Siemens SIMATIC ET 200SP HA System Manual page 54

Plant planning
4.9 Time synchronization and time stamping
Result
● A network (labeled "TIME-NET" here) only connects the central system clock to the first
CPU configured for time stamping.
This CPU sends time frames to other nodes in the TIME-NET.
● A central system clock of SICLOCK TC400 type sends the time frames via Industrial
Ethernet.
● There is a direct connection between the central system clock and the integrated PN-IO
interface of the CPU.
● The time synchronization of the CPU is performed with the SIMATIC procedure.
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ET 200SP HA Distributed I/O system
System Manual, 08/2019, A5E39261167-AD