On Fri, Feb 10, 2012 at 2:53 PM, paul swed <[email protected]> wrote: > Just for fun have built up a simple multi-chip project to try my hand at > locking the FE5680 using the external efc connection mod. mentioned in > time-nuts. Typical counter micro rs 232 port stuff. > > Essentially the system is 2 X 24 bit counters that toggle back and fourth > every interval selectable from 1 to 65000 seconds accumulating counts. I am > measuring the 10 Mhz of the RB and using a novatel superstar II GPS rcvr. I > do have a better timing rcvr but this was handy and at this point most > likely good enough.
Do you ever need such a large counter? As you say the counts are only small integers. If the two are close they would not overflow even a 4-bit counter. One way to go is to have only a two bit counter (just a pair of flop flops) and end the integration as soon as the second bit flips. If you are building a FLL you only need to know which is faster. If you want faster convergence I think you have to measure relative phase and use a PLL. Then you don't need to wait for a full cycle. Maybe only a few degrees of phase difference is enough My plan is to use the 74HC4096 is the detector. It has the required flip flops inside. Use that to dive the RB5680 and then when they are reasonably close the 74HC4096 also contains an XOR type phase detector, so switch to that. Chris Albertson Redondo Beach, California _______________________________________________ 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.
