50 | EdgeSync Manual rev 1
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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).
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.
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 EdgeSync 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.
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.
GNSS Interface
The EdgeSync 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 Interface :: GNSS Webpage.
