#include <at89x51.h>
#include "Key.h"
typedef unsigned char uchar;
bit g_KeyDown;
data unsigned char g_KeyValue;
void key_down(void) interrupt 0 using 1
{
	EX0=0;
	if(g_KeyDown) //if has Old Key Discard New Key
    {
        EX0=1;
        return;
    }
  	g_KeyDown=1;
  	g_KeyValue=P1;
  	g_KeyValue=g_KeyValue & 0x0f;
	EX0=1;	
}
uchar WaitKey()
{
	uchar t;
	g_KeyDown=0;
	while(!g_KeyDown){};
	t=g_KeyValue;
	g_KeyDown=0;
	return t;
}