MIAO      EQU    21H
      GEWEI     EQU    22H
      SHIWEI    EQU    23H
      SCANLED  BIT     01H
      ORG  000H          ;ORG偽指令使用于程序定位
      JMP   START
      ORG   0BH
      JMP   TIMER0       ;定時0中斷入口地址
      ORG   100H
START:MOV  SP,#40H       ;設(shè)定堆棧指針
MOV  P0,#0FFH
      MOV  P1,#0FFH
      MOV  P2,#0FFH
      MOV  P3,#0FFH
      MOV   R0,#20H      ;清空RAM(20H-7FFH)
      MOV   R5,#60H
 CLR0:MOV  @R0,#00H
      INC    R0
      DJNZ  R5,CLR0
      MOV  TMOD,#01H   ;設(shè)定定時器1為工作方式1
      MOV  TH0,#HIGH(65536-5000)
      MOV  TL0,#LOW(65536-5000)
      SETB  TR0
      MOV  IE,#10000010B
      MOV  R7,#200
      MOV  MIAO,#99
      AJMP  $

TIMER0:PUSH   ACC              ;定時器1中斷服務(wù)子程序
       PUSH    PSW
       MOV    TH0,#HIGH(65536-5000)
       MOV    TL0,#LOW(65536-5000)
       DJNZ    R7,TIM0_LP
       MOV    R7,#200
DJNZ   MIAO,TIM0_LP
       MOV   MIAO,#99          ;
TIM0_LP: MOV   A,MIAO
          LCALL  BIN_BCD
          MOV    SHIWEI,A
          MOV   GEWEI,B
          CPL    SCANLED
          JB     SCANLED,SCAN_L1
          JMP    SCAN_L2          
SCAN_L1: MOV   P2,#01111111B    ;顯示十位
          MOV   A,SHIWEI
          JMP     END_SCAN
SCAN_L2: MOV   P2,#10111111B    ;顯示個位
          MOV    A,GEWEI
          JMP     END_SCAN
END_SCAN:MOV   DPTR,#TABLE
           MOVC  A,@A+DPTR
           MOV   P0,A
           POP    PSW
           POP    ACC
           RETI

 BIN_BCD:MOV  B,#10
          DIV   AB
          RET

TABLE:DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H
       END