;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-

	CLKMASK	=	%00000010
	CTRL2	=	$DC00

coldstart:
	lda #$0
	sta $400
waitstart:
	lda $dc01
	and #$01
	bne waitstart
	lda #$00
	sta $d020
teststart:
	jsr check_for_load_start
	jmp $c000
	beq teststart
	bcs @error
	jmp $c000
@error:
	lda #0
	sta $0400
	rts

check_for_load_start:
	lda #CLKMASK
	bit CTRL2
	bne start
	lda #$00
	rts
start:
	sei
	ldx #$02
	stx $d020
	ldy #$00
	jmp new_byte

wait_for_bit_start:
	lda #CLKMASK
@loop:
	bit CTRL2
	beq @loop

	lda #CLKMASK
	bit CTRL2
	beq error
	lda CTRL2

	lsr
	ror BYTE
	bcc wait_for_bit_end
	txa			; get the zero flag from X
	beq @normal
	dex
	lda BYTE
	sta LEN,x
	txa
	bne @notdone
	;; Computing stop address
	clc
	lda LEN
	adc z:progdest
	sta stop
	lda LEN+1
	adc z:progdest+1
	sta stop+1
	jmp @notdone
@normal:
	;; Byte finished, storing
	lda BYTE
	sta (progdest), y
	inc z:progdest
	bne @noinchi
	inc z:progdest+1
@noinchi:
	;; Comparing progdest against stop address
	lda z:progdest
	cmp stop
	bne @notdone
	lda z:progdest+1
	cmp stop+1
	bne @notdone
	jmp done
@notdone:
new_byte:
	lda #%10000000
	sta BYTE
wait_for_bit_end:
	lda #CLKMASK
@loop:
	bit CTRL2
	bne @loop
	jmp wait_for_bit_start

done:
	lda #$01
	cli
	clc
	rts

error:
	;; TODO
	cli
	sec
	rts

BYTE		= $400
LEN		= $402
progdest	= $fe
stop:		.word $0000
loaded:		.byte 0