Siemens CP 1243-1 Operating Instructions Manual page 44

Configuration
4.4 Time-of-day synchronization
Dependence of the synchronization method on the use of the CP
Depending on the use of the telecontrol communication or the security functions, the
following synchronization methods can be selected:
● Telecontrol communication disabled, security disabled
– NTP
– Time from the CPU
● Telecontrol communication disabled, security enabled
– NTP
– NTP (secure)
– Time from the CPU
● Telecontrol communication and security enabled
– Time from partner
– NTP
– NTP (secure)
– Time from the CPU
Time-of-day synchronization with the S7-1200
When using an external time source, the S7-1200 station can obtain the current time of day
both via the CPU as well as via a CP.
With the S7-1200 there is no forwarding of the time of day from the station to the subnet.
Note
Recommendation: Time-of-day synchronization only by 1 module
Only have the time of day of the station from an external time source synchronized by a
single module so that a consistent time of day is maintained within the station.
When the CPU takes the time from the CP, disable time-of-day synchronization of the CPU.
Time-of-day synchronization of the CPU
The following synchronization methods are possible for the CPU:
● NTP
Only this option can be configured actively for the CPU:
● Time from CP
The CPU adopts the time of day from a CP of the station if time forwarding from the CP to
the CPU is enabled (see below).
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Operating Instructions, 04/2017, C79000-G8976-C365-03
CP 1243-1