Siemens ET 200SP Operating Instructions Manual page 44

Configuration and operation
4.3 Ethernet interface
Note
No forwarding of the time of day with NTP / NTP (secure)
Both the CPU and CP can have the time of day synchronized using NTP. If you enable time-
of-day synchronization for both modules, it is recommended that you use the same NTP
server to retain a consistent time-of-day within the station.
The CP supports the following time-of-day synchronization method:
● NTP
You configure the addresses of the NTP server(s), the synchronization interval and the
"Accept time from non-synchronized NTP servers" option
CP 1542SP-1 IRC
With telecontrol communication enabled (parameter group "Communication types" the time
of day is normally taken from the partner:
● Time from partner
The CP sets its clock using the time of day that it receives in frames from the
communications partner.
The CP 1542SP-1 IRC provides the CPU with the option of it taking its time from the CP
using a PLC tag. See section Auto-Hotspot for information on this.
Note
No time-of-day synchronization of the CPU when the time is taken from the CP
When the CPU takes the time from the CP using a PLC tag, disable the CPU's own time-of-
day synchronization.
CP 1543SP-1
Note
Ensuring a valid time of day
If you use security functions, a valid time of day is extremely important. It is recommended to
use the NTP (secure)NTP (secure) method.
The CP supports the following time-of-day synchronization methods:
● NTP
● NTP (secure)
The secure method NTP (secure) uses authentication with symmetrical keys according to
the hash algorithms MD5 or SHA-1.
In the global security settings, you can create and manage additional NTP servers also of
the type NTP (secure).
See also
Communication with the CPU (Page 56)
44
CP 1542SP-1, CP 1542SP-1 IRC, CP 1543SP-1
Operating Instructions, 01/2017, C79000-G8976-C426-03