all repos — mgba @ 773e0d26ffd5e15c99d50bc6e5cb66fe167d85f4

mGBA Game Boy Advance Emulator

GB Memory: Better emulate 0xFEA0 region on DMG, MGB and AGB
Vicki Pfau vi@endrift.com
Sat, 06 Jul 2019 16:13:39 -0700
commit

773e0d26ffd5e15c99d50bc6e5cb66fe167d85f4

parent

c471d03c7dfcd5048599aa5ab37b1e6e9fefae4b

2 files changed, 13 insertions(+), 1 deletions(-)

jump to
M CHANGES → CHANGES 
@@ -34,6 +34,7 @@ - GB Audio: Deschedule channel 3 when disabled (fixes mgba.io/i/1463)
  - GB Audio: Deschedule channel 1 when disabled by sweep (fixes mgba.io/i/1467)
  - GBA Memory: Fix STM/LDM to invalid VRAM
  - GB: Fix savedata initialization (fixes mgba.io/i/1473, mgba.io/i/1478)
+ - GB Memory: Better emulate 0xFEA0 region on DMG, MGB and AGB
 Other fixes:
  - Qt: Fix some Qt display driver race conditions
  - Core: Improved lockstep driver reliability (Le Hoang Quyen)
M src/gb/memory.c → src/gb/memory.c 
@@ -234,7 +234,7 @@ enum GBBus accessBus = block[address >> 13];
 		if (dmaBus != GB_BUS_CPU && dmaBus == accessBus) {
 			return 0xFF;
 		}
-		if (address >= GB_BASE_OAM && address < GB_BASE_UNUSABLE) {
+		if (address >= GB_BASE_OAM && address < GB_BASE_IO) {
 			return 0xFF;
 		}
 	}

@@ -471,6 +471,17 @@ return 0xFF;
 		}
 		if (address < GB_BASE_IO) {
 			mLOG(GB_MEM, GAME_ERROR, "Attempt to read from unusable memory: %04X", address);
+			if (gb->video.mode < 2) {
+				switch (gb->model) {
+				case GB_MODEL_AGB:
+					return (address & 0xF0) | ((address >> 4) & 0xF);
+				case GB_MODEL_CGB:
+					// TODO: R/W behavior
+					return 0x00;
+				default:
+					return 0x00;
+				}
+			}
 			return 0xFF;
 		}
 		if (address < GB_BASE_HRAM) {