stella/src/emucore/CartDPC.hxx

//============================================================================
//
//   SSSS    tt          lll  lll       
//  SS  SS   tt           ll   ll        
//  SS     tttttt  eeee   ll   ll   aaaa 
//   SSSS    tt   ee  ee  ll   ll      aa
//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
//  SS  SS   tt   ee      ll   ll  aa  aa
//   SSSS     ttt  eeeee llll llll  aaaaa
//
// Copyright (c) 1995-2014 by Bradford W. Mott, Stephen Anthony
// and the Stella Team
//
// See the file "License.txt" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id$
//============================================================================

#ifndef CARTRIDGE_DPC_HXX
#define CARTRIDGE_DPC_HXX

class System;

#include "bspf.hxx"
#include "Cart.hxx"
#ifdef DEBUGGER_SUPPORT
  #include "CartDPCWidget.hxx"
#endif

/**
  Cartridge class used for Pitfall II.  There are two 4K program banks, a 
  2K display bank, and the DPC chip.  The bankswitching itself is the same
  as F8 scheme (hotspots at $1FF8 and $1FF9).  DPC chip access is mapped to
  $1000 - $1080 ($1000 - $103F is read port, $1040 - $107F is write port).

  For complete details on the DPC chip see David P. Crane's United States
  Patent Number 4,644,495.

  @author  Bradford W. Mott
  @version $Id$
*/
class CartridgeDPC : public Cartridge
{
  friend class CartridgeDPCWidget;

  public:
    /**
      Create a new cartridge using the specified image

      @param image     Pointer to the ROM image
      @param size      The size of the ROM image
      @param settings  A reference to the various settings (read-only)
    */
    CartridgeDPC(const uInt8* image, uInt32 size, const Settings& settings);
 
    /**
      Destructor
    */
    virtual ~CartridgeDPC();

  public:
    /**
      Reset device to its power-on state
    */
    void reset();

    /**
      Notification method invoked by the system right before the
      system resets its cycle counter to zero.  It may be necessary
      to override this method for devices that remember cycle counts.
    */
    void systemCyclesReset();

    /**
      Install cartridge in the specified system.  Invoked by the system
      when the cartridge is attached to it.

      @param system The system the device should install itself in
    */
    void install(System& system);

    /**
      Install pages for the specified bank in the system.

      @param bank The bank that should be installed in the system
    */
    bool bank(uInt16 bank);

    /**
      Get the current bank.
    */
    uInt16 bank() const;

    /**
      Query the number of banks supported by the cartridge.
    */
    uInt16 bankCount() const;

    /**
      Patch the cartridge ROM.

      @param address  The ROM address to patch
      @param value    The value to place into the address
      @return    Success or failure of the patch operation
    */
    bool patch(uInt16 address, uInt8 value);

    /**
      Access the internal ROM image for this cartridge.

      @param size  Set to the size of the internal ROM image data
      @return  A pointer to the internal ROM image data
    */
    const uInt8* getImage(int& size) const;

    /**
      Save the current state of this cart to the given Serializer.

      @param out  The Serializer object to use
      @return  False on any errors, else true
    */
    bool save(Serializer& out) const;

    /**
      Load the current state of this cart from the given Serializer.

      @param in  The Serializer object to use
      @return  False on any errors, else true
    */
    bool load(Serializer& in);

    /**
      Get a descriptor for the device name (used in error checking).

      @return The name of the object
    */
    string name() const { return "CartridgeDPC"; }

  #ifdef DEBUGGER_SUPPORT
    /**
      Get debugger widget responsible for accessing the inner workings
      of the cart.
    */
    CartDebugWidget* debugWidget(GuiObject* boss, const GUI::Font& lfont,
        const GUI::Font& nfont, int x, int y, int w, int h)
    {
      return new CartridgeDPCWidget(boss, lfont, nfont, x, y, w, h, *this);
    }
  #endif

  public:
    /**
      Get the byte at the specified address.

      @return The byte at the specified address
    */
    uInt8 peek(uInt16 address);

    /**
      Change the byte at the specified address to the given value

      @param address The address where the value should be stored
      @param value The value to be stored at the address
      @return  True if the poke changed the device address space, else false
    */
    bool poke(uInt16 address, uInt8 value);

  private:
    /** 
      Clocks the random number generator to move it to its next state
    */
    void clockRandomNumberGenerator();

    /** 
      Updates any data fetchers in music mode based on the number of
      CPU cycles which have passed since the last update.
    */
    void updateMusicModeDataFetchers();

  private:
    // The ROM image
    uInt8 myImage[8192 + 2048 + 256];

    // (Actual) Size of the ROM image
    uInt32 mySize;

    // Pointer to the 8K program ROM image of the cartridge
    uInt8* myProgramImage;

    // Pointer to the 2K display ROM image of the cartridge
    uInt8* myDisplayImage;

    // Indicates which bank is currently active
    uInt16 myCurrentBank;

    // The top registers for the data fetchers
    uInt8 myTops[8];

    // The bottom registers for the data fetchers
    uInt8 myBottoms[8];

    // The counter registers for the data fetchers
    uInt16 myCounters[8];

    // The flag registers for the data fetchers
    uInt8 myFlags[8];

    // The music mode DF5, DF6, & DF7 enabled flags
    bool myMusicMode[3];

    // The random number generator register
    uInt8 myRandomNumber;

    // System cycle count when the last update to music data fetchers occurred
    Int32 mySystemCycles;

    // Fractional DPC music OSC clocks unused during the last update
    double myFractionalClocks;
};

#endif