Qg 2 Multi-Sync Gateway User Guide
Managed Clock Engine Overview
SJC-DEV7250-HR Rev. 1.14
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Managed Clock Engine Overview
6.1
Ts2 Engine Modes
The Ts2 Managed Clock Engine can operate in four different modes. The operational mode defines the
functionality supported by the engine, Ts2 clock behavior and its properties in different operating
conditions. The operational mode is specified upon startup and can only be changed by restarting the
engine on the
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.
PTP Only
GNSS Only
GNSS Primary, PTP Secondary
PTP Primary, GNSS Secondary.
In addition to these four modes, a Slave Only mode is supported. The clock can be switched to the Slave
Only mode and back at any time and from any of above operational modes. The Slave Only mode is
selected on the
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Webpage.
6.1.1
PTP Only mode
This is an ordinary PTP master-slave mode. The GNSS interface is disabled. In this mode, the clock
normally acts as a PTP slave, but may also become a PTP master if no better clock exists on the network
based on the Best Master Clock Algorithm (BMCA).
The clock class is initialized to value of DEFAULT (248).
6.1.2
GNSS Only mode
In this mode, the clock is a GNSS-clock and the GNSS is the only source of synchronization. The clock can
never become a slave to another clock regardless of its clock class.
In this mode, the clock class is automatically controlled by the engine. The clock is initialized with class of
DEFAULT (248), and when it locks to a stable GNSS signal it raises the class to PRC_SYNC (6) or APP_SYNC
(13). If only the 1PPS-input signal is available, then the class APP_SYNC (13) is selected. If the ToD-input
signal is available as well, then the timescale is automatically switched to PTP and the clock class is
PRC_SYNC (6).
Later, if the GNSS-signal is lost, the clock switches to the holdover mode and lowers its class to
PRC_HOLDOVER (7) or APP_HOLDOVER (14). If after the holdover period, the GNSS-signal is still not
available the clock downgrades its class PRC_DEGRADATION_A (52) or APP_DEGRADATION_A (58) and
stays as the PTP master in the free running mode. If a better clock exists on the network based on
BMCA, the clock will switch to the PTP passive state.
6.1.3
GNSS Primary, PTP Secondary mode
This mode is almost the same as Mode 1, but after the holdover interval the clock degrades its class to
PRC_DEGRADATION_B (187) or APP_DEGRADATION_B (193), so clock can potentially become a PTP
slave if a better clock appears on the network.
This mode means that the Ts2 clock has the GNSS-signal as its primary source of synchronization and the
PTP as a backup source, i.e. when no GNSS-signal present.
