[internet.com]

Chào bạn! Chương trình nháy led port C của bạn có thể như sau, bạn tham khảo:

// MCU  : 16f887
// XTAL : 4MHz

#include <htc.h>

__CONFIG(XT & WDTDIS & LVPDIS & DEBUGDIS);
__CONFIG(BORV21);

#define _XTAL_FREQ 4000000		

unsigned char count=0;			

//Ham main *******************************
void main(void){
        ANSEL=0;					//ALL PORTS ARE DIGITAL
        ANSELH=0;

	TRISC=0;
	PORTC=0;

	T0CS=0;						//USE INTERNAL CLOCK
	
		
	PSA=0;						//USE PRESCALER
	PS2=0; PS1=1; PS0=0;		                //1:8

	T0IF=0;						//Clear int flag
	T0IE=1;						//Enable tmr0 int
	GIE=1;						//Enable glb int
	
	TMR0=5;						//Timer0 will overflow after: 8*250*1us = 2ms 
	
	while(1);					//Waiting for int
}

void interrupt isr(){			                //Do not rename isr ("interrupt isr()")
	if(T0IE && T0IF){
		T0IF = 0;
		TMR0=5;
		++count;
		if(count == 125){		        //125*2ms = 250ms
			count = 0;
			PORTC ^= 0xff;	
		}
	}
}