External Atomic Clock (Gm) / Ptp - Safran WR-ZEN Series User Manual

It is recommended to use this preset when a third-party GNSS is providing the ref-
erence 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.
5.2.1.4

External Atomic Clock (GM) / PTP

Web GUI selection: GM: ext AC | PTP
It is recommended to use this preset when the device is configured to be the
Grand-Master in the timing network and is disciplined using an Atomic Clock as
external reference.
Here, Atomic Clocks means that a very stable oscillator based on hyperfine trans-
ition (e.g, Caesium) that provides very low daily uncertainties (e.g., 1 ns/day) is
combined with a GNSS receiver to remove its slow drift using averaging
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5 WR-ZEN Series User Manual Rev. v5.1
Alignment of PPS_in VS PPS_out is done automatically (adding ~50ps of
uncertainties).
PPS_in is mandatory to announce a valid time.
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 situation, 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
detection 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-Run-
ning Grand-Master (see VSC-10102 in
Code)" on page 189).
The primary timing source is provided using an external atomic clock ref-
erence through the front-panel 10 MHz and 1PPS inputs (Grand-Master).
All timing ports (i.e., wr0-wr1) are configured as PTP masters.
Clock accuracy is announced below or equal to 25 nanoseconds.
Alignment of PPS_in VS PPS_out must be done manually (within pico-
seconds)
PPS only needed at startup
5.2 General Timing Management
"Grand Master (GM VCS
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