*************************************************
*						*
*     Program:	Port H Output			*
*						*
*     Name   :	phoa4evb.asm			*
*						*
*     Date   :	29 May 2001			*
*						*
*     By     :	Steven J. Dombrowski		*
*						*
*						*
*     This program outputs all 8 bits on	*
* the M68HC12A4EVB and continuously updates all	*
* outputs.					*
*						*
*						*
*     To execute this program type G 5000 <CR>	*
*						*
*************************************************
*			      *
*  program origin and equates *
*			      *
*******************************
	 org $5000
putchar	 equ $fe04
porth    equ $0024
ddrh     equ $0025
************************
*		       *
* Introductory message *
*		       *
************************
	ldab #$1a		* clear screen
	jsr [putchar,PCR]
	ldx #line1		* prints program title
	ldaa #$2e
loop	ldab 0,x
	pshd
	pshx
	jsr [putchar,PCR]
	pulx
	puld
	inx
	deca
	cmpa #0
	bne loop
************************
*		       *
* Main part of program *
*		       *
************************
	ldaa #$FF		*set porth to outputs
	staa ddrh
start	ldaa #$FE
	staa porth
	jsr  delay 	
	ldaa #$FD
	staa porth
	jsr  delay
	ldaa #$FB
	staa porth
	jsr  delay
	ldaa #$F7
	staa porth
	jsr  delay
	ldaa #$EF
	staa porth
	jsr  delay
	ldaa #$DF
	staa porth
	jsr  delay
	ldaa #$BF
	staa porth
	jsr  delay
	ldaa #$7F
	staa porth
	jsr  delay
	jmp start	* continue program
*******************************
*			      *
* Subroutine to delay 1/2 sec *
*			      *
*******************************
delay	ldy #2
dly	ldx #$e000
dly1	dex
	cpx #0
	bne dly1
	dey
	cpy #0
	bne dly
	rts
******************************************************
*						     *
*		   Screen messages		     *
*						     *
******************************************************
line1  fcc 'Port H Output Program using the M68HC12A4EVB'
       fcb 4