dl-breadcrumbs__homedl-breadcrumb-item__separatorConfiguration and programmingdl-breadcrumb-item__separatorConfiguration in Automation Builderdl-breadcrumb-item__separator...dl-breadcrumb-item__separatorProtocols and special serversdl-breadcrumb-item__separatorNTP/SNTP protocoldl-breadcrumb-item__separatorIntroduction of the NTP/SNTP protocol
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Introduction of the NTP/SNTP protocoldl-permalink__symbolPermalink

The PLC supports the NTP and the SNTP protocol ((Simple) Network Time Protocol). Compared to SNTP, the NTP protocol achieves higher accuracy in time synchronization, meeting advanced requirements for accuracy and reliability of a PLC solution.

In case a configured NTP protocol cannot be used, SNTP protocol is used as a fallback solution.

The S500 I/O modules do not support the functionality to create and transfer a timestamp with an event directly at the I/O channel. A workaround is using SoE logging (Sequence of Event) for a root-cause analysis. An ‎⮫ application example explains how events are processed.

The protocols NTP and SNTP provide the functionality to synchronize the clock of a PLC to an external time source. An ‎⮫ application example demonstrates how to synchronize the PLC time with a time server.

Detailed information about the parameters for the NTP implementation used in AC500 V3 PLCs is provided in the ‎⮫ application note.

A specification of the (S)NTP protocol itself can be found in the document RFC4330.

The following modes are supported by the implementation of the PLC:

  • (S)NTP client

  • (S)NTP server

  • (S)NTP client and server

The server implements the NTP protocol version NTPv4 and is also compatible to NTPv3.

For the client only, the NTP protocol version NTPv4 is supported, it is not compatible with external NTPv3 servers.

The function block PmSntpInfo can be used to read diagnosis information of the protocol.

Refer to the documentation of the library ABB_Pm_AC500.lib for further information.

  • If a high precision of system time is wanted, use a fully functional NTP server or at least an SNTP server with a high-precision time-source (e.g. DCF-77 receiver). Avoid cascading several levels of (S)NTP server / (S)NTP clients.

  • Client requests are normally sent at intervals depending on the frequency tolerance of the client clock and the required accuracy. However, under no conditions requests should be sent at less than one minute intervals (see RFC 4330). Keep that in mind when setting polling-interval of the (S)NTP client, especially if a huge amount of clients use one single server.

  • Be sure not to use broadcast or multicast addresses as server or backup-server since current (S)NTP implementation does not support manycast mode.