数字电压表程序
       ORG  0000H
       SJMP  START 
START：MOV SP，#60H
       MOV 50H，#00H
       MOV B，#00H
       MOV R6，#04H
       MOV DPTR，#7FF8H
 TTO：MOVX @DPTR,A
      NOP 
      NOP 
      JB P3.2,$
      MOVX A,@DPTR
      ADD A,50H
      MOV 50H,A
      JNC TT1
      INC  B
  TT1:DJNZ R6,TTO
      CLR C
      XCH A,B
      RRC A
      XCH A,B
      RRC A
      CLR C
      XCH A,B
      RRC A
      XCH A,B
      RRC A
      MOV 50H,A
      SJMP DATA
  *****数据处理*******
  DATA:MOV A,50H
       MOV B,#33H
       DIV AB
       MOV 20H,A
       XCH A,B
       MOV B,#05H
       DIV AB
       MOV 21H,A
       MOV 22H,B
   *****显示程序*******
   MODE:MOV R3,#00H
        MOV A,#80H
        MOV DPTR,#7FFFH
        MOV @DPTR,A
   DISP:MOV R0,#22H
        MOV R2,#01H 
   LOOP:MOV A,#00H
        MOV DPTR,#7FFFH
        MOVX @DPTR,A
        MOV A,R2
        MOV DPTR,#7FFEH
        MOVX @DPTR,A
        MOV DPTR,#7FFCH
        MOV A,@R0
        INC  R3
        ADD A,#19H
        MOVC A,@A+PC
        CJNE R3,#03H,L1
        ORL  A,#80H
    L1: MOV @DPTR,A
        ACLL D1MS
        DEC  R0
        MOV A,R2
        JB ACC.2,EXIT
        RL A
        MOV R2,A
        AJMP LOOP
    EXIT:AJMP START
    ****数表*******
    TAB:DB 3FH,06H,5BH,4FH,66H
        DB 6DH,7DH,07H,7FH,6FH
        DB 77H,7CH,39H,5EH,79H,71H
  *****延时子程序*********
    D1MS:MOV R7,#02H
     DL0:MOV R6,#0FFH
     DL1:DJNZ R6,DL1
         DJNZ R7,DL0
         RET
         END