The document discusses the Programmable Peripheral Interface 8255 (PPI), which is an I/O port chip used for interfacing I/O devices with microprocessors. It has 24 pins for I/O that are programmable in groups of 12 pins and has three distinct modes of operation. The PPI is commonly used in microprocessor labs for interfacing experiments and knowledge of it is essential for students. It describes the basic modes of operation and how to program the 8255.

1. 1
PROGRAMMABLE
PERIPHERAL
INTERFACE - 8255
Department of Mechanical Engineering
DHIRAJLAL GANDHI COLLEGE OF
TECHNOLOGY
Name of Faculty : Dr.P.Parandaman
Designation : Associate Professor
Department : Mechanical Engineering
Year/Semester : IV /VII

3. Intel 8255 PPI
PPI – Programmable Peripheral Interface
It is an I/O port chip used for interfacing I/O
devices with microprocessor
Very commonly used peripheral chip
Knowledge of 8255 essential for students in the
Microprocessors lab for Interfacing experiments
3

4. About 82C55
• The 82C55 is a popular interfacing component, that can
interface any TTL-compatible I/O device to a
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 are programmable in groups
of 12 pins and has three distinct modes of operation.

5. 8255 : Pin Layout

11. 8255 Control Word

12. Basic Mode Definitions and Bus Int
• Mode 0
– Basic I/O
• Mode 1
– Strobe I/O
• Mode 2
– Bi-Dir Bus

13. 11-13
Programming 8255
 8255 has three operation modes: mode 0, mode 1, and mode 2

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Department of Mechanical Engineering