need help about distance measurement using ping ultrasonic sensor and PIC16f84a

#include <htc.h>
#include <pic1684.h>
unsigned char a;
unsigned char c;

/*void interrupt isr()
{
TMR0=0;
c=TMR0;
if(T0IF!=1)
{
c++;
}
else if(T0IF==1)
{
T0IF=0;
}
T0IF = 0; /* Clear timer interrupt */
// }

void delay()
{
for(a=0; a<4; a++)
{}
}
void delay2()
{
for(a=0; a<1; a++)
{}
}
void delay1()
{
for(a=0; a<250; a++)
{}
}

void lambat()
{
a=254;
while(a<255)
{
a++;
}
}

void main()
{
unsigned char d;
TRISB=0x00;
PORTB=0x00;
//OPTION=0x07;
//INTCON=0xA0;
GIE=1;
while(1)
{
c=0;
//TMR0=0;
//c=TMR0;
T0IF=0;
TRISA=0x00;
RA2=1;
delay();
RA2=0;
delay1();
delay1();
delay1();
RA2=1;
delay();
TRISA=0x1f;
while(TRISA==0x1f)
{
// INTCON=0xA0;
while(RA2==1 && c<255)
{

c++;
#asm
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
nop;
#endasm
}
//PORTB=c;
while(RA2==0)
{PORTB=c;}
}
delay1();
}
}

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