偶今天折騰了好久，搞了個正反轉的程序，竟然不執行，求指點
#include <reg52.h>
sbit s4=P3^6;
sbit s5=P3^7;
sbit km1=P1^3;
sbit km2=P1^5;
void main()
{ 
km1=1;
km2=1;
while(1){
if (s4==0)
{
km1=0;
km2=1;
}
if (s5==0){
km1=1;
km2=0;
}  
}
}

你是用什么去驅動繼電器,有沒加上拉電阻