mirror of https://github.com/stella-emu/stella.git
207 lines
7.0 KiB
C++
207 lines
7.0 KiB
C++
//============================================================================
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//
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// SSSS tt lll lll
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// SS SS tt ll ll
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// SS tttttt eeee ll ll aaaa
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// SSSS tt ee ee ll ll aa
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// SS tt eeeeee ll ll aaaaa -- "An Atari 2600 VCS Emulator"
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// SS SS tt ee ll ll aa aa
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// SSSS ttt eeeee llll llll aaaaa
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//
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// Copyright (c) 1995-2020 by Bradford W. Mott, Stephen Anthony
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// and the Stella Team
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//
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// See the file "License.txt" for information on usage and redistribution of
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// this file, and for a DISCLAIMER OF ALL WARRANTIES.
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//============================================================================
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#ifndef CARTRIDGE_3EPLUS_HXX
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#define CARTRIDGE_3EPLUS_HXX
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class System;
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#include "bspf.hxx"
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#include "Cart.hxx"
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#ifdef DEBUGGER_SUPPORT
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class Cartridge3EPlusWidget;
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#include "Cart3EPlusWidget.hxx"
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#endif
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/**
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Cartridge class from Thomas Jentzsch, mostly based on the 'DASH' scheme
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with the following changes:
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RAM areas:
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- read $x000, write $x200
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- read $x400, write $x600
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- read $x800, write $xa00
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- read $xc00, write $xe00
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@author Thomas Jentzsch and Stephen Anthony
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*/
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class Cartridge3EPlus: public Cartridge
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{
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friend class Cartridge3EPlusWidget;
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public:
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/**
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Create a new cartridge using the specified image and size
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@param image Pointer to the ROM image
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@param size The size of the ROM image
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@param md5 The md5sum of the ROM image
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@param settings A reference to the various settings (read-only)
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*/
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Cartridge3EPlus(const ByteBuffer& image, size_t size, const string& md5,
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const Settings& settings);
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virtual ~Cartridge3EPlus() = default;
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public:
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/** Reset device to its power-on state */
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void reset() override;
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/**
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Install cartridge in the specified system. Invoked by the system
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when the cartridge is attached to it.
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@param system The system the device should install itself in
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*/
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void install(System& system) override;
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/**
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Get the current bank.
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@param address The address to use when querying the bank
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*/
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uInt16 getBank(uInt16 address = 0) const override;
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/**
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Query the number of banks supported by the cartridge.
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*/
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uInt16 bankCount() const override;
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/**
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Patch the cartridge ROM.
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@param address The ROM address to patch
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@param value The value to place into the address
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@return Success or failure of the patch operation
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*/
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bool patch(uInt16 address, uInt8 value) override;
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/**
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Access the internal ROM image for this cartridge.
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@param size Set to the size of the internal ROM image data
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@return A pointer to the internal ROM image data
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*/
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const uInt8* getImage(size_t& size) const override;
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/**
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Save the current state of this cart to the given Serializer.
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@param out The Serializer object to use
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@return False on any errors, else true
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*/
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bool save(Serializer& out) const override;
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/**
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Load the current state of this cart from the given Serializer.
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@param in The Serializer object to use
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@return False on any errors, else true
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*/
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bool load(Serializer& in) override;
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/**
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Get a descriptor for the device name (used in error checking).
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@return The name of the object
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*/
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string name() const override { return "Cartridge3E+"; }
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#ifdef DEBUGGER_SUPPORT
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/**
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Get debugger widget responsible for accessing the inner workings
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of the cart.
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*/
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CartDebugWidget* debugWidget(GuiObject* boss, const GUI::Font& lfont,
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const GUI::Font& nfont, int x, int y, int w, int h) override
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{
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return new Cartridge3EPlusWidget(boss, lfont, nfont, x, y, w, h, *this);
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}
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#endif
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public:
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/**
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Get the byte at the specified address
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@return The byte at the specified address
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*/
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uInt8 peek(uInt16 address) override;
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/**
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Change the byte at the specified address to the given value
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@param address The address where the value should be stored
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@param value The value to be stored at the address
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@return True if the poke changed the device address space, else false
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*/
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bool poke(uInt16 address, uInt8 value) override;
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private:
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bool bankRAM(uInt8 bank); // switch a RAM bank
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bool bankROM(uInt8 bank); // switch a ROM bank
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void bankRAMSlot(uInt16 bank); // switch in a 512b RAM slot (lower or upper 1/2 bank)
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void bankROMSlot(uInt16 bank); // switch in a 512b RAM slot (read or write port)
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void initializeBankState(); // set all banks according to current bankInUse state
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// We have an array that indicates for each of the 8 512 byte areas of the address space, which ROM/RAM
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// bank is used in that area. ROM switches 1K so occupies 2 successive entries for each switch. RAM occupies
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// two as well, one 512 byte for read and one for write. The RAM locations are +0x800 apart, and the ROM
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// are consecutive. This allows us to determine on a read/write exactly where the data is.
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static constexpr uInt16 BANK_UNDEFINED = 0x8000; // bank is undefined and inaccessible
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std::array<uInt16, 8> bankInUse; // bank being used for ROM/RAM (eight 512 byte areas)
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static constexpr uInt16 BANK_SWITCH_HOTSPOT_RAM = 0x3E; // writes to this address cause bankswitching
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static constexpr uInt16 BANK_SWITCH_HOTSPOT_ROM = 0x3F; // writes to this address cause bankswitching
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static constexpr uInt8 BANK_BITS = 6; // # bits for bank
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static constexpr uInt8 BIT_BANK_MASK = (1 << BANK_BITS) - 1; // mask for those bits
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static constexpr uInt16 BITMASK_LOWERUPPER = 0x100; // flags lower or upper section of bank (1==upper)
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static constexpr uInt16 BITMASK_ROMRAM = 0x200; // flags ROM or RAM bank switching (1==RAM)
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static constexpr uInt16 MAXIMUM_BANK_COUNT = (1 << BANK_BITS);
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static constexpr uInt16 RAM_BANK_TO_POWER = 9; // 2^n = 512
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static constexpr uInt16 RAM_BANK_SIZE = (1 << RAM_BANK_TO_POWER);
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static constexpr uInt16 BITMASK_RAM_BANK = (RAM_BANK_SIZE - 1);
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static constexpr uInt32 RAM_TOTAL_SIZE = MAXIMUM_BANK_COUNT * RAM_BANK_SIZE;
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static constexpr uInt16 ROM_BANK_TO_POWER = 10; // 2^n = 1024
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static constexpr uInt16 ROM_BANK_SIZE = (1 << ROM_BANK_TO_POWER);
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static constexpr uInt16 BITMASK_ROM_BANK = (ROM_BANK_SIZE - 1);
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static constexpr uInt16 ROM_BANK_COUNT = 64;
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static constexpr uInt16 RAM_WRITE_OFFSET = 0x200;
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ByteBuffer myImage; // Pointer to a dynamically allocated ROM image of the cartridge
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size_t mySize{0}; // Size of the ROM image
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std::array<uInt8, RAM_TOTAL_SIZE> myRAM;
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private:
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// Following constructors and assignment operators not supported
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Cartridge3EPlus() = delete;
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Cartridge3EPlus(const Cartridge3EPlus&) = delete;
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Cartridge3EPlus(Cartridge3EPlus&&) = delete;
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Cartridge3EPlus& operator=(const Cartridge3EPlus&) = delete;
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Cartridge3EPlus& operator=(Cartridge3EPlus&&) = delete;
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};
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#endif
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