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Kod: Markera allt

	list      p=16F84A            ; list directive to define processor
	#include <p16F84A.inc>        ; processor specific variable definitions

	__CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC

; '__CONFIG' directive is used to embed configuration data within .asm file.
; The lables following the directive are located in the respective .inc file.
; See respective data sheet for additional information on configuration word.

;***** VARIABLE DEFINITIONS
		Cblock	0x0C		;Beginning of RAM
		HIcnt
		LOcnt
		LOOPcnt
		direction
		ledpos
		endc				;No variables

;**********************************************************************
		ORG     0x000             ; processor reset vector
  		goto    main              ; go to beginning of program


		ORG     0x004             ; interrupt vector location
		goto	main
		#include "pause.inc"

main
		banksel TRISB			;Select the bank containing TRISB
		clrf TRISB				;Port B is output
		banksel PORTB			;Select the bank containing PORTB
		banksel TRISA
		bsf TRISA,3
		banksel PORTA
		clrf direction
		movlw B'00000001'
		movwf ledpos
Loop
		goto nobutton
		btfsc PORTA,3			;Check if pin 3 on port A is clear (0)
		goto nobutton			;if bit = 1, then no button was pressed
		incf direction,1		;Increse direction-variable.
		movlw B'00000001'
		andwf direction,0		;Mask bits, store result in w-reg.
		movwf direction			;store new value in direction-variable
								
nobutton 
		movf direction,1		;Check if direction = 0
		btfsc STATUS,Z			;Check zeroflag in STATUS-register.
		goto down				;if zeroflag is set, goto down
		movf ledpos,0			;Get ledpos into w-reg
		movwf PORTB
		pausems .50				;500ms
		rlf ledpos,1			;Rotate bits left, store in ledpos.
		movfw ledpos
		addlw 0
		btfss STATUS,Z
		goto Loop				;Jump to label Loop
		movlw B'00000001'
		movwf ledpos
		goto Loop
down
		movf ledpos,0			;Get ledpos into w-reg
		movwf PORTB
		pausems .50				;500ms
		rrf ledpos,1			;Rotate bits right, store in ledpos.
		btfss STATUS,Z
		goto Loop
		movlw B'01000000'
		movwf ledpos
		goto Loop
		END                     ; directive 'end of program'