51单片机定时器(汇编)

  ORG   0000H
  LJMP  MIAN
  ORG   000BH
  LJMP  T0_break
  ORG   0200H
INIT:
  MOV   TMOD,#01H ;定时器0为方式1
  ;定时器0计时100us
  MOV   TL0,#0B0H
  MOV   TH0,#3CH
  SETB  ET0
  ;开启总中断
  SETB  EA
  RET
MIAN:
  LCALL   INIT
  ACALL PS0
LOOP: 
  JMP   LOOP
PS0:
  MOV   R5,#0EFH
  MOV   R4,#0AH
  MOV   P2,#0FFH
  CPL   TR0
  RET
T0_1:
  RETI
Inv_C:
  CPL   C
  LJMP  D2
  RET
T0_L:
  RR    A
  MOV   R5,A
  CPL   P1.5
  RETI
T0_break:
  ;重新装载初始值
  MOV   TL0,#0B0H
  MOV   TH0,#3CH
  ;每10次流动一次
  DJNZ  R4,T0_1;
  MOV   R4,#0AH
  MOV   P2,R5;
  MOV   A,R5
  ;判断是否反向
  JNB   P2.7, Inv_C 
  JNB   P2.0, InV_C
D2: JC    T0_L
  RL    A
  MOV   R5,A
  CPL   P1.5
  RETI
end