*************************************************
*						*
*     Program:	Port B Output			*
*						*
*     Name   :	pboevbu.src			*
*						*
*     Date   :	22 Mar 2001			*
*						*
*     By     :	Steven J. Dombrowski		*
*						*
*						*
*     This program outputs all 8 bits on	*
* the M68HC11EVBU and continuously updates all	*
* outputs.					*
*						*
*						*
*     To execute this program type G 0100 <CR>	*
*						*
*************************************************
*			      *
*  program origin and equates *
*			      *
*******************************
	 org $0100
outcrlf  equ $ffc4
outstrg0 equ $ffca
outa	 equ $ffb8
portb    equ $1004
************************
*		       *
* Introductory message *
*		       *
************************
	ldaa #$1a		* clear screen
	jsr outa	
	ldx #line1		* prints program title
	jsr outstrg0		* message
************************
*		       *
* Main part of program *
*		       *
************************
start	ldaa #$FE
	staa portb
	jsr  delay 	
	ldaa #$FD
	staa portb
	jsr  delay
	ldaa #$FB
	staa portb
	jsr  delay
	ldaa #$F7
	staa portb
	jsr  delay
	ldaa #$EF
	staa portb
	jsr  delay
	ldaa #$DF
	staa portb
	jsr  delay
	ldaa #$BF
	staa portb
	jsr  delay
	ldaa #$7F
	staa portb
	jsr  delay
	jmp start	* continue program
*******************************
*			      *
* Subroutine to delay 1/2 sec *
*			      *
*******************************
delay	ldy #2
dly	ldx #$e000
dly1	dex
	cpx #0
	bne dly1
	dey
	cpy #0
	bne dly
	rts
******************************************************
*						     *
*		   Screen messages		     *
*						     *
******************************************************
line1  fcc 'Port B Output Program using the M68HC11EVBU'
       fcb 4
