Prioritization of the data exchange with VLAN

For privileged forwarding of the PROFINET RT frames the real-time communication uses the VLAN tag according to IEEE802.1Q. So it is possible to define 7 different priorities. With the VLAN tag it is ensured that the PROFINET RT frames have the highest priority. Thereby “real-time” communication is made possible if PROFINET RT is used together with other network protocols (for example TCP/IP, basic network communication, internet).

The PROFINET RT communication is realizable with every commercial ETHERNET controller that supports VLAN.

The VLAN tag has the following structure:

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Contents of the VLAN-tag

The individual parts have the following sense:

  • Type: Identifies the following data as a VLAN information
  • Priority: Defines the priority of the telegram
  • VLAN_ID: ID of the associated VLAN group

Caution

:strong:Risk of communication faults!

PROFINET IO does not work in networks if ETHERNET components do not support VLAN.

Make sure that all ETHERNET components support the VLAN-tag.

Additional notices for the conformance classes

The MRP (Media Redundancy Protocol) is necessary for ring topology. It has to be integrated in the IO Controller as well as in the IO Devices and ensures the communication at a bus disconnect.

The I&M functions (Identification & Maintenance) are necessary for reading out the vendor and system specific information of an IO Device. The contents of these functions are defined in a specific PNO specification (Profile Guidelines Part 1: I&M fuctions, Rev. 1.1.1, order no. 3.502).

Note

AC500 PROFINET RT is certified according to IEC 61158 and is conform to the conformance class CC A.

Further information on PROFINET can be found on the website of the “PNO” following this link: http://www.profibus.com