---
title: "Technical benefits of 8255 PPI"
subject: "Instrumentation II"
chapter: 2
key: "semester_5/instrumentation_ii:ppi-benefits"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/ppi-benefits
site: BCT Engineering
---

# Technical benefits of 8255 PPI

Instrumentation II · Chapter 2: Parallel Interfacing With Microprocessor Based System

- Asked in: 2072 Chaitra, 2 marks; 2073 Chaitra, 2 marks (asked 2 times)
- Video: [8255 IC Introduction |Programmable Peripheral Interface Explained |Microprocessor Peripheral Device](https://www.youtube.com/watch?v=MLFsT2eLu64) — Polytechnic Class (READBY) 
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/ppi-benefits
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-2

## Question

List out the technical benefits of using 8255 PPI in a MBI system.

## Short answer

The 8255 PPI provides 24 programmable I/O lines across three ports, supports three modes (simple, strobed, bidirectional), and allows software-configurable direction with bit set/reset. It offers handshake signals for interrupt transfers, is TTL-compatible, and reduces external logic when interfacing keyboards, displays, ADCs, and relays.

## Answer

Technical benefits of the 8255 PPI in an MBI system:

1. It gives 24 programmable I/O lines (ports A, B and C) from a single 40-pin chip.
2. Three operating modes (mode 0 simple I/O, mode 1 strobed I/O, mode 2 bidirectional bus) allow interfacing with many devices.
3. Each port direction is set by software (control word), and individual bits of port C can be set or reset (BSR mode).
4. Handshake signals (STB', IBF, OBF', ACK', INTR) allow interrupt driven transfer with slow peripherals.
5. TTL compatible, can directly drive LEDs and transistors; reduces external glue logic and cost.
6. It interfaces keyboards, displays, ADC/DAC, relays and printers.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How many programmable I/O lines does the 8255 provide?
   A. 24 lines in ports A, B and C
   B. 16 lines
   C. 8 lines
   D. 32 lines
   Answer: A. Three 8-bit ports give 24 lines. (Key point: I/O lines)

2. Which are the 8255 operating modes?
   A. Mode 0 DMA, mode 1 serial, mode 2 analog
   B. Mode 0 simple I/O, mode 1 strobed I/O, mode 2 bidirectional
   C. Only mode 0
   D. Mode 0 to mode 5
   Answer: B. The 8255 has modes 0, 1 and 2 plus BSR. (Key point: Modes)

3. What does BSR mode allow?
   A. Reset of port A
   B. Serial transfer
   C. Setting or resetting individual bits of port C
   D. DMA request
   Answer: C. BSR mode controls single port C bits. (Key point: BSR)

## Related in Instrumentation II

- [Double handshake data transfer with 8255-PPI](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Adouble-handshake-8255) — Instrumentation II, chapter 2
- [Ice cream factory MBI with 8255 at 5000H](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aicecream-ppi-5000h) — Instrumentation II, chapter 2
- [Closed loop MBI system](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aclosed-loop-mbi-define) — Instrumentation II, chapter 1, asked 2×
- [Case study: revamping MBI system for CEO](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-ceo-revamp) — Instrumentation II, chapter 10
- [Gas chamber STP monitoring with 8255 and ADCs](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Agas-chamber-stp) — Instrumentation II, chapter 4
- [PC based concrete purifying factory with 8255](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aconcrete-purifying-ppi-4000h) — Instrumentation II, chapter 2

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