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IO Communication

IO Communication

Lively and open standard

PI's technologies are now proven. For decades, PI’s technologies have provided reliable and high-performance IO communication with a wide range of profiles for application-specific tasks, perfect IO-Link integration and the most comprehensive  diagnostics. Technologies from PI meet the real-time requirements of all sectors of industrial automation and they are also very powerful with regard to the data volumes to be transmitted as well.


But the "total package" is decisive. In practice equally important is the functioning of the infrastructure and associated ecosystem. This includes many details, such as how plugs or cables are to be installed, guidelines for the construction and acceptance of robust networks, or the handling of security requirements.


Users and equipment manufacturers are supported in all these measures by numerous suppliers of basic technology components and the globally networked organization of test labs, competence centers, training centers for technical support Regional PI Associations (RPAs) and marketing working groups in promotional activities. PROFINET users can therefore rely not only on a practical and proven technology, but also on the fact that help is provided when getting started or when expanding.


The world of automation does not stand still

Technologies must remain alive and be developed further in an agile manner. PI's technologies have always been adapted to new challenges in automation and communication. Only those who face up to and meet new requirements, which are now coming particularly through the implementation of Industrie 4.0 applications and digitization, are future-proof.


In summary, this means

  • continuous access to extended data in the field
  • object modeling
  • openness to new basic technologies
  • maintaining fast and robust IO communication.


Compatible and open systems are the future drivers of Industrie 4.0

The issue of compatibility is a decisive factor in terms of future development. New developments and additions are based on today's proven technology. The modular and open architecture of PI’s technologies set up 20 years ago enables a seamless integration of new technologies such as Time Senstive Networking (TSN), OPC UA and Advanced Physical Layer (APL).

Open TCP/IP access has always been part of PROFINET technology and will become increasingly important in the future.  Clearly traceable processes during development ensure that lasting and reliable solutions are created.

Incidentally, this further development always takes place in close cooperation with the large PI community, which contributes its practical experience.


Standardization is the foundation for Industrie 4.0 applications

PROFINET and the Industrial Internet of Things (IIoT): Openness

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Openness for TCP/IP is the basis for a wide range of applications

The latest figures for devices brought to market speak for themselves:

For example, PROFINET set a new record with 6.4 million devices installed in 2019. This corresponds to an annual growth rate of 25% and gives a total number of 32.4 million.

What is interesting here is the wide range of applications - PI technologies are at home in all industries. What is often overlooked is that the foundations for today's success were laid decades ago.

This includes the use of Ethernet standards, the consistent decision for modular solutions or the openness for TCP/IP, or other IT protocols.


The advantage of the PROFINET architecture is that TCP/IP is independent and parallel to IO communication. No additional hardware is required. Moreover, this approach works even in the event of failure or problems in the controller and it does not require any computing power in a controller. For example, it is easy to integrate additional edge gateways for data acquisition next to the controller or devices with other protocols, directly into the network.

Firmware architecture for a TCP IP
Pic. 1: Basic firmware architecture for a TCP IP integration

Diagnostic data easily obtained

Industrie 4.0 is based on a wide range of information from the field of production facilities. In addition to the control of automated production and equipment, this information is increasingly required for remote maintenance, asset management, predictive maintenance, condition monitoring, and data analytics for optimizing and making production more flexible.

A diagnostic message is first transmitted to the control system when it occurs and is acknowledged by an alarm mechanism. Detailed information can be requested from the controller for display in an HMI or from other participants, such as maintenance stations in the network.


Diagnosis alarm principle
Pic. 2: Alarm and acyclic reading of diagnostic information and reaction in the control system.

Alarm and acyclic reading of diagnostic information enables reaction in the control system. However, superimposed systems can also collect this information independently.


Another example:

At times it is necessary to centrally record the firmware and hardware version of a device used throughout the plant for an update. Both are typical diagnostic tasks that do not sound particularly complex at first glance. In practice, however, it is a challenge to prepare this information in such a way that it can be used in practice.


Without the work of PI, this information would not be available to users at all or only to a limited extent.


Determinism and speed included in the design

Real-time and TCP/IP data coexist plainly in a PROFINET network. Appropriate mechanisms are used to ensure scalability according to requirements. With RT, real-time data in PROFINET is given priority over TCP/IP data by means of prioritization. As a result, bus cycle times in the range of a few milliseconds can be achieved. With Isochronous Real-Time (IRT), in which networks and applications are synchronized with an accuracy of one microsecond, IO communication is precisely planned. IRT is therefore particularly suitable for networks with high requirements, such as those required in printing presses, where a large number of drives must run synchronously with high precision. This enables cycle times of 31.25 microseconds. These mechanisms are now also used for Time Sensitive Networking (TSN) (see PROFINET over TSN)

Distribution of network traffic between IO data and TCP/IPRealtime
Pic. 3: Distribution of network traffic between IO data and TCP/IPRealtime

Customer benefit: Openness and cross-vendor data modelling

To ensure openness and vendor independence, the topic of standardization is necessary, but also complex, since experts from different companies must work together. To support efficiency, clear, open and comprehensible processes form the necessary basis. This applies not only to communication systems such as PROFINET, but also to user profiles such as PROFIsafe, PROFIenergy, or PROFIdrive, which have been used successfully for many years.


PI is responsible for coordinating the many different tasks, otherwise each device manufacturer would have to specify in detail (including documentation) which data which user may access and how this data is displayed. In turn, the user would have to integrate this specifically for each of his devices. This would be far too complex in detail.


Thanks to PI, there is virtually a standard solution and the programmer of the device to be integrated is relieved. The same applies to the start-up of a system. Here the user does not have to worry about parameterization or when a particular device is switched on. The user can also put aspects such as isochronousness, redundancy and fast start-up into the hands of PI with peace of mind. The device manufacturer simply uses the technology packages provided.


For the simple solution of specific requirements or use-cases, a number of different optional features are available, e.g:


  • Shared Device / Shared Input: Access from different controllers to the same device


      o  Parallel reading of inputs saves copying routines between controllers
      o  Connection of safety and standard controllers


  • Fast Start-up: Fast run-up of a device for tool change on robots
  • Various redundancy mechanisms
  • Various media


Integration made easy throughout

PI takes care of the smooth workflow and interfaces between standardization bodies, security experts and IT professionals, providers of basic technologies, equipment manufacturers, OEMs and users. This also leads to stronger cooperation, for example with the OPC Foundation, eCl@ss, Fieldcomm Group, AIDA or Namur.

An important focus here is on developing migration strategies so that previous investments remain protected.


In other words: PI has an eye for the big picture and takes up suggestions from the community. New topics can thus be implemented more quickly in a large market.

To top

Topology acquisition and display

During the planning phase, but also when setting up a plant or machine, numerous changes or adjustments are made. Of course, the changes should be transferred directly into the existing plant documentation. In reality, this usually works only insufficiently. Such inconsistencies can run through the entire life cycle of a plant. Finally when maintenance or repairs cannot be carried out as planned because the wrong spare part has been ordered, everyone will probably wish for simpler and more reliable documentation.


The asset identification feature of PROFINET already offers a wide range of support, allowing the plant topology to be recorded and devices, modules, and submodules to be identified automatically.


Asset management

All relevant information can be accessed easily and quickly - completely independent of the manufacturer and independent of the status and function of the control system. This is particularly interesting for asset management information, i.e. which devices are installed, which version is involved and in what state they are available. It is the basis for more extensive diagnostic functions, maintenance plans, or availability statements.

With the introduction of a service for asset recording (mapped to the Asset Management Record (AMR)), the existing services for Identification & Maintenance (I&M) are being supplemented. This enables automated site-wide asset management, even of components that were not modeled via PROFINET.



Simple and fast diagnostic mechanisms improve the availability of machines and systems and are therefore the basis for high productivity. The consistent diagnostics of PROFINET make it possible to obtain an overview of the status of a machine or system in a very short time.
Accordingly, there is now a whole range of tools and devices that collect a general overview as well as detailed diagnostics for commissioning, ongoing operation or in the event, of a fault and prepare them in a userfriendly manner. A large number of error possibilities are standardized (e.g. short circuit), so that the same message is sent to the user for the same error, regardless of the manufacturer. In addition, there are device- or manufacturer-specific errors which are explained by the General Station Description (GSD) file with text in localized languages.

OPC UA, Time sensitive Networking (TSN) or Field Device Integration (FDI) also offer interesting possibilities to getimportant information better and faster. However, these technologies alone cannot provide the data. But the more than 30 million devices in the field that have a PROFINET interface can.

Now it is important to bring these two worlds together and this is what PI has given itself the task of doing. For this reason, the data is mapped into an OPC UA data model using the OPC UA Companion Specification for PROFINET.
Due to the openness of PROFINET, additional sensors with OPC UA interface can be added, which send their values directly to corresponding cloud services or edge gateways without having to laboriously rebuild the automation solution.


Isochronicity for Motion Control

The synchronization (working clock) of an Isochronous Real-Time (IRT) network is the basis for the synchronization of the internal processes in devices. Thus, the inputs of all distributed devices can be recorded synchronously and processed in a control system. This also includes the synchronous output in motion controldrives and other devices.



A great advantage of PI technologies is the scalable redundancy in order to obtain a suitable solution for the respective requirement, depending on the effort, costs, or desired availability.

PROFINET offers two media redundancy solutions:

Media Redundancy Protocol (MRP) & Media Redundancy for Planned Duplication (MRPD).


  • MRP is the basic redundancy protocol for PROFINET and must be applied when operating PROFINET network ring structures. MRP is sufficient for standard real-time communication in PROFINET.
  • MRPD is additionally requiredif fast PROFINET IRT control data is transmitted.


System redundancy also plays a role, for example, where two controllers have access to one device (S2) or where there are duplicate interfaces to two different controllers (R1). A combination of media and system redundancy is also possible, which might be required in process automation or infrastructure projects.

Integration of IO-Link

IO-Link enables data to be exchanged between an IO-Link device (sensors and actuators) and an IO-Link master (IO module or controller). Entirely in line with Industrie 4.0, this makes data available from all levels of machines and systems down to the sensor/actuator level - the potential for completely new and better machine functions.


In the configuration of the automation system or the fieldbus, the IO-Link system is represented by the IO-Link master and integrated by the corresponding device description. The IO-Link master itself can be a fieldbus subscriber or part of a modular IO system connected to the fieldbus. In both cases, the device description of the IO-Link master describes the number of ports, the address range and the module properties.



Application profiles take into account application-specific features and allow a higher level of standardization. Numerous application profiles round out the portfolio, such as PROFIsafe, PROFIenergy, PROFIdrive or Process Control Devices. Application profiles enable the manufacturer-independent exchange of data and information from production.



Here you can find several frequently asked questions:


PI organizes numerous seminars and workshops that are dedicated to a wide range of topics related to PROFINET technology. The workshops are aimed at users or developers and are an ideal opportunity to find out about the latest developments and make new contacts.

In addition, more than 60 PI Competence Centers in 30 countries are available to answer questions as contact persons. Thanks to this global network, it is possible to access expert support anytime and anywhere. The Competence Centers are also available to first-time developers of PROFINET devices and systems with advice and practical support.

Thanks to the unique community, a large number of technology manufacturers are available. They offer assistance with planning, integration and FW-HW packages.

There are different solutions depending on the platform. The decisive factor is that there is not just one solution. For this, optimal adaptation to your own device design is possible. Here you can find further information: Implementation of PROFINET

Technologies are constantly evolving. Therefore, we are also working on a continuous expansion of functionality. PI supports users in this way, always taking their requirements into account. In addition, the specification is supplemented by the experience and feedback from device manufacturers.

The more users and manufacturers read and implement a standard, the more such a specification grows. At the same time, however, the technology becomes more secure and robust, since PI keeps an eye on compatibility with existing technology.

Important to know: This further development process is always communicated openly and clearly to everyone. There is no hidden information or own interpretations. This openness is the DNA of PI. Once the annual update is published, every user can adopt it. It is a procedure that has proven itself for decades.

PI provides a detailed document that guides device manufacturers step-by-step through the procedure to obtain a certificate for a PROFINET device. The document contains many tips for successful preparation for the certification test as well as a description of the procedure for branding and handling device variants. The document is always kept up to date by the responsible departments at PI.

TSN alone will never be able to replace PROFINET because it is a basic technology on which communication protocols are based.

For detailed information see also the FAQs of PROFINET over TSN.

PROFINET Specification

Learn more about the application layer service characteristics and the protocols, which provide a set of rules for communication in a decentralized periphery.

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PROFINET Technology

The leading Industrial Ethernet Standard in the market uniquely combines the highest performance with the highest degree of openness.

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PROFINET Implementation

To familiarize yourself with PROFINET, you can take advantage of acomprehensive collection of tips here.

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