#include "reg51.h"
void main()
{	unsigned char KeyValue;
	for(;;)
	{	P3|=0xc3;
		KeyValue=P3|0xfb;
		if(KeyValue!=0xff)
			P1=0;
		KeyValue=P3|0xf7;
		if(KeyValue!=0xff)
			P1=0xff;
	}
}