This document summarizes a lab project on the 8255 Programmable Peripheral Interface (PPI) chip. The authors acknowledge their faculty member for providing guidance and the opportunity to do the project. The document then provides a brief overview of the 8255 PPI, describing its architecture with three 8-pin ports that can be programmed for input or output functions. It also lists the key features of the 8255 including its compatibility and operating modes, with further details provided on the different input/output and handshake modes. Reference sources are included at the end.

1. EC304: Microprocessors and Microcontrollers Lab
Birla Institute of Technology, Mesra
• Riddhima Varshney (BTech/25077/20)
• Sujal Gupta (BTech/25098/20)
1

2. 2
ACKNOWLEDGEMENT
We would like to express our special thanks of gratitude to our faculty Mr. Snehanshu Shekhar who
gave us the golden opportunity to do this wonderful project on the topic 8255 PPI, which also
helped us in doing a lot of Research and we came to know about so many new things. We would also
like to thank our professor for guidance and constant source of encouragement in finishing this
assignment.
Lastly, we would also like to thank our parents and friends who helped us a lot in finalizing this
project within the limited time frame.

3. Table Of Content
8255 PPI
4
8255 PPI Architecture
5-6
Features of 8255
7
8255 PPI Pin Diagram
8
Operating modes of 8255 PPI
9-10
Reference
11

4. 8255 PPI (Programmable Peripheral Interface)
• PPI 8255 is a general purpose
programmable I/O device
designed to interface the CPU
with its outside world such as
ADC, DAC, keyboard etc.
• We can program it according to
the given condition. It can be
used with almost any
microprocessor.
• It consists of three 8-bit
bidirectional I/O ports i.e.
PORT A, PORT B and PORT C.
We can assign different ports as
input or output functions.
4

5. 8255 PPI
Architecture

6. 8

7. Features of 8255
WIDELY USED,
PROGRAMMABLE,
PARALLEL I/O DEVICE
PROGRAMMED TO
TRANSFER DATA UNDER
VARIOUS CONDITIONS
COMPATIBLE WITH ALL
INTEL AND MOST OTHER
MICROPROCESSORS
TTL COMPATIBLE
HAS THREE 8-BIT PORTS:
PORT A, PORT B, PORT C
6

8. 8255 PPI Pin Diagram
• PA0-PA7: Pins of Port A
• PB0-PB7: Pins of Port B
• PC0-PC7: Pins of Port C
• D0-D7: Data pins for the
transfer of data
• RESET: Reset input
• RD’: Read input
• WR’: Write input
• CS’: Chip select
• A1 and A0: Address pins
8

9. 9
Operating modes of 8255 PPI
Operating Modes
Bit Set Reset
(BSR Mode)
Input-Output Mode
Mode 0 Mode 1 Mode 2

10. 10
Operating Modes:
1. Bit Set Reset (BSR Mode): If MSB of control word (D7)
is 0, PPI works in BSR mode. In this mode only port C bits
are used for set or reset.
2. Input-Output Mode: If MSB of control word (D7) is 1,
PPI works in input-output mode. This is further divided
into three modes:
• Mode 0 –In this mode all the three ports (port A, B, C) can
work as simple input function or simple output function. In
this mode there is no interrupt handling capacity.
• Mode 1 – Handshake I/O mode or strobed I/O mode. In
this mode either port A or port B can work as simple input
port or simple output port, and port C bits are used for
handshake signals before actual data transmission. It has
interrupt handling capacity and input and output are latched.
• Mode 2 – Bi-directional data bus mode. In this mode only
port A works, and port B can work either in mode 0 or
mode 1. 6 bits port C are used as handshake signals. It also
has interrupt handling capacity.

11. Reference
11
• https://www.geeksforgeeks.org/programmable-peripheral-interface-8255/
• https://www.tutorialspoint.com/microprocessor/microprocessor_intel_8255a_programmable_periphera
l_interface.htm
• https://www.eeeguide.com/features-of-8255-microprocessor/

12. THANK YOU!