Sorry. The Shera counter is 16 bits and not 12 bits but that does not change what I posted.
On Thu, 06 Dec 2012 19:17:48 -0600, David <[email protected]> wrote: >It is not a 16 bit capture and it does not run at 1/4 the clock rate. > >The Shera uses a 12 bit counter to capture the phase difference >between the OCXO frequency divided by 16 and GPS pulse per second >output to a resolution of about 42ns. > >What I suggested effectively captures the same phase difference but >divides the OCXO by 65536 and only has a resolution of 100ns. The >OCXO division is just conceptual though as it comes from the 16 bit >timer/counter overflow internal to the microcontroller so in practice, >the timer/counter is arbitrary length with an interrupt about every >6.5ms doing the housekeeping for the extra bits. It directly measures >the pulse per second period to a resolution of 100ns using the OCXO as >a clock. If a 20 MHz OCXO was used (limited by the maximum clock >frequency of the microcontroller), then the resolution would be 50ns. > >That is not how I plan on designing my own GPSDO which has taken a >significant turn from what I posted about here some time ago but I >have stopped discussing that until I have some results to share. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
