mirror of https://github.com/stella-emu/stella.git
Added support for 3E bankswitch scheme (3F plus 32K RAM).
git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@618 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba
This commit is contained in:
urchlay
parent
2be337302a
commit
07786e3faf
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@ -0,0 +1,269 @@
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//============================================================================
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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) 1995-2005 by Bradford W. Mott and the Stella team
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//
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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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//
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// $Id: Cart3E.cxx,v 1.1 2005-07-08 04:00:09 urchlay Exp $
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//============================================================================
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#include <assert.h>
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#include "Cart3E.hxx"
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#include "System.hxx"
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#include "Serializer.hxx"
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#include "Deserializer.hxx"
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#include <iostream>
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Cartridge3E::Cartridge3E(const uInt8* image, uInt32 size)
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: mySize(size)
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{
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// Allocate array for the ROM image
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myImage = new uInt8[mySize];
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// Copy the ROM image into my buffer
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for(uInt32 addr = 0; addr < mySize; ++addr)
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{
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myImage[addr] = image[addr];
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}
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Cartridge3E::~Cartridge3E()
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{
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delete[] myImage;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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const char* Cartridge3E::name() const
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{
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return "Cartridge3E";
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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void Cartridge3E::reset()
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{
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// We'll map bank 0 into the first segment upon reset
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bank(0);
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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void Cartridge3E::install(System& system)
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{
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mySystem = &system;
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uInt16 shift = mySystem->pageShift();
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uInt16 mask = mySystem->pageMask();
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// Make sure the system we're being installed in has a page size that'll work
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assert((0x1800 & mask) == 0);
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// Set the page accessing methods for the hot spots (for 100% emulation
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// I would need to chain any accesses below 0x40 to the TIA but for
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// now I'll just forget about them)
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System::PageAccess access;
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for(uInt32 i = 0x00; i < 0x40; i += (1 << shift))
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{
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access.directPeekBase = 0;
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access.directPokeBase = 0;
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access.device = this;
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mySystem->setPageAccess(i >> shift, access);
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}
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// Setup the second segment to always point to the last ROM slice
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for(uInt32 j = 0x1800; j < 0x2000; j += (1 << shift))
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{
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access.device = this;
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access.directPeekBase = &myImage[(mySize - 2048) + (j & 0x07FF)];
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access.directPokeBase = 0;
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mySystem->setPageAccess(j >> shift, access);
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}
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// Install pages for bank 0 into the first segment
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bank(0);
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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uInt8 Cartridge3E::peek(uInt16 address)
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{
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address = address & 0x0FFF;
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if(address < 0x0800)
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{
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if(myCurrentBank < 256)
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return myImage[(address & 0x07FF) + myCurrentBank * 2048];
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else
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return myRam[(address & 0x03FF) + (myCurrentBank - 256) * 1024];
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}
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else
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{
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return myImage[(address & 0x07FF) + mySize - 2048];
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}
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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void Cartridge3E::poke(uInt16 address, uInt8 value)
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{
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address = address & 0x0FFF;
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// Switch banks if necessary
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if(address == 0x003F)
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{
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bank(value);
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}
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else if(address == 0x003E)
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{
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bank(value + 256);
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}
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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bool Cartridge3E::patch(uInt16 address, uInt8 value)
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{
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address = address & 0x0FFF;
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if(address < 0x0800)
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{
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myImage[(address & 0x07FF) + myCurrentBank * 2048] = value;
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}
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else
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{
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myImage[(address & 0x07FF) + mySize - 2048] = value;
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}
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return true;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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void Cartridge3E::bank(uInt16 bank)
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{
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if(bank < 256)
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{
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// Make sure the bank they're asking for is reasonable
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if((uInt32)bank * 2048 < mySize)
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{
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myCurrentBank = bank;
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}
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else
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{
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// Oops, the bank they're asking for isn't valid so let's wrap it
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// around to a valid bank number
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myCurrentBank = bank % (mySize / 2048);
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}
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uInt32 offset = myCurrentBank * 2048;
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uInt16 shift = mySystem->pageShift();
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// Setup the page access methods for the current bank
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System::PageAccess access;
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access.device = this;
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access.directPokeBase = 0;
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// Map ROM image into the system
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for(uInt32 address = 0x1000; address < 0x1800; address += (1 << shift))
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{
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access.directPeekBase = &myImage[offset + (address & 0x07FF)];
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mySystem->setPageAccess(address >> shift, access);
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}
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}
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else
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{
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bank -= 256;
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bank %= 32;
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myCurrentBank = bank + 256;
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uInt32 offset = bank * 1024;
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uInt16 shift = mySystem->pageShift();
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// Setup the page access methods for the current bank
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System::PageAccess access;
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access.device = this;
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access.directPokeBase = 0;
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// Map read-port RAM image into the system
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for(uInt32 address = 0x1000; address < 0x1400; address += (1 << shift))
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{
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access.directPeekBase = &myRam[offset + (address & 0x03FF)];
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mySystem->setPageAccess(address >> shift, access);
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}
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access.directPeekBase = 0;
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// Map write-port RAM image into the system
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for(uInt32 address = 0x1400; address < 0x1800; address += (1 << shift))
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{
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access.directPokeBase = &myRam[offset + (address & 0x03FF)];
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mySystem->setPageAccess(address >> shift, access);
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}
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}
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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int Cartridge3E::bank() {
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return myCurrentBank;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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int Cartridge3E::bankCount() {
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return mySize/2048;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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bool Cartridge3E::save(Serializer& out)
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{
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string cart = name();
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try
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{
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out.putString(cart);
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out.putLong(myCurrentBank);
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}
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catch(char *msg)
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{
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cerr << msg << endl;
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return false;
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}
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catch(...)
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{
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cerr << "Unknown error in save state for " << cart << endl;
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return false;
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}
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return true;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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bool Cartridge3E::load(Deserializer& in)
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{
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string cart = name();
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try
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{
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if(in.getString() != cart)
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return false;
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myCurrentBank = (uInt16) in.getLong();
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}
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catch(char *msg)
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{
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cerr << msg << endl;
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return false;
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}
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catch(...)
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{
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cerr << "Unknown error in load state for " << cart << endl;
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return false;
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}
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// Now, go to the current bank
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bank(myCurrentBank);
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return true;
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}
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@ -0,0 +1,160 @@
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//============================================================================
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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) 1995-2005 by Bradford W. Mott and the Stella team
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//
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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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//
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// $Id: Cart3E.hxx,v 1.1 2005-07-08 04:00:09 urchlay Exp $
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//============================================================================
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#ifndef CARTRIDGE3E_HXX
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#define CARTRIDGE3E_HXX
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class Cartridge3E;
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class Serializer;
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class Deserializer;
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#include "bspf.hxx"
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#include "Cart.hxx"
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/**
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This is the cartridge class for Tigervision's bankswitched
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games with RAM (basically, 3F plus up to 32K of RAM). This
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code is basically Brad's Cart3F code plus 32K RAM support.
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In this bankswitching scheme the 2600's 4K cartridge
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address space is broken into two 2K segments. The last 2K
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segment always points to the last 2K of the ROM image.
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The lower 2K of address space maps to either one of the 2K ROM banks
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(up to 256 of them, though only 240 are supposed to be used for
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compatibility with the Kroko Cart and Cuttle Cart 2), or else one
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of the 1K RAM banks (up to 32 of them). Like other carts with RAM,
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this takes up twice the address space that it should: The lower 1K
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is the read port, and the upper 1K is the write port (maps to the
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same memory).
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To map ROM, the desired bank number of the first 2K segment is selected
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by storing its value into $3F. To map RAM in the first 2K segment
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instead, store the RAM bank number into $3E.
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This implementation of 3E bankswitching numbers the ROM banks 0 to
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256, and the RAM banks 256 to 287. This is done because the public
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bankswitching interface requires us to use one bank number, not one
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bank number plus the knowledge of whether it's RAM or ROM.
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All 32K of potential RAM is available to a game using this class, even
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though real cartridges might not have the full 32K: We have no way to
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tell how much RAM the game expects. This may change in the future (we
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may add a stella.pro property for this), but for now it shouldn't cause
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any problems. (Famous last words...)
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@author B. Watson
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@version $Id: Cart3E.hxx,v 1.1 2005-07-08 04:00:09 urchlay Exp $
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*/
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class Cartridge3E : public Cartridge
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{
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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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*/
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Cartridge3E(const uInt8* image, uInt32 size);
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/**
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Destructor
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*/
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virtual ~Cartridge3E();
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public:
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/**
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Get a null terminated string which is the device's name (i.e. "M6532")
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@return The name of the device
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*/
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virtual const char* name() const;
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/**
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Reset device to its power-on state
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*/
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virtual void reset();
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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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virtual void install(System& system);
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/**
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Saves the current state of this device to the given Serializer.
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@param out The serializer device to save to.
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@return The result of the save. True on success, false on failure.
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*/
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virtual bool save(Serializer& out);
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/**
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Loads the current state of this device from the given Deserializer.
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@param in The deserializer device to load from.
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@return The result of the load. True on success, false on failure.
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*/
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virtual bool load(Deserializer& in);
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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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virtual uInt8 peek(uInt16 address);
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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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*/
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virtual void poke(uInt16 address, uInt8 value);
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bool patch(uInt16 address, uInt8 value);
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/**
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Map the specified bank into the first segment
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@param bank The bank that should be mapped
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*/
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void bank(uInt16 bank);
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int bank();
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int bankCount();
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private:
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// Indicates which bank is currently active for the first segment
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uInt16 myCurrentBank;
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// Pointer to a dynamically allocated ROM image of the cartridge
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uInt8* myImage;
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// RAM contents. For now every ROM gets all 32K of potential RAM
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uInt8 myRam[32768];
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// Size of the ROM image
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uInt32 mySize;
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};
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#endif
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@ -4,6 +4,7 @@ MODULE_OBJS := \
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src/emucore/Booster.o \
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src/emucore/Cart2K.o \
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src/emucore/Cart3F.o \
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src/emucore/Cart3E.o \
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src/emucore/Cart4K.o \
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src/emucore/CartAR.o \
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src/emucore/CartCV.o \
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