Technical data

Configurations for time synchronization of a PCS 7 plant
3.2 Rules for time synchronization in PCS 7
Time synchronization (V7.1)
34 Function Manual, 03/2009, A5E01216578-01
3.2 Rules for time synchronization in PCS 7
Rules
● A network may only contain one active time master.
● Time synchronization with an external time source (e.g. GPS, DDF 77) is required if the
time within the PCS 7 plant is to match the local time.
● Central plant clocks (synchronized with an external time source wherever possible) are
high-grade internal time sources for PCS 7 plants.
● A time slave can be the time master for lower-level components and systems.
● Any domain controllers that are available in a network will synchronize all of the nodes in
this network. A synchronization cycle using domain controllers has a duration of eight
hours as standard. For reasons of precision, additional synchronization corrections using
integrated PCS 7 tools (WinCC time synchronization) are required. You can define an
interval at which the OS synchronizes its time with that of an external time source.
● The WinCC "time synchronization" application can be used to configure an OS server as
a time master, a cooperative time master, and a time slave.
● An OS server can be configured as a time master either with or without external time
synchronization.
● A direct time synchronization of the plant bus is necessary if the "high-precision time
stamping" function is used for selected signals in an automation system. The accuracy for
high-precision time stamping is insufficient if the central plant clock fails. The
chronological order of the signals displayed remains intact.
Time synchronization using NTP mode
The following components are synchronized using NTP mode:
● PC stations that are not operated as OS client or OS servers
● CPU types with integrated Ethernet interface: Please note the following restrictions:
– Maximum of 50 NTP requests/s
– When connecting to the OSM (6GK1105-0AA00 and 6GK1105-1AA00), please check
whether you have SIMATIC NET - Current edition 2000/025 (incompatibility with
tagged frames in Industrial Ethernet OSM networks)
(
http://support.automation.siemens.com/WW/view/en/4247019).
– These CPU types may not be used in PCS 7 configurations with only a plant bus
(without a terminal bus).
Criteria for time synchronization in existing PCS 7 plants
Compare the configuration of your existing PCS 7 plant with the configurations outlined in
this documentation, and configure the time synchronization according to the present
configuration.