Problem on using TIMER1 on PIC16F877A as counter

[leeyung]

hi all, i am very new in electronics, but i would like to do a very simple counter to count the pulse. I have an opto sensor which produce 5V when blocked and 0V when unblocked, this will create a train of 0-5-0-5-0-5 pulses, i wan to count the pulse using Timer1 (Pin RC0 as TIMER1). The following is my simple program to test if 3 pulses were counted, the LED will light up.. however, it seems like the counter doesnt count my input... anyone can guide me please?

#include<16f877a.h>
#use delay(clock=20000000)
#fuses hs,noprotect,nowdt,nolvp
#byte PORTC=7 //Call Port C
#byte PORTD=8 //Call Port D

void main() //Main Block
{
int count=0; //Receives timer count
set_tris_D(0b00000000); //Set Port D as I/O
setup_timer_1(T1_EXTERNAL);// The timer is set up for external input

do{
set_timer1(0); //Reset counter
count=get_timer1(); //Resulting count is read using get_timer()
if (count==3) //if 3 pulse were counted
{output_high(pin_D7);}// LED light up
else
{output_low(pin_D7);}//LED light off

}while(1);


}

[Ttelmah]

Hint use code buttons....

[leeyung]