Interfacing 8255 - SlideShare Aug 13, 2012Interfacing 8255 1. PPI : 82C55 The 82C55 is a popular interfacing component, that can interface any TTL-compatible I/O device to the microprocessor. It is used to interface to the keyboard and a parallel printer port in PCs (usually as part of an integrated chipset). Requires insertion of wait states if used with a microprocessor using higher that an 8 MHz clock. PPI has 24 pins for I/O that[PDF] 8254 PROGRAMMABLE INTERVAL TIMER - Stanford University The 8254 is a programmable interval timer/counter designed for use with Intel microcomputer systems. It is a general purpose, multi-timing element that can be treated as an array of I/O ports in the system software. The 8254 solves one of the most common problems in any microcomputer system, the generation of ac-curate time delays under software control.