CCP module pic18f2550 +CCS

I want to measure pulse width of a signal.I wrote this.but It always gives constant pulse width whether frequency is changed.What is the wrong with this?


#include <18f2550.h>
#include <math.h>
#use delay(clock=8000000)
#fuses HSPLL,NOWDT,NOPROTECT,BROWNOUT, PUT, NOLVP,NODEBUG,USBDIV,CPUDIV1,VREGEN
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7,errors)
static unsigned int8 x,y,ex;
static float duration;
static char vt[5];
static int1 got_RE,got_P,display;

#INT_CCP1
void detect(){
disable_interrupts(global);

if(got_RE){

x=ccp_1;
setup_CCP1(CCP_CAPTURE_FE);
got_RE=FALSE;
printf("\r%d\n",x);

}

else{
y=ccp_1;
duration=frexp(ccp_1,&ex);
duration=duration+y;

setup_CCP1(CCP_CAPTURE_RE);
got_RE=TRUE;
printf("\r%d\n",(y-x));
got_P=TRUE;

}

clear_interrupt(INT_CCP1);
enable_interrupts(INT_CCP1);
enable_interrupts(GLOBAL);

}

void main()
{

setup_ccp1(CCP_CAPTURE_RE);
setup_timer_1(T1_EXTERNAL | T1_DIV_BY_2);
enable_interrupts(INT_CCP1);
enable_interrupts(global);
x=0;
y=0;
got_RE=TRUE;
got_P=FALSE;
ccp_1=0;


while(1){

if(got_P){

ccp_1=0;

}

}

}