#include <reg51.h>
void delay(void)
{uchar i;
 for(i=200;i>0;i--);
 }
uchar scankb(void)
{uchar sccode,recode;
 P2=0xf0;
 if((P2&0xf0)!=0xf0)//有鍵按下
   {delay();
    if((P2&0xf0)!=0xf0)//仍然有鍵按下
   	  {sccode=0xfe;
	   while((sccode&0x10)!=0)//移位沒(méi)完
	       {P2=sccode;//行掃描開(kāi)始
		    if((P2&0xf0)!=0xf0)//若在該行
		      {recode=(P2&0xf0)|0x0f;//中間結(jié)果
	           P2=0xff;              //關(guān)P2
			   return((~sccode)+(~recode));//返回Keyword
		       }
	        else sccode=(sccode<<1)|0x01;//不在該行則掃下一行
		    }
	   }
   }
 return(0);
}