static void Main(string[] args)
{
var memory = Cpu6502Compiler.Compile("main.s");
var memManager = new MemoryManager(memory);
var obs = new OutputObserver();
memManager.RegisterObserver(obs);
var cpu = new Cpu6502(memManager);
cpu.Reset();
Console.WriteLine();
}
public NesBus()
{
Devices = new List<IResetableDevice>();
// Connect devices
Cpu6502 = new Cpu6502();
Cpu6502.ConnectBus(this);
Devices.Add(Cpu6502);
Ppu2C02 = new Ppu2C02();
Ppu2C02.ConnectBus(this);
Devices.Add(Ppu2C02);
Apu2A03 = new Apu2A03();
Apu2A03.ConnectBus(this);
Devices.Add(Apu2A03);
// init 2k RAM
Ram = Enumerable.Repeat((byte)0, 2 * 1024).ToList();
// Controlers
Controller = new byte[] { 0x00, 0x00 };
ControllerState = new byte[] { 0x00, 0x00 };
}
public bool Clock()
{
// Clocking. The heart and soul of an emulator. The running
// frequency is controlled by whatever calls this function.
// So here we "divide" the clock as necessary and call
// the peripheral devices clock() function at the correct
// times.
// The fastest clock frequency the digital system cares
// about is equivalent to the PPU clock. So the PPU is clocked
// each time this function is called...
Ppu2C02.Clock();
// ...also clock the APU
Apu2A03.Clock();
// The CPU runs 3 times slower than the PPU so we only call its
// clock() function every 3 times this function is called. We
// have a global counter to keep track of this.
if (SystemClockCounter % 3 == 0)
{
// Is the system performing a DMA transfer form CPU memory to
// OAM memory on PPU?...
if (dma_transfer)
{
// ...Yes! We need to wait until the next even CPU clock cycle
// before it starts...
if (dma_dummy)
{
// ...So hang around in here each clock until 1 or 2 cycles
// have elapsed...
if (SystemClockCounter % 2 == 1)
{
// ...and finally allow DMA to start
dma_dummy = false;
}
}
else
{
// DMA can take place!
if (SystemClockCounter % 2 == 0)
{
// On even clock cycles, read from CPU bus
dma_data = CpuRead((ushort)(dma_page << 8 | dma_addr), false);
}
else
{
// On odd clock cycles, write to PPU OAM
Ppu2C02.OAM[dma_addr] = dma_data;
// Increment the lo byte of the address
dma_addr++;
// If this wraps around, we know that 256
// bytes have been written, so end the DMA
// transfer, and proceed as normal
if (dma_addr == 0x00)
{
dma_transfer = false;
dma_dummy = true;
}
}
}
}
else
{
// No DMA happening, the CPU is in control of its
// own destiny. Go forth my friend and calculate
// awesomeness for many generations to come...
Cpu6502.Clock();
}
}
// Synchronising with Audio
bool bAudioSampleReady = false;
dAudioTime += dAudioTimePerNESClock;
if (dAudioTime >= dAudioTimePerSystemSample)
{
dAudioTime -= dAudioTimePerSystemSample;
dAudioSample = Apu2A03.GetOutputSample();
bAudioSampleReady = true;
}
// The PPU is capable of emitting an interrupt to indicate the
// vertical blanking period has been entered. If it has, we need
// to send that irq to the CPU.
if (Ppu2C02.Nmi)
{
Ppu2C02.Nmi = false;
Cpu6502.NMI();
}
// Check if cartridge is requesting IRQ
if (Cartridge.GetMapper().IrqState)
{
Cartridge.GetMapper().IrqClear();
Cpu6502.IRQ();
}
SystemClockCounter++;
return bAudioSampleReady;
}
public Register(Cpu6502 cpu)
{
_cpu = new(cpu);
Value = 0;
}
