GBHawk: ppu cleanup and more aaccuracy edge case work

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_GB_PPU.cs

@@ -273,7 +273,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public override void tick()
 		{
 			// Do HDMA ticks
-			if (HDMA_active)
+			if (HDMA_active && !Core.cpu.halted && !Core.cpu.stopped)
 			{
 				if (HDMA_length > 0)
 				{
@@ -701,11 +701,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			// i.e. just keeping track of the lowest x-value sprite
 			if (render_cycle == 0)
 			{
-				/*
-				OAM_access_read = false;
-				OAM_access_write = true;
-				VRAM_access_read = false;
-				*/
 				// window X is latched for the scanline, mid-line changes have no effect
 				window_x_latch = window_x;
 
@@ -1200,6 +1195,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 								OAM_access_write = true;
 								VRAM_access_read = true;
 								VRAM_access_write = true;
+
+								read_case = 18;
 							}
 							else
 							{
@@ -1228,6 +1225,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					case 17:
 						read_case--;
 						break;
+					case 18:
+						// end of rendering
+						break;
 				}
 				internal_cycle++;
 				

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_PPU.cs

@@ -269,7 +269,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public override void tick()
 		{
 			// Do HDMA ticks
-			if (HDMA_active)
+			if (HDMA_active && !Core.cpu.halted && !Core.cpu.stopped)
 			{
 				if (HDMA_length > 0)
 				{
@@ -704,11 +704,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			// i.e. just keeping track of the lowest x-value sprite
 			if (render_cycle == 0)
 			{
-				/*
-				OAM_access_read = false;
-				OAM_access_write = true;
-				VRAM_access_read = false;
-				*/
 				// window X is latched for the scanline, mid-line changes have no effect
 				window_x_latch = window_x;
 
@@ -1158,7 +1153,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					case 8: // done reading, we are now in phase 0
 						pre_render = true;
 
-						// the other interrupts appear to be delayed by 1 CPU cycle, so do the same here
 						if (hbl_countdown > 0)
 						{
 							hbl_countdown--;
@@ -1169,6 +1163,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 								OAM_access_write = true;
 								VRAM_access_read = true;
 								VRAM_access_write = true;
+
+								read_case = 18;
 							}
 							else
 							{
@@ -1197,6 +1193,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					case 17:
 						read_case--;
 						break;
+					case 18:
+						// end of rendering
+						break;
 				}
 				internal_cycle++;
 				

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GB_PPU.cs

@@ -459,11 +459,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			// i.e. just keeping track of the lowest x-value sprite
 			if (render_cycle == 0)
 			{
-				/*
-				OAM_access_read = false;
-				OAM_access_write = true;
-				VRAM_access_read = false;
-				*/
 				// window X is latched for the scanline, mid-line changes have no effect
 				window_x_latch = window_x;
 
@@ -620,6 +615,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 
 					if (pixel_counter == 160)
 					{
+						hbl_countdown = 2;
 						read_case = 8;
 					}
 				}
@@ -874,15 +870,26 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					case 8: // done reading, we are now in phase 0
 						pre_render = true;
 
+						if (hbl_countdown > 0)
+						{
+							hbl_countdown--;
+							if (hbl_countdown == 0)
+							{
+								VRAM_access_read = true;
+								VRAM_access_write = true;
+								OAM_access_read = true;
+								OAM_access_write = true;
+
+								read_case = 18;
+							}
+							else
+							{
 								STAT &= 0xFC;
 								STAT |= 0x00;
 
 								if (STAT.Bit(3)) { HBL_INT = true; }
-
+							}
-						OAM_access_read = true;
+						}
-						OAM_access_write = true;
-						VRAM_access_read = true;
-						VRAM_access_write = true;					
 						break;
 
 					case 9:
@@ -902,6 +909,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					case 17:
 						read_case--;
 						break;
+					case 18:
+						// end of rendering
+						break;
 				}
 				internal_cycle++;
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/MemoryMap.cs

@@ -58,14 +58,23 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				{
 					return RAM[addr - 0xE000];
 				}
+
 				if (addr >= 0xF000 && addr < 0xFE00)
 				{
 					return RAM[(RAM_Bank * 0x1000) + (addr - 0xF000)];
 				}
-				if (addr >= 0xFE00 && addr < 0xFEA0 && ppu.DMA_OAM_access)
+
+				if (addr >= 0xFE00 && addr < 0xFEA0)
+				{
+					if (ppu.DMA_OAM_access)
 					{
 						return OAM[addr - 0xFE00];
 					}	
+					else 
+					{
+						return 0xFF;
+					}				
+				}
 
 				if (addr >= 0xFF00 && addr < 0xFF80) // The game GOAL! Requires Hardware Regs to be accessible
 				{
@@ -323,15 +332,23 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				{
 					return RAM[addr - 0xE000];
 				}
+
 				if (addr >= 0xF000 && addr < 0xFE00)
 				{
 					return RAM[(RAM_Bank * 0x1000) + (addr - 0xF000)];
 				}
 
-				if (addr >= 0xFE00 && addr < 0xFEA0 && ppu.DMA_OAM_access)
+				if (addr >= 0xFE00 && addr < 0xFEA0)
+				{
+					if (ppu.DMA_OAM_access)
 					{
 						return OAM[addr - 0xFE00];
 					}
+					else
+					{
+						return 0xFF;
+					}
+				}
 
 				if (addr >= 0xFF00 && addr < 0xFF80) // The game GOAL! Requires Hardware Regs to be accessible
 				{