Frequently Asked Questions (FAQ)
General Topics/Formalities
All PROFINET components have two associated IDs: A Vendor ID and a Device ID. Device manufacturer must obtain a Vendor ID and define a Device ID before testing since both IDs are included in the device’s GSD file.
Vendor IDs are unique, and therefore managed and assigned by PI to each company. Device manufacturers can obtain their PROFINET Vendor ID at no charge by sending an email to: certification{AT}profibus.com. Vendor IDs are the same for PROFIBUS, PROFINET, and IO-Link. If a device manufacturer already has a Vendor ID for PROFIBUS, there is no need to request a new one for PROFINET.
The Device ID is chosen and managed by the device manufacturer. Each device should have a unique Device ID specifically for the device. The “GSDML Technical Specification for PROFINET” document in the PROFINET Test Bundle contains details about Device ID formatting.
PROFINET and Ethernet are complementing technologies, not competing technologies.
IEEE 802.3 specifies the standards that makeup Ethernet. Ethernet sits on Layer 1 (physical layer) and Layer 2 (data link layer) of the ISO/OSI model. Ethernet frames include information such as the MAC addresses of sender and receiver, virtual LAN (VLAN) tagging, and Quality of Service (QoS). Ethernet is used to connect nodes in a Local Area Network. The physical link between nodes in an Ethernet network can be, for example, a twisted pair cable, or a fiber optic cable. Nowadays, Ethernet is the most common communication medium worldwide; used in homes, enterprises, factories, and in general infrastructure due to its speed, affordability, and versatility.
PROFINET is an Industrial Ethernet solution. It is a communication protocol to exchange data between controllers and devices. Controllers can be PLCs, DCSs, or PACs. Devices can be I/O blocks, vision systems, RFID readers, drives, process instruments, proxies, or even other controllers. PROFINET sits on Layer 7 of the ISO/OSI model since it is an application. It defines cyclic and acyclic communication between components, including diagnostics, functional safety, alarms, and other related information. Also, PROFINET is based on standard Ethernet for its communication medium. High bandwidth, large message size, and versatility are just some of the benefits of having Ethernet on the factory floor.
The development of a PROFINET device or adding a PROFINET interface to an existing device will depend on a number of factors, and there is no ‘one size fits all’ approach.
Therefore, PI offers this comprehensive guideline “PROFINET Field Devices - Recommendations for Design and Implementation”, which discusses all implementation aspects from start to finish:
Any product which employs the PROFINET protocol and is sold in the market as a “PROFINET product” must be certified (IO Controllers, IO Devices, Network components). Passive network components such as PROFINET cables and connectors do not have to be certified, nor software tools such as engineering tools.
No, PROFINET is an open technology. Everybody who is member of PI can download the PROFINET specification and implement PROFINET in both controller and device without paying any license fees.
There are also no license fees necessary for implementing PROFINET into chips like FPGAs or ASICs or any other Ethernet device controller as well as for PROFINET SDK providers. Of course, SDK providers may charge license fees for their PROFINET stack development kits they place on the market for device builders, but the PROFINET technology itself is completely without any licensing.
Tech Topics
Every PROFINET device has a defined set of features which are mandatory based on its conformance class. The conformance classes are divided into three categories, class A, B, and C. Conformance Class A (CC-A) is the most basic while C (CC-C) is the most advanced and it should be noted that they build upon each other, so Class C also contains all functions from Class B and A. For example the simplest “Class A”, provides real time and acyclic real time, as well as support for standard TCP/IP and basic functions such as topology information. CC-B adds in simple network management protocol (SNMP) support to make it possible to read statistics with standard SNMP tools. And finally, for the most demanding applications, there is Conformance Class C which has support for motion control applications with a jitter of less than a microsecond and distributed clock synchronization protocol (allowing deterministic Ethernet).
CC-A and CC-B are also called PROFINET RT (Real-Time), and CC-C is called PROFINET IRT (Isochronous Real-Time). Recently Conformance Class D (CC-D) was defined for PROFINET over TSN.
MAC addresses are used for Ethernet Layer 2 communication. Each Ethernet frame has a source and destination MAC address, globally managed and assigned to be unique for every Ethernet port. PROFINET RT is a Layer 2 protocol, and therefore every port on a PROFINET product has a unique MAC address. In addition, a PROFINET device also has a chassis MAC address. To avoid double MAC addresses, it is recommended to increment the MAC address by one for each port.
PROFINET RT itself is an Ethernet Layer 2 protocol and therefore based on MAC addresses, not IP addresses. However, PROFINET devices typically also have an IP address for non-real time acyclic data exchange or other services (OPC UA, HTTP, SNMP, etc.).
EtherType is a two-octet field in an Ethernet frame. It is used to indicate which protocol is encapsulated in the payload of the frame and is used at the receiving end by the data link layer to determine how the payload is processed. The same field is also used to indicate the size of some Ethernet frames.
Many EtherTypes are assigned by the IEEE Registration Authority. IANA (Internet Assigned Numbers Authority) has a comprehensive list of EtherTypes published.
The PROFINET protocol uses the EtherType 0x8892. An arriving PROFINET Real-Time Ethernet frame uses EtherType 0x8892 so the frame is directed to the PROFINET application. This avoids the variable time it takes to be processed through the TCP/IP layers, thus improving both speed and determinism.
APL is a new Ethernet physical Layer. The goal of APL is to bring Ethernet down to field level instruments in hazardous areas. Ethernet at the field level will make digitalization for process industries a reality. Ethernet adds its universality and speed to existing field device installations.
APL will limit current and voltage in the physical Layer to have an intrinsically safe solution for Zones 0 & 1 / Div 1. The physical connection will be a rugged two-wire connection with power over this cable. Finally, APL will exceed the 100 m limit of 100BASE-TX Ethernet networks to be suitable for large process manufacturing facilities.
As of today, you cannot land a standard PROFINET cable directly on an instrument that is located in a hazardous environment, where a spark might cause an explosion. This is not a limitation of PROFINET but of its physical layer: standard Ethernet. For connections such as these, users have employed PROFIBUS PA connectivity via Proxies for a long time. With the introduction of APL, PROFINET can finally reach field devices located in hazardous environments.
APL only changes the physical layer –Layer 1 of the 7-layer ISO/OSI Model. All other layers (e.g., TCP/IP or UDP/IP) remain untouched –including Layer 7 and the PROFINET protocol.
Outlook
Since version 2.4 PROFINET is specified to be used over selected IEEE 802.1/802.3 base mechanisms to utilize Time Sensitive Networks.
This offers benefits like Gigabit speed, standard-ethernet chipsets and a converged network carrying IT and OT traffic at the same time without mutual influence.
The market availability of PROFINET TSN products depends on the product planning of technology suppliers and product vendors.
PI is supporting device development by their Embedded Test System (ETS), which is implementing PROFINET TSN tests in the latest test bundles.
PROFINET is the best choice for deterministic and robust communication between controllers and various field devices.
OPC UA is agreed to be the best choice for “field to cloud” and “controller to controller” communication.
Thanks to the use of standard Ethernet, PROFINET and OPC UA can be used in the same converged network.
Either independent or combined, PROFINET and OPC UA is the best combination of both worlds.
Test System / Test Process
With the switch from Test Bundle 2.42 to Test Bundle 2.43.1, the first mandatory test cases were adapted to the new hardware "ETS" (Embedded Test System). When setting up the ART (Automated RT-Tester) project, you can now also create an "ETS device test project" in which these migrated test cases are located. So these test cases are not missing in Test Bundle 2.43.1 but have just been moved from the "device test project".
For the PROFINET certification the customer has to deliver a GSDML, which must be based on one of the the latest 3 GSDML versions. Thus the Automated RT Tester (ART Tester) only allows to import such GSDML files. There are different rules for the PROFIsafe certification, which allow to test only the PROFIsafe part (in case the PROFINET part is unchanged). So it is possible to import a GSDML with version V2.32 and newer having PROFIsafe submodules inside. For devices with a GSDML version V2.32 and newer but older than the latest 3 GSDML version, only the PROFIsafe test cases are displayed.
Right now we are in a transistion phase from the different test setups (like standard test setup), using different additional neighborhood devices, to the Embedded Test System setup (ETS setup). With the ETS setup, only the ETS hardware is needed, which is simulating the neighborhood devices. With this approach, the test cases run more efficently and the test coverage could be increased. As all new test cases are only developed on the ETS and all existing test cases will be migrated to ETS (step-by-step), the existing hardware cannot be used anymore.
Lead times in the test lab depend on lab availability and vary from ‘immediately’ to several weeks out. Device manufacturers can obtain the current lead time by contacting the testlab directly.
The PROFINET Trial Bundle provides the latest state of all available test cases (including bug fixes) in a separate bundle. It is released on a quarterly base and enables quality for both the product and the test system already during the development. It is not used for the official certification at the PI testlab but a rewarding look into the future, e.g. for TSN.