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Fixed RAM timings: it's at least two and possibly three cycles to access RAM, and an access that overlaps with video fetch in Modes 0–3 will cost the length of the video fetch rather than somehow finishing in time.

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This commit is contained in:
Thomas Harte 2016-03-10 19:04:43 -05:00
parent 7255408313
commit f232a12fad
1 changed files with 31 additions and 15 deletions
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46
Machines/Electron/Electron.cpp
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@ -80,13 +80,13 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
// for the entire frame, RAM is accessible only on odd cycles; in modes below 4
// it's also accessible only outside of the pixel regions
cycles += (_fieldCycles&1)^1;
cycles += 1 + ((_fieldCycles&1));
if(_screen_mode < 4)
{
const int current_line = _fieldCycles >> 7;
const int line_position = _fieldCycles & 127;
const int line_position = (_fieldCycles+cycles) & 127;
if(current_line >= first_graphics_line && current_line < first_graphics_line+256 && line_position >= first_graphics_cycle && line_position < first_graphics_cycle + 80)
cycles = (unsigned int)(80 + first_graphics_cycle - line_position);
cycles += (unsigned int)(80 + first_graphics_cycle - line_position);
}
}
else
@ -95,9 +95,6 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
{
if((address & 0xff00) == 0xfe00)
{
cycles += (_fieldCycles&1)^1;
// printf("%c: %02x: ", isReadOperation(operation) ? 'r' : 'w', *value);
switch(address&0xf)
{
case 0x0:
@ -294,29 +291,48 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
update_audio();
signal_interrupt(Interrupt::RealTimeClock);
}
// if(_fieldCycles < real_time_clock_interrupt_time+128 && _fieldCycles + cycles >= real_time_clock_interrupt_time+128)
// {
// update_audio();
// _interrupt_status &= ~Interrupt::RealTimeClock;
// evaluate_interrupts();
// }
else if(_fieldCycles < display_end_interrupt_time && _fieldCycles + cycles >= display_end_interrupt_time)
{
update_audio();
signal_interrupt(Interrupt::DisplayEnd);
}
// if(_fieldCycles < display_end_interrupt_time+128 && _fieldCycles + cycles >= display_end_interrupt_time+128)
// {
// update_audio();
// _interrupt_status &= ~Interrupt::DisplayEnd;
// evaluate_interrupts();
// }
_fieldCycles += cycles;
if(_fieldCycles >= cycles_per_frame)
{
update_display();
update_audio();
_fieldCycles -= cycles_per_frame;
_displayOutputPosition = 0;
_audioOutputPosition -= _audioOutputPosition;
_currentOutputLine = 0;
}
switch(_fieldCycles)
{
case 64*128:
case 196*128:
update_audio();
break;
case cycles_per_frame:
update_display();
update_audio();
_fieldCycles = 0;
_displayOutputPosition = 0;
_audioOutputPosition = 0;
_currentOutputLine = 0;
break;
//
// case cycles_per_frame:
// break;
}
_tape.run_for_cycles(cycles);