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MBC1 issues should be mostly fixed

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This commit is contained in:
Braiden Gent
2024-04-18 18:47:16 -07:00
parent 34ca656771
commit 056cd02375
2 changed files with 32 additions and 8 deletions
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10
README.md
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@@ -1,13 +1,17 @@
# GameBoy++
## Limitations and Features
Currently supports 32 KiB roms and MBC1 roms.
Currently passes [dmg-acid2](https://github.com/mattcurrie/dmg-acid2?tab=readme-ov-file), [blargg's cpu_instrs test](https://github.com/retrio/gb-test-roms/tree/master/cpu_instrs), and the [jsmoo SM83 JSON tests](https://github.com/raddad772/jsmoo-json-tests/tree/main/tests/sm83)
Currently
passes [dmg-acid2](https://github.com/mattcurrie/dmg-acid2?tab=readme-ov-file), [blargg's cpu_instrs test](https://github.com/retrio/gb-test-roms/tree/master/cpu_instrs),
and the [jsmoo SM83 JSON tests](https://github.com/raddad772/jsmoo-json-tests/tree/main/tests/sm83)
Tested running Super Mario Land, Dr Mario and Tetris.
Does not currently support MBC3 (needed for games like Pokemon) or loading saves. Some MBC1 games have issues still.
Does not currently support MBC3 (needed for games like english versions of Pokemon Red and Blue) or loading saves.
## Building
`mkdir build && cd build`
`cmake ..`
@@ -15,13 +19,13 @@ Does not currently support MBC3 (needed for games like Pokemon) or loading saves
`./GameBoy++ <bios> <rom>`
## Controls
WASD is mapped to the d-pad
K and L are mapped to A and B
O and P are mapped to select and start
H enters and exits debug mode
N steps through one instruction

30
src/mbc.cpp
View File

@@ -68,16 +68,37 @@ Byte* AddressSpace::MBCRead(const Word address) {
}
void AddressSpace::MBCUpdate() {
//TODO: multicart roms need to be able to switch the first rom bank as well
//see: https://gbdev.io/pandocs/MBC1.html
if (MBC == MBC1) {
//TODO: multicart roms need to be able to switch the first rom bank as well
//see: https://gbdev.io/pandocs/MBC1.html
//Selected ROM Bank = (Secondary Bank << 5) + ROM Bank
romBankRegister &= 0x1F;
twoBitBankRegister &= 0x3;
//512 KiB can only have 8KiB of ram
if (romSize > 524288) {
if (romSize >= 524288) {
if (romBankRegister == 0)
selectedRomBank = (twoBitBankRegister << 5) + 1;
selectedRomBank = (twoBitBankRegister << 5) + romBankRegister;
}
else {
if (romBankRegister == 0)
selectedRomBank = 1;
else
selectedRomBank = romBankRegister;
}
selectedExternalRamBank = 0;
loadRomBank();
loadRamBank();
}
if (MBC == MBC1Ram || MBC == MBC1RamBattery) {
//Selected ROM Bank = (Secondary Bank << 5) + ROM Bank
romBankRegister &= 0x1F;
twoBitBankRegister &= 0x3;
//512 KiB can only have 8KiB of ram
if (romSize >= 524288) {
if (romBankRegister == 0)
selectedRomBank = (twoBitBankRegister << 5) + 1;
selectedRomBank = (twoBitBankRegister << 5) + romBankRegister;
@@ -93,7 +114,6 @@ void AddressSpace::MBCUpdate() {
loadRomBank();
loadRamBank();
}
if (MBC == MBC1Ram || MBC == MBC1RamBattery) {}
}
void AddressSpace::loadRomBank() {