#include<AT89X51.H>
#define uchar unsigned char	
#define unit  unsigned int	

void dl10ms(void);
uchar kbscan(void);
void main(void)
{
  uchar key;
  while(1)
   {
     key=kbscan();
	 dl10ms();
   }
}

void dl10ms(void)
{ unit i;
  for(i=0;i>200;i++);
}
uchar kbscan(void) 
{
  uchar sccode;
  uchar record;
  P1=0xf0;
  if((P1&0xf0)!=0xf0)
  { 
    dl10ms();
	if((P1&0xf0)!=0xf0)
	 {
	   sccode=0xf0;
	   while((sccode&0x10)!=0)
	   { P1=sccode;
		 if((P1&0xf0)!=0xf0)
		 {
		   record=(P1&0xf0)|0x0f;
		   return((~sccode)+(~record));
		 }
		 else
		   sccode=(sccode<<1)|0x01;
		}
	}
   }
   return (0);
}