Myth 3: PROFINET requires a proprietary chip.
Reality: A standard Ethernet controller chip can be used for PROFINET, even for real-time data. Just add a PROFINET stack (the software that knows how 
to direct the PROFINET message as well as the TCP/IP traffic). In order to achieve motion control, PROFINET does require that the stack be implemented in silicon; that is, in a chip. Otherwise the required speed cannot be achieved. However, the chip is not proprietary. Proprietary means “owned by a company.” That is not the case here; in fact, PROFINET chips are available from dozens of companies. (And many of these same chip companies have implemented all the major Industrial Ethernets in their chips.) Just because you do not need a chip, does not mean you should avoid using one. You can use a chip even for non-motion applications. Looking back at the success of PROFIBUS, PROFIBUS is almost always implemented in a chip. You could use a separate RS485 chip and implement PROFIBUS in software, but that is rarely done. By having the communications processing in its own chip, the main processor for the device is free to handle its main purpose, whether that is simple IO blocks or complex devices like vision systems.
Myth 4: PROFINET does not use standard Ethernet.
Reality: If you examine a PROFINET frame on an Ethernet line using a sniffer like Wireshark, you can see that PROFINET is in an IEEE802.3-standard Ethernet frame. All the Ethernet header and trailer fields are there, and it is carrying the PROFINET data.
Myth 5: PROFINET is not an open technology.
Reality: Anyone can buy the PROFINET standard from the IEC and implement PROFINET in their device on their own. This is in contrast to EtherNet/IP which requires that a contract be signed with ODVA, the organization that controls EtherNet/IP. This is also in contrast to EtherCAT where the technology is owned by a single company which receives a royalty for every node. Of course, although you can develop PROFINET from scratch there is little reason to do so; there are dozens of companies that have already created PROFINET stacks, chips, and modules. Using one of them greatly accelerates the development process.
Myth 6: PROFINET is owned by Siemens.
Reality: PROFINET was created and is owned by PI (PROFIBUS and PROFINET International), an international trade organization with over 1400 members. PROFINET has been adopted by Siemens as their sole backbone Industrial Ethernet, but GE Intelligent Platforms and Phoenix Contact have also adopted PROFINET as their sole Industrial Ethernet backbone. Almost every other controller manufacturer has PROFINET as one of their Industrial Ethernet choices.
–Carl Henning
More PROFINET realities: Slide set description of PROFINET