Central Plant Clock; Time Levels For A Pcs 7 Plant (Stratum) - Siemens SIMATIC PCS 7 Function Manual

Further information
● Section "Setting the time displayed (Page 48)"
● WinCC online help
2.5

Central plant clock

Using a central plant clock
You should always synchronize all Process Control Systems using either a precise time or a
standard time. In the case of PCS 7 plants, we recommend performing synchronization by
means of a central plant clock. The central plant clock manages the time centrally for the entire
plant and synchronizes all of the other plant components via their interfaces.
Recommendation:
Using the SICLOCK TC 400 as the central plant clock. The SICLOCK should be synchronized
with a standard time, e.g. using GPS or DCF 77, as this ensures that a correct reference to
the actual time is constantly available.
Standard time
The following standard times are typical for PCS 7 plants:
● GPS
● DCF 77
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:
Time synchronization (V8.0)
Function Manual, 03/2012, A5E02779849-02
The GPS signal is provided by a global satellite system.
The DCF 77 signal is available in Germany and in certain parts of Europe using
corresponding radio signal receivers.
2.6 Time levels for a PCS 7 plant (stratum)
Fundamentals
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