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Merge pull request #4 from TomHarte/AccuratePaging

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Implements more accurate paging behaviour.
This commit is contained in:
Thomas Harte 2016-05-05 08:31:17 -04:00
commit 383c389523
2 changed files with 27 additions and 28 deletions
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54
Machines/Electron/Electron.cpp
View File

@ -175,26 +175,25 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
if( interruptDisable&0x40 ) _interrupt_status &= ~Interrupt::HighToneDetect;
evaluate_interrupts();
// TODO: NMI (?)
// TODO: NMI
}
// else
{
uint8_t nextROM = (*value)&0xf;
// if(nextROM&0x08)
// {
// _activeRom = (Electron::ROMSlot)(nextROM&0x0e);
// printf("%d -> Paged %d\n", nextROM, _activeRom);
// }
if(((_active_rom&12) != 8) || (nextROM&8))
// latch the paged ROM in case external hardware is being emulated
_active_rom = (Electron::ROMSlot)(*value & 0xf);
// apply the ULA's test
if(*value & 0x08)
{
if(*value & 0x04)
{
_active_rom = (Electron::ROMSlot)nextROM;
_keyboard_is_active = false;
_basic_is_active = false;
}
else
{
_keyboard_is_active = !(*value & 0x02);
_basic_is_active = !_keyboard_is_active;
}
// else
// {
// printf("Ignored!");
// }
// printf("%d -> Paged %d\n", nextROM, _activeRom);
}
}
break;
@ -375,19 +374,18 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
{
if(isReadOperation(operation))
{
switch(_active_rom)
*value = _roms[_active_rom][address & 16383];
if(_keyboard_is_active)
{
case ROMSlotKeyboard:
case ROMSlotKeyboard+1:
*value = 0xf0;
for(int address_line = 0; address_line < 14; address_line++)
{
if(!(address&(1 << address_line))) *value |= _key_states[address_line];
}
break;
default:
*value = _roms[_active_rom][address & 16383];
break;
*value &= 0xf0;
for(int address_line = 0; address_line < 14; address_line++)
{
if(!(address&(1 << address_line))) *value |= _key_states[address_line];
}
}
if(_basic_is_active)
{
*value &= _roms[ROMSlotBASIC][address & 16383];
}
}
}

1
Machines/Electron/Electron.hpp
View File

@ -187,6 +187,7 @@ class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
uint8_t _palette[16];
uint8_t _key_states[14];
ROMSlot _active_rom;
bool _keyboard_is_active, _basic_is_active;
uint8_t _screen_mode;
uint16_t _screenModeBaseAddress;
uint16_t _startScreenAddress;