Logitek is the only approved Competence Center for Profibus and Profinet in Spain. Therefore, we receive questions and queries about Profinet technology and the following text tries to provide some explanations.
Is PROFINET a PROFIBUS over Ethernet?
This is a common query, since Profinet is thought to be a Profibus encapsulated in Ethernet frames. Although initially the International Profibus/Profinet Association thought that this was the right way, they noticed that it was not suitable. In order to achieve the fieldbus requirements in Ethernet, it would be required to start from the bottom up. Certainly some Profibus concepts are used in Profinet, but only the concepts, not the way they are implemented.
Does PROFINET comply with the Ethernet IEEE 802.3 standard?
Yes. Profinet comply with the Ethernet standard at the same time in the three automation fields it represents:
– Profinet TCP/IP: by definition Profinet is compatible with this level
– Profinet Real Time (RT): the TCP/IP stack is skipped to achieve higher speeds, but it complies with the Ethernet standard
– Profinet Isochronous Real-Time (IRT): it holds an Ethernet bandwidth. All these domains comply with the Ethernet IEEE 802.3 standard. One of the initial requirements to define Profinet was precisely the compliance with this standard.
Can an unmanaged switch be used in PROFINET?
Profinet complies with the Ethernet standard, so an unmanaged switch can be used to interconnect Profinet elements. However, being able to do something does not mean that it is advisable. A managed switch provides a valuable diagnostics information that will enable the production line to be on. It is sometimes preferable to spend more money in elements that deliver a high added value.
Is PROFINET a proprietary technology?
Absolutely not; it’s an open standard, IEC 61158, unlike other Ethernet-based fieldbuses. An
yone could develop a Profinet product from the specification. You don’t even have to sign an agreement – which is mandatory with Ethernet/IP. Although the product can be developed from scratch, it is not necessary to do it, since there are companies that sell development tools to make it faster.