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rewrite 3E/3F functionality and optimal usage of ROM when RAM blocks overwrite. 

git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@2906 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba
This commit is contained in:
adavie 2014-06-04 14:29:33 +00:00
parent a583ea7532
commit f99afe12dd
2 changed files with 96 additions and 54 deletions
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93
src/emucore/CartDASH.cxx
View File

@ -68,6 +68,7 @@ void CartridgeDASH::reset() {
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void CartridgeDASH::install(System& system) {
mySystem = &system;
uInt16 shift = mySystem->pageShift();
@ -104,7 +105,7 @@ void CartridgeDASH::install(System& system) {
// Initialise bank values for the 4x 1K bank areas
// This is used to reverse-lookup from address to bank location
for (uInt32 b = 0; b < 4; b++)
for (uInt32 b = 0; b < 8; b++)
bankInUse[b] = BANK_UNDEFINED; // bank is undefined and inaccessible!
// Install pages for the startup bank into the first segment
@ -113,8 +114,9 @@ void CartridgeDASH::install(System& system) {
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt8 CartridgeDASH::peek(uInt16 address) {
uInt8 value = 0;
uInt32 bank = (address >> ROM_BANK_TO_POWER) & 3; // convert to 1K bank index (0-3)
uInt32 bank = (address >> (ROM_BANK_TO_POWER - 1)) & 7; // convert to 512 byte bank index (0-7)
Int16 imageBank = bankInUse[bank]; // the ROM/RAM bank that's here
if (imageBank == BANK_UNDEFINED) { // an uninitialised bank?
@ -130,7 +132,9 @@ uInt8 CartridgeDASH::peek(uInt16 address) {
value = myRAM[offset];
} else { // accessing ROM
Int32 offset = imageBank << ROM_BANK_TO_POWER; // base bank address in image
Int32 romBank = imageBank & BIT_BANK_MASK; // discard irrelevant bits
Int32 offset = romBank << ROM_BANK_TO_POWER; // base bank address in image
offset += (address & BITMASK_ROM_BANK); // + byte offset in image bank
value = myImage[offset];
}
@ -140,13 +144,19 @@ uInt8 CartridgeDASH::peek(uInt16 address) {
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeDASH::poke(uInt16 address, uInt8 value) {
bool myBankChanged = false;
address &= 0x0FFF; // restrict to 4K address range
// Check for write to the bank switch address. RAM/ROM and bank # are encoded in 'value'
// There are NO mirrored hotspots.
if (address == BANK_SWITCH_HOTSPOT)
bank(value);
if (address == BANK_SWITCH_HOTSPOT_RAM)
myBankChanged = bankRAM(value);
else if (address == BANK_SWITCH_HOTSPOT_ROM)
myBankChanged = bankROM(value);
// Pass the poke through to the TIA. In a real Atari, both the cart and the
// TIA see the address lines, and both react accordingly. In Stella, each
@ -154,24 +164,23 @@ bool CartridgeDASH::poke(uInt16 address, uInt8 value) {
// don't chain the poke to the TIA, then the TIA can't see it...
mySystem->tia().poke(address, value);
return false;
return myBankChanged;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeDASH::bank(uInt16 bank) {
bool CartridgeDASH::bankRAM(uInt8 bank) {
if (bankLocked())
return false; // debugger has locked the bank
bool changed = false;
uInt16 shift = mySystem->pageShift();
uInt16 bankNumber = (bank >> BANK_BITS) & 3; // which bank # we are switching TO (BITS D6,D7)
uInt16 bankID = bank & BIT_BANK_MASK; // The actual bank # to switch in (BITS D5-D0)
if (bank & BITMASK_ROMRAM) { // switching to a 512 byte RAM bank
uInt16 bankNumber = ((bank >> BANK_BITS) & 3) << 1; // which bank # we are switching TO (BITS D6,D7) to 512byte block
uInt16 currentBank = bank & BIT_BANK_MASK; // Wrap around/restrict to valid range
// Each RAM bank uses two slots, separated by 0x800 in memory -- one read, one write.
bankInUse[bankNumber] = (Int16) (BITMASK_ROMRAM | currentBank); // Record which bank switched in (marked as RAM)
bankInUse[bankNumber + 4] = (Int16) (BITMASK_ROMRAM | currentBank); // Record which (write) bank switched in (marked as RAM)
uInt32 startCurrentBank = currentBank << RAM_BANK_TO_POWER; // Effectively * 512 bytes
// Setup the page access methods for the current bank
@ -180,7 +189,7 @@ bool CartridgeDASH::bank(uInt16 bank) {
// Map read-port RAM image into the system
for (uInt32 byte = 0; byte < RAM_BANK_SIZE; byte += (1 << shift)) {
access.directPeekBase = &myRAM[startCurrentBank + byte];
access.codeAccessBase = &myCodeAccessBase[mySize + startCurrentBank + byte];
access.codeAccessBase = &myCodeAccessBase[mySize + startCurrentBank + byte]; //TODO: check usage of 'mySize' here
mySystem->setPageAccess((startCurrentBank + byte) >> shift, access);
}
@ -190,16 +199,32 @@ bool CartridgeDASH::bank(uInt16 bank) {
// Map write-port RAM image into the system
for (uInt32 byte = 0; byte < RAM_BANK_SIZE; byte += (1 << shift)) {
access.directPokeBase = &myRAM[startCurrentBank + RAM_WRITE_OFFSET + byte];
access.codeAccessBase = &myCodeAccessBase[mySize + startCurrentBank + RAM_WRITE_OFFSET + byte];
access.codeAccessBase = &myCodeAccessBase[mySize + startCurrentBank + RAM_WRITE_OFFSET + byte]; // TODO: check usage of 'mySize' here
mySystem->setPageAccess((startCurrentBank + byte) >> shift, access);
}
} else // ROM 1K banks
{
return changed; // TODO: does RAM change banks or not????
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeDASH::bankROM(uInt8 bank) {
bool changed = false;
if (!bankLocked()) { // debugger can lock ROM
uInt16 shift = mySystem->pageShift();
uInt16 bankNumber = ((bank >> BANK_BITS) & 3) << 1; // which bank # we are switching TO (BITS D6,D7)
uInt16 currentBank = bank & BIT_BANK_MASK; // Wrap around/restrict to valid range
// Map ROM bank image into the system into the correct slot
// Memory map is 1K slots at 0x1000, 0x1400, 0x1800, 0x1C00
// Each ROM uses 2 consecutive 512 byte slots
bankInUse[bankNumber] = (Int16) bankID; // Record which bank switched in (as ROM)
uInt32 startCurrentBank = bankID << ROM_BANK_TO_POWER; // Effectively *1K
bankInUse[bankNumber] = bankInUse[bankNumber + 1] = (Int16) currentBank; // Record which bank switched in (as ROM)
uInt32 startCurrentBank = currentBank << ROM_BANK_TO_POWER; // Effectively *1K
// Setup the page access methods for the current bank
System::PageAccess access(0, 0, 0, this, System::PA_READ);
@ -211,9 +236,18 @@ bool CartridgeDASH::bank(uInt16 bank) {
access.codeAccessBase = &myCodeAccessBase[startCurrentBank + byte];
mySystem->setPageAccess((bankStart + byte) >> shift, access);
}
changed = true;
}
return myBankChanged = true;
return changed;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeDASH::bank(uInt16 bank) {
// Doesn't support bankswitching in the normal sense
return false;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@ -227,8 +261,7 @@ uInt16 CartridgeDASH::bank() const {
uInt16 CartridgeDASH::bankCount() const {
// Doesn't support bankswitching in the normal sense
// There is are 4 'virtual' ROM banks that can change in many different ways, and 4 virtual RAM banks...
return 8;
return 1;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@ -238,8 +271,8 @@ bool CartridgeDASH::patch(uInt16 address, uInt8 value) {
myBankChanged = true;
uInt32 bankNumber = (address >> ROM_BANK_TO_POWER) & 3; // now 1K bank # (ie: 0-3)
Int32 whichBankIsThere = bankInUse[bankNumber]; // ROM or RAM bank reference
uInt32 bankNumber = (address >> RAM_BANK_TO_POWER) & 7; // now 512 byte bank # (ie: 0-7)
Int16 whichBankIsThere = bankInUse[bankNumber]; // ROM or RAM bank reference
if (whichBankIsThere == BANK_UNDEFINED) {
@ -252,6 +285,8 @@ bool CartridgeDASH::patch(uInt16 address, uInt8 value) {
uInt32 baseAddress = ((whichBankIsThere & BIT_BANK_MASK) << RAM_BANK_TO_POWER) + byteOffset;
myRAM[baseAddress] = value; // write to RAM
// TODO: Stephen -- should we set 'myBankChanged' true when there's a RAM write?
} else { // patching ROM (1K banks)
uInt32 byteOffset = address & BITMASK_ROM_BANK;
@ -272,26 +307,22 @@ const uInt8* CartridgeDASH::getImage(int& size) const {
bool CartridgeDASH::save(Serializer& out) const {
try {
out.putString(name());
for (uInt32 b = 0; b < 4; b++)
for (uInt32 b = 0; b < 8; b++)
out.putShort(bankInUse[b]);
out.putByteArray(myRAM, RAM_TOTAL_SIZE);
} catch (...) {
cerr << "ERROR: CartridgeDASH::save" << endl;
{
return false;
}
return true;
}
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeDASH::load(Serializer& in) {
try {
if (in.getString() != name())
return false;
for (uInt32 b = 0; b < 4; b++) {
for (uInt32 b = 0; b < 8; b++) {
bank(bankInUse[b] = in.getShort()); // read, and switch it in
}
in.getByteArray(myRAM, RAM_TOTAL_SIZE);

21
src/emucore/CartDASH.hxx
View File

@ -245,22 +245,33 @@ public:
private:
bool bankRAM(uInt8 bank); // switch a RAM bank
bool bankROM(uInt8 bank); // switch a ROM bank
uInt32 mySize; // Size of the ROM image
uInt8* myImage; // Pointer to a dynamically allocated ROM image of the cartridge
Int16 bankInUse[4]; // bank being used for ROM/RAM (-1 = undefined)
static const uInt16 BANK_SWITCH_HOTSPOT = 0x3F; // writes to this address cause bankswitching
// We have an array that indicates for each of the 8 512 byte areas of the address space, which ROM/RAM
// bank is used in that area. ROM switches 1K so occupies 2 successive entries for each switch. RAM occupies
// two as well, one 512 byte for read and one for write. The RAM locations are +0x800 apart, and the ROM
// are consecutive. This allows us to determine on a read/write exactly where the data is.
static const uInt8 BANK_BITS = 5; // # bits for bank
Int16 bankInUse[8]; // bank being used for ROM/RAM (eight 512 byte areas) (-1 = undefined)
static const uInt16 BANK_SWITCH_HOTSPOT_RAM = 0x3E; // writes to this address cause bankswitching
static const uInt16 BANK_SWITCH_HOTSPOT_ROM = 0x3F; // writes to this address cause bankswitching
static const uInt8 BANK_BITS = 6; // # bits for bank
static const uInt8 BIT_BANK_MASK = (1 << BANK_BITS) - 1; // mask for those bits
static const uInt8 BITMASK_ROMRAM = 0x80; // flags ROM or RAM bank switching (D7--> 1==RAM)
static const uInt16 RAM_BANK_COUNT = 32;
static const uInt16 MAXIMUM_BANK_COUNT = (1<<BANK_BITS);
static const uInt16 RAM_BANK_TO_POWER = 9; // 2^n = 512
static const uInt16 RAM_BANK_SIZE = (1 << RAM_BANK_TO_POWER);
static const uInt16 BITMASK_RAM_BANK = (RAM_BANK_SIZE - 1);
static const uInt32 RAM_TOTAL_SIZE = RAM_BANK_COUNT * RAM_BANK_SIZE;
static const uInt32 RAM_TOTAL_SIZE = MAXIMUM_BANK_COUNT * RAM_BANK_SIZE;
static const uInt16 ROM_BANK_TO_POWER = 10; // 2^n = 1024
static const uInt16 ROM_BANK_SIZE = (1 << ROM_BANK_TO_POWER);