> much simpler programming i think. i need to adc at 25Hz precisely.
> i'm using 16F870 @ 20Mhz, so, a 5Mhz instruction clock. So, even
> using Timer1 (16 bit), with the maximum prescaler, i still have to
> handle 9 full rollover interupts and then time an odd number of clocks

9 ?

If you can change to 19.6608MHz (commonly available) it
will be very simple

19660800 / 4 / 256 / 256 = 75 rollover IRQs/sec from Timer1

=============================

A 4060 would be usable with many crystals if it weren't for the fact
that not all of the 4060's Q outputs are available for 4081 ANDing

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