Siemens SIMATIC PCS 7 Function Manual page 76

Configuring time synchronization
5.5 Configuring the time synchronization of the OS
3. Select Open from the shortcut menu.
4. Select the check box "Synchronization via terminal bus (slave)".
5. Select the "Use time from a connected WinCC server" check box.
6. Click "OK".
Execute these steps for every OS client that will be synchronized.
Configuring time-of-day mode for a communications processor (CP 1613, CP 1623)
To configure time-of-day mode for the communications processor, proceed as follows:
1. Open SIMATIC Manager.
2. Select the station to be synchronized from the tree view.
3. Open the configuration of the station.
4. Select the communications processor (CP 1613, CP 1623).
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The "Time Synchronization" dialog box opens.
Thus all associated check boxes and text boxes can be selected.
Time synchronization (V8.0)
Function Manual, 03/2012, A5E02779849-02