Table Of Contents

1. Complete Video Course on PIC18F4550 Microcontroller
2. Configuring Interrupt Module of PIC18F4550 – Step-by-Step Practical Guide
3. What is an Interrupt?
4. Types of Interrupts in PIC18F4550
5. Example: External Interrupt on INT0 (RB0 Pin)
   • 1️⃣ Circuit Description
6. Explanation
7. Other Common Interrupts in PIC18F4550
8. Practical Applications
9. Ready to learn interrupts in real projects using PIC18F4550?
10. Complete Video Course on PIC18F4550 Microcontroller
    • Software development tools & documents:
11. Frequently Asked Questions (FAQ)

Complete Video Course on PIC18F4550 Microcontroller

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Configuring Interrupt Module of PIC18F4550 – Step-by-Step Practical Guide

Interrupts are one of the most powerful features of microcontrollers – they allow your system to respond immediately to important events like a button press, timer overflow, or received data, without continuously polling for changes. In this post, you’ll learn how to configure and handle an interrupt in PIC18F4550 microcontroller using MPLAB X IDE and the XC8 compiler through a simple LED blinking on an external interrupt example.

Goal: By the end, you’ll know how to enable, configure, and write ISR (Interrupt Service Routine) functions that make your embedded systems more responsive and efficient.

What is an Interrupt?

An interrupt is a signal that temporarily stops the normal execution of your main program to run a special function called the Interrupt Service Routine (ISR).

For example, if your PIC is busy running code and a button connected to an external interrupt pin is pressed — the microcontroller pauses the main loop, executes the ISR, and then resumes normal operation.

Types of Interrupts in PIC18F4550

The PIC18F4550 supports:

• External Interrupts (INT0, INT1, INT2)
• Peripheral Interrupts (like UART, ADC, Timer, CCP, etc.)
• Timer Interrupts
• USB and Special Event Triggers

Each interrupt has:

• Enable bit – turns it ON/OFF
• Flag bit – indicates if it occurred
• Priority bit – decides high or low priority

Example: External Interrupt on INT0 (RB0 Pin)

1️⃣ Circuit Description

• Connect a push button to RB0 (INT0) pin.
• Connect an LED to PORTD (RD0) with a 330Ω resistor.
• When the button is pressed → the LED toggles using an interrupt.

#include <xc.h>
#define _XTAL_FREQ 8000000

void __interrupt() ISR(void) {
    if (INT0IF) {          // Check if INT0 caused interrupt
        LATDbits.LATD0 = !LATDbits.LATD0;  // Toggle LED
        INT0IF = 0;        // Clear interrupt flag
    }
}

void main(void) {
    TRISBbits.TRISB0 = 1;  // RB0 as input (button)
    TRISDbits.TRISD0 = 0;  // RD0 as output (LED)
    LATDbits.LATD0 = 0;

    INT0IF = 0;   // Clear flag
    INT0IE = 1;   // Enable external interrupt INT0
    GIE = 1;      // Global interrupt enable

    while(1) {
        // Main loop can do other tasks
    }
}

#include <xc.h>
#define _XTAL_FREQ 8000000

void __interrupt() ISR(void) {
    if (INT0IF) {          // Check if INT0 caused interrupt
        LATDbits.LATD0 = !LATDbits.LATD0;  // Toggle LED
        INT0IF = 0;        // Clear interrupt flag
    }
}

void main(void) {
    TRISBbits.TRISB0 = 1;  // RB0 as input (button)
    TRISDbits.TRISD0 = 0;  // RD0 as output (LED)
    LATDbits.LATD0 = 0;

    INT0IF = 0;   // Clear flag
    INT0IE = 1;   // Enable external interrupt INT0
    GIE = 1;      // Global interrupt enable

    while(1) {
        // Main loop can do other tasks
    }
}

Circuit Diagram Description

VCC (5V) and GND → common reference.

Button → connected to RB0 (INT0) with a pull-down resistor.

LED → connected to RD0 via 330Ω resistor.

Explanation

• When the button is pressed, RB0 changes state → INT0 flag is set.
• MCU automatically jumps to the ISR.
• LED toggles and flag clears.
• MCU returns to the main loop — all automatically handled by hardware.

Other Common Interrupts in PIC18F4550

Practical Applications

• Detect button presses or sensor triggers
• Implement real-time event handling
• Perform multitasking without RTOS
• Efficient energy management in low-power devices

Ready to learn interrupts in real projects using PIC18F4550?

If you enjoyed this tutorial and want to learn the complete practical side of PIC18F4550, including:

• Timers, Interrupts, and UART Communication
• PWM for Motor Control
• USB Interface & Sensors Integration
• Real-world Project Building

👉 Then don’t miss our Premium Course: “Mastering PIC18F4550 Microcontroller”
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Software development tools & documents:

• MPLAB X IDE
• MPLAB X, XC8 Compiler
• Microchip Technology, pic18f4550

Frequently Asked Questions (FAQ)