单片机 keil程序编写

怎么根据这个图和代码价格外部中断控制啊

#include <stc15.h>
#include <intrins.h>
#define uchar unsigned char
#define uint unsigned int 
void delay()
{
    unsigned char a,b;
    for(a=0;a<200;a++)
    for(b=0;b<200;b++);
}
void main()
{
    uchar k;
    k=0xfe;
    while(1)
    {
    P0=k;
    delay();
    k=_crol_(k,1);//11111110
    }              //11111101 
}