ORG 0000H
LJMP MAIN
ORG  0030H
MAIN: MOV P0,#0FFH;若不要该指令,则键按下后灯一直亮.
      JNB P2.0,KEY1 ;键按下转KEY1按键处理程序,否则转MAIN等待键按下.
      JNB p2.1,KEY2
      JNB P2.2,KEY3
JMP MAIN
KEY1:CLR P0.0 
    ACALL DELAY 
    JMP MAIN
KEY2:CLR P0.1
     ACALL DELAY 
     JMP MAIN
KEY3:CLR P0.2
     ACALL DELAY 
     JMP MAIN
DELAY:MOV    R7,#250        ;延时子程序
D1:  MOV     R6,#250
D2:  DJNZ    R6,D2
     DJNZ    R7,D1
     RET
     END