; ADDAC.A11
;
; control MAXIM 512 via MOSI Port
; 23-Dec-1997 dl3mhb@qsl.net
;

PORTC	equ	$1003
DDRC	equ	$1007
PORTD	equ	$1008
DDRD	equ	$1009
SPCR	equ	$1028
SPSR	equ	$1029
SPDR	equ	$102A
ADCTL	equ	$1030
ADR1	equ	$1031
OPTION	equ	$1039

STACK	equ	$00ff

;-------------------------------
	org	$b600

start	lds	#STACK		; we know where he is

	ldaa	OPTION
	oraa	#%10000000	; ADC on
	staa	OPTION
	clr	ADCTL		; reset A/D registers

	ldaa	#%11111111	; make 'em outputs
	staa	DDRC

	ldaa	#%00111000	; make SPI to output
	staa	DDRD
	ldaa	#%00100000
	staa	PORTD		; and set SS high

	ldaa	#%01011100	; SPE ! MSTR ! SCK ! CPHA ! clock
	staa	SPCR

s1	jsr	convert		; into A
	staa	PORTC
	jsr	daca		; go to DA on port A

	bra	s1

;-------------------------------
convert	ldaa	ADCTL
	staa	ADCTL
c1	tst	ADCTL
	bpl	c1
	ldaa	ADR1
	rts

;-------------------------------
daca	clr	PORTD		; enable SS

	ldab	#%00110001	; DAC A on and select
	stab	SPDR		; store control byte

d1	tst	SPSR
	bpl	d1

	staa	SPDR		; send data byte

d2	tst	SPSR
	bpl	d2

	ldab	#%00100000	; execute instruction
	stab	PORTD
	rts