MSXPPI.hh

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// This class implements the PPI (8255)
//
//   PPI    MSX-I/O  Direction  MSX-Function
//  PortA    0xA8      Out     Memory primary slot register
//  PortB    0xA9      In      Keyboard column inputs
//  PortC    0xAA      Out     Keyboard row select / CAPS / CASo / CASm / SND
//  Control  0xAB     In/Out   Mode select for PPI
//
//  Direction indicates the direction normally used on MSX.
//  Reading from an output port returns the last written byte.
//  Writing to an input port has no immediate effect.
//
//  PortA combined with upper half of PortC form groupA
//  PortB               lower                    groupB
//  GroupA can be in programmed in 3 modes
//   - basic input/output
//   - strobed input/output
//   - bidirectional
//  GroupB can only use the first two modes.
//  Only the first mode is used on MSX, only this mode is implemented yet.
//
//  for more detail see
//    http://w3.qahwah.net/joost/openMSX/8255.pdf
 
#ifndef MSXPPI_HH
#define MSXPPI_HH
 
#include "MSXDevice.hh"
#include "I8255Interface.hh"
#include "I8255.hh"
#include "Keyboard.hh"
#include "KeyClick.hh"
 
namespace openmsx {
 
class CassettePortInterface;
class RenShaTurbo;
 
class MSXPPI final : public MSXDevice, public I8255Interface
{
public:
        explicit MSXPPI(const DeviceConfig& config);
        ~MSXPPI() override;
 
        void reset(EmuTime::param time) override;
        void powerDown(EmuTime::param time) override;
        [[nodiscard]] byte readIO(word port, EmuTime::param time) override;
        [[nodiscard]] byte peekIO(word port, EmuTime::param time) const override;
        void writeIO(word port, byte value, EmuTime::param time) override;
 
        template<typename Archive>
        void serialize(Archive& ar, unsigned version);
 
private:
        // I8255Interface
        [[nodiscard]] byte readA(EmuTime::param time) override;
        [[nodiscard]] byte readB(EmuTime::param time) override;
        [[nodiscard]] nibble readC0(EmuTime::param time) override;
        [[nodiscard]] nibble readC1(EmuTime::param time) override;
        [[nodiscard]] byte peekA(EmuTime::param time) const override;
        [[nodiscard]] byte peekB(EmuTime::param time) const override;
        [[nodiscard]] nibble peekC0(EmuTime::param time) const override;
        [[nodiscard]] nibble peekC1(EmuTime::param time) const override;
        void writeA(byte value, EmuTime::param time) override;
        void writeB(byte value, EmuTime::param time) override;
        void writeC0(nibble value, EmuTime::param time) override;
        void writeC1(nibble value, EmuTime::param time) override;
 
private:
        CassettePortInterface& cassettePort;
        RenShaTurbo& renshaTurbo;
        I8255 i8255;
        KeyClick click;
        Keyboard keyboard;
        nibble prevBits = 15;
        nibble selectedRow = 0;
};
 
} // namespace openmsx
 
#endif