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Merge pull request #4 from TomHarte/AccuratePaging
Implements more accurate paging behaviour.
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commit
383c389523
@ -175,26 +175,25 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
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if( interruptDisable&0x40 ) _interrupt_status &= ~Interrupt::HighToneDetect;
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evaluate_interrupts();
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// TODO: NMI (?)
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// TODO: NMI
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}
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// else
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{
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uint8_t nextROM = (*value)&0xf;
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// if(nextROM&0x08)
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// {
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// _activeRom = (Electron::ROMSlot)(nextROM&0x0e);
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// printf("%d -> Paged %d\n", nextROM, _activeRom);
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// }
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if(((_active_rom&12) != 8) || (nextROM&8))
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// latch the paged ROM in case external hardware is being emulated
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_active_rom = (Electron::ROMSlot)(*value & 0xf);
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// apply the ULA's test
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if(*value & 0x08)
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{
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if(*value & 0x04)
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{
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_active_rom = (Electron::ROMSlot)nextROM;
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_keyboard_is_active = false;
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_basic_is_active = false;
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}
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else
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{
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_keyboard_is_active = !(*value & 0x02);
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_basic_is_active = !_keyboard_is_active;
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}
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// else
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// {
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// printf("Ignored!");
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// }
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// printf("%d -> Paged %d\n", nextROM, _activeRom);
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}
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}
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break;
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@ -375,19 +374,18 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
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{
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if(isReadOperation(operation))
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{
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switch(_active_rom)
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*value = _roms[_active_rom][address & 16383];
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if(_keyboard_is_active)
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{
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case ROMSlotKeyboard:
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case ROMSlotKeyboard+1:
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*value = 0xf0;
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for(int address_line = 0; address_line < 14; address_line++)
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{
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if(!(address&(1 << address_line))) *value |= _key_states[address_line];
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}
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break;
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default:
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*value = _roms[_active_rom][address & 16383];
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break;
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*value &= 0xf0;
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for(int address_line = 0; address_line < 14; address_line++)
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{
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if(!(address&(1 << address_line))) *value |= _key_states[address_line];
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}
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}
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if(_basic_is_active)
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{
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*value &= _roms[ROMSlotBASIC][address & 16383];
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}
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}
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}
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@ -187,6 +187,7 @@ class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
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uint8_t _palette[16];
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uint8_t _key_states[14];
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ROMSlot _active_rom;
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bool _keyboard_is_active, _basic_is_active;
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uint8_t _screen_mode;
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uint16_t _screenModeBaseAddress;
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uint16_t _startScreenAddress;
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