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Frequency division:unusual ratios

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Peppew

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Hi,
I'm wondering how to build a fractional frequency divider with unusual ratios like 7/12 or 7/16.

I know that ratios like 4.5 can be achieved with a sigma delta based freq divider, and I know how to build integer-N freq dividers with counters.

But how about unusual ratios?

Thanks
 

Hi,
example 7/12. But I think this is sigma delta.
Code:
101010101010101010101010 (repeating, 12 rising edges) use a counter
011001001100100110110011 (repeating, 7 rising edges) use a decoder logic, FSM

Klaus

added:
This example uses both edges of the input signal. This is not always possible. It depends on your hardware.

***
If you want it exact: use a PLL.

Klaus
 

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