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added ppu register access

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This commit is contained in:
Lauchmelder 2021-10-23 20:16:29 +02:00
parent 19d138fb5f
commit 7c0957325f
7 changed files with 113 additions and 19 deletions
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3
.gitmodules vendored Normal file
View file

@ -0,0 +1,3 @@
[submodule "vendor/SDL"]
path = vendor/SDL
url = https://github.com/libsdl-org/SDL

16
NES Emulator/bus.c
View file

@ -33,15 +33,15 @@ struct Bus* createBus()
}
memset(bus->ram, 0x00, 0x18);
// Create and insert cartridge
bus->cartridge = createCartridge(bus, "roms/nestest.nes");
// Create CPU and attach it
bus->cpu = createCPU(bus);
// Create PPU and attack it
bus->ppu = createPPU(bus);
// Create and insert cartridge
bus->cartridge = createCartridge(bus, "roms/nestest.nes");
printf("Reset vector: $%x\n", ((Word)readCartridge(bus->cartridge, 0xFFFD) << 8) | (readCartridge(bus->cartridge, 0xFFFC)));
return bus;
@ -49,9 +49,9 @@ struct Bus* createBus()
void destroyBus(struct Bus* bus)
{
destroyCartridge(bus->cartridge);
destroyPPU(bus->ppu);
destroyCPU(bus->cpu);
destroyCartridge(bus->cartridge);
free(bus->io);
free(bus->ram);
@ -67,6 +67,10 @@ Byte readBus(struct Bus* bus, Word addr)
{
val = bus->ram[addr & 0x7FF];
}
else if (0x2000 <= addr && addr < 0x4000)
{
val = ppuRead(bus->ppu, addr & 0x2007);
}
else if (0x4000 <= addr && addr <= 0x4017) // I/O space
{
val = bus->io[addr - 0x4000];
@ -91,6 +95,10 @@ void writeBus(struct Bus* bus, Word addr, Byte val)
{
bus->ram[addr & 0x7FF] = val;
}
else if (0x2000 <= addr && addr < 0x4000)
{
ppuWrite(bus->ppu, addr & 0x2007, val);
}
else if (0x4000 <= addr && addr <= 0x4017) // I/O space
{
bus->io[addr - 0x4000] = val;

4
NES Emulator/cartridge.c
View file

@ -85,7 +85,7 @@ Byte readCartridge(struct Cartridge* cartridge, Word addr)
}
else if (0x8000 <= addr && addr <= 0xFFFF) // PRG ROM
{
val = cartridge->prg_rom[addr & 0x3FFF];
val = cartridge->prg_rom[addr % 0x4000];
}
return val;
@ -101,7 +101,7 @@ void writeCartridge(struct Cartridge* cartridge, Word addr, Byte val)
}
else if (0x8000 <= addr && addr <= 0xFFFF) // PRG ROM
{
cartridge->prg_rom[addr & 0x1FFF] = val;
cartridge->prg_rom[addr % 0x4000] = val;
}
}

3
NES Emulator/cpu.c
View file

@ -25,7 +25,8 @@ struct CPU* createCPU(struct Bus* parent)
}
// TODO: THIS IS JUST FOR THE TEST ROM
cpu->pc.word = 0xC000;
// cpu->pc.word = 0xC000;
cpu->pc.word = ((Word)readBus(parent, 0xFFFD) << 8) | readBus(parent, 0xFFFC);
cpu->status.raw = 0x34;
cpu->acc = 0;

78
NES Emulator/ppu.c
View file

@ -54,12 +54,17 @@ struct PPU* createPPU(struct Bus* parent)
exit(1);
}
ppu->ppuctrl.raw = 0b00000000;
ppu->ppumask.raw = 0b00000000;
ppu->ppustatus.raw = 0b10100000;
ppu->ppuCtrl.raw = 0b00000000;
ppu->ppuMask.raw = 0b00000000;
ppu->ppuStatus.raw = 0b10100000;
ppu->oamaddr = 0x00;
ppu->ppuAddr = 0x00;
ppu->ppuData = 0x00;
ppu->scrollX = 0;
ppu->scrollY = 0;
ppu->scrollWriteTarget = 0;
ppu->ppuAddress.raw = 0x00;
ppu->ppuAddressWriteTarget = 0;
ppu->x = 0;
ppu->y = 0;
@ -79,11 +84,72 @@ void destroyPPU(struct PPU* ppu)
Byte ppuRead(struct PPU* ppu, Word addr)
{
return 0x00;
Byte val = 0x00;
switch (addr)
{
case 0x2000:
break;
case 0x2001:
break;
case 0x2002:
val = ppu->ppuStatus.raw;
break;
case 0x2005:
break;
case 0x2006:
break;
case 0x2007:
val = ppu->nametables[ppu->ppuAddress.raw & 0x2000][ppu->ppuAddress.raw & 0x1FFF];
ppu->ppuAddress.raw += ppu->ppuCtrl.increment;
break;
default:
fprintf(stderr, "Read access violation at PPU register $%04X", addr);
exit(1);
}
return val;
}
void ppuWrite(struct PPU* ppu, Word addr, Byte val)
{
switch (addr)
{
case 0x2000:
ppu->ppuCtrl.raw = val;
break;
case 0x2001:
ppu->ppuMask.raw = val;
break;
case 0x2002:
break;
case 0x2005:
*((&ppu->scrollX) + ppu->scrollWriteTarget) = val;
ppu->scrollWriteTarget = 1 - ppu->scrollWriteTarget;
break;
case 0x2006:
*((&ppu->ppuAddress.lo) + ppu->ppuAddressWriteTarget) = val;
ppu->ppuAddressWriteTarget = 1 - ppu->ppuAddressWriteTarget;
break;
case 0x2007:
ppu->nametables[ppu->ppuAddress.raw & 0x2000][ppu->ppuAddress.raw & 0x1FFF] = val;
ppu->ppuAddress.raw += ppu->ppuCtrl.increment;
break;
default:
fprintf(stderr, "Write access violation at PPU register: $%04X", addr);
exit(1);
}
}
void tickPPU(struct PPU* ppu)

27
NES Emulator/ppu.h
View file

@ -23,7 +23,7 @@ struct PPU
Byte raw;
} ppuctrl;
} ppuCtrl;
union
{
@ -39,7 +39,7 @@ struct PPU
Byte raw;
} ppumask;
} ppuMask;
union
{
@ -53,13 +53,26 @@ struct PPU
Byte raw;
} ppustatus;
} ppuStatus;
Byte oamaddr;
Byte oamdata;
Byte ppuScroll;
Byte ppuAddr;
Byte ppuData;
Byte scrollX, scrollY;
Byte scrollWriteTarget;
union
{
struct
{
Byte lo;
Byte hi;
};
Word raw;
} ppuAddress;
Byte ppuAddressWriteTarget;
Byte oamdma;
Byte* patternTables[2];
@ -81,6 +94,8 @@ struct PPU
Word x, y;
struct Bus* bus;
};

1
vendor/SDL vendored Submodule

@ -0,0 +1 @@
Subproject commit a76b73dd2cbf50102c7c9a8fa1ebdda128db72fc