QuestionHow closely are the 10MHZ and the 1PPS slaved together?
AnswerExcept during power-up, there are always 10 million cycles of 10MHz between each 1PPS output. After a reboot or power cycle, when the SecureSync or TSync-PCIe timing board syncs to a reference for the first time, the 1PPS and 10MHz are not guaranteed to be locked together during tracking setup.
When the Disciplining State transitions to “Locked”, we lock the 1PPS and 10MHz together, and guarantee that there will be 10 million clock cycles between PPS’s as long as the Disciplining State remains “Locked”. (We can keep both the 10 MHz and 1PPS synchronized to the reference in this state without slipping the signals relative to each other).
If a unit loses all of its references, and the holdover timeout expires, and the unit enters the Freerun state for a long time, there is a chance that upon acquiring a reference again the relationship between the 10MHz and 1PPS may drift again. But once the disciplining state becomes “Locked” again, the 10 MHZ and 1PPS will be locked together again, and there will be exactly 10 million 10MHz cycles in between PPS’s.