# INCLUDE "AT89X51.H"
	   ORG  0000H
       LJMP  MAIN
       ORG  0100H
MAIN :：MOV  SP，#60H
       MOV   P1,#00H            
KEY:   MOV  P2,#0FFH
   	   MOV  A,P2
	   CPL  A
	   ANL  A,#0FH
	   JZ  KEY
	   LCALL  D10MS
	   MOV  A,P2
	   CPL  A
       ANL  A,#0FH
       JZ  KEY
      JB  ACC.0.,PKEY1
	  JB  ACC.1,PKEY2
	  JB  ACC.2,PKEY3
	  JB  ACC.3,PKEY4 
      SJMP   KEY 
PKEY1:LCALL  SR
PKEY2:LCALL  SL
PKEY3:LCALL  SS
PKEY4:LCALL  SC
SR:  MOV  A,#20H
     MOV  P1,A	  
	 LCALL  D10MS
	 RR  A
     MOV  P1, A
     LCALL  D10MS
	 RR  A
	 MOV  P1, A
     LCALL  D10MS
     JNB  P2.0, SR
	 LCALL  D10MS
     JNB  P2.0 , SR
     MOV  P1,#00H
     RET
SL:  MOV  A,#01H
     MOV  P1,A	  
	 LCALL  D10MS
	 RL  A
     MOV  P1, A
     LCALL  D10MS
	 RL  A
	 MOV  P1, A
     LCALL  D10MS
     JNB  P2.1, SL
	 LCALL  D10MS
     JNB   P2.1 , SL
     MOV  P1,#00H
     RET
SS:  MOV  A, P1
     CPL   A
     MOV  P1,A 
     LCALL  D10MS
     JNB  P2.2, SS
	 LCALL  D10MS
     JNB   P2.2 , SS
     MOV  P1,#00H
     RET
SC:  MOV  P1,#0FFH
     LCALL  D10MS
     JNB  P2.3, SC
	 LCALL  D10MS
     JNB   P2.3, SC
     MOV  P1,#00H
     RET
D10MS: MOV  R7, #10H
DS1:   MOV  R6, #0FFH
DS2:   DJNZ  R6, DS2
       DJNZ  R7,DS1
       RET
       END