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NTP Server for PLC Clock Synchronization
FP Web-Server V2.11
140
11.1 (S)NTP Servers
This function is used to synchronized the PLC clock with a network time server.
For a detailed description of each field or button in the dialog, set the cursor into the field and
press <F1> or highlight the button with <Tab> and press <F1>.
In most LANs a Network Time Server (NTP or SNTP) is available to synchronize the real-time
clock (RTC) and calendar date of the network units (computers). Such NTP servers provide
accurate world date/time information in UTC format (Universal Time Coordinate).
The FP Web-Server can request the current UTC time from the NTP server. Optionally the FP
Web-Server can calculate the local time with a daylight saving time (DST) offset. And then the
FP Web-Server can update the date/time RTC registers within the PLC. The update of the PLC
clock can be done independently of the PLC program in constant time intervals.
Additionally the FP Web-Server can be set up in this way so that a PLC-controlled internal relay
can trigger a PLC clock update.
The FP Web-Server can also save clock information in a user-definable DT register address.
This is especially useful for PLCs having no integrated RTC.
The separate battery must be installed to use the RTC functions of the FP-Sigma.
The time function is mainly designed to request the current time from an NTP server located in
the LAN to update the PLC clock. "Example15" also shows how to dial up the Internet to request
the time from an Internet NTP server to update the PLC clock.
For more information on world time and DST see:
• http://www.worldtimezone.com/
• http://www.twinsun.com/tz/tz-link.htm