8255A/8255A·5

PROGRAMMABLE PERIPHERAL INTERFACE

MCS.85Compatible 8255A·5

24 Programmable 1/0 Pins

Completely TTL Compatible

Fully Compatible with Intel® Micro· processor Families

Improved Timing Characteristics

Direct Bit SetlReset Capability Easing Control Application Interface

40·Pin Dual In·Line Package

Reduces System Package Count

Improved DC Driving Capability

The Intel@ 8255A is a general purpose programmable I/O device designed for use with Intel@ microprocessors. It has 24110 pins which may be individually programmed in 2 groups of 12 and used in 3 major modes of operation. In the first mode (MODE 0), each group of 12 1/0 pins may be programmed in sets of 4 to be input or output. In MODE 1, the second mode, each group may be programmed to have 8 lines of input or output. Of the remaining 4 pins, 3 are used for hand- shaking and interrupt control signals. The third mode of operation (MODE 2) is a bidirectional bus mode which uses 8 lines for a bidirectional bus, and 5 lines, borrowing one from the other group, for handshaking.

PIN CONFIGURATION

8255A BLOCK DIAGRAM

S~~;l~;S { --m

 

- _ GND

10

 

PA,-PAO

PIN NAMES

0,-°0

OAT A BUS (BI·DIRECTIONAl)

RESET

RESET INPUT

 

CHIP SELECT

 

READ INPUT

WR

WAITE INPUT

AD,A,

PORT AODRESS

PA7·PM

PORT A IBITI

ps,._

PORTB IBITI

~,-'CO

PORT C (BIT)

Vee

<Ii VOLTS

GND

'VOLTS

9-17

AFN-00744A-01

 

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Image 332
Intel mcs-48 manual Programmable Peripheral Interface, PIN Configuration 8255A Block Diagram