A sample program to learn pin change interrupt of PIC16F877A microcontroller

pic16f877a_pin_change_interrupt.c

//Pin change interrupt example program written for
//PIC programming tutorial.
//Target Device :	PIC16F877A
//Compiler	: 	HITECH C
//Author 	:	Anil C S 
//Website	: 	www.technoburst.net

#include <htc.h>
__CONFIG(0x3f7a);  		//Setting the configuration bits

#define _XTAL_FREQ 20000000 	//setting the crystal frequency to 20MHz

void toggleLED();

void main()
{

INTCON = 0b10001000; 		//Sets GIE,RBIE bits of INTCON register
TRISB = 0xff; 			//Sets port B as input port

TRISD = 0x00;			//Setting port D as output port
PORTD = 0xff;			//Initializing port D

while(1) continue;

}

//Interrupt routine

void interrupt pin_chg_interrupt(void)
{
	unsigned char data;
	INTCON &= 0b01110111;	//Clears GIE,RIE for disabling interrupts while ISR is running

	if(INTCON&0b00000001)	//Checking whether the source of interrupt was a pin status change at PORTB
	{		
		toggleLED();
		data = PORTB;		//Reading the PORTB. This will clear the mismatch condition
		INTCON&=0b11111110;	//Clearing the interrupt flag RBIF
	}
	INTCON |= 0b10001000;	//Re enabling the interrupt
}	

//Function to toggle LED connected to PORTD
void toggleLED()
{
	static unsigned char i = 0;

	if(i)
	{
		PORTD = 0x00;
		i=0;
	}
	else
	{
		PORTD = 0xff;
		i=1;
	}
}