8086-8251 USART Serial Communication System

Overview

This project demonstrates serial communication between the 8086 microprocessor and the 8251 USART using assembly language.
A Proteus simulation is used with a virtual terminal for real-time input/output.

Features

• Serial communication using 8251 USART
• ASCII input handling
• Input validation (numeric + character matching)
• Partial string verification
• Dynamic output generation
• Error handling with feedback message
• Continuous operation (infinite loop)

How It Works

1. System initializes 8251 USART (asynchronous mode).
2. User enters a number (0–9).
3. Based on input:
   • 0 → prints full string (HELLO WORLD)
   • n → checks next n characters
4. If input matches → sends remaining characters
5. If mismatch → displays " ERROR "

Proteus Simulation

• 8086 Microprocessor
• 8251 USART
• Virtual Terminal for I/O
• Serial communication fully simulated

Files

• main.asm → Assembly program
• serial_communication_with_8251.pdsprj → Proteus simulation file

Run Instructions

1. Open project in Proteus
2. Load assembled .hex file into 8086
3. Run simulation
4. Use virtual terminal to provide input

Example

Input: 5HELLO Output: WORLD

Input: 3ABC Output: ERROR