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//============================================================================
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// MM MM 6666 555555 0000 2222
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// MMMM MMMM 66 66 55 00 00 22 22
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// MM MMM MM 66 55 00 00 22
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// MM M MM 66666 55555 00 00 22222 -- "A 6502 Microprocessor Emulator"
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// MM MM 66 66 55 00 00 22
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// MM MM 66 66 55 55 00 00 22
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// MM MM 6666 5555 0000 222222
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// Copyright (c) 1995-2008 by Bradford W. Mott and the Stella team
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// See the file "license" for information on usage and redistribution of
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// this file, and for a DISCLAIMER OF ALL WARRANTIES.
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// $Id: System.hxx,v 1.19 2008/02/19 12:33:07 stephena Exp $
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//============================================================================
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#include "NullDev.hxx"
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#include "Serializable.hxx"
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This class represents a system consisting of a 6502 microprocessor
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and a set of devices. The devices are mapped into an addressing
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space of 2^n bytes (1 <= n <= 16). The addressing space is broken
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into 2^m byte pages (1 <= m <= n), where a page is the smallest unit
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a device can use when installing itself in the system.
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In general the addressing space will be 8192 (2^13) bytes for a
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6507 based system and 65536 (2^16) bytes for a 6502 based system.
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TODO: To allow for dynamic code generation we probably need to
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add a tag to each page that indicates if it is read only
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memory. We also need to notify the processor anytime a
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page access method is changed so that it can clear the
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dynamic code for that page of memory.
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@author Bradford W. Mott
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@version $Id: System.hxx,v 1.19 2008/02/19 12:33:07 stephena Exp $
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class System : public Serializable
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Create a new system with an addressing space of 2^n bytes and
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@param n Log base 2 of the addressing space size
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@param m Log base 2 of the page size
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System(uInt16 n, uInt16 m);
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Reset the system cycle counter, the attached devices, and the
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attached processor of the system.
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Attach the specified device and claim ownership of it. The device
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will be asked to install itself.
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@param device The device to attach to the system
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void attach(Device* device);
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Attach the specified processor and claim ownership of it. The
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processor will be asked to install itself.
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@param m6502 The 6502 microprocessor to attach to the system
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void attach(M6502* m6502);
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Attach the specified processor and claim ownership of it. The
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processor will be asked to install itself.
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@param m6532 The 6532 microprocessor to attach to the system
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void attach(M6532* m6532);
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Attach the specified TIA device and claim ownership of it. The device
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will be asked to install itself.
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@param tia The TIA device to attach to the system
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void attach(TIA* tia);
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Answer the 6502 microprocessor attached to the system. If a
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processor has not been attached calling this function will fail.
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@return The attached 6502 microprocessor
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Answer the 6532 processor attached to the system. If a
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processor has not been attached calling this function will fail.
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@return The attached 6532 microprocessor
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Answer the TIA device attached to the system.
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@return The attached TIA device
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Get the null device associated with the system. Every system
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has a null device associated with it that's used by pages which
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aren't mapped to "real" devices.
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@return The null device associated with the system
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NullDevice& nullDevice()
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Get the total number of pages available in the system.
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@return The total number of pages available
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uInt16 numberOfPages() const
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return myNumberOfPages;
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Get the amount to right shift an address by to obtain its page.
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@return The amount to right shift an address by to get its page
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uInt16 pageShift() const
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Get the mask to apply to an address to obtain its page offset.
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@return The mask to apply to an address to obtain its page offset
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uInt16 pageMask() const
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Get the number of system cycles which have passed since the last
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time cycles were reset or the system was reset.
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@return The number of system cycles which have passed
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uInt32 cycles() const
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Increment the system cycles by the specified number of cycles.
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@param amount The amount to add to the system cycles counter
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void incrementCycles(uInt32 amount)
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Reset the system cycle count to zero. The first thing that
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happens is that all devices are notified of the reset by invoking
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their systemCyclesReset method then the system cycle count is
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Get the current state of the data bus in the system. The current
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state is the last data that was accessed by the system.
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@return the data bus state
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inline uInt8 getDataBusState() const
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return myDataBusState;
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Get the byte at the specified address. No masking of the
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address occurs before it's sent to the device mapped at
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@return The byte at the specified address
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uInt8 peek(uInt16 address);
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Change the byte at the specified address to the given value.
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No masking of the address occurs before it's sent to the device
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mapped at the address.
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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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void poke(uInt16 address, uInt8 value);
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Lock/unlock the data bus. When the bus is locked, peek() and
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poke() don't update the bus state. The bus should be unlocked
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while the CPU is running (normal emulation, or when the debugger
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is stepping/advancing). It should be locked while the debugger
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is active but not running the CPU. This is so the debugger can
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use System.peek() to examine memory/registers without changing
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the state of the system.
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void unlockDataBus();
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Structure used to specify access methods for a page
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Pointer to a block of memory or the null pointer. The null pointer
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indicates that the device's peek method should be invoked for reads
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to this page, while other values are the base address of an array
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to directly access for reads to this page.
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uInt8* directPeekBase;
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Pointer to a block of memory or the null pointer. The null pointer
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indicates that the device's poke method should be invoked for writes
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to this page, while other values are the base address of an array
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to directly access for pokes to this page.
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uInt8* directPokeBase;
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Pointer to the device associated with this page or to the system's
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null device if the page hasn't been mapped to a device
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Set the page accessing method for the specified page.
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@param page The page accessing methods should be set for
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@param access The accessing methods to be used by the page
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void setPageAccess(uInt16 page, const PageAccess& access);
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Get the page accessing method for the specified page.
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@param page The page to get accessing methods for
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@return The accessing methods used by the page
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const PageAccess& getPageAccess(uInt16 page);
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Save the current state of this system 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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bool save(Serializer& out) const;
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Load the current state of this system from the given Deserializer.
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@param in The Deserializer object to use
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@return False on any errors, else true
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bool load(Deserializer& in);
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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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virtual string name() const { return "System"; }
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// Mask to apply to an address before accessing memory
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const uInt16 myAddressMask;
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// Amount to shift an address by to determine what page it's on
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const uInt16 myPageShift;
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// Mask to apply to an address to obtain its page offset
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const uInt16 myPageMask;
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// Number of pages in the system
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const uInt16 myNumberOfPages;
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// Pointer to a dynamically allocated array of PageAccess structures
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PageAccess* myPageAccessTable;
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// Array of all the devices attached to the system
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Device* myDevices[100];
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// Number of devices attached to the system
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uInt32 myNumberOfDevices;
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// 6502 processor attached to the system or the null pointer
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// 6532 processor attached to the system or the null pointer
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// TIA device attached to the system or the null pointer
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// Number of system cycles executed since the last reset
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// Null device to use for page which are not installed
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NullDevice myNullDevice;
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// The current state of the Data Bus
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uInt8 myDataBusState;
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// Whether or not peek() updates the data bus state. This
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// is true during normal emulation, and false when the
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// debugger is active.
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bool myDataBusLocked;
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// Copy constructor isn't supported by this class so make it private
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System(const System&);
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// Assignment operator isn't supported by this class so make it private
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System& operator = (const System&);
added
removed
src/emucore/m6502/src/System.hxx
