KEY  BIT   P3.3
   SW1  BIT   P2.2
         ORG  000H
   START: mov  sp,#40h
          mov  p2,#0ffh
          mov  p3,#0ffh
          MOV  P1,#0ffh;
          clr  key
    WAIT: JB    KEY,$       ;等候按鍵!
          JB   SW1,$
          lcall delay
          cpl   P1.0
          JNB   SW1,$
          JMP   wait
 DELAY:   MOV  R3,#300
 D1:      MOV  R4,#300
          DJNZ  R4,$
          DJNZ  R3,D1
          RET
    END