static enum TimerType getIrqTimerMode(uint8_t ciaIdx) {
if (envIsPSID() == 1) {
return vicIsIrqActive() ? RASTER_TIMER : CIA1_TIMER;
} else {
// todo: the below impl neglects that both raster and cia1 interrupts may be active at the same
// time. the strategy to give priority to raster (and then ignore the cia1) works for some of
// the affected songs (see Face_It.sid) but it is not correct
if (vicIsIrqActive()) {
return RASTER_TIMER;
} else if (isCiaActive(ciaIdx)) {
return CIA1_TIMER;
} else {
return NO_IRQ;
}
}
}
enum timertype getIrqTimerMode(struct timer *t) {
if (sIsPSID == 1) {
return isRasterIrqActive() ? RASTER_TIMER : CIA1_TIMER;
} else {
// todo: the below impl neglects that both raster and cia1 interrupts may be active at the same
// time. the strategy to give priority to raster (and then ignore the cia1) works for some of
// the affected songs (see Face_It.sid) but it is not correct
if (isRasterIrqActive()) {
return RASTER_TIMER;
} else if (isCiaActive(t)) {
return CIA1_TIMER;
} else {
return NO_IRQ;
}
}
}
static void runScreenSimulation(int16_t *synthBuffer, uint32_t cyclesPerScreen, uint16_t samplesPerCall, int16_t **synthTraceBufs) {
setupVolumeHack();
// cpu cycles used during processing
int32_t irqCycles= 0, nmiCycles= 0, mainProgCycles= 0; // only mainProgCycles can become negative..
// reminder: timings of IRQ and NMI are calculated as if these where independent (which is
// of course flawed). A proper premptive scheduling is not simulated.
int32_t availableIrqCycles= cyclesPerScreen; // cpu cycles still available for processing (limitation: only the waiting time is currently considered..)
int32_t availableNmiCycles= cyclesPerScreen;
uint32_t synthPos= 0; // start time for the samples synthesized from SID settings (measured in cycles)
/*
* process NMI and IRQ interrupts in their order of appearance - and as long as they fit into this screen
*/
uint32_t currentIrqTimer= forwardToNextInterrupt(getIrqTimerMode(CIA1), CIA1, availableIrqCycles);
// FIXME: the assumption that only RSID uses NMI meanwhile proved to be wrong (see MicroProse_Soccer_V1.sid
// tracks >4) .. also an IRQ run may also update the NMI schedule! flawed: ciaForwardToNextInterrupt
// calculation does NOT consider the time when the timer is actually started but only the time that some
// interrupt returns (which will lead to distortions)
uint32_t currentNmiTimer= envIsRSID() ? ciaForwardToNextInterrupt(CIA2, availableNmiCycles) : NO_INT;
// KNOWN LIMITATION: ideally all 4 timers should be kept in sync - not just A/B within the same unit!
// however progs that actually rely on multiple timers (like Vicious_SID_2-Carmina_Burana.sid) probably
// need timer info that is continuously updated - so that effort would only make sense in a full fledged
// cycle-by-cycle emulator.
uint8_t hack= vicIsIrqActive() && isCiaActive(CIA1);
uint32_t tNmi= currentNmiTimer; // NMI simulation progress in cycles
uint32_t tIrq= currentIrqTimer; // IRQ simulation progress in cycles
uint32_t tDone= 0;
uint16_t mainProgStep= 100; // periodically give the main prog a chance to run..
uint16_t mainProgStart= mainProgStep;
if (0 || (envIsRSID() && (currentIrqTimer == NO_INT) && (currentNmiTimer == NO_INT))) {
_mainLoopOnlyMode= 1;
mainProgStart= 0; // this might be the better choice in any case.. but to avoid regression testing lets use it here for now..
} else {
_mainLoopOnlyMode= 0;
// Wonderland_XII-Digi_part_4 has high interrupt rate..
#define ABORT_FUSE 400 // better safe than sorry.. no need to crash the player with an endless loop
uint16_t fuse;
for (fuse= 0; (fuse<ABORT_FUSE) && ((currentIrqTimer != NO_INT) || (currentNmiTimer != NO_INT)) ; fuse++) {
// periodically give unused cycles to main program (needed, e.g. by THCM's stuff)
if (tDone > mainProgStart) {
// todo: the handing of main prog cycles is rather flawed (timing for main code that would normally run before
// 'mainProgStep'). In an alternative "improved" impl I ran "main" directly before "processInterrupt" calls below - letting
// "main" use all cycles unused up to that moment. also I had added interruption for "LDA#00; BEQ .." based endless main-loop
// logic (which would require IRQ logic to break out) to avoid unnecessary cycle usage.. while those changes work fine for
// THCM's recent stuff they broke stuff like "Arkanoid", etc (so I rolled them back for now..)
// -> now that the D012 handling has been improved I might give it another try..
int32_t availableMainCycles= tDone - (nmiCycles + irqCycles + mainProgCycles);
if (availableMainCycles > 0) {
processMain(cyclesPerScreen, mainProgStart, availableMainCycles);
mainProgCycles+= availableMainCycles;
}
mainProgStart= tDone + mainProgStep;
}
// FIXME: better allow NMI to interrupt IRQ, i.e. set respective cycle-limit
// accordingly - and then resume the IRQ later. see Ferrari_Formula_One.sid
if (!isIrqNext(currentIrqTimer, currentNmiTimer, tIrq, tNmi)) { // handle next NMI
tDone= tNmi;
// problem: songs like Arcade_Classics re-set the d418 volume nowhere else but in their
// NMI digi-player: when only used for the short intervals between NMIs the respective changing
// settings do not seem to pose any problems for the rendering of the regular SID output
// (or are even intentionally creating some kind of tremolo) but when SID output rendering
// is performed for longer intervals (e.g. like is done here) then "wrong" settings are also
// used for these longer intervals which may cause audible clicking/pauses in the output.
// if the handled NMIs were preemtively scheduled/properly timed, then renderSynth() could
// be performed also for these shorter intervals.. but unfortunately they are not and respective
// rendering cannot be done here, i.e. the IRQ based rendering then has no clue regarding the
// validity/duration of respectice NMI-volume infos..
nmiCycles+= processInterrupt(NMI_OFFSET_MASK, getNmiVector(), tNmi, cyclesPerScreen);
availableNmiCycles-= currentNmiTimer;
if (availableNmiCycles <= 0) {
availableNmiCycles= 0; // see unsigned use below
}
currentNmiTimer= ciaForwardToNextInterrupt(CIA2, availableNmiCycles);
tNmi+= currentNmiTimer; // will be garbage on last run..
} else { // handle next IRQ
tDone= tIrq;
renderSynth(synthBuffer, cyclesPerScreen, samplesPerCall, synthPos, tIrq, synthTraceBufs);
synthPos= tIrq;
if (hack) {
// in case CIA1 has also been configured to trigger IRQs, our current "raster IRQ or timer IRQ" impl
// is obviously flawed.. this hack will fix simple scenarios like Cycles.sid
ciaSignalUnderflow(CIA1, TIMER_A);
}
// FIXME: multi-frame IRQ handling would be necessary to deal with songs like: Musik_Run_Stop.sid
uint32_t usedCycles= processInterrupt(IRQ_OFFSET_MASK, getIrqVector(), tIrq, _irqTimeout);
// flaw: IRQ might have switched off NMI, e.g. Vicious_SID_2-Blood_Money.sid
if (usedCycles >=_irqTimeout) { // IRQ gets aborted due to a timeout
if (cpuIrqFlag()) {
// this IRQ handler does not want to be interrupted.. (either the code got stuck due to some impossible
// condition - e.g. waiting for a timer which we don't update - or it is an endless IRQ routine that needs to
// continue..)
} else {
// this IRQ handler was intentionally waiting to get interrupted - and it would normally not have burned
// the same amount of cycles (we have no chance to get the timing right here..)
usedCycles= 1;
}
}
irqCycles+= usedCycles;
availableIrqCycles-= currentIrqTimer;
if (availableIrqCycles <= 0) {
availableIrqCycles= 0; // see unsigned use below
}
currentIrqTimer= forwardToNextInterrupt(getIrqTimerMode(CIA1), CIA1, availableIrqCycles);
tIrq+= currentIrqTimer; // will be garbage on last run..
if (envIsTimerDrivenPSID() && (currentIrqTimer != NO_INT)) {
if(usedCycles > currentIrqTimer) {
currentIrqTimer= NO_INT; // hack for Eye_of_the_Tiger
}
}
// some dumbshit timer-PSIDs do not ackn IRQ (MasterComposer rips & Automatas.sid)
if(envIsTimerDrivenPSID()) { ciaReadMem(0xdc0d); }
}
}
#ifdef DEBUG
if (fuse >= ABORT_FUSE) {
EM_ASM_({ console.log('fuse blown: ' + $0); }, fuse);
EM_ASM_({ console.log('last IRQ timer: ' + $0); }, currentIrqTimer);