[BradAMiller]

I found the same issues with not saving those sections. And saw the same timing latency. It's pretty annoying for me - I was working on WPILib which allows user written interrupt handlers, so it has to save everything since it doesn't know what the user might do in their driver.

The gear tooth sensor was impossible to use for direction because there was no guarantee on the latency for the interrupt handler for the gear tooth sensor. And it was entering that interrupt service routine that started the timing. With the interrupt save/restore time being so long, and only one priority available to us, if there was another interrupt routine running when the gear tooth sensor interrupted, the time to get to the ISR was too variable to accurrately time the pulse.

Hence, no direction output available.

Brad