Profinet

Key takeaways

Profinet belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Profinet to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Profinet from memory before moving on to harder problems.

Reference excerpt

Profinet (usually styled as PROFINET, as a portmanteau for Process Field Network) is an industry technical standard for data communication over Industrial Ethernet, designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data under tight time constraints. The standard is maintained and supported by Profibus & Profinet International, an umbrella organization headquartered in Karlsruhe, Germany.

Functionalities

Overview Profinet implements the interfacing to peripherals. It defines the communication with field connected peripheral devices. Its basis is a cascading real-time concept. Profinet defines the entire data exchange between controllers (called "IO-Controllers") and the devices (called "IO-Devices"), as well as parameter setting and diagnosis. IO-Controllers are typically a PLC, DCS, or IPC; whereas IO-Devices can be varied: I/O blocks, drives, sensors, or actuators. The Profinet protocol is designed for the fast data exchange between Ethernet-based field devices and follows the provider-consumer model. Field devices in a subordinate Profibus line can be integrated in the Profinet system seamlessly via an IO-Proxy (representative of a subordinate bus system).

Conformance Classes (CC) Applications with Profinet can be divided according to the international standard IEC 61784-2 into four conformance classes:

In Conformance Class A (CC-A), only the devices are certified. A manufacturer certificate is sufficient for the network infrastructure. This is why structured cabling or a wireless local area network for mobile subscribers can also be used. Typical applications can be found in infrastructure (e.g. motorway or railway tunnels) or in building automation. Conformance Class B (CC-B) stipulates that the network infrastructure also includes certified products and is structured according to the guidelines of Profinet. Shielded cables increase robustness and switches with management functions facilitate network diagnostics and allow the network topology to be captured as desired for controlling a production line or machine. Process automation requires increased availability, which can be achieved through media and system redundancy. For a device to adhere to Conformance Class B, it must communicate successfully via Profinet and support SNMP. With Conformance Class C (CC-C), positioning systems can be implemented with additional bandwidth reservation and application synchronization. Conformance Class C devices additionally communicate via Profinet IRT. For Conformance Class D (CC-D), Profinet is used via Time-Sensitive Networking (TSN). The same functions can be achieved as with CC-C. In contrast to CC-A and CC-B, the complete communication (cyclic and acyclic) between controller and device takes place on Ethernet layer 2. The Remote Service Interface (RSI) was introduced for this purpose.

Device types A Profinet system consists of the following devices:

The IO-Controller, which controls the automation task. The IO-Device, which is a field device, monitored and controlled by an IO-Controller. An IO-Device may consist of several modules and sub-modules. The IO-Supervisor is software typically based on a PC for setting parameters and diagnosing individual IO-Devices.

System structure A minimal Profinet IO-System consists of at least one IO-Controller that controls one or more IO-Devices. In addition, one or more IO-Supervisors can optionally be switched on temporarily for the engineering of the IO-Devices if required. If two IO-Systems are in the same IP network, the IO-Controllers can also share an input signal as shared input, in which they have read access to the same submodule in an IO-Device. This simplifies the combination of a PLC with a separate safety controller or motion control. Likewise, an entire IO-Device can be shared as a shared device, in which individual submodules of an IO-Device are assigned to different IO-Controllers. Each automation device with an Ethernet interface can simultaneously fulfill the functionality of an IO-Controller and an IO-Device. If a controller for a partner controller acts as an IO-Device and simultaneously controls its periphery as an IO-Controller, the tasks between controllers can be coordinated without additional devices.

Relations An Application Relation (AR) is established between an IO-Controller and an IO-Device. These ARs are used to define Communication Relations (CR) with different characteristics for the transfer of parameters, cyclic exchange of data and handling of alarms.

Engineering The project engineering of an IO system is nearly identical to the Profibus in terms of "look and feel":

The properties of an IO-Device are described by the device manufacturer in a GSD file (General Station Description). The language used for this is GSDML (GSD Markup Language) - an XML-based language. The GSD file serves an engineering environment as a basis for planning the configuration of a Profinet IO system. All Profinet field devices determine their neighbors. This means that field devices can be exchanged in the event of a fault without additional tools and prior knowledge. By reading out this information, the plant topology can be displayed graphically for better clarity. The engineering can be supported by tools such as PROFINET Commander or PRONETA.

Dependability Profinet is also increasingly being used in critical applications. There is always a risk that the required functions cannot be fulfilled. This risk can be reduced by specific measures as identified by a dependability analyses. The following objectives are in the foreground:

Safety: Ensuring functional safety. The system should go into a safe state in the event of a fault. Availability: Increasing the availability. In the event of a fault, the system should still be able to perform the minimum required function. Security: Information security is to ensure the integrity of the system. These goals can interfere with or complement each other.

Functional safety: Profisafe

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Profinet

Start with the simplest possible case. Write down what Profinet claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Profinet before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Profinet ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Profinet

In research: Profinet appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Profinet in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Profinet is common in secondary-school and first-year university syllabi. It links to neighbouring topics Industrial Ethernet, so understanding it makes those chapters shorter.
In everyday life: Look for Profinet outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Profinet in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Profinet means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Profinet out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Profinet in simple terms?

Profinet (usually styled as PROFINET, as a portmanteau for Process Field Network) is an industry technical standard for data communication over Industrial Ethernet, designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data unde…

Why does Profinet matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Profinet?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Profinet.