//NES-CNROM (treble mapper)

class Settings {
  integer mirror;  //0 = horizontal, 1 = vertical
}

Settings settings;
integer chr_bank;

function prg_read(integer addr) returns integer {
  if(addr & 0x8000) return prg.read(addr & 0x7fff);
  return cpu.mdr();
}

function prg_write(integer addr, integer data) {
  if(addr & 0x8000) chr_bank = data & 0x03;
}

function chr_read(integer addr) returns integer {
  if(addr & 0x2000) {
    if(settings.mirror == 0) addr = ((addr & 0x0800) >> 1) | (addr & 0x03ff);
    return ciram.read(addr & 0x07ff);
  }
  addr = (chr_bank * 0x2000) + (addr & 0x1fff);
  return chr.read(addr);
}

function chr_write(integer addr, integer data) {
  if(addr & 0x2000) {
    if(settings.mirror == 0) addr = ((addr & 0x0800) >> 1) | (addr & 0x03ff);
    return ciram.write(addr & 0x07ff, data);
  }
  addr = (chr_bank * 0x2000) + (addr & 0x1fff);
  chr.write(addr, data);
}

function power() {
  settings.mirror = manifest("cartridge/mirror/mode") == "vertical";
}

function reset() {
  chr_bank = 0;
}

function serialize(serializer& s) {
  s.integer(chr_bank);
}