RomColecoMegaCart.cc

Go to the documentation of this file.

#include "RomColecoMegaCart.hh"
#include "serialize.hh"
#include "MSXException.hh"
#include "CacheLine.hh"
#include "one_of.hh"
 
// information source:
// https://github.com/openMSX/openMSX/files/2118720/MegaCart.FAQ.V1-2.pdf
 
namespace openmsx {
 
RomColecoMegaCart::RomColecoMegaCart(const DeviceConfig& config, Rom&& rom_)
        : Rom16kBBlocks(config, std::move(rom_))
{
        if (auto size = rom.size() / 1024;
            size != one_of(128u, 256u, 512u, 1024u)) {
                throw MSXException(
                        "MegaCart only supports ROMs of 128kB, 256kB, 512kB and 1024kB "
                        "size and not of ", size, "kB.");
        }
        reset(EmuTime::dummy());
}
 
void RomColecoMegaCart::reset(EmuTime::param /*time*/)
{
        setUnmapped(0);
        setUnmapped(1);
        // The first 16K of the cartridge (CV 8000h-BFFFh) is fixed and will
        // always contain the highest/last 16K segment of the EPROM.
        setRom(2, unsigned(-1)); // select last block
        setRom(3, 0);
        invalidateDeviceRCache(0xFFC0 & CacheLine::HIGH, CacheLine::SIZE);
}
 
byte RomColecoMegaCart::readMem(word address, EmuTime::param time)
{
        // The last 64 locations will switch banks (FFC0-FFFF). If you have
        // fewer than 64 banks, then the strobe addresses simply repeat where
        // they end. If you have 16 banks, then bank 0 can be strobed at FFC0,
        // FFD0, FFE0, or FFF0.
        if (address >= 0xFFC0) {
                setRom(3, address); // mirroring is handled in superclass
                invalidateDeviceRCache(0xFFC0 & CacheLine::HIGH, CacheLine::SIZE);
        }
        return Rom16kBBlocks::readMem(address, time);
}
 
const byte* RomColecoMegaCart::getReadCacheLine(word start) const
{
        if (start >= (0xFFC0 & CacheLine::HIGH)) {
                return nullptr;
        } else {
                return Rom16kBBlocks::getReadCacheLine(start);
        }
}
 
REGISTER_MSXDEVICE(RomColecoMegaCart, "RomColecoMegaCart");
 
} // namespace openmsx