Qg 2 Multi-Sync Gateway User Guide
Managed Clock Engine Overview
SJC-DEV7250-HR Rev. 1.14
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6.1.4
PTP Primary, GNSS Secondary Mode
This mode is designed for unstable GNSS-reception environments, where the node having a better signal
reception becomes a PTP master and all others become PTP slaves, even if they have their own GNSS-
signal.
The clock is initialized with class DEFAULT (248) and the class is not changed by the engine while
operating. Instead after detecting the stable GNSS-signal the engine increases the priority2 member of
the Default Dataset (lowers its value) by some small margin, which might depend on the reception
quality. That clock which has a higher priority2 (better GNSS signal reception) becomes the PTP master
on the network and all others synchronize with it.
6.2
GNSS Interface
The Ts2 supports GNSS L1 input signals from a GNSS antenna. Signal frequency is 1575.42 MHz for GPS;
1561.098 MHz for Beidou; and 1602.0 MHz for Glonass. The status and configuration of GNSS interface
can be accessed via the
Error! Reference source not found.
Webpage.
6.3
Ts2 Clock Sync States
Ts2 clock at any instance of time can be in one of four following sync states:
FREE RUNNING
SYNTONIZING
SYNCHRONIZING
HOLDOVER
UNKNOWN/ERROR
6.3.1
FREE RUNNING State
The Ts2 clock comes into this state upon initialization. The Ts2 clock time is not set, the clock class is
DEFAULT (248), clock accuracy is UNKNOWN (0xFE).
The timescale is PTP, the UTC offset is initially set to 37 secs, leap flags are FALSE. In Free Running state,
the clock frequency comes from the on-board oscillator.
6.3.2
SYNTONIZING State
This state is only possible when the 1PPS-input signal from the GNSS interface is available, but not the
ToD-input signal and the clock become a PTP master.
When the Ts2 engine is running in GNSS Only mode or PTP Only mode, the clock class is automatically
changed to either PRC_SYNC (6) or APP_SYNC (13) and the clock accuracy is set to WITHIN_100_NS. In
GNSS Primary, PTP Secondary mode, the clock class remains unchanged.
Note that the frequency can be traced, but not the time in this state. Once the ToD-input signal
becomes available the clock switches to SYNCHRONIZING state.
6.3.3
SYNCHRONIZING State
The Ts2 clock enters this state when it starts to synchronize its time and frequency with either a PTP or
GNSS source. If the synchronization source is the GNSS, then both time and frequency are present and
traceable. The timescale is changed to PTP, the clock class is changed to PRC_SYNC (6) and the clock
accuracy is set to WITHIN_100_NS.
