ST78C34 查看數據表（PDF） - Exar Corporation

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ST78C34

GENERAL PURPOSE PARALLEL PRINTER PORT WITH 83 BYTE FIFO

Exar Corporation 

ST78C34

SYMBOL DESCRIPTION

Symbol

GND

Pin

40 44

20 23

Signal

type

O

Pin Description

Signal and power ground.

RESET

21 24

I

Master reset (active high). A high on this pin will reset all the

outputs and internal registers.

-STROBE

22 25 I/O General purpose I/O or strobe output (open drain active low, with

internal pull-up). To transfer latched data to the external peripheral

or printer.

-AUTOFDXT 23

26 I/O

General purpose I/O or line printer auto feed (open drain active

low, with internal pull-up). To signal the printer for continuous form

feed.

INIT

24 27 I/O General purpose I/O or line printer initialize (open drain active

high, with internal pull-up). To signal the line printer to enter

internal initialization routine.

-SLCTIN

25 28 I/O General purpose I/O or line printer select (open drain active low,

with internal pull-up). To select the line printer.

GND

26

30

O

Power and signal ground.

PD0-PD7

27-34 31-38 I/O

Bi-directional parallel ports (three state). To transfer data in or out

of the ST78C34 parallel port. PD7-PD0 are latched during output

mode.

A0-A1

36-37 40-41 I

Address lines. To select internal registers.

-IOW

38 42

I

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

of the CPU data bus to the addressed register.

-IOR

39 43

I

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

contents of the ST78C34 data bus to the CPU.

VCC

40 44

I

Power supply input.

Rev. 3.00

6-7

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