#include <reg52.h>  
#include <intrins.h>  

unsigned char a,b;
unsigned int x,y,z;

void delay(unsigned z);
{
    for(x=z; x>0;x--)
    for(y = 144;y>0;y--);
}

a = 0xfe;
void main()
{
    while()
    {
    P0=a;
    delay(100);
    b=_ctrl_(a,1);
    a=b;
    P0=a;
    }
}