PasswordCart.cc

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/*
 * Password Cartridge
 *
 * Access: write 0x00 to I/O port 0x7e
 *         provide 0xaa, <char1>, <char2>, continuous 0xff sequence reading I/O port 0x7e
 *         write any non-zero to I/O port 0x7e
 *         provide 0xff at all time reading I/O port 0x7e
 */
 
#include "PasswordCart.hh"
#include "narrow.hh"
#include "serialize.hh"
#include <algorithm>
 
namespace openmsx {
 
PasswordCart::PasswordCart(const DeviceConfig& config)
        : MSXDevice(config)
        , password(narrow_cast<word>(config.getChildDataAsInt("password", 0)))
{
        reset(EmuTime::dummy());
}
 
void PasswordCart::reset(EmuTime::param /*time*/)
{
        pointer = 3;
}
 
void PasswordCart::writeIO(word /*port*/, byte value, EmuTime::param /*time*/)
{
        pointer = (value == 0) ? 0 : 3;
}
 
byte PasswordCart::readIO(word port, EmuTime::param time)
{
        byte result = peekIO(port, time);
        pointer = byte(std::min(3, pointer + 1));
        return result;
}
 
byte PasswordCart::peekIO(word /*port*/, EmuTime::param /*time*/) const
{
        switch (pointer) {
        case 0:
                return 0xAA;
        case 1:
                return narrow_cast<byte>(password >> 8);
        case 2:
                return narrow_cast<byte>(password & 0xFF);
        default:
                return 0xFF;
        }
}
 
template<typename Archive>
void PasswordCart::serialize(Archive& ar, unsigned /*version*/)
{
        ar.template serializeBase<MSXDevice>(*this);
        ar.serialize("pointer", pointer);
}
INSTANTIATE_SERIALIZE_METHODS(PasswordCart);
REGISTER_MSXDEVICE(PasswordCart, "PasswordCart");
 
} // namespace openmsx