ESE_SCC.cc

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/*
 * 'Ese-SCC' cartridge and 'MEGA-SCSI with SCC'(alias WAVE-SCSI) cartridge.
 *
 * Specification:
 *  SRAM(MegaROM) controller: KONAMI_SCC type
 *  SRAM capacity           : 128, 256, 512kB and 1024kb(WAVE-SCSI only)
 *  SCSI Protocol controller: Fujitsu MB89352A
 *
 * ESE-SCC sram write control register:
 *  0x7FFE, 0x7FFF SRAM write control.
 *   bit4       = 1..SRAM writing in 0x4000-0x7FFD can be done.
 *                   It is given priority more than bank changing.
 *              = 0..SRAM read only
 *   other bit  = not used
 *
 * WAVE-SCSI bank control register
 *             6bit register (MA13-MA18, B0-B5)
 *  5000-57FF: 4000-5FFF change
 *  7000-77FF: 6000-7FFF change
 *  9000-97FF: 8000-9FFF change
 *  B000-B7FF: A000-BFFF change
 *
 *  7FFE,7FFF: 2bit register
 *       bit4: bank control MA20 (B7)
 *       bit6: bank control MA19 (B6)
 *  other bit: not used
 *
 * WAVE-SCSI bank map:
 *  00-3F: SRAM read only. mirror of 80-BF.
 *     3F: SCC
 *  40-7F: SPC (MB89352A)
 *  80-FF: SRAM read and write
 *
 * SPC BANK address map:
 * 4000-4FFF spc data register (mirror of 5FFA)
 * 5000-5FEF undefined specification
 * 5FF0-5FFE spc register
 *      5FFF unmapped
 *
 * WAVE-SCSI bank access map (X = accessible)
 *           00-3F 80-BF C0-FF SPC  SCC
 * 4000-5FFF   X     X     X    X    .
 * 6000-7FFF   X     X     .    .    .
 * 8000-9FFF   X     .     .    .    X
 * A000-BFFF   X     .     .    .    .
 */
 
#include "ESE_SCC.hh"
#include "MB89352.hh"
#include "MSXException.hh"
#include "narrow.hh"
#include "one_of.hh"
#include "ranges.hh"
#include "serialize.hh"
#include "xrange.hh"
#include <memory>
 
namespace openmsx {
 
size_t ESE_SCC::getSramSize(bool withSCSI) const
{
        size_t sramSize = getDeviceConfig().getChildDataAsInt("sramsize", 256); // size in kb
        if (sramSize != one_of(1024u, 512u, 256u, 128u)) {
                throw MSXException(
                        "SRAM size for ", getName(),
                        " should be 128, 256, 512 or 1024kB and not ",
                        sramSize, "kB!");
        }
        if (!withSCSI && sramSize == 1024) {
                throw MSXException("1024kB SRAM is only allowed in WAVE-SCSI!");
        }
        return sramSize * 1024; // in bytes
}
 
ESE_SCC::ESE_SCC(const DeviceConfig& config, bool withSCSI)
        : MSXDevice(config)
        , sram(getName() + " SRAM", getSramSize(withSCSI), config)
        , scc(getName(), config, getCurrentTime())
        , spc(withSCSI ? std::make_unique<MB89352>(config) : nullptr)
        , romBlockDebug(*this, mapper, 0x4000, 0x8000, 13)
        , mapperMask(narrow<byte>((sram.size() / 0x2000) - 1))
{
        // initialized mapper
        ranges::iota(mapper, byte(0));
}
 
void ESE_SCC::powerUp(EmuTime::param time)
{
        scc.powerUp(time);
        reset(time);
}
 
void ESE_SCC::reset(EmuTime::param time)
{
        setMapperHigh(0);
        for (auto i : xrange(byte(4))) {
                setMapperLow(i, i);
        }
        scc.reset(time);
        if (spc) spc->reset(true);
}
 
void ESE_SCC::setMapperLow(unsigned page, byte value)
{
        value &= 0x3f; // use only 6bit
        bool flush = false;
        if (page == 2) {
                bool newSccEnable = (value == 0x3f);
                if (newSccEnable != sccEnable) {
                        sccEnable = newSccEnable;
                        flush = true;
                }
        }
        byte newValue = value;
        if (page == 0) newValue |= byte(mapper[0] & 0x40);
        newValue &= mapperMask;
        if (mapper[page] != newValue) {
                mapper[page] = newValue;
                flush = true;
        }
        if (flush) {
                invalidateDeviceRWCache(0x4000 + 0x2000 * page, 0x2000);
        }
}
 
void ESE_SCC::setMapperHigh(byte value)
{
        writeEnable = (value & 0x10) != 0; // no need to flush cache
        if (!spc) return; // only WAVE-SCSI supports 1024kB
 
        bool flush = false;
        byte mapperHigh = value & 0x40;
        bool newSpcEnable = mapperHigh && !writeEnable;
        if (spcEnable != newSpcEnable) {
                spcEnable = newSpcEnable;
                flush = true;
        }
 
        byte newValue = ((mapper[0] & 0x3F) | mapperHigh) & mapperMask;
        if (mapper[0] != newValue) {
                mapper[0] = newValue;
                flush = true;
        }
        if (flush) {
                invalidateDeviceRWCache(0x4000, 0x2000);
        }
}
 
byte ESE_SCC::readMem(word address, EmuTime::param time)
{
        unsigned page = address / 0x2000 - 2;
        // SPC
        if (spcEnable && (page == 0)) {
                address &= 0x1fff;
                if (address < 0x1000) {
                        return spc->readDREG();
                } else {
                        return spc->readRegister(address & 0x0f);
                }
        }
        // SCC bank
        if (sccEnable && (address >= 0x9800) && (address < 0xa000)) {
                return scc.readMem(narrow_cast<uint8_t>(address & 0xff), time);
        }
        // SRAM read
        return sram[mapper[page] * 0x2000 + (address & 0x1fff)];
}
 
byte ESE_SCC::peekMem(word address, EmuTime::param time) const
{
        unsigned page = address / 0x2000 - 2;
        // SPC
        if (spcEnable && (page == 0)) {
                address &= 0x1fff;
                if (address < 0x1000) {
                        return spc->peekDREG();
                } else {
                        return spc->peekRegister(address & 0x0f);
                }
        }
        // SCC bank
        if (sccEnable && (address >= 0x9800) && (address < 0xa000)) {
                return scc.peekMem(narrow_cast<uint8_t>(address & 0xff), time);
        }
        // SRAM read
        return sram[mapper[page] * 0x2000 + (address & 0x1fff)];
}
 
const byte* ESE_SCC::getReadCacheLine(word address) const
{
        unsigned page = address / 0x2000 - 2;
        // SPC
        if (spcEnable && (page == 0)) {
                return nullptr;
        }
        // SCC bank
        if (sccEnable && (address >= 0x9800) && (address < 0xa000)) {
                return nullptr;
        }
        // SRAM read
        return &sram[mapper[page] * 0x2000 + (address & 0x1fff)];
}
 
void ESE_SCC::writeMem(word address, byte value, EmuTime::param time)
{
        unsigned page = address / 0x2000 - 2;
        // SPC Write
        if (spcEnable && (page == 0)) {
                address &= 0x1fff;
                if (address < 0x1000) {
                        spc->writeDREG(value);
                } else {
                        spc->writeRegister(address & 0x0f, value);
                }
                return;
        }
 
        // SCC write
        if (sccEnable && (0x9800 <= address) && (address < 0xa000)) {
                scc.writeMem(narrow_cast<uint8_t>(address & 0xff), value, time);
                return;
        }
 
        // set mapper high control register
        if ((address | 0x0001) == 0x7FFF) {
                setMapperHigh(value);
                return;
        }
 
        // SRAM write (processing of 0x4000-0x7FFD)
        if (writeEnable && (page < 2)) {
                sram.write(mapper[page] * 0x2000 + (address & 0x1FFF), value);
                return;
        }
 
        // Bank change
        if (((address & 0x1800) == 0x1000)) {
                setMapperLow(page, value);
                return;
        }
}
 
byte* ESE_SCC::getWriteCacheLine(word /*address*/) const
{
        return nullptr; // not cacheable
}
 
 
template<typename Archive>
void ESE_SCC::serialize(Archive& ar, unsigned /*version*/)
{
        ar.template serializeBase<MSXDevice>(*this);
        ar.serialize("sram", sram,
                     "scc",  scc);
        if (spc) ar.serialize("MB89352", *spc);
        ar.serialize("mapper",      mapper,
                     "spcEnable",   spcEnable,
                     "sccEnable",   sccEnable,
                     "writeEnable", writeEnable);
}
INSTANTIATE_SERIALIZE_METHODS(ESE_SCC);
REGISTER_MSXDEVICE(ESE_SCC, "ESE_SCC");
 
} // namespace openmsx