Technical data

Configurations for time synchronization of a PCS 7 plant
3.4 Configuration for time synchronization in a Windows domain
Time synchronization (V7.1)
Function Manual, 03/2009, A5E01216578-01
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Time synchronization on the terminal bus
● Active time master:
The time master is the domain controller (DC), which is parameterized as the main
structure master and/or the PDC emulator (usually the first domain controller installed).
● Time source:
The domain controller receives the time from the SICLOCK central plant clock. The
SICLOCK TC 400 is connected to the terminal bus by means of an Ethernet connection.
The SICLOCK TC 400 central plant clock synchronizes the domain controllers by means
of the NTP method.
● All other plant PCs automatically become time slaves of the domain controller (PDC
emulator) due to their membership in the Windows domain.
● The Windows time service (w32tm) synchronizes the date and time of all computers in a
Windows domain. Since the Windows-internal time synchronization only takes place
every eight hours, the OS servers are also configured for operation as time slaves of the
domain controller (PDC emulator) using the WinCC time synchronization function.
The PDC emulator is an operation master role of a domain controller. The domain
controller with this operation master role synchronizes the members of the Windows
domain every 8 hours.
● Passive time master:
If the authenticated domain controller (PDC operation master) fails, another domain
controller automatically takes over time synchronization within the network.
● The OS clients are configured as time slaves of the OS servers connected and receive
their time signal via the terminal bus.
● PC stations without WinCC time synchronization, such as a BATCH PC or engineering
station, are synchronized using a DCF 77 reception service, which must be installed
separately. As time master one of the domain controllers or an OS server is possible
here.
Time synchronization on the plant bus
● The time master for the plant bus is the SICLOCK connected to the plant bus as the
central plant clock. It sends a high-precision broadcast time signal to the plant bus
(SIMATIC mode).
The OS servers are configured as what are known as cooperative masters. If the AS no
longer sends a time signal then an OS server becomes time master and then sends time
signals itself on the plant bus, as a replacement.
● Time synchronization is configured for all automation systems on the plant bus.
Further information
● Section "Configuration steps for time synchronization with a central time master in a
Windows domain with a hierarchy (Page
58)"
● For information on configuring authorizing time servers in Windows Server 2003, refer to
the relevant Microsoft reference material at the following Internet address:
http://support.microsoft.com, subject: Configuring an authorizing time server in Windows
Server 2003 (
http://support.microsoft.com/kb/816042/en)