Technical data
Fundamentals
2.6 Time levels for a PCS 7 plant (stratum)
Time synchronization (V7.1)
Function Manual, 03/2009, A5E01216578-01
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2.6 Time levels for a PCS 7 plant (stratum)
Introduction
Time synchronization of a system involves one component synchronizing the next
component by forwarding a time message frame. Forwarding time message frames will
result in time delays. You should make allowances for this fact when setting up a PCS 7
plant.
The following figure shows an example of the structure of a PCS 7 plant with several
domains:
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Definition stratum
A PCS 7 plant component such as the central time clock (SICLOCK) receives the definitive
time from an external time source (e.g. a GPS signal) and forwards it to other components to
be synchronized. As a result, the SICLOCK is the time master for those components whose
time is determined in relation to the SICLOCK time. Components which are capable of
providing a time are considered time masters if other components use their time information.
All time masters form a hierarchy that consists of higher-level and lower-level time masters.
Relative position within this hierarchy is designated with a number; the "stratum". Multiple
time masters may be located within a single stratum. These time masters use the time
message frame at the same point in time to synchronize their own clock.
The stratum indicates the following:
● The number of time levels between the stratum in which the time master is located and
the stratum in which the time source (e.g. the GPS satellite) is located
● The time level where the components in a network are located