When resetting the clock....

[firedoc]

In NCAA my guess would be that it is the time of the whistle. There is a normal reaction time for officials to first see the foul, register the information in the brain, and then blow the whistle. It is almost impossible to quantify the time for the first two steps, so the only definitive time frame is the whistle. Otherwise, you would have to put time back on the clock after EVERY whistle, whether for a foul or a violation.