I don't think there is any real coding help needed (not to be smug!) - I have any number of common sketches that demo setting up ISR's and timers and just edit either the OCRxA value when prescaleing, and also have all the Prescale bit settings in place, commented out. I just uncomment the one I want to try. Most work fine and as expected.
I guess I just need some clarification as what to expect when using any TTCRxA/B with bit 1 set to 1. In all 3 timers this setting is called "No Prescale - CLK_io" (in Timer2 it is CLK_t2s - where I believe it is set to use the system clock (16mhz) as the input.
I'm just trying to fully understand all the possibilities - I do understand a 62.5 ns interrupt might be a tad quick (!!!) but then what SHOULD one expect with this setting?
What would it be used for? Finally - what would be the settings for the shortest, practical interrupt be?
=A.