; xkas

; register definitions
MSU_STATUS  = $2000
MSU_READ    = $2001
MSU_ID      = $2002
MSU_SEEK    = $2000
MSU_TRACK   = $2004
MSU_VOLUME  = $2006
MSU_CONTROL = $2007

CheckForMSU:
; assuming 16-bit xy

	ldx   MSU_ID		;
	cpx.w #$2D53		; 'S-'
	bne   NoMSU
	ldx   MSU_ID + 2
	cpx.w #$534D		; 'MS'
	bne   NoMSU
	ldx   MSU_ID + 4
	cpx.w #$3155		; 'U1'
	bne   NoMSU

MSUFound:
	; Do something when it's detected...
	jsr PlayMSUTrack
	rts

NoMSU:
	; Jump somewhere else when it's not...
	rts

PlayMSUTrack:
	lda #$FF
	sta MSU_VOLUME
	ldx #$0001	; Writing a 16-bit value will automatically set $2005 as well
	stx MSU_TRACK
	lda #$01	; Set audio state to play, no repeat.
	sta MSU_CONTROL
	rts

PlayMSUTrack_WithLooping:
	lda #$FF
	sta MSU_VOLUME
	ldx #$0001	; Writing a 16-bit value will automatically set $2005 as well
	stx MSU_TRACK
	lda #$03	; Set audio state to play, with repeat.
	sta MSU_CONTROL
	rts

SeekMSUData:
	ldx #$0410	; seek to $00000410
	stx MSU_SEEK
	ldx #$0000
	stx MSU_SEEK+2
-	bit MSU_STATUS	; Wait for the Data Busy bit to clear.
	bmi -
	rts

LoadTilemapFromMSU:
; to load a tileset, do the same thing but load the data directly
; (no separate tile/attribute bytes)
	ldx #$4000	; Set target address
	stx VMADDL	; to VRAM
	ldy #$0000	; Initialize counter
-	lda MSU_DATA	; Grab tile byte
	sta VMDATAL
	iny
	lda MSU_DATA	; Grab attribute byte
	sta VMDATAH
	iny
	cpy #$0800	; length of $800 bytes
	bne -
	rts

LoadPaletteFromMSU:
	lda #$10	; Set starting point - color #16
	sta CGADD
	ldy #$0000	; Initialize counter
-	lda MSU_DATA
	sta CGADD
	iny
	cpy #$20	; Colors are 16-bit values, so we must copy 32 bytes, not 16.
	bne -
	rts