prog26.asm

主要是8051源代码

;  PROG26 -  Using Interrupts to Debounce a Button 
;
;  This Application Toggles the LED at P1.0 After the Button on
;   P3.2 (Int0 Pin) has been debounced.  
;
;  Myke Predko
;  98.03.01
;
;  Hardware Notes:
;  80C520 Running at 4 MHz
;  The 80C520's Clock will be running at 1/4 Second "Ticks"
;  P1.0 is Connected to a Set of LEDs
define PressButton=P3.2         ;  P3.2 is Connected to a Button that pulls down the Pin

;  Variable Declarations
Flags EQU 020h                  ;  When Bit 0 Set, then Button Pressed

 org 000h
  ajmp   Mainline

 org 003h                       ;  Int0 Pin

  mov    TH0,#2*256/3           ;  Wait 20 msec for Key to be Active

  setb    IE.1                  ;  Enable Timer Interrupts
  
  clr     TCON.5                ;  Make Sure Overflow is Turned Off  

  reti

 org 00Bh                       ;  Timer0 (Real Time) Interrupt
                                ;  When This is Executed, Set Flags.0 
                                ;   and Turn Off Interrupts

  mov    IE,#%10000001          ;  Enable Button Interrupts

  jb     P3.2,IntT0_End         ;  If Button Not Pressed, Don't Mark it

  setb   0                      ;  Set the Button Interrupt

IntT0_End:                      ;  End of T0 Overflow Interrupt

  reti

 org 020h                       ;  Program Mainline
Mainline:

  mov    CKCON,#%00001000       ;  Use Internal /4 Clock for Timer0
  mov    TMOD,#%00000001        ;  Timer0 - Uses Internal Clock
                                ;         - Run in Mode 1
  mov    TCON,#%00010001        ;  Start Timer0 running
                                ;   Make Edge Triggered Interrupts

  mov    IE,#%10000001          ;  Enable Button Interrupts

;  Now, Do the Looping Output

MainLoop:                       ;  Come Back Here After Inverting the LED
  jnb    PressButton,MainLoop   ;  Loop Waiting for the Button to be Pressed

  clr    0                      ;  Clear the Button Press Flag

ButtonLoop:                     ;  Wait for the Button to be Pressed
  jnb    0,ButtonLoop           ;  Wait for the Bit to be Set

  cpl    P1.0                   ;  Invert the LED State

  ajmp   MainLoop               ;  Wait to Decrement the Next Time