流水灯的来回闪烁

#include<reg52.h>
sbit L4 = P2^0;
sbit L3 = P2^1;
sbit L2 = P2^2;
sbit L1 = P2^3;
void main()
{
    int cnt = 0;
    int i = 0;
    char k = 0;
    L4 = 1;
    L3 = 1;
    L2 = 1;
    L1 = 1;
    while (1) 
     {
                P2 = 0xFE <<cnt; 
             for (i=0; i < 30000; i++); 
             cnt++; 
             if (cnt >= 4) 
             {
                 while(k != 4)
                 {
                        P2 = 0xF7 >>cnt; 
                         for (i=0; i < 30000; i++); 
                         cnt++;
                        k++;
                 }
                 cnt = 0;
                 k = 0;
             }
     }
}