count-down.asm

我自己编的一个一位数码管减计数的学习程序

 list		p=16f73		; list directive to define processor
  #include	<p16f73.inc>; processor specific

PORTB     EQU     0X006
PORTC     EQU     0X007
COUNT     EQU     0X021
default   equ     0x022

  BSF     PORTC,0
;  MOVLW   0X00
  clrw
  TRIS    PORTB
  TRIS    PORTC
  clrf    default
loop1
  movlw   0x0f
  movwf   default
loop
  movf    default,w
  call    decode
  movwf   PORTB
  call    delay
  decfsz  default  
  goto    loop
  movlw   0x00
  call    decode
  movwf   PORTB
  call    delay
  goto    loop1
decode                   ;二进制到七段数码显示的查表程序
   addwf   PCL,f         
   retlw   b'00111111'   ;0
   retlw   b'00000110'   ;1
   retlw   b'01011011'   ;2
   retlw   b'01001111'   ;3
   retlw   b'01100110'   ;4
   retlw   b'01101101'   ;5
   retlw   b'01111101'   ;6
   retlw   b'00000111'   ;7
   retlw   b'01111111'   ;8
   retlw   b'01101111'   ;9
   retlw   b'01110111'   ;A
   retlw   b'01111100'   ;b
   retlw   b'00111001'   ;C
   retlw   b'01011110'   ;d
   retlw   b'01111001'   ;E
   retlw   b'01110001'   ;F
   return
delay                   ;延时子程序
  MOVLW   0X7f
  MOVWF   COUNT
dLOOP1
  DECFSZ  COUNT
  GOTO    dLOOP1
  return
   END