new class for 64K Megaboy cart

git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@34 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba

stella/src/emucore/CartMB.cxx

@@ -0,0 +1,120 @@
+//============================================================================
+//
+//   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) 1995-1998 by Bradford W. Mott
+//
+// See the file "license" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//
+// $Id: CartMB.cxx,v 1.1 2002-01-18 16:01:43 estolberg Exp $
+//============================================================================
+
+#include <assert.h>
+#include "CartMB.hxx"
+#include "System.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+CartridgeMB::CartridgeMB(const uInt8* image)
+{
+  // Copy the ROM image into my buffer
+  for(uInt32 addr = 0; addr < 65536; ++addr)
+  {
+    myImage[addr] = image[addr];
+  }
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+CartridgeMB::~CartridgeMB()
+{
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+const char* CartridgeMB::name() const
+{
+  return "CartridgeMB";
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeMB::reset()
+{
+  // Upon reset we switch to bank 1
+  myCurrentBank = 0;
+  incbank();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeMB::install(System& system)
+{
+  mySystem = &system;
+  uInt16 shift = mySystem->pageShift();
+  uInt16 mask = mySystem->pageMask();
+
+  // Make sure the system we're being installed in has a page size that'll work
+  assert((0x1000 & mask) == 0);
+
+  // Set the page accessing methods for the hot spots
+  System::PageAccess access;
+  for(uInt32 i = (0x1FF0 & ~mask); i < 0x2000; i += (1 << shift))
+  {
+    access.directPeekBase = 0;
+    access.directPokeBase = 0;
+    access.device = this;
+    mySystem->setPageAccess(i >> shift, access);
+  }
+
+  // Install pages for bank 1
+  myCurrentBank = 0;
+  incbank();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt8 CartridgeMB::peek(uInt16 address)
+{
+  address = address & 0x0FFF;
+
+  // Switch to next bank
+  if(address == 0x0FF0) incbank();
+
+  return myImage[myCurrentBank * 4096 + address];
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeMB::poke(uInt16 address, uInt8)
+{
+  address = address & 0x0FFF;
+
+  // Switch to next bank
+  if(address == 0x0FF0) incbank();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void CartridgeMB::incbank()
+{
+  // Remember what bank we're in
+  myCurrentBank ++;
+  myCurrentBank &= 0x0F;
+  uInt16 offset = myCurrentBank * 4096;
+  uInt16 shift = mySystem->pageShift();
+  uInt16 mask = mySystem->pageMask();
+
+  // Setup the page access methods for the current bank
+  System::PageAccess access;
+  access.device = this;
+  access.directPokeBase = 0;
+
+  // Map ROM image into the system
+  for(uInt32 address = 0x1000; address < (0x1FF0U & ~mask);
+      address += (1 << shift))
+  {
+    access.directPeekBase = &myImage[offset + (address & 0x0FFF)];
+    mySystem->setPageAccess(address >> shift, access);
+  }
+}
+