AT89C51 External Interrupt (INT0) LED Toggle

Description

This project demonstrates the use of the External Interrupt 0 (INT0) feature of the AT89C51 microcontroller. A push button connected to the INT0 pin triggers an interrupt, causing the LEDs to toggle between two alternate patterns.

Features

• Uses AT89C51 External Interrupt 0 (INT0)
• Interrupt-driven LED control
• Alternate LED pattern on every button press
• Embedded C implementation
• Proteus simulation

Hardware Required

• AT89C51 Microcontroller
• 4 LEDs
• Push Button

Software Required

• Keil µVision
• Proteus 8 Professional

Pin Connections

• LED1 → P2.0
• LED2 → P2.1
• LED3 → P2.2
• LED4 → P2.3
• Push Button → P3.2 (INT0)

Working

1. Initially, LED1 and LED3 are ON, while LED2 and LED4 are OFF.
2. Pressing the push button connected to INT0 generates an external interrupt.
3. The interrupt service routine toggles the LED pattern.
4. Each subsequent button press alternates between the two LED patterns.

Applications

• External Interrupt Demonstration
• Embedded Systems Learning
• Event-Driven Control
• AT89C51 Programming Practice