Sat May 17 19:34:40 EDT 2014

Capture / Compare

Since we're already creating an interrupt when comparator is
triggering, the capture is easy to do manually.  If there are no
branches before the manual capture, there will only be a fixed delay.

Capture mode can be used to measure the frequency of the other signal,
translated to square wave.  Triggering on the rising edge, it can be
switch to 1x, 4x or 16x depending on expected frequency.

Compare mode can be used to create fixed width pulses.

Maybe interesting: using combinations of set/reset/toggle, it might be
possible to use the output compare to make more flexible binary