Incandencent Lamp dimmer using PIC16F877A

I am trying to control Intensity of AC lamp. For this my steps are as follows
1. Initialise ports, timers.
2. wait for zero cross, if detect a zero cross point set a flag.
3. When zero cross flag set,enable timer0 & start timerto overflow after 8msec.
4. wait untill overflow.
5. When overflow, turn ON triac for some duration (may be 600usec) untill it latches.
6. Poll the keys.
7. If key pressed, change timer0 value & repeate a process from step 3.
My program of zero cross & timer0 working OK independently, but when combine both ,
i am not getting expected o/p waveform, but getting extra pulse at each zero cross.
I am trying this from last two weeks, but i am not getting o/p... Plz..plz. help me


/////////////////////////////////////////////////////////////////////////


#include <16F877A.h>

#device ICD=TRUE
#fuses XT,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)


//////////////////////////////////////////////////////////////////////////////////////

/**** I/O Ports ****/
/*** Inputs ***/
#define LED PIN_A1
#define ZCD PIN_B4

/*** Outputs ***/
unsigned char ZCD_flag, Dimming_time;



//----------------------------------------------------------------------------
void main (void);
void main()
{
unsigned char dc ;
setup_adc_ports(NO_ANALOGS); /*defines RA0,RA1,RA2,RA3 & RA5 as Digital I/O*/
SET_TRIS_A(0x00); /* Port A with RA0-RA4 as outputs */
SET_TRIS_B(0x11);
output_low(LED);
ZCD_flag=0x00;
Dimming_time=0x00;
ENABLE_INTERRUPTS(GLOBAL); // enable All interrupts

while(1)
{
ENABLE_INTERRUPTS(INT_RB); // enable External interrupt
DISABLE_INTERRUPTS(INT_TIMER0);
if(ZCD_flag==1)
{
ZCD_flag =0;
DISABLE_INTERRUPTS(INT_RB);
ENABLE_INTERRUPTS(INT_TIMER0); // enable Timer0 interrupt
SET_TIMER0(242); // set timer0 reg.to 0
SETUP_TIMER_0(T0_INTERNAL);
SETUP_TIMER_0(T0_DIV_32);
}
}


}




/**** Zero Cross Interrupt ****/
#INT_RB
void ext_int_zerocross()
{
CLEAR_INTERRUPT(INT_RB); /* Clear External Interrupt Flag */
ZCD_flag=1; /* Indicate 10ms Interrupt Occured */
}

#INT_TIMER0
void InterruptHandler_Timer0 ()
{
CLEAR_INTERRUPT(INT_TIMER0); /* Clear the Timer0 Flag */
// DISABLE_INTERRUPTS(INT_TIMER0);
output_high(LED); // invert the state of output
delay_us(500);
output_low(LED); // invert the state of output
}

/*************** END OF PhaseControl ****************************/

are u getting pwm pulses?

whether ur sensing signal is coming properly?

Just check this.

Regards
Chanchal