麻烦各位进来看下，谢谢了

测试开关K0，当K0开关开置ON时，6个数码管同时亮“8“，当开关拨置OFF时，6个数码管同时灭，同时亮地交替进行。
我自己写的代码如下，请问有问题么？？谢谢啦！！
#include<reg51.h>
void melay(unsigned int t)
{
    unsigned int i;
    for(i = 0; i < t; i++);
}

sbit P_1 = P1^0;
sbit P_2 = P1^1;
sbit P_3 = P1^2;
sbit P_4 = P1^3;
sbit P_5 = P1^4;
sbit P_6 = P1^5;

void main()
{
    while(1)
    {
        if(P_1 = 1)
        {
            P_1;
            melay(20000);
               P_2;
            melay(20000);
               P_3;
            melay(20000);
               P_4;
            melay(20000);
               P_5;
            melay(20000);
               P_6;
            melay(20000);
        }
        if(P_1 = 0)
        {
            P_1 = 1;
            for( ; ; )
             {
              P_1 != P_1;
              melay(20000);
                 P_2 != P_2;
              melay(20000);
                 P_3 != P_3;
              melay(20000);
                 P_4 != P_4;
              melay(20000);
                 P_5 != P_5;
              melay(20000);
                 P_6 != P_6;
              melay(20000);
            }
        }
    }