Time-Of-Day Synchronization - Siemens S7-400 Equipment Manual

Configuration and operation

6.11 Time-of-day synchronization

6.11 Time-of-day synchronization
General rules
The CP supports the two modes explained below for timeofday synchronization:
• SIMATIC mode
• NTP / NTP (secure)
The secure method NTP (secure) uses authentication with symmetrical keys according to
the hash algorithms MD5 or SHA-1. The method NTP (secure) can only be selected if the
security functions are enabled.
– STEP 7 Professional
– STEP 7 V5
Note
No automatic changeover to daylight saving is defined in the NTP protocol. As a result,
you may need to implement this changeover using a program application.
If an NTP frame is detected by the CP as "not exact", the time-of-day frame is not
forwarded on the K bus. This can occur with time-of-day frames from non-synchronized
NTP servers with stratum 16. In this case, none of the NTP servers is displayed as "NTP
master" in the diagnostics; but rather only as being "reachable".
Note
Ensuring a valid time of day
If you have enabled the security functions, a valid time of day is extremely important. If you
do not obtain the time-of-day from the station (CPU), we therefore recommend that you use
an NTP server of the type NTP (secure).
Project engineering
For more detailed information on configuration, refer to the online help of the "Time-of-day
synchronization" parameter group and in the manual /2/ (Page 103).
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In the global Security settings of the STEP 7 project, you can create and manage
additional NTP servers also of the type NTP (secure).
In the extended NTP configuration, you can create and manage additional NTP servers
including those of the type NTP (secure).
Equipment Manual, 03/2023, C79000-G8976-C256-07
CP 443-1 Advanced