;本程序為數字電壓表
;輸入電壓經89k電阻和10k精密電位器分壓
;測試電壓為0～51v，可用表校對
DO BIT P3.6
DI BIT P3.7
CLK BIT P3.5
CS BIT P3.4
MOV DPTR,#TABLE
MOV R4,#30
MAIN:DJNZ R4,LOOD
     MOV R4,#30
      CALL CADB  ;調用轉換程序
     MOV 36H,A
     CALL L1
     CALL L3
     CALL DISP
LOOD:CALL SCAN  ;調用顯示掃描
     JMP MAIN
CADB:CLR CS
     MOV A,#03h
     MOV R7,#03h ;寫3位指令
 LOOPB1:CLR CLK
        RRC A
        MOV DI,C
        NOP
        SETB CLK
        DJNZ R7,LOOPB1
        CLR CLK
        NOP
        SETB CLK
        MOV R7,#08H ;讀8位數據
  LOOPB2:CLR CLK
        MOV C,DO
        RLC A
        SETB CLK
        DJNZ R7,LOOPB2
        SETB CS
        RET
  L1:  CLR C         ;十進制轉換
       MOV 30H,#00
       MOV 31H,#00
       MOV R2,#08H
  NEXT:RLC A
       MOV R3,A
       MOV A,30H
       ADDC A,30H
       DA A
       MOV 30H,A
       MOV A,31H
       ADDC A,31H
       MOV 31H,A
       MOV A,R3
       DJNZ R2,NEXT
  L2:  MOV A,30H
       ADD A,30H
      DA A
      MOV 30H,A
      MOV A,31H
      ADDC A,31H
      DA A
      MOV 31H,A
      RET
 L3:MOV A,31H

    MOV B,#10H
    DIV AB
    MOV 21H,A
    MOV 22H,B
    MOV A,30H

    MOV B,#10H
    DIV AB
    MOV 23H,A
    MOV 24H,B
    RET

  SCAN:mov p2,#11110111b ;掃描子程序
     mov a,24H
     MOVC A,@A+DPTR

     mov p0,a
     call delay1
     mov p2,#11111011b
     mov a,23H
     movc a,@a+dptr
     ORL A,#80H
     mov p0,a
     call delay1
     MOV P2,#11111101B
     MOV A,22H
     MOVC A,@A+DPTR
     MOV P0,A
     CALL DELAY1
     MOV P2,#11111110B
     MOV A,21H
     MOVC A, @A+DPTR
     MOV P0,A
     CALL DELAY1
        RET
  DISP:
        RET
DELAY1:MOV R6,#5    ;掃描延時
D3:    MOV R7,#248
        DJNZ R7,$
       DJNZ R6,D3
       RET
TABLE:DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H    ;共陽字碼表
END