Back to MSX1 palette on MSX2

Thanks.

Since the palette registers are write-only, a copy of the palette is stored in VRAM. Where exactly depends on the screen mode.

See https://www.msx.org/wiki/VDP_Color_Palette_Registers

Afaik INIPLT resets to the default palette, and it resets the mirror in VRAM as well. RSTPLT is equivalent to BASIC's COLOR=RESTORE which you would typically invoke after BLOAD "",S-ing an image that includes the palette data to apply it.

As for me, I wonder why they put two routines to call the sub-Rom routines.

Here's a supplement just in case anyone is interested.

Under MSX-DOS, you can do like in these examples.

By using the Sub-ROM routine:

; Routine to initialize colors palette under MSX-DOS

EXBRSA	equ	0FAF8h		; Sub-ROM slot number
CALLF	equ	00030h		; Inter slot call
INIPLT	equ	00141h		; MSX2 colors palette initialization 

	org	0100h

IniColPalDOS:
	ld	ix,INIPLT	; Routine address
	call	CalSUB		; Call routine in sub-ROM
	ret			; Back to MSX-DOS

; Routine to call a Sub-ROM routine under MSX-DOS
;
; Entry: Routine parameters
;        IX = Address of the routine to call into Sub-ROM

CalSUB:
	push	af
	ld	a,(EXBRSA)
	ld	(CalSUBslt),a	; Set slot number
	push	ix
	ex	(sp),hl
	ld	a,l
	ld	(CalSUBadrs),a	; Set low byte of the routine address
	ld	a,h
	ld	(CalSUBadr+1),a	; Set high byte of the routine address
	ex	(sp),hl
	pop	ix		
	pop	af		
	rst	030h		; Inter slot call
CalSUBslt:
	db	0		; Slot number
CalSUBadrs:
	dw	0		; Address
	ret

By direct access to VDP:

VDP_DW	equ	00007h
RG16SAV	equ	0FFEFh

; Routine to initialize colors palette (MSX2~)
;
; Modify: AF, BC, HL
; Note: Data in VRAM are not initialized

IniMSX2palette:
	ld	a,(VDP_DW)
	ld	c,a		; C= Writing port 1 of VDP

	xor	a		; Set color 0 ...
	di
	out	(c),a
	ld	(RG16SAV),a
	ld	a,80h+16
	out	(c),a		; ...into register 16 (+80h)
	ei

	inc	c		; C= Writing port 2 of VDP
	ld	b,31
	ld	hl,IniPaletteData
	otir
	ret			; Back to MSX-DOS

IniPaletteData:
	db	00h,0	; Color 0
	db	00h,0	; 1
	db	11h,6	; 2
	db	33h,6	; 3
	db	17h,1	; 4
	db	27h,3	; 5
	db	51h,1	; 6
	db	27h,6	; 7
	db	71h,1	; 8
	db	73h,3	; 9
	db	61h,6	; 10
	db	64h,0	; 11
	db	11h,4	; 12
	db	65h,2	; 13
	db	55h,5	; 14
	db	77h,7	; 15

If you replace the data by those below, you will get colors close to those of the MSX1s.

	db	00h,0	; Color 0
	db	00h,0	; 1
	db	11h,5	; 2
	db	33h,6	; 3
	db	26h,2	; 4
	db	37h,3	; 5
	db	52h,2	; 6
	db	27h,6	; 7
	db	62h,2	; 8
	db	63h,3	; 9
	db	52h,5	; 10
	db	63h,6	; 11
	db	11h,4	; 12
	db	55h,2	; 13
	db	55h,5	; 14
	db	77h,7	; 15

Oups, direct access method will not work under DOS without read VDP_DW with the RDSLT (0000Ch) routine. I forgot to replace ld a,(VDP_DW) by:

	ld	a,(0fcc1h)
	ld	hl,VDP_DW
	call	000ch