#include "dma.i65"
#include "msu1.i65"

msu1init:
	sep #$20 : .as
	rep #$10 : .xl
	ldx #$0000
	stx MSU_SEEK_OFFSET
	stx MSU_SEEK_BANK
-	bit MSU_STATUS
	bmi -

	stx MSU_TRACK
-	bit MSU_STATUS
	bvs -
	ldx #$0000
	stx $2116

	lda #$04
	sta charptr
	sta $210b

	; prepare DMA
	ldx #$2001
	stx $4302
	stz $4304

	lda #$01
	sta firstframe

	rts


msu1loop:
	sep #$20 : .as
	rep #$10 : .xl
	stz dispcnt
	lda $2001
	sta numframes
	lda $2001
	sta numframes+1
	lda $2001
	sta curdur
	sta stddur
	lda $2001
	sta altdur
	lda $2001
	sta altcnt
	lda #$01
	sta curcnt
ldx #$0000
stx $1000 ;temp var
	ldx numframes
	dex
        lda #$21                ;V-Count IRQ + Auto Joypad Read
        sta $4200

lda numframes
sta @$306000
lda numframes+1
sta @$306001
lda stddur
sta @$306002
lda altdur
sta @$306003
lda altcnt
sta @$306004
lda curdur
sta @$306005
lda curcnt
sta @$306006
msu1loop2
	lda isr_flag
	beq msu1loop2
	stz isr_flag
	lda dispcnt	;load field count
	cmp #$02	;if >= 2 don't draw anymore
	bpl +
	;load half picture
	lda #$18
phx
ldx $1000
sta @$306100, x
inx
stx $1000
plx
	sta $4301
	lda #$09
	sta $4300
	ldy #16256
	sty $4305
	lda #$01
	sta $420b
+	inc dispcnt	;inc field count
	lda dispcnt	;and compare with current duration
phx
ldx $1000
sta @$306100, x
inx
stx $1000
plx
	cmp curdur	;if not reached...
	bne msu1loop2   ;...wait another field

	lda firstframe	;first frame ready for display?
	beq +

	lda #$01	;then start audio
	sta MSU_CONTROL
	stz firstframe

+
	lda curcnt	;
	cmp altcnt	;compare with alternation frequency
	bne +		;if reached...
	stz curcnt	;...reset current frame count
	lda altdur	;use alternate duration for next frame
	bra skip
+	lda stddur	;else use normal duration
	inc curcnt	;and inc current frame count
skip	sta curdur	;store in current duration
	stz dispcnt	;reset field counter
	dex		;countdown total frames
	beq msu1stop	;stop if end of movie

	;load palette
	stz $2121
	lda #$22
	sta $4301
	lda #$08
	sta $4300
	ldy #512
	sty $4305
	lda #$01
	sta $420b
	lda charptr
	bne ptr2
ptr1
	lda #$04
	sta $210b
	sta charptr
	ldy #$0000
	sty $2116
	jmp msu1loop2
ptr2
	stz $210b
	stz charptr
	ldy #$4000
	sty $2116
	jmp msu1loop2

msu1stop:
;	lda #$80
;	sta $2100
;	stz $420c
	stz MSU_CONTROL
	rts