PIC16F877A PortB Interrupt on Change Programming with XC8

 In previous post, I showed the external interrupt programming of PIC16F877A. Here I use another interrupt source of PortB. It's Port B Interrupt on Change. This interrupt creates by any logic change between RB4 and RB7 of PortB.

To use this interrupt source, we must

1- Set any pins between RB4 and RB7 as a digital input.

2- Set its transition

3- Turn on PortB weak pull up resistors (optional)

4- Write the ISR

Simulation sample in Proteus 8

In this example, I use all PortB interrupt on change source from RB4 to RB7. These interrupt sources connect to input buttons. They will toggle RB1 and RB2. RB0 blinks an output LED regularly.

/*
 * PIC16F877a Port B Interrupt On Change
 * Example in xc8
 */
#include <xc.h>
 
// PIC16F877A Configuration Bit Settings
// CONFIG
#pragma config FOSC = HS
#pragma config WDTE = OFF
#pragma config PWRTE = OFF
#pragma config BOREN = ON
#pragma config LVP = OFF
#pragma config WRT = OFF
#pragma config CP = OFF
 
#define _XTAL_FREQ 20e6
 
void main(void){
    /*Clear IO port*/
    PORTB=0x00;
    /*RB0...1 input*/
    TRISB=0xF0;
    /*Turn on Pull Up Resistor*/
    nRBPU=0;
    /*Turn On External Interrupt*/
    RBIE=1;
    /*Turn On Global Interrupt*/
    GIE=1;
    /*Clear Interrupt Flag*/
    RBIF=0;
    while(1){
        RB0^=1;
        __delay_ms(500);
    }
}
 
/*Interrupt Service Routine*/
void interrupt portBChange(void){
    /*Check RB Port Change Interrupt Present*/
    if(RBIE&&RBIF){
        if(RB4^1) RB1=1;
        if(RB5^1) RB1=0;
        if(RB6^1) RB2=1;
        if(RB7^1) RB2=0;
        RBIF=0;
    }
}

Its clock source is 20MHz from a crystal oscillator.

Schematic Diagram

Click here to download source file.