;;; expanddemo.s
;;; puts HC11 in expanded mode,
;;; writes sequentially increasing values to address 0x5000,
;;; and delays and clicks on PA4 between each write
;;; Fred G. Martin / UML CS 2002

PORTA=	0x1000	
HPRIO=	0x103c			; highest priority bit int and misc reg

  	ldaa HPRIO		; read the reg
  	oraa #0x20		; set MDA bit -> expanded mode
  	staa HPRIO		; write it back

	clrb			; init b at 0
loop:	
	stab 0x5000		; write b to target
	incb			; inc it for next time
	
	ldaa PORTA
	eora #0x10		; toggle piezo bit (click)
	staa PORTA
	
	ldy #0			; delay for 65k loops
delay:	dey
	bne delay
	
	bra loop		; again