[time-nuts] Generating a solid PPS from 10Mhz source

Morris Odell vilgotch at bigpond.net.au
Thu Jan 14 23:44:00 UTC 2016

Am I missing something here?

I understand the ease and fun of programming up an AVR as much as anyone but 
surely this task could be accomplished  easily with a chain of fast 
synchronous TTL or CMOS dividers. A resynchronising FF could also be added 
at the end to  clean up the 1 pps if required. You wouldn't need to worry 
about the maths or OBOBs either.

Admittedly you would need more PCB real estate but that shouldn't be a big 
deal in most cases.


>> If anyone is interested in the equivalent functionality using an ATTiny25 
>> (for instance, if you’re already heavily invested in AVR instead of PIC, 
>> like I am), ping me. I’ve privately written code to solve almost the same 
>> problem and it could easily be adapted into doing the same job.

>>>> Is there an easy circuit to build that can consistently deliver a 1 PPS 
>>>> from a 10MHz source with excellent resolution and repeatability?  My 
>>>> first application is to test different 10MHz oscillators without a TIC 
>>>> always attached and then compare the PPS output change over time 
>>>> against a master GPSDO PPS with an HP53132A.
>>>> The circuit used for PPS generation would have to deliver consistent 
>>>> PPS output with preferably not more than 100ps noise or jitter, 
>>>> assuming a perfect source.  I'm totally guessing that for this 
>>>> resolution, the PPS would have to be generated and accurate to within 
>>>> 0.001Hz every second.  If this is too difficult, maybe the integration 
>>>> time can be increased to generate one pulse every 10second or every 
>>>> 100,000,000.00 cycles?

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