Emulate ICD desyncing

bsnes/gb/Core/display.c

@@ -127,13 +127,13 @@ static void display_vblank(GB_gameboy_t *gb)
     if (GB_is_hle_sgb(gb)) {
         GB_sgb_render(gb);
     }
-
+    
     if (gb->turbo) {
         if (GB_timing_sync_turbo(gb)) {
             return;
         }
     }
-
+    
     if (!gb->disable_rendering && ((!(gb->io_registers[GB_IO_LCDC] & 0x80) || gb->stopped) || gb->frame_skip_state == GB_FRAMESKIP_LCD_TURNED_ON)) {
         /* LCD is off, set screen to white or black (if LCD is on in stop mode) */
         if (gb->sgb) {
@@ -423,8 +423,7 @@ static void render_pixel_if_possible(GB_gameboy_t *gb)
             gb->screen[gb->position_in_line + gb->current_line * WIDTH] = gb->sprite_palettes_rgb[oam_fifo_item->palette * 4 + pixel];
         }
     }
-
-    /* byuu: gotta do this later so it's only done once ... you'll probably wanna refactor this somehow :/ */
+	
     if (gb->model & GB_MODEL_NO_SFC_BIT) {
         if (gb->icd_pixel_callback) {
             gb->icd_pixel_callback(gb, icd_pixel);
@@ -770,7 +769,13 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
             fifo_push_bg_row(&gb->bg_fifo, 0, 0, 0, false, false);
             /* Todo: find out actual access time of SCX */
             gb->position_in_line = - (gb->io_registers[GB_IO_SCX] & 7) - 8;
-            gb->current_lcd_line++; // Todo: unverified timing
+            
+            // Todo: unverified timing
+            gb->current_lcd_line++;
+            if (gb->icd_hreset_callback) {
+                gb->icd_hreset_callback(gb);
+            }
+            
             if (gb->current_lcd_line == LINES && GB_is_sgb(gb)) {
                 display_vblank(gb);
             }
@@ -910,11 +915,6 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
             }
             GB_SLEEP(gb, display, 11, LINE_LENGTH - gb->cycles_for_line);
             gb->mode_for_interrupt = 2;
-            
-            /* TODO: Can this timing even be verified? */
-            if (gb->icd_hreset_callback) {
-                gb->icd_hreset_callback(gb);
-            }
         }
         
         /* Lines 144 - 152 */

bsnes/sfc/coprocessor/icd/icd.cpp

@@ -16,7 +16,6 @@ namespace SameBoy {
 
   static auto vreset(GB_gameboy_t*) -> void {
     icd.ly = 0;
-    icd.ppuScanline();
   }
 
   static auto icd_pixel(GB_gameboy_t*, uint8_t pixel) -> void {
@@ -122,7 +121,8 @@ auto ICD::power() -> void {
   readBank = 0;
   readAddress = 0;
   writeBank = 0;
-  writeAddress = 0;
+  writeX = 0;
+  writeY = 0;
 
   packetSize = 0;
   joypID = 3;
@@ -148,7 +148,8 @@ auto ICD::reset() -> void {
   readBank = 0;
   readAddress = 0;
   writeBank = 0;
-  writeAddress = 0;
+  writeX = 0;
+  writeY = 0;
 
   packetSize = 0;
   joypID = 3;

bsnes/sfc/coprocessor/icd/icd.hpp

@@ -61,7 +61,8 @@ private:
   uint readBank;
   uint readAddress;
   uint writeBank;
-  uint writeAddress;
+  uint writeX;
+  uint writeY;
 
   struct Information {
     uint pathID = 0;
@@ -73,7 +74,7 @@ public:
   //as the offsets of all member variables will be wrong compared to what the C SameBoy code expects.
   GB_gameboy_t sameboy;
   uint32_t bitmap[160 * 144];
-  uint ly = 0;
+  uint8_t ly = 0;
 };
 
 extern ICD icd;

bsnes/sfc/coprocessor/icd/interface.cpp

@@ -1,18 +1,19 @@
 auto ICD::ppuScanline() -> void {
-  if(ly > 143) return;  //Vblank
-  if((ly & 7) == 0) {
+  if(++writeY == 8) {
     writeBank = (writeBank + 1) & 3;
-    writeAddress = 0;
+    writeY = 0;
   }
+  writeX = 0;
 }
 
 auto ICD::ppuOutput(uint2 color) -> void {
-  uint y = writeAddress / 160;
-  uint x = writeAddress % 160;
-  uint addr = writeBank * 512 + y * 2 + x / 8 * 16;
+  if(writeX >= 160) return; // Unverified behavior
+  if(writeY >= 8) return; // Should never happen
+  
+  uint addr = writeBank * 512 + writeY * 2 + writeX / 8 * 16;
   output[addr + 0] = (output[addr + 0] << 1) | !!(color & 1);
   output[addr + 1] = (output[addr + 1] << 1) | !!(color & 2);
-  writeAddress = (writeAddress + 1) % 1280;
+  writeX++;
 }
 
 auto ICD::apuOutput(float left, float right) -> void {

bsnes/sfc/coprocessor/icd/serialization.cpp

@@ -38,5 +38,6 @@ auto ICD::serialize(serializer& s) -> void {
   s.integer(readBank);
   s.integer(readAddress);
   s.integer(writeBank);
-  s.integer(writeAddress);
+  s.integer(writeX);
+  s.integer(writeY);
 }