Caution: 10 MHz + PPS signal calibration: When using this preset, the PPS
must always keep the same delay in respect to the 10 MHz signal. The user
can use the GM Offset field to compensate this fixed delay.
5.2.1.3 External GNSS Receiver (GM)
The primary timing source is provided using an external GNSS receiver reference
through the front-panel 10 MHz and 1PPS inputs (Grand-Master).
All SFP ports (i.e., wr0-wr1) are configured as WR masters.
Clock accuracy is announced below or equal to 100 nanoseconds.
Alignment of PPS_in VS PPS_out is done automatically (adding ~50ps of uncer-
tainties).
PPS_in is mandatory to announce a valid time.
It is recommended to use this preset when a third-party GNSS is providing the reference to
the Grand-Master device. This preset will also ensure the automatic alignment of the PPS
input to the PPS output after each time the GNSS locked itself.
Caution: GNSS PPS output: The GM can lock to the PPS from the GNSS
receiver before GNSS signal locked (before its 10MHz are locked in phase
to its PPS). This causes a jump in the time reference. To avoid this situ-
ation, the user should configure the GNSS to not output any PPS before
locking to GNSS signals.
Note: Inform GNSS status via PPS: This preset enforces a continuous detec-
tion of the PPS input. This means that if the GNSS receiver is configured to
disable its PPS when it unlocks (e.g., signal lost), the Grand-Master will then
automatically degrade itself as a Free-Running Grand-Master (see VSC-
10102 in "Grand Master (GM VCS Code)" on page142).
5.2.1.4 WR Slave @ wr0 à wr1 (BC)
The primary timing source is provided using WR through interface wr0. It can fail-
over to a secondary timing source provided using WR through interface wr1.
This preset provides multi-source redundancy by allowing to configure the two first optical
ports as possible timing sources. This means that in case of failure of the first port (i.e.,
wr0), the device will automatically switch to wr1 as it is configured as secondary source.
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CHAPTER 5 • WR-Z16 User Manual Rev. v3.4
5.2 General Timing Management
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