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Fixed: paging is based directly on the access, independent of the read/write line (since it isn't actually exposed to catridges).

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This commit is contained in:
Thomas Harte 2015-08-13 15:04:30 +01:00
parent 59c872ada6
commit 323aa27e13
1 changed files with 19 additions and 19 deletions
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38
Machines/Atari2600.cpp
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@ -269,29 +269,29 @@ int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t add
if(operation != CPU6502::BusOperation::Ready) {
// check for a ROM or paging access
if ((address&0x1000) && isReadOperation(operation)) {
// check for a paging access
if(_rom_size > 4096 && ((address & 0x1f00) == 0x1f00)) {
uint8_t *base_ptr = _romPages[0];
uint8_t first_paging_register = 0xf8 - (_rom_size >> 14)*2;
if(_rom_size > 4096 && ((address & 0x1f00) == 0x1f00)) {
uint8_t *base_ptr = _romPages[0];
uint8_t first_paging_register = 0xf8 - (_rom_size >> 14)*2;
const uint8_t paging_register = address&0xff;
if(paging_register >= first_paging_register) {
const uint16_t selected_page = paging_register - first_paging_register;
if(selected_page * 4096 < _rom_size) {
base_ptr = &_rom[selected_page * 4096];
}
}
if(base_ptr != _romPages[0]) {
_romPages[0] = base_ptr;
_romPages[1] = base_ptr + 1024;
_romPages[2] = base_ptr + 2048;
_romPages[3] = base_ptr + 3072;
const uint8_t paging_register = address&0xff;
if(paging_register >= first_paging_register) {
const uint16_t selected_page = paging_register - first_paging_register;
if(selected_page * 4096 < _rom_size) {
base_ptr = &_rom[selected_page * 4096];
}
}
if(base_ptr != _romPages[0]) {
_romPages[0] = base_ptr;
_romPages[1] = base_ptr + 1024;
_romPages[2] = base_ptr + 2048;
_romPages[3] = base_ptr + 3072;
}
}
// check for a ROM read
if ((address&0x1000) && isReadOperation(operation)) {
returnValue &= _romPages[(address >> 10)&3][address&1023];
}