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My understanding now is that object position counting will begin the cycle after the call is made, not that cycle, and that the timer loops just once, with the logic for counter pumping being whether the relevant flag is still set, irregardless of whether the counter is still going.

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This commit is contained in:
Thomas Harte 2015-08-13 18:59:23 +01:00
parent b440fed323
commit 033655835a
2 changed files with 26 additions and 9 deletions
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29
Machines/Atari2600.cpp
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@ -24,6 +24,7 @@ Machine::Machine()
_piaTimerStatus = 0xff;
memset(_collisions, 0xff, sizeof(_collisions));
_rom = nullptr;
_hMoveWillCount = false;
setup6502();
set_reset_line(true);
@ -163,22 +164,26 @@ void Machine::output_pixels(int count)
const int32_t start_of_sync = 214;
const int32_t end_of_sync = 198;
_timestamp += count;
while(count--)
{
OutputState state;
// update hmove
if (!(_horizontalTimer&3) && _hMoveFlags) {
if (!(_horizontalTimer&3)) {
const uint8_t counterValue = _hMoveCounter ^ 0x7;
for(int c = 0; c < 5; c++) {
if ((_hMoveCounter^8^(_objectMotion[c] >> 4)) == 0xf)
if (counterValue == (_objectMotion[c] >> 4))
_hMoveFlags &= ~(1 << c);
if (_hMoveFlags&(1 << c))
_objectCounter[c] = (_objectCounter[c]+1)%160;
}
if(_hMoveIsCounting) {
_hMoveIsCounting = !!_hMoveCounter;
_hMoveCounter = (_hMoveCounter-1)&0xf;
}
}
// logic: if in vsync, output that; otherwise if in vblank then output that;
// otherwise output a pixel
@ -245,6 +250,8 @@ void Machine::output_pixels(int count)
_horizontalTimer--;
const int32_t sign_extension = _horizontalTimer >> 31;
_horizontalTimer = (_horizontalTimer&~sign_extension) | (sign_extension&horizontalTimerReload);
_timestamp ++;
}
}
@ -254,7 +261,7 @@ int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t add
uint8_t returnValue = 0xff;
int cycles_run_for = 1;
const int32_t ready_line_disable_time = 225;//horizontalTimerReload;
const int32_t ready_line_disable_time = 227;//horizontalTimerReload;
if(operation == CPU6502::BusOperation::Ready) {
int32_t distance_to_end_of_ready = (_horizontalTimer - ready_line_disable_time + horizontalTimerReload + 1)%(horizontalTimerReload + 1);
@ -264,6 +271,13 @@ int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t add
output_pixels(3);
}
if(_hMoveWillCount) {
_hMoveCounter = 0x0f;
_hMoveFlags = 0x1f;
_hMoveIsCounting = true;
_hMoveWillCount = false;
}
if(_horizontalTimer == ready_line_disable_time)
set_ready_line(false);
@ -387,7 +401,9 @@ int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t add
case 0x21:
case 0x22:
case 0x23:
case 0x24: _objectMotion[decodedAddress - 0x20] = *value; break;
case 0x24:
_objectMotion[decodedAddress - 0x20] = *value;
break;
case 0x25: _playerGraphicsLatchEnable[0] = *value; break;
case 0x26: _playerGraphicsLatchEnable[1] = *value; break;
@ -402,8 +418,7 @@ int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t add
case 0x2a:
_vBlankExtend = true;
_hMoveCounter = 15;
_hMoveFlags = 0x1f;
_hMoveWillCount = true;
break;
case 0x2b:
_objectMotion[0] =

4
Machines/Atari2600.hpp
View File

@ -66,8 +66,10 @@ class Machine: public CPU6502::Processor<Machine> {
int32_t _horizontalTimer;
bool _vSyncEnabled, _vBlankEnabled;
bool _vBlankExtend;
uint8_t _hMoveCounter, _hMoveFlags;
uint8_t _hMoveCounter;
bool _hMoveIsCounting, _hMoveWillCount;
uint8_t _objectCounter[5], _objectMotion[5];
uint8_t _hMoveFlags;
// collisions
uint8_t _collisions[8];