;;; beep.s
;;; toggles Port A4 with delay loops between each toggle,
;;; creating an oscillation in the audible range.

	ldx #0x1000		; point at register base
loop:	bset 0,x,#0x10		; set bit 4 in PORTA register
declp1:	deca			; decrement reg A
	bne declp1		;   and loop till it hits zero.
	bclr 0,x,#0x10		; clear bit 4 of PORTA
declp2:	deca			; decrement reg A
	bne declp2		;   till it hits zero.
	bra loop		; now recycle at the beginning.