NESemu/src/Bus.cpp

#include "Bus.hpp"
#include "Log.hpp"

#include <stdexcept>

Bus::Bus() :
	cpu(this), ppu(this), cartridge(this)
{
	LOG_CORE_INFO("Allocating RAM");
	RAM = std::vector<Byte>(0x800);

	LOG_CORE_INFO("Allocating VRAM");
	VRAM = std::vector<Byte>(0x1000);

	LOG_CORE_INFO("Inserting cartridge");
	cartridge.Load("roms/nestest.nes");

	LOG_CORE_INFO("Powering up CPU");
	cpu.Powerup();

	LOG_CORE_INFO("Powering up PPU");
	ppu.Powerup();
}

void Bus::Reboot()
{
	cpu.Powerup();
	ppu.Powerup();
}

void Bus::Reset()
{
	cpu.Reset();
	ppu.Reset();
}

uint8_t Bus::Tick()
{
	uint8_t result = cpu.Tick();

	// 3 ppu ticks per cpu tick
	ppu.Tick();
	ppu.Tick();
	ppu.Tick();

	return result;
}

bool Bus::Instruction()
{
	try
	{
		while (Tick());
	}
	catch (const std::runtime_error& err)
	{
		LOG_CORE_FATAL("Fatal Bus error: {0}", err.what());
		cpu.Halt();
		return true;
	}

	return true;
}

bool Bus::Frame()
{
	try
	{
		while (!ppu.IsFrameDone())
			Tick();
	}
	catch (const std::runtime_error& err)
	{
		LOG_CORE_FATAL("Fatal Bus error: {0}", err.what());
		cpu.Halt();
		return true;
	}

	return true;
}

Byte Bus::ReadCPU(Word addr)
{
	if (0x0000 <= addr && addr < 0x2000)
	{
		return RAM[addr & 0x7FF];
	}
	else if (0x2000 <= addr && addr < 0x4000)
	{
		return ppu.ReadRegister(addr & 0x7);
	}
	else if (0x8000 <= addr && addr <= 0xFFFF)
	{
		return cartridge.ReadCPU(addr);
	}

	return 0x00;
}

Byte Bus::ReadPPU(Word addr)
{
	addr &= 0x3FFF;

	if (0x0000 <= addr && addr < 0x2000)
	{
		return cartridge.ReadPPU(addr);
	}
	else if(0x2000  <= addr && addr < 0x4000)
	{
		return VRAM[addr & 0xFFF];
	}
	
	return 0x00;
}

void Bus::WriteCPU(Word addr, Byte val)
{
	if (0x0000 <= addr && addr < 0x2000)
	{
		RAM[addr & 0x7FF] = val;
	}
	else if (0x2000 <= addr && addr < 0x4000)
	{
		ppu.WriteRegister(addr & 0x7, val);
	}
	else if (0x8000 <= addr && addr <= 0xFFFF)
	{
		cartridge.WriteCPU(addr, val);
	}
}

void Bus::WritePPU(Word addr, Byte val)
{
	addr &= 0x3FFF;

	if (0x0000 <= addr && addr < 0x2000)
	{
		cartridge.WritePPU(addr, val);
	}
	else if (0x2000 <= addr && addr < 0x4000)
	{
		VRAM[addr & 0xFFF] = val;
	}
}