Siemens SIMATIC PCS 7 Function Manual page 21

A cooperative time master does not have to belong to a redundant server.
Note
This setting applies both for the configuration with and without a central time master (central
plant clock e.g. SICLOCK TC 400).
Function of the cooperative time master
The following process is initiated at the startup of a PC station that is configured as a
cooperative time master. A time message frame must be received within the wait time once
the PC station has powered up. The wait time amounts to four times the set synchronization
interval.
Possible response of cooperative time masters within the phase until the wait time has expired:
● A cooperative time master that receives a time message frame from a different time master
● A cooperative time master that has not received a time message frame on expiry of the
Within the set synchronization interval, all cooperative time masters check whether time
message frames have been received from the active time master on a cyclical basis. The first
cooperative master that detects three missing time message frames in succession assumes
the time master function. This ensures that only one time master exists.
Synchronization response
All time slaves and cooperative time masters on the terminal bus synchronize their internal
clock with the time message frames received . The time is synchronized as follows:
● Deviation ± 5 s:
● Deviation > 5 s:
Time synchronization (V8.0)
Function Manual, 03/2012, A5E02779849-02
within the wait time becomes a time slave.
wait time sends time message frames as the time master.
Delay/acceleration of the internal clock
Immediate conversion (possible errors: Data packets sent off prior to the change will have
more recent time stamps than those sent off later)
2.7 Time synchronization in PCS 7 - mode of operation
Fundamentals
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