nedoPC.org

;Drive a 8 digit, 7 segment LED display

    list      p=16F84A             ; list directive to define processor
    #include <p16F84a.inc>         ; processor specific variable definitions

    __CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _RC_OSC

;***** VARIABLE DEFINITIONS
porta  equ  0x05
portb  equ  0x06
delay  equ  0x0c   
digit  equ  0x0d
dmask  equ  0x0e
value  equ  0x0f

  org  0x000  ; processor reset vector
  goto    start ; go to beginning of program

  org  0x004; interrupt vector location
  goto  isrv

start
;Clear the PORTB
  clrf   PORTB
  bsf    STATUS, RP0 ; Select bank 1
;configure all port A bits for output
  clrw
;  tris  porta
  movwf  TRISB;

;configure all port B bits for output
  clrw
;  tris  portb
  movwf  TRISA
  bcf    STATUS, RP0 ; Select bank 0

loop
  movlw  b'01110110' ; H
  movwf  value
  movlw  0x00; digit
  call  displaydigit
  movlw  b'01111001' ; E
  movwf  value
  movlw  0x01; digit
  call  displaydigit
  movlw  b'00111000' ; L
  movwf  value
  movlw  0x02; digit
  call  displaydigit
  movlw  b'00111000' ; L
  movwf  value
  movlw  0x03; digit
  call  displaydigit
  movlw  b'00111111' ; O
  movwf  value
  movlw  0x04; digit
  call  displaydigit
  movlw  b'00001000' ; _
  movwf  value
  movlw  0x05; digit
  call  displaydigit
  movlw  b'01111111' ; 8
  movwf  value
  movlw  0x06; digit
  call  displaydigit
  movlw  b'01100110' ; 4
  movwf  value
  movlw  0x07; digit
  call  displaydigit
  goto  loop

d250
  movlw  0x25
  movwf  delay
l250  decfsz  delay,f
  goto  l250
  return

displaydigit
  andlw  b'00000111'
;select a digit
  movwf  porta
;display a value on the selected digit
  movfw  value
  movwf  portb
;wait for a while
  call  d250
  return

isrv
  retfie
  end