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PROFINET FAQ's

The most frequently asked questions about PROFINET

General

What is PROFINET?

PROFINET is a data communication protocol for industrial automation. It uses open standards that provide an Ethernet based connection between the field level devices and the management control environment. PROFINET can also be used directly in the field to automate real-time machine connections where PROFIBUS has reached its limit . PROFINET and PROFIBUS can be combined to create well rounded industrial network solutions.

Is it allowed to have a 1 port PN-device with only one MAC address?

According to the PROFINET standard a device shall have an Interface MAC address for every interface as well as a separate port MAC address for every port. Therefore, a 1-port device shall have 2 MAC addresses (Interface and port).

Under special circumstances a 1-port device may have the same MAC address for both interface and port. This shall be accepted during a test. A remark in the test report mentions the exception.

The exception is only acceptable within CC-A and CC-B when only LLDP frames are used as port to port protocol i.e. no PTCP protocol is supported. A manufacturer declaration is required that the use of the 2nd MAC address is either not possible or very difficult to be realized with the implemented operating system.

Background information regarding the use of the PTCP-protocol:
If the device is connected to a MRP-ring the device may send out PTCP frames (org-frames with highest priority). So it may happen that due to the multiplication of that PTCP-frame the Controller receives two PTCP frames and stores that device address. If the 2nd frame is received via a blocked port the MAC address of this PTCP frame is stored. This means that this device can be reached via this path. But this communication will then lead over the blocked port (the device is not reachable).

Is it worth getting switches for PROFINET that support LLDP?

If you have the financial resources to buy an LLDP (PROFINET class B) switch, I recommend you to do it. There are more and more tools and devices coming on the market that can work with this protocol and it can be beneficial to your asset management / maintenance work.

Can I use the ERTEC ASIC as standard Ethernet controller?

YES, The ERTEC 200/400 can be used as standard Ethernet controller with up to 4 ports.

In Wireshark I cannot see the VLAN tag in the PROFINET messages. What is the reason for this?

Probably the Ethernet card and/or driver of your PC filters away the VLAN tag. You have to enable it with the properties in Windows or add some lines in the Registry. You can request a document from us that describes what to add to the Registry.

Do I still require a mirror port on a switch if I monitor a PROFINET network with a ProfiTap?

NO, the ProfiTap has to be placed between the PLC (PNIO controller) and the 1st switch. You save a mirror port and there is no risk that the Laptop/PC sends data on your network, but you have to "break" the cable to insert the ProfiTap and that automatically means a temporarily disturbance. I recommend to insert the ProfiTap during the cabling phase and leave it permanently in the loop.