Technical data

Fundamentals
2.7 Time synchronization in PCS 7 - mode of operation
Time synchronization (V7.1)
22 Function Manual, 03/2009, A5E01216578-01
2.7.2 Time sources for a PCS 7 plant
Overview
In PCS 7 plants, it is necessary to define which component is capable of providing the plant
with a satisfactory time in terms of quality. You can use either internal or external time
sources for this purpose.
External time source Internal time source
Suitability External time sources provide an ultra-
precise time and are suitable for all plant
configurations.
Internal time sources supply a continuous time signal. The
time provided does not have to match the local time or
Coordinated Universal Time (UTC).
Note:
Internal time sources are generally not approved for the
validation of processes.
Examples
• GPS decoder
• DCF 77 receiver
• External NTP server
BIOS clock for a component without external time
synchronization.
Internal time source for a PCS 7 plant
Using an internal time source ensures system-wide time consistency. This time does not
have to agree with real UTC or with real local time. The following table shows which internal
time source can be used for the time master:
Internal time source Requirement Active time master
BIOS clock of a central plant
clock
The central plant clock is connected to a PCS
7 plant network.
Central plant clock
BIOS clock of a domain
controller
The computer to be synchronized belongs to a
Windows 2000/2003 domain.
Domain controller
BIOS clock of an OS server The real time is not important for the project. OS server
External time source for a PCS 7 plant
Using an external time source ensures system-wide time consistency. This time matches
UTC or local time. The following table shows which external time source can be used for the
time master:
External time source Requirement Active time master of the PCS 7 plant
DCF 77 or GPS signal Radio signal synchronizes SICLOCK Central plant clock
DCF 77 signal The DCF 77 receiver is connected to a COM
interface of an OS server.
OS server with DCF 77 receiver
GPS signal The GPS decoder is connected to a COM
interface of an OS server.
OS server with GPS decoder
NTP server Internet connection Domain controller