Intel 8086 Assembly Microcomputer

A complete Intel 8086 microprocessor system designed and simulated in Proteus, featuring external RAM/ROM interfacing, Intel 8255 PPI, keypad input, seven-segment display output, and firmware written entirely in Intel 8086 Assembly.

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Project Overview

This project implements a complete Intel 8086-based microcomputer using external memory and peripherals. The processor communicates with SRAM, EPROM, and an Intel 8255 Programmable Peripheral Interface through custom address decoding logic. User input is collected from a 3×4 keypad, stored in external RAM, translated using a lookup table in ROM, and displayed on a seven-segment display.

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System Architecture

Intel 8086 Microprocessor

The Intel 8086 serves as the central processing unit, executing the Assembly firmware and controlling communication with memory and peripherals.

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Address Decoder

The address decoder generates the chip-select signals required for each external device, ensuring that RAM, ROM, and the Intel 8255 respond only within their assigned address ranges.

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External RAM

The SRAM stores every digit entered from the keypad sequentially until the display operation is requested.

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External ROM

The EPROM stores the BCD-to-Seven-Segment lookup table used to convert numeric digits into display patterns.

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I/O Interface (Intel 8255)

The Intel 8255 provides communication between the processor, the keypad, and the seven-segment display.

• Port A → Keypad Rows
• Port C → Keypad Columns
• Port B → Seven-Segment Display

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Software Workflow

Initialize 8086
        │
        ▼
Configure Intel 8255
        │
        ▼
Scan Keypad
        │
        ▼
Store Digits in SRAM
        │
        ▼
'*' Pressed?
        │
       Yes
        ▼
Read SRAM
        │
        ▼
Read Lookup Table from EPROM
        │
        ▼
Output Seven-Segment Code

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Features

• Intel 8086 Assembly Firmware
• External SRAM Interface
• External EPROM Interface
• Intel 8255 Programmable Peripheral Interface
• Address Decoding Logic
• Memory Mapping
• Matrix Keypad Scanning
• Seven-Segment Display Driver
• BCD-to-Seven-Segment Lookup Table
• Proteus Simulation

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Technologies

• Intel 8086
• Intel 8255 PPI
• Assembly Language
• Proteus Design Suite
• Digital Logic
• Memory Mapping
• Address Decoding

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Repository Structure

.
├── Assembly/
│   └── main.asm
│
├── ROM/
│   └── lookuptable.bin
│
├── Proteus/
│   └── 8086_System.pdsprj
│
├── images/
│   ├── 8086.png
│   ├── address-decoder.png
│   ├── ram.png
│   ├── rom.png
│   └── io.png
│
└── README.md

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How to Run

1. Open the Proteus project.
2. Load lookuptable.bin into the EPROM.
3. Assemble the firmware.
4. Start the simulation.
5. Enter digits using the keypad.
6. Press * to display the stored sequence.

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License

Developed for educational purposes as part of a Microprocessor Laboratory course.