SEVEN WR-Z16, Руководство пользователя

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Chapter 5: Timing
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v3.3-a 12/07/2022
5.2 General Timing Management
To ease the configuration of the device the WRZ-OS implements presets to allow a quick setup
of the timing sources and of the master ports to redistribute time.
If the device has been shipped with the holdover option, this timing source will be, by
default, configured as the last timing source independently of the preset.
5.2.1 Presets
5.2.1.1 WR Slave @ wr0 (BC) [default]
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The primary timing source is provided using WR protocol through interface wr0.
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The other (wr1) is configured as WR master.
This is the default preset as it is the standard/legacy configuration of most of the WR devices.
This is the simplest Boundary Clock behavior where the device is disciplined by a single reference
and forward its timing to the down layers through all the other ports.
5.2.1.2 External Atomic Clock (GM)
•
The primary timing source is provided using an external atomic clock reference through
the front-panel 10 MHz and 1PPS inputs (Grand-Master).
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All timing ports (i.e., wr0-wr1) are configured as WR masters.
•
Clock accuracy is announced below or equal to 25 nanoseconds.
•
Alignment of PPS_in VS PPS_out must be done manually (within picoseconds)
•
PPS only needed at startup
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 transition (e.g,
Caesium) that provides very low daily uncertainties (e.g., 1ns/day) is combined with a GNSS
receiver to remove its slow drift using averaging methods. For telecom, this combination is also
known as ePRTC and typically provides a UTC representation accurate within 10ns or less.
Moreover, in order to guarantee the best timing performance (phase noise & determinism) the
automatic alignment of the PPS output onto the PPS input has been disabled.
10MHz + PPS signal calibration
When using this preset, the PPS must always keep the same delay in respect to the