Technical data

Fundamentals
2.7 Time synchronization in PCS 7 - mode of operation
Time synchronization (V7.1)
20 Function Manual, 03/2009, A5E01216578-01
2.7 Time synchronization in PCS 7 - mode of operation
2.7.1 Time master and time slave
Introduction
To ensure that all Process Control System components operate with as precise a time as
possible, one system component must be the time source for all other components. The
precise time must be permanently available and be used for synchronization on a cyclical
basis (synchronization interval).
Time master
The component that provides the precise time within a bus system is referred to as the time
master. Only one component within a stratum can be the active time master.
Time slave
The time slaves within a bus system are components which receive or fetch their time from a
time master.
Cooperative time master
On OS servers, in the WinCC Editor "Time Synchronization" permanently defined computers
are set for the time synchronization.
The OS server works as a cooperative time master, i.e. the first active OS server on the
plant bus which does not receive time message frames on the plant bus automatically
switches to time "Master" mode. All other OS servers on the plant bus detect the time
message frame from the time master and automatically switch to time "slave" mode.
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).