); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY From: Dr Bruce Griffiths <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Timing on Ethernet Date: Mon, 06 Aug 2007 15:04:48 +1200 Message-ID: <[EMAIL PROTECTED]>
> Hej Magnus Hej Bruce, > One could always make use of the 2 spare pairs on a 100Mbit/s connection. > Its not that much more difficult to build a custom interface using these > than one doing precision timing on the receiver outputs. Indeed. The trouble is that cross-talk from the transmitter side will be your enemy. It will smooth out over time, as the transmitted data is DC balanced, but there is a small symbol dependent component. By listening to the transmitted data and choosing a "wise" point in that data you are operating synchronously with that data. You can use the spare pairs for queueing or for a separate site-channel with measurements. Considering that delay in cables varies very slowly, the two one-way measures does not have to be taken exactly at the same time. Time-stamping the events, transfering the data over to the other side and then take the difference between the time-stamps and divide by two you have the time-difference between the two nodes clocks (which was part of the time-stamping) and using that it is easy to steer the slaving clock since this is the delay-compensated time-error- detector in action. It is a trivial control-loop to keep the slaving node on time. Cheers, Magnus _______________________________________________ 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.
