACK

Acknowledge (with internal pull-up) - General purpose input

or line printer acknowledge (active low). a logic 0 from the

printer, indicates successful data transfer to the print buffer.

-AutoFDXT

I/O

General purpose I/O (open drain, with internal pull-up) or

automatic line feed (open drain input with internal pull-up).

When this signal is low the printer should automatically line

feed after each line is printed.

BIDEN

Bi-Direction Enable - PD7-PD0 direction select. A logic 0

sets the parallel port for I/O Select Register Control. A logic

1 sets the parallel port for Control Register Bit-5 Control.

BUSY

Busy (with internal pull-up) - General purpose input or line

printer busy (active high). can be used as an output from the

printer to indicate printer is not ready to accept data.

CLK

Clock Input. - An external clock must be connected to this

pin to clock the baud rate generator and internal circuitry

(see Programmable Baud Rate Generator). This input is not

5V tolerant.

-CSA

Chip Select A - A logic 0 at this pin enables the serial

channel-A UART registers for CPU data transfers.

-CSB

Chip Select B - A logic 0 at this pin enables the serial

channel-B UART registers for CPU data transfers.

-CSP

Printer Port Chip Select - (active low). A logic 0 at this pin

enables the parallel printer port registers and/or PD7-PD0

for external CPU data transfers.

D0-D7

14-21

I/O

Data Bus (Bi-directional) - These pins are the eight bit, three

state data bus for transferring information to or from the

controlling CPU. D0 is the least significant bit and the first

data bit in a transmit or receive serial data stream.

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