From: kub <derkub@gmail.com>
Date: Sun, 2 Mar 2025 19:10:28 +0000 (+0100)
Subject: sms, improved vdp register latching
X-Git-Tag: v2.04~32
X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4c10007b6902d15d9a8fd564ca6b50ddb3e0b65c;p=picodrive.git

sms, improved vdp register latching
---

diff --git a/pico/mode4.c b/pico/mode4.c
index cc5c5883..43bc2556 100644
--- a/pico/mode4.c
+++ b/pico/mode4.c
@@ -26,7 +26,6 @@ static unsigned char sprites_map[2+256/8+2]; // collision detection map
 unsigned int sprites_status;
 
 int sprites_zoom; // latched sprite zoom flag
-int sprites_sat, sprites_base; // latched sprite table data
 int xscroll; // horizontal scroll
 
 /* sprite collision detection */
@@ -169,14 +168,14 @@ static void ParseSpritesM4(int scanline)
   if (Pico.m.hardware & PMS_HW_LCD)
     xoff -= 48; // GG LCD, adjust to center 160 px
 
-  sat = (u8 *)PicoMem.vram + ((sprites_sat & 0x7e) << 7);
+  sat = (u8 *)PicoMem.vram + ((pv->reg[5] & 0x7e) << 7);
   if (sprites_zoom & 2) {
     addr_mask = 0xfe; h = 16;
   } else {
     addr_mask = 0xff; h = 8;
   }
   if (zoomed) h *= 2;
-  sprite_base = (sprites_base & 4) << (13-2-1);
+  sprite_base = (pv->reg[6] & 4) << (13-2-1);
 
   m = pv->status & SR_C;
   memset(sprites_map, 0, sizeof(sprites_map));
@@ -443,14 +442,14 @@ static void ParseSpritesTMS(int scanline)
 
   xoff = line_offset;
 
-  sat = (u8 *)PicoMem.vramb + ((sprites_sat & 0x7f) << 7);
+  sat = (u8 *)PicoMem.vramb + ((pv->reg[5] & 0x7f) << 7);
   if (sprites_zoom & 2) {
     addr_mask = 0xfc; h = 16;
   } else {
     addr_mask = 0xff; h = 8;
   }
   if (zoomed) h *= 2;
-  sprite_base = (sprites_base & 0x7) << 11;
+  sprite_base = (pv->reg[6] & 0x7) << 11;
 
   m = pv->status & SR_C;
   memset(sprites_map, 0, sizeof(sprites_map));
@@ -851,8 +850,6 @@ void PicoLineSMS(int line)
 
   // latch current register values (may be overwritten by VDP reg writes later)
   sprites_zoom = (Pico.video.reg[1] & 0x3) | (Pico.video.reg[0] & 0x8);
-  sprites_sat = Pico.video.reg[5];
-  sprites_base = Pico.video.reg[6];
   xscroll = Pico.video.reg[8];
 
   if (FinalizeLineSMS != NULL)
diff --git a/pico/sms.c b/pico/sms.c
index 5bc9ebd9..214601f3 100644
--- a/pico/sms.c
+++ b/pico/sms.c
@@ -24,7 +24,7 @@ extern void YM2413_regWrite(unsigned reg);
 extern void YM2413_dataWrite(unsigned data);
 
 extern unsigned sprites_status; // TODO put in some hdr file!
-extern int sprites_zoom, sprites_sat, sprites_base, xscroll;
+extern int sprites_zoom, xscroll;
 
 static unsigned char vdp_data_read(void)
 {
@@ -88,12 +88,16 @@ static void vdp_data_write(unsigned char d)
 //   23 px right border+blanking,
 //   26 px hsync,
 //   37 px left blanking+border
-// VINT is at the beginning of hsync, and HINRT is one px later. Relative TO V/HINT:
-//   -10 px sprite mode latching (r1)
-//   -8 px sprite mode latching (r0)
-//   -6 px sprite attribute table latching (r5)
-//   -4 px sprite pattern table latching (r6)
-//   -2 px xscroll latching (r8)
+// VINT is at the beginning of hsync, and HINT is one px later. Relative TO V/HINT:
+//   -18..-2 px 1st half of sprite attribute table (r5) scan
+//   -10 px sprite mode latching (r1,r0)
+//   -2 px hscroll latching (r8)
+// hscroll is probably latched internally due to it depending on the horizontal
+// scroll lock, which has this at 0 for the top 16 lines.
+// I don't think the sprite mode is really latched. The SAT scan determines the
+// relative y position within the sprite pattern, which will break since SAT
+// scanning is done in one go here, while in reality it is distributed over
+// several slots. Cache it here to avoid backward effects of later changes to r1
 // TODO: off by 2 CPU cycles according to VDPTEST?
 
 static NOINLINE void vdp_reg_write(struct PicoVideo *pv, u8 a, u8 d)
@@ -106,7 +110,7 @@ static NOINLINE void vdp_reg_write(struct PicoVideo *pv, u8 a, u8 d)
     l = pv->pending_ints & (d >> 3) & 2;
     elprintf(EL_INTS, "hint %d", l);
     z80_int_assert(l);
-    if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(8*1.5)+2)
+    if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(10*1.5)+2)
       sprites_zoom = (pv->reg[1] & 0x3) | (pv->reg[0] & 0x8);
     break;
   case 1: // mode control 2
@@ -116,14 +120,6 @@ static NOINLINE void vdp_reg_write(struct PicoVideo *pv, u8 a, u8 d)
     if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(10*1.5)+2)
       sprites_zoom = (pv->reg[1] & 0x3) | (pv->reg[0] & 0x8);
     break;
-  case 5: // sprite attribute table
-    if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(6*1.5)+2)
-      sprites_sat = d;
-    break;
-  case 6: // sprite pattern table
-    if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(4*1.5)+2)
-      sprites_base = d;
-    break;
   case 8: // horizontal scroll
     if (z80_cyclesDone() - Pico.t.z80c_line_start < 228 - (int)(2*1.5)+2)
       xscroll = d;