From 01454ec65fd6ae9b7b87d7a763f8893dc91015e4 Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Wed, 3 Jan 2024 12:44:29 +0200
Subject: [PATCH] clear vram/cram/vsram on init

---
 src/vdp.S |   46 ++++++++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 16 deletions(-)

diff --git a/src/vdp.S b/src/vdp.S
index 1d62565..5727a56 100644
--- a/src/vdp.S
+++ b/src/vdp.S
@@ -1,12 +1,12 @@
 	.text
 
+#define ASM
 #include "hwregs.h"
 
 	.globl vdp_init
 vdp_init:
-	| initialize registers
-	move.l #def_reg_tab, %a0
-	clr.w %d1
+	movea.l #def_reg_tab, %a0
+	move.w #0, %d1
 0:	move.w %d1, %d0
 	lsl.w #8, %d0
 	or.w #0x8000, %d0
@@ -16,17 +16,32 @@ vdp_init:
 	cmp.w def_reg_tab_size, %d1
 	bne.s 0b
 
-	| clear VRAM
-	clr.l %d0
+	| clear vram
+	movea.l #VDP_DATA_PORT, %a0
+	moveq #0, %d0
 	move.l #VDP_VRAM, %d1
 	bsr setup_addr
-	clr.w %d0
-	move.w #0xffff, %d1
-0:	move.w %d0, VDP_DATA_PORT
-	dbra.w %d1, 0b
-	
-	rts
+	moveq #0, %d0
+	move.l #0x7fff, %d1	| 64k / 2 - 1
+0:	move.w %d0, (%a0)
+	dbra %d1, 0b
 
+	| clear colormaps
+	move.l #VDP_CRAM, %d1
+	bsr setup_addr
+	moveq #0, %d0
+	move.l #63, %d1		| 4 palettes * 16 col * 2 bytes / 2 - 1
+0:	move.w %d0, (%a0)
+	dbra %d1, 0b
+
+	| clear vscroll
+	move.l #VDP_VSRAM, %d1
+	bsr setup_addr
+	moveq #0, %d0
+	move.l #39, %d1		| 80 bytes / 2 - 1
+0:	move.w %d0, (%a0)
+	dbra %d1, 0b
+	rts
 
 	| address in d0, type in d1
 setup_addr:
@@ -40,9 +55,8 @@ setup_addr:
 	.globl vdp_setcolor
 vdp_setcolor:
 	move.l 4(%sp), %d0	| palette number
-	lsl.l #4, %d0
+	lsl.l #5, %d0
 	add.l 8(%sp), %d0	| add index
-	lsl.l #1, %d0
 	move.l #VDP_CRAM, %d1
 	bsr setup_addr
 	move.w 22(%sp), %d0	| blue
@@ -54,12 +68,12 @@ vdp_setcolor:
 	move.w %d0, VDP_DATA_PORT
 	rts
 
-	.section .rodata
+	.data
 def_reg_tab:
 	.byte VDP_M1_INIT			| 0: mode 1
 	.byte VDP_M2_INIT + VDP_M2_DISP		| 1: mode 2
 	.byte VDP_NA_ADDR(0xc000)		| 2: scroll A nametable addr.
-	.byte VDP_NW_ADDR(VDP_ADDR_INVAL)	| 3: window nametable addr.
+	.byte 0					| 3: window nametable addr.
 	.byte VDP_NB_ADDR(0xd000)		| 4: scroll B nametable addr.
 	.byte VDP_SPRTAB_ADDR(0xe000)		| 5: sprite table addr.
 	.byte 0
@@ -68,7 +82,7 @@ def_reg_tab:
 	.byte 0					| 10: horiz. interrupt interval
 	.byte 0					| 11: mode 3
 	.byte VDP_M4_H40			| 12: mode 4
-	.byte 0					| 13: hscroll table addr.
+	.byte VDP_HSTAB_ADDR(0xf000)		| 13: hscroll table addr.
 	.byte 0
 	.byte 2					| 15: autoincrement 2 bytes
 	.byte VDP_SCR_H64			| 16: scroll size (64x32)
-- 
1.7.10.4