_nextIterationTime = _stopTime;
// First look at interrupt events.
while (!_interruptQueue.isEmpty()) {
DEEvent interruptEvent = _interruptQueue.get();
Time timeStamp = interruptEvent.timeStamp();
if (timeStamp.compareTo(getModelTime()) < 0) {
// This should never happen.
throw new IllegalActionException(this,
"external input in the past: " + "input time stamp is "