// 鍵盤動態控制P1外接的LED循環右、左移顯示，或靜止
#include <REGX51.H>
extern void delay(unsigned int i);

ex32( )  // C語言的主函數
{
  unsigned char LED,key,action=1;
  LED = 0x01;
  while(1)
  {
     P1 = ~LED;   // LED取反送P1
	 delay();
	 P3 = 0xff;
	 key=~P3;
	 if (key){
		 if (key == 0x01) action = 1;
		 else if (key == 0x80) action = 3;
		 else action = 2;
	  }
	 switch(action)
	 {
	 	case 1:
			 if(LED) LED >>=1;
			 else LED = 0x80;
			 break;
	 	case 2:
			 break;
	 	case 3:
			 if(LED) LED <<=1;
			 else LED = 0x01;
			 break;
	 }
  }
}