Electrical Engineering

8255 Programmable Peripheral Interface (PPI) Intel 8255A is a general purpose parallel I/O interface. The peripheral devices are slower than the microprocessor. PPI makes an inter-relation between microprocessor and peripheral devices. It provides three I/O port (Port A, Port B and Port C) and can be programmed as a) Simple Parallel I/O (No handshaking) b) Simple Strobe I/O (Use STB handshake) c) Single Handshake I/O (Use STB-ACK handshake) d) Double handshake I/O (Uses STB-ACK and STB-ACK) Handshaking and Handshaking Signal The making of inter relation between slower peripheral device and microprocessor is called handshaking. Before making the inter-relation between peripheral device and microprocessor the PPI send some signals to microprocessor and peripheral device to perform the process, these signals are called handshaking signal. 8255-based devices that perform handshaking support four handshaking signals: • Strobe Input (STB) • Input Buffer Full (IBF) •