Yes I can use a prescaler but that doesn't change the situation that I don't know how to set a counting period (THE TIME) Because Frequency is number of oscillations per period so I need to know number of impulses and the time in what these impulses appeared. OK then Is it possible to use Timer0 and Timer2 at the same time and stop them at the same time if yes then how. Don't think I'm crazy or stupid I couldn't find an answer to this one.

Thanks