ORG 0000h
   ajmp main
   ORG 0003h  ;外部中断0
   AJMP ZS
   ORG 000BH  ;定时计数器0中断
   AJMP JS
   ORG 0100H
main: mov sp,#60h
      CLR PSW.5    ;清零标志位
   SETB P1.0    ;置位检测位
   setb et0
   SETB IT0 ;外部中断0下降沿有效
   SETB EX0 ;允许T0中断
   mov DPTR,#5FFFH ;8279初始化
   MOV A,#0DCH
   MOVX @DPTR,A
WAIT: MOVX A,@DPTR
      JB ACC.7,WAIT
   MOV A,#00H
   MOVX @DPTR,A
   MOV A,#34H
   MOVX @DPTR,A

   MOV R0,#30H ;清零所用数值缓冲区
CL:   MOV A,#00H
   MOV @R0,A
   INC R0
   CJNE R0,#36H,CL
   MOV 36H,#200
   MOV 37H,#20
   ACALL DIR
TIME: MOV TMOD,#02H ;一秒定时
      MOV TH0,#6
   MOV TL0,#6
   SETB TR0  ;开启T0中断
   SETB EA

LOP2: JNB PSW.5,LOP3
      CLR PSW.5
   ACALL DIR   ;到一秒显示转速
   JMP LOP2
LOP3: MOV DPTR,#9FF4H ;启动a/d
   MOVX @DPTR,A
   ;ACALL DELAY1
   JB P1.0, $
   MOVX A,@DPTR
   MOV DPTR,#7FFFH ;启动d/a
   MOVX @DPTR,A
   AJMP LOP2

JS:   PUSH ACC   ;T0中断子程序
      DJNZ 36H,OUT
   DJNZ 37H,next
   ajmp next1 
next: MOV 36H,#200
   ajmp out
next1:SETB PSW.5
   MOV 33H,30H
   MOV 34H,31H
   MOV 35H,32H
   MOV 30H,#0
   MOV 31H,#0
   MOV 32H,#0
   MOV 36H,#200
   MOV 37H,#20
OUT:  POP ACC
      RETI

ZS:   PUSH ACC   ;外部中断子程序
      CLR EX0
   MOV A,30H
   ADD A,#1
   DA A
   MOV 30H,A
   CJNE A,#99H,OUT1
   MOV 30H,#0
   MOV A,31H
   ADD A,#1
   DA A
   MOV 31H,A
   CJNE A,#99H,OUT1
   MOV 31H,#0
   MOV A,32H
   ADD A,#1
   DA A
   MOV 32H,A
OUT1: SETB EX0
   POP ACC
      
   RETI   
   
DIR:  MOV R0,#33H
      MOV DPTR,#5FFFH
   MOV A,#92H
   MOVX @DPTR,A
   MOV R2,#03H
LED:  MOV A,@R0
      ANL A,#0FH
      MOV DPTR,#LEDTAB
   MOVC A,@A+DPTR
   MOV DPTR,#5EFFH
   MOVX @DPTR,A
   MOV A,@R0
   SWAP A
   ANL A,#0FH
   MOV DPTR,#LEDTAB
   MOVC A,@A+DPTR
   MOV DPTR,#5EFFH
   MOVX @DPTR,A
   INC R0
   DJNZ R2,LED
   RET

LEDTAB:DB 0c0H,0f9H,0a4H,0b0H,99H,92H,82H,0f8H,80H,90H

DELAY1: MOV R6,#5
DELAY2: MOV R7,#200
        DJNZ R7,$
        DJNZ R6,DELAY2  
  RET
  
END