SEVEN WR-Z16, Руководство пользователя

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Chapter 5: Timing
61
v3.3-a 12/07/2022
Another key aspect of FOCA is how to determine when there is a “failure”
on a timing source.
Some cases are obvious such as the link is down, no packets are exchange but other cases can be
more complex to identify: all these cases are detailed in the appendix VCS code tables (§0).
For a deeper understanding of the behavior of the FOCA algorithm it is recommend reading the
section §0 in the appendix where more scenarios are detailed.
FOCA/BMCA compatibility
FOCA is based on BMCA, thus it is compatible with all the clock quality and timing
information fields. In other words, this means that a device running FOCA strategy can
provide timing to a BMCA device and BMCA information is provided to FOCA algorithm.
5.1.3 Virtual Clock Overview
The concept of “Virtual Clock” has been introduced in the new version of WRZ
-OS to ease the
monitorization of the global timing status of the device. It allows to abstract the way the timing
sources discipline the local oscillator and summarizes how the device will announce its own clock
information through the outputs.
Figure 5:3 4
–
Data-flow between timing sources, virtual clock and outputs
When using the FOCA policy (Figure 5:3 4), the virtual clock will be fed by the active timing source
(e.g., tsrc
1
), then this information (clock quality & time properties) will be forwarded by all the
outputs:
•
directly in case of PTP/WR protocol.
•
by properly modifying the corresponding fields in the case of NTP, NMEA, etc.
The Figure 5:4 5 displays the overview panel of the virtual clock information when the device is
using an external reference from front-panel (GM) as the active source where: