[time-nuts] How to get 32.768KHz from 10MHz.

Tom Van Baak tvb at LeapSecond.com
Wed Jul 23 11:55:34 EDT 2008


Since synchronization is more important than jitter in this
application it's easy to generate 32 kHz from 10 MHz.

A 10 MHz clock into a PIC gives a 400 ns/instruction time.

To produce 32.768 kHz you flip an output pin put every 38
instructions, except that 9632 times per second you make
it 39 instructions instead.

The result is 65536 bit flips per second (giving a frequency
of exactly 32768 Hz) consuming 2 500 000 instructions per
second. The output accuracy equals the input accuracy.
The output jitter is as most 400 ns.

/tvb





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