Configuration and operation   
4.7 Time-of-day synchronization 
  IE/PB LINK PN IO 
66  Operating Instructions, 11/2017, C79000-G8976-C393-02 
Both in NTP and in the SIMATIC mode, the time-of-day is transferred as UTC (Universal 
Time Coordinated). 
With the SIMATIC mode you require a time master in a network. 
If time-of-day synchronization is enabled in the configuration, you can set whether the LINK 
simply adopts the time-of-day or adopts it and forwards it. The following options are 
available: 
● 
 
–  Adopt the time of day 
–  Adopt the time of day and forward it to PROFIBUS 
● 
 
–  Adopt the time of day from Ethernet (no forwarding to PROFIBUS) 
–  Adopt the time of day from PROFIBUS (no forwarding to Ethernet ) 
–  Adopt the time of day from Ethernet and forward it to PROFIBUS 
–  Adopt the time of day from PROFIBUS and forward it to Ethernet 
With the NTP method, the LINK sends time-of-day queries at regular intervals to one to four 
NTP servers in the subnet (LAN). 
●  The update interval (synchronization cycle) specifies the interval between the time 
queries. 
●  "Accept time from non-synchronized NTP servers" option 
If the option is enabled, the LINK also accepts the time-of-day from non-synchronized 
NTP servers with stratum 16. 
If the option is disabled, the response is as follows: If the LINK receives a time-of-day 
frame from an unsynchronized NTP server with stratum 16, the time of day is not set 
according to the frame. In this case, none of the NTP servers is displayed as "NTP 
master" in the diagnostics; but rather only as being "reachable".