IBM-PC in the laboratory: 8255 Programmable Peripheral Interface data sheets

Although cryptic, data sheets contain all of the detailed information about a particular device. But, be warned!, they are sometimes inaccurate due to typos and poor editing. The data sheets on the following pages of the 8255 PPI seem to be accurate. ▪ I MCS-85 TM Compatible 8255A-5 ▪ 24 Programmable I/O Pins ▪ Completely TTL Compatible ▪ Fully Compatible with Intel Microprocessor Families ▪ Improved Timing Characteristics ▪ Direct Bit Set/Reset Capability Easing Control Application Interface ▪ Reduces System Package Count ▪ Improved DC Driving Capability ▪ Available in EXPRESS — Standard Temperature Range — Extended Temperature Range ▪ 40 Pin DIP Package or 44 Lead PLCC (See Intel Packaging: Order Number: 231369) The Intel 8255A is a general purpose programmable I/O device designed for use with Intel microprocessors. It has 24 I/O 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 I/O 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 handshaking 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. General The 8255A is a programmable peripheral interface (PPI) device designed for use in Intel microcomputer systems. Its function is that of a general purpose I/O component to interface peripheral equipment to the microcomputer system bus.