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Description

The Intel 8255A is a general purpose programmable I/O device which is designed for use with all Intel and most other microprocessors. It provides 24 I/O pins which may be individually programmed in 2 groups of 12 and used in 3 major modes of operation.

In MODE 0, each group of 12 I/O pins may be programmed in sets of 4 and 8 to be inputs or outputs. In MODE 1, each group may be programmed to have 8 lines of input or output. 3 of the remaining 4 pins are used for handshaking and interrupt control signals. MODE 2 is a strobed bi-directional bus configuration.

The 8255 is a 40 pin integrated circuit (IC), designed to perform a variety of interface functions in a computer environment. The 8255 wasn't originally designed to be connected to the Z80. It was manufactured by Intel for the 8080 microprocessor.

Block Diagram