Qg 2 Multi-Sync Gateway User Guide
Managed Clock Engine Overview
SJC-DEV7250-HR Rev. 1.14
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If the ToD-input signal becomes unavailable, while the 1PPS-input is still present, the Ts2 clock switches
to SYNTONIZED state.
If the synchronization source is a PTP master, then the clock quality remains unchanged. The timescale is
set according to what is distributed by the PTP master. If the timescale distributed is PTP then the UTC
offset (if valid) and leap flags are also set to master’s values and the time source is set to PTP.
6.3.4
HOLDOVER State
The Ts2 clock enters this state when the synchronization source is lost. If the clock was synchronized
with PTP master its clock class remains unchanged. Otherwise the clock class is modified according the
engine’s operational mode and the clock accuracy is changed based on the time spent in the holdover
state.
There is a static parameter which defines the clock stability. Currently it is fixed to 1 ns/s for a
temperature-stable environment. During the holdover state an estimated error value is calculated and
the clock accuracy is set according to that value.
The maximum time the clock stays in holdover state is defined by a holdover interval. By default, this
value is set to 1000 seconds which gives about 1 microsecond error at the end of holdover interval. After
holdover interval expires, the clock switches to the FREE RUNNING state, and its accuracy is reset to
UNKNOWN (0xFE).
6.3.5
UNKNOWN/ERROR State
The Ts2 clock has entered a failed or error condition and the sync state is unknown.
6.4
Unicast Operations
By default, unicast operations are disabled and the Ts2 port operates in multicast mode. After unicast is
enabled no multicast communications are possible.
The PTP port can be switched to unicast operations and back at any time using the
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source not found.
and
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Sections of this User Guide.
6.4.1
Unicast Master
A Ts2 port in unicast master state can support:
Slave nodes which dynamically request unicast message transmission services from the master
using the unicast negotiation mechanism.
Slave nodes which do not support the unicast negotiation and simply rely on the reception of
unicast messages from the master.
To accept unicast negotiation requests from slave nodes the master needs to be configured as follows:
Unicast negotiation must be enabled.
Slave acceptance filter must be populated. Note that in the current design, the slave acceptance
filter is not user configurable and it is set to accept all slaves.
To provide message transmission services to slave nodes which do not support the unicast negotiation
the master needs to be manually configured with the list of static slave nodes.
