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8.3
Time acceptance
System startup:
After finishing the boot procedure, the time reception from any source usually takes 10
minutes or more. The first source available will be taken to set system time even if it
does not have priority 1.
Outputs activation:
As soon as the system time was set successfully within nanosecond accuracy to its
source, the outputs are activated.
Source changes:
Time source change decisions are either done automatically or manually, depending
on user settings.
Automatic mode:
The priority is based on deviation estimations of each source. The
source with lowest deviation has highest priority.
Manual mode:
Uses the user defined source priority list.
Source failures:
The active source is permanently supervised. If it fails for more than 1 minute, DTS will
choose the next best source (e.g. from priority 1 to priority 2). Source changes happen
immediately but maximal once per 60 seconds, which prevents source hopping.
Variants of time synchronization:
•
Adjusting slowly (Adjust Mode = follow):
After starting the DTS, the time is set for a first time (from a source). Afterwards,
the time will only be aligned with maximum adjusting speed of a few ns / sec. if
deviating from the source.
Configuration: see chapter “6.5.10 Time adjustment / Time-keeping“
•
Adjust immediately (Adjust Mode = set):
this mode is currently not
implemented!
Manual time set:
The time is always set immediately. The stratum is set to 1.
Notice:
Manual time setting is intended to use only for testing purposes.
8.4
Stratum handling
Stratum in synchronized operation:
The Stratum value behaves as follows for synchronization from the time source:
- When a fix stratum is configured, the system will always have this configured Stratum.
- If the system has auto stratum configured then the system will have the Stratum of its
source plus 1. GNSS has Stratum 0 => DTS therefore Stratum 1. A PTP master clock
may have Stratum 1 => DTS therefore has Stratum 2.
Stratum in case of time source loss:
The Stratum value behaves as follows in the case of a time source loss:
When a fix Stratum is configured, the system will always have this configured Stratum.
When the Stratum is set to auto mode the Stratum is calculated as follow:
The Stratum can count from 1 up to 16, which means 15 steps
1 hour => 60 minutes => 3600 seconds, 3600 / 15 steps = 240 s/step
E.g. the Stratum timeout is configured to 2 hours, the Stratum is increasing:
2h => 120min => 7200 sec
