FMA Unit 5. 2 8255 - PPI_Pin Description

8255 - Programmable Peripheral Interface

The 8255 is a general purpose programmable I/O device designed to transfer the data from I/O to interrupt I/O under certain conditions as required. It can be used with almost any microprocessor.

It consists of three 8-bit bidirectional I/O ports which can be configured as per the requirement.

 

Intel 8255 - Pin Description

Pins	Name	Functions
D0 - D7	Data Bus	8-bit data bi-directional data bus lines, which are used to interface the microprocessor to the system data bus for data transfer between microcontroller and 8255.
CS	Chip Select	This is active LOW input signal, used to enables the communication between the 8255A and microcontroller
WR	Write	This is active LOW input signal, used to control signal enables the write operation. When this signal goes low, the microprocessor writes into a selected I/O port or control register.
RD	Read	This is active LOW input signal, used to control signal enables the read operation. When the signal is low, the microprocessor reads the data from the selected I/O port of the 8255.
A0 - A1	Address Lines	This is active HIGN input signal, used to select different port of 8255. A1 A0 Selected Port 0 0 Port A 0 1 Port B 1 0 Port C 1 1 Control Register
RESET	Reset	This is active HIGN input signal, used to reset 8255.
PA0 - PA7	Port A    pins 0 - 7	These are bi-directional I/O pins used to communicate between microcontroller and peripheral.
PB0 - PB7	Port B    pins 0 - 7	These are bi-directional I/O pins used to communicate between microcontroller and peripheral.
PC0 - PC7	Port C    pins 0 - 7	These are bi-directional I/O pins divided in two sections i.e. lower port C (PC0 - PC3) and upper port C (PC4 - PC7) which is individually communicate between microcontroller and peripheral.