vgbc/memory/mbc/mbc1.cpp

#include <memory/mbc/mbc1.h>
#include <misc/exception.h>

MBC1::MBC1(Cartridge& cart)
  : cart(cart),
    main_bankreg(0),
    external_ram(0x8000)
{}

u8 MBC1::read8(u16 addr)
{
  if((addr & 0xC000) == 0x0000)
    return cart[addr];
  else if((addr & 0xC000) == 0x4000)
    {
      u8 bank = main_bankreg ? main_bankreg : 1;
      u8 numbanks = cart.size() >> 14;
      return cart[(bank % numbanks) << 14 | (addr - 0x4000)];
    }
  else if((addr & 0xE000) == 0xA000)
    {
      if(!ram_enabled) return 0xFF;
      return external_ram.read8(ram_bankreg << 13 | (addr - 0xA000));
    }
  else
    return 0xFF;
}

void MBC1::write8(u16 addr, u8 data)
{
  if((addr & 0xE000) == 0x0000)
    ram_enabled = ((data & 0x0F) == 0x0A);
  else if((addr & 0xE000) == 0x2000)
    main_bankreg = data & 0x1F;
  else if((addr & 0xE000) == 0x4000)
    ram_bankreg = data & 0x03;
  else if((addr & 0xE000) == 0x6000)
    throw EmulatorException("MBC1: banking mode not supported");
}