At 06:24 PM 5/25/2007 +0200, you wrote: >Hi Martyn, > >I work with other people in the timing system for CERN's particle >accelerator complex in Geneva (Switzerland), which includes the Large >Hadron Collider (LHC), hopefully to start operation in spring 2008. Our >timing system consists basically of a lot of complicated high level >software orchestrating the transfer of particles from one accelerator to >another, and the subsequent acceleration cycles. Hardware-wise, we have >home-made VME modules which receive the 10 MHz and PPS signals from a >commercial GPSDO (Symmetricom XLi) and use these two signals to encode >messages (as decided in advance by the high level software) on a serial >link. Using the 10 MHz, the second is broken in millisecond slots and >then further in 125 microsecond slots. Each 125 us slot can carry a >message signaling some event to occur in the accelerators. On the >receiving side, we have home-made PCI, PMC and VME boards which can >react to any of these messages by starting a counter, generating an >output pulse on their front panel or an interrupt on the bus. This >allows hardware and software synchronization all around the complex (the >LHC is 27 km in circumference). > >Now, to come to your question: we rely heavily in the PPS containing >exactly 10 million ticks of the 10 MHz. All our UTC time-tagging logic >is based on that, so we definitely need a stable phase between the 10 >MHz and the PPS. But as Tom says, I thought you got that by design in >every GPSDO. Maybe we have misunderstood the question?
I read his original message to say his customers were asking for coicidence of pulse edge, rather than a finite (not zero) phase relationship. >Cheers, > >Javier > >_______________________________________________ >time-nuts mailing list >[email protected] >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
