[DMG] Trigger STAT-LYC IRQs whenever LYC is rewritten. Also trigger L…

…ine 153 and Line 0 STAT-LYCs IRQs on Line 153

src/dmg/lcd.cpp

@@ -1997,16 +1997,22 @@ void DMG_LCD::step(int cpu_clock)
 					lcd_stat.current_scanline++;
 
 					//By line 153, LCD has actually reached the top of the screen again
-					//It will sit at Line 0 for 456 before entering Mode 2 properly
-					//Line 0 STAT-LYC IRQs should be triggered here
+					//LY will read 153 for only a few cycles, then go to 0 for the rest of the scanline
+					//Line 153 and Line 0 STAT-LYC IRQs should be triggered here
 					if(lcd_stat.current_scanline == 153)
 					{
+						//Do a scanline compare for Line 153 now
+						mem->memory_map[REG_LY] = lcd_stat.current_scanline;
+						scanline_compare();
+
+						//Set LY to 0, also trigger Line 0 STAT-LYC IRQ if necessary
+						//Technically this should fire 8 cycles into the scanline
 						lcd_stat.current_scanline = 0;
 						mem->memory_map[REG_LY] = lcd_stat.current_scanline;
 						scanline_compare();
 					}
 
-					//After sitting on Line 0 for 456 cycles, reset LCD clock, scanline count
+					//After Line 153 reset LCD clock, scanline count
 					else if(lcd_stat.current_scanline == 1) 
 					{
 						lcd_stat.lcd_clock -= 70224;

src/dmg/mmu.cpp

@@ -908,6 +908,21 @@ void DMG_MMU::write_u8(u16 address, u8 value)
 		lcd_stat->current_scanline = 0;
 	}
 
+	//LYC
+	else if(address == REG_LYC)
+	{
+		memory_map[REG_LYC] = value;
+
+		//Perform LY-LYC compare immediately
+		if(memory_map[REG_LY] == memory_map[REG_LYC]) 
+		{
+			memory_map[REG_STAT] |= 0x4; 
+			if(memory_map[REG_STAT] & 0x40) { memory_map[IF_FLAG] |= 2; }
+		}
+
+		else { memory_map[REG_STAT] &= ~0x4; }
+	}
+
 	//LCDC
 	else if(address == REG_LCDC)
 	{