PROFINET, Industrial Ethernet for advanced manufacturing

PROFINET is the world’s most advanced Industrial Ethernet solution for the networking of production assets (sensors, actuators, sub-systems and production units) and equipment such as PLCs, DCS and enterprise-wide IT systems.
PROFINET is fully compatible with – and leverages all the features of – office Ethernet. However there are differences, notably that office Ethernet is not capable of the real time performance required of industrial automation. Office Ethernet is also much less able to withstand harsh industrial environments.

Based on its experiences with PROFIBUS, a real time fieldbus that is the most popular automation networking solution in automation today, PI Working Groups comprising more than 500 experts from major automation suppliers spent many man years creating a comprehensive real time Ethernet solution for automation.

This solution is able to operate in the difficult environments of industry and is capable of delivering the speed and precision required by manufacturing plants. It can also provide additional functions – for example Safety, Energy Management and IT Integration. These can be used in combination with the control and monitoring functions. Which services to use, and how they are utilized, are up to you the users.

Here are some other advantages of working with PROFINET at the IO level:

• Highly scalable architectures.
• Access to field devices over the network.
• Maintenance and servicing from anywhere (even over the internet).
• Lower costs for production/quality data monitoring.

Recommended Reading: PROFINET Brochure (6 pages), PROFINET System Description (52 pages)

PROFINET copes with the conflicting demands of IT and plant floor automation using three communications services:

• Standard TCP/IP: This is used for non-deterministic functions such as parametrization, video/audio transmissions and data transfer to higher level IT systems.
• Real Time (PROFINET RT): Here the TCP/IP layers are bypassed in order to give deterministic performance for automation applications in the 1-10mS range. This represents a software-based solution suitable for typical I/O applications, including motion control and high performance requirements.
• Isochronous Real Time (PROFINET IRT): Here, signal prioritization and scheduled switching deliver high precision synchronization for applications such as motion control. Cycle rates in the sub-millisecond range are possible, with jitter in the sub-microsecond range. This service requires hardware support in the form of (readily-available) ASICs.

All three services can be used simultaneously. Bandwidth sharing ensures that at least 50% of every I/O cycle remains available for TCP/IP communications, whatever other functionality is being supported. Combined with ruggedized cabling, connectors and Ethernet switches, this means that PROFINET can meet all the needs of automation. Further below you can read about PROFINET’s features, which make it the world’s most advanced Industrial Ethernet.

It’s important to understand that PROFINET is fully compliant with internationally-accepted Ethernet standards. So are other popular Industrial Ethernet’s of course, although individual approaches to the challenges of automation differ. Some Industrial Ethernets break Ethernet conventions and are not truly compatible with office-based systems. These cannot interoperate as easily within enterprise architectures, or indeed alongside those Industrial Ethernets which are fully compliant.

As experience with fieldbus grew, users realized that tighter integration with IT would become more and more important. Fieldbus systems can be integrated into plant networking hierarchies using gateways and other devices but that approach can be cumbersome and expensive.

Users wondered if office networking technologies – i.e. Ethernet – could be brought onto the plant floor. The ideal scenario, they argued, was for automation systems themselves to be based on Ethernet.

Actually, Ethernet has been used on the factory floor almost as long as it has been used in the office, though mainly for inter-cell communications and not for IO. There has never been a standardized way to implement it however so installations have tended to be proprietary. In addition, there are practical difficulties, including:

• Office Ethernet cannot deliver the real time responses needed for industrial IO.
• Office Ethernet cannot meet the high precision determinism needed for advanced motion control.
• Office Ethernet is unable to withstand the physical conditions found in manufacturing i.e. dusty, hot, humid or corrosive environments, or environments subject to strong electromagnetic interference.

Fortunately, all these difficulties can be overcome, leading to what we now know as ‘Industrial Ethernet’.

Fieldbus is a digital industrial networking technology for transporting data between control devices (such as a PLC or DCS) and field devices (such as I/O, drives, actuators and transmitters) for the purposes of controlling production lines and equipment.

By improving communications between these devices, fieldbus facilitates significant improvements in the way plants are controlled, monitored and managed in both process and factory automation environments.

The advantages of fieldbus include its ability to connect multiple devices over a single cable or ‘bus’. This factor alone – experience has shown – can cut design, engineering, commissioning and maintenance costs by up to 40%. The greater accuracy of ‘digital’ also means big improvements in production speeds and quality, while better diagnostics allow fieldbus-connected production lines to benefit from advanced asset management techniques. Fieldbus can also deliver the real-time performance demanded by automation today.

PROFIBUS, the world’s most widely used fieldbus, was introduced in 1989 and is standardized under IEC61158. It is supported by more than 1400 equipment vendors around the world. The single standardized approach means users have a wide choice of vendors and products, factors that encourage higher performance and lower costs. A fieldbus-enabled plant also delivers more and better data to supervisory systems, to support improved management strategies across the enterprise.

The vast field experience gained from PROFIBUS is embedded deeply in the PROFINET solutions available today.

RECOMMENDED READING: Why Use a Fieldbus? White Paper.

Because PROFINET is fully compatible with office Ethernet, it can reside (and be fully operational) on a single network cable alongside other Industrial Ethernet’s that are also based on standard Ethernet. There are several of these, including EtherNet/IP and Modbus/TCP.

However, ‘coexistence’ does not mean different systems are ‘interoperable’. It means only that it is possible to use the same network infrastructure to support multiple Industrial Ethernets. Protocol differences mean that Industrial Ethernets cannot communicate with each other except by using additional hardware such as protocol converters.

It’s also important to recognize that some Industrial Ethernets do not conform with the international Ethernet standard and that these require deployment on a closed network. Although these are not necessarily ‘proprietary’, they are non-standard from an Ethernet point of view.

RECOMMENDED READING: the PROFINET and IT White Paper is the definitive source.

PROFINET was developed by PI Working Groups involving over 500 engineers from major automation vendors. Their vast field experience with PROFIBUS was usedas the starting point. Ethernet’s particular attributes were then selectively incorporated to meet the specific needs of automation.

PROFINET delivers a rich set of specialist features that sit on top of other communications.

They are aimed at automation applications of all types and designed to make life easier for the designer, engineer, maintenance staff and manager. You don’t have to use all functions at once – just choose what you need to meet your particular circumstances.

Think of PROFINET as a modular solution, offering the flexibility to start simple and add functionality as required.

PROFINET treats I/O very much like PROFIBUS does.  An engineering tool is associated with the controller and obtains information about the IO Devices from a GSD file just like PROFIBUS does.  After a project is configured in the software, it is downloaded to the controller.  The controller can then communicate with the I/O Devices.  The I/O Devices are structured hierarchically as Device, Module, and Channel.  Inputs and Outputs are exchanged between the controller and I/O Device as ‘cyclic’ data.  The controller sets the update cycle time.  Additional information such as diagnostic data that is not required as frequently is communicated as ‘acyclic’ data.

Additional details of I/O functionality are available in Section 2 of the PROFINET System Description Technology and Application.

PI is active in helping standardize wireless networking solutions for industrial applications in both Process and Factory Automation arenas.

Across the Enterpise

For enterprise applications, PI promotes WLAN (IEEE802.11.1,b, g and n) because these are proven and well-understood. WLAN is based on Ethernet-oriented principles and therefore affords simple interfacing with PROFINET by means of wireless access points.

In Process Automation

PI is a primary supporter of the WirelessHART protocol (based on IEEE802.15.4). A standard adapter interface for WirelessHART has been agreed by PI in conjunction with other process automation organizations including HART Communication Foundation and Fieldbus Foundation, so users benefit from a single technology offer from vendors.

In Discrete Automation

Factory Automation differs from process in many respects. For example, bandwidth requirements are greater and network resilience, security and redundancy are critical. As with the enterprise, WLAN solutions based on IEEE802.11a, b, g and n are already used in factory situations.

In addition, a set of standards is currently being developed by PI Working Groups for sensor/actuator communications in conjunction with both PROFIBUS and PROFINET. Bluetooth (IEEE802.15.1) has been selected as the communications medium, complemented by IO-Link as the interface to end devices.

RECOMMENDED WEBINAR: Industrial Wireless Networking

PROFINET offers an unprecedented level of diagnostics capability, both locally and remotely using standardized displays.

Diagnostic overviews provide levels of detail according to your needs, showing device, module, channel and interrupt activity. Current fault events can be acknowledged and PROFINET’s I&M (Identification and Maintenance) functions are facilitated at the same time.

Comprehensible naming conventions mean you don’t have to look up obscure tag names or numbers before getting down to business. Even topology layouts showing the geography of your plant network become possible with PROFINET.

Integrated web servers are incorporated in automation devices and these mean that a standard Internet browser (such as Explorer or Firefox) can be used to access diagnostic displays. It also means that engineers don’t necessarily have to be on site in order to diagnose a fault as access to plant networks can easily be facilitated over an intranet or even the internet. Automated, event-driven messages can be dispatched by SMS or e-mail to your engineering staff.

Cable diagnostics are just as simple. Again, displays are standardized to give accurate topology views of the network for fast location of faults. Standard Ethernet tools such as SNMP and Ethereal can be utilized. There’s also easy access to vendor-specific tools for complex devices using the Tool Calling Interface (TCI), which ensures accurate data sharing with PROFINET.

Our webinar Diagnostics for PROFINET and other Industrial Ethernets provides additional details. For an introduction to detailed PROFINET diagnostics (that are very similar to PROFIBUS’) see the white paper PROFINET IO Device Diagnostics – an Overview.

PROFINET is fully compatible with standard Ethernet and so can provide classic TCP/IP performance whenever required. That means it is easily scaled to match the needs of almost any size of production facility.

It also means that PROFINET networks are easily integrated with existing Ethernet networks such as higher level enterprise systems including MES and ERP (Manufacturing Execution Systems and Enterprise Resource Planning). Within reason, and working within your own security and management strategies, it is possible for PROFINET to reach across the enterprise. See the MES and PROFINET White Paper for more detail.

With PROFINET, production data can be made available to supervisory staff in real time from almost anywhere in the enterprise. This can provide better management of plant, skills and assets and lead to improved production scheduling and order processing.

And, because PROFINET makes use of standard Ethernet tools such as web browsers, no special equipment is needed. PROFINET can even deliver full Internet connectivity, enabling global enterprises to operate more efficiently across the globe.

Click to enlarge

PROFIenergy offers a completely new way of saving energy in automation systems. With PROFIenergy, automation controllers on a PROFINET network determine when end devices are switched into ‘sleep’ or OFF modes to save on energy usage during:

1. Expected short breaks – e.g. lunchtime and shift changes
2. Planned longer breaks – e.g. nights and weekends
3. Unplanned pauses – e.g. breakdowns, maintenance and upgrades

By defining a standardized open profile PI has made it possible for vendors and users to collaborate on intelligent energy management strategies using PROFIenergy.  A study was performed by the University of Cologne, the results of which quantify the savings potential, and are described in this PROFIenergy White Paper.

User Benefits

• Energy and cost savings
• Fulfill laws / regulations for environmental protection

OEM Benefits

• Easy to program – using loadable function blocks
• Competitive Advantage

Device Maker Benefits

• Unique Selling Proposition and Competitive Advantage
• Builds on existing PROFINET protocol

PROFINET transmits standardized PROFIenergy commands to end devices and receives back status information and energy consumption data. It does this using the acyclic slots of the PROFINET communications protocol and so does not interfere with normal PROFINET processes. PROFIenergy can therefore be fully integrated into existing automation architectures.

PROFIenergy can be used to balance energy demand and match peak load conditions, enabling expensive cost penalties to be avoided.

RECOMMENDED READING: As an introduction, it is best to start with the PROFIenergy brochure. Also there is a White Paper – The PROFIenergy Profile which deals with the background. A White Paper called Assessing PROFIenergy’s Potential reports on a real-world project that quantifies the energy saving possibilities of PROFIenergy. And finally, you can view a PROFIenergy webinar if you choose.

PROFINET’S Fast Start Up (FSU) feature makes it possible for an IO Device to go instantly into a ‘power on’ state in response to signals from an IO Controller. Such functionality is a high priority for industrial robots with Automatic Tool Change (ATC) since it can increase the flexibility of production lines as well as reduce the number of robots per cell.

In car body production, the total cycle time for a single robot cell can be as low as 45 seconds, including the delay for tool change. Many Industrial Ethernets suffer from slow start up, typically in the range of seconds compared with 100mS for fieldbuses, and this can be too slow for many production needs. By optimizing the PROFINET protocol and how data is utilized by end devices it is possible to reduce start up times dramatically.

PROFINET FSU defines the time between ‘power on’ and receipt of the first cyclic input data to be less than 500 ms. The protocol optimizations needed to achieve this are standardized in the PROFINET specification as follows:

• Use of fixed transmission parameters (only for copper wires), instead of automatic detection, which reduces start up by up to three seconds.
• The network address is not passed to the IO device on every cycle, but only at first start up. Parameters are stored in the IO device memory and re-used. This may save several seconds.
• IO Devices announce their readiness to establish communication instead of waiting for the IO Controller to search. It is possible to save up to one second this way.

From the OEM/end user point of view, a number of other optimizations are possible. For example, start-up can also be reduced through the use of suitable hardware. Wireless may also help, either through keeping communication up all the time or by establishing communication in advance of ‘power on’. However, wireless requires additional planning effort and care.

The openness of Ethernet guarantees easy access from anywhere in the world using readily available tools such as web browsers. This great advantage has implications for the security of networks across the enterprise.

PROFINET addresses these sometimes critical security issues in various ways, as defined in a special security specification:

• By guarding against errors and improper operation.
• By preventing unauthorized access that could lead to network manipulation or espionage
• By using proven and certified security standards (e.g. firewalls and VPN)

The integrity of a PROFINET control network can therefore be fully protected, without presenting any restrictions to those personnel who rightfully need access.

RECOMMENDED READING: the PROFINET Security Guideline gives details to the approach taken.

Click to enlarge

PROFIsafe

Safety systems protect equipment, people and the environment. Traditionally, they rely on separately wired circuits that are expensive to build, commission, and maintain.

Adding functional safety to an existing automation network therefore makes sense, because it can mean less engineering effort, reduced cabling, faster commissioning and easier maintenance. Networked safety systems also offer greater flexibility, in that the safety strategy can be easily zoned, partitioned and changed. Innovative safety architectures become possible with new generations of safety devices such as laser scanners.

The challenge is to ensure that the integrity of failsafe signals transmitted between safety devices and a safety controller meet relevant safety standards.

PI’s answer is PROFIsafe, an additional software layer that is used on top of existing PROFIBUS and PROFINET protocols. It works independently of any automation functions even though it is running on the same network. It can be used with either PROFINET or PROFIBUS, in combination if required, in factory and process automation applications.

PROFIsafe has been available since 2001 and nearly 1 million PROFIsafe devices are operational. PROFIsafe is approved for wireless transmission channels such as WLAN and Bluetooth. It can even be used on open Industrial Ethernet backbones.

Please note: Safety is a sensitive area of automation. The dissemination, implementation, and deployment of PROFIsafe technology must be treated seriously. All companies and institutions involved with PROFIsafe conduct themselves according to the PROFIsafe Policy.

More about how PROFIsafe works

• The PROFIsafe profile reduces error probabilities in the data being transmitted between F-devices and F-controllers to the level required by, or better than, relevant safety standards. A series of safety checks is carried out by the PROFIsafe protocol to ensure this.
• PROFIsafe does not have any impact on standard bus protocols and the automation system connected to the same network operates as normal without interference.
• PROFIsafe can be used for safety applications up to SIL3 according to IEC 61508 / IEC 62061, or Category 4 according to EN 954-1, or PL “e” according to ISO 13849-1.
• All F-devices and F-controllers are tested for conformance to the PROFIsafe protocol by PI Test Laboratories and certified by PI for use in the field.

RECOMMENDED READING: To start, please consult the PROFIsafe flyer. The PROFIsafe Environment advises on the development and deployment of F-Devices and F-Hosts and the PROFIsafe System Description is an easily accessible, yet comprehensive description of the PROFIsafe Profile. Finally, you can view a webinar on the topic:  PROFIsafe: Functional Safety over PROFIBUS and PROFINET

A series of White Papers by ARC describe the benefits of using PROFIsafe:

• PROFIsafe: Networked Safety for Process and Factory Automation
• PROFIsafe and PROFIBUS for High Availability and Safety

A number of Application Stories are available that discuss real-world implementations of the technology:

• PROFINET in the Steel Industry
• PROFINET in Automotive Manufacturing
• KUKA Reduces Machine Safety Components by 85% while Increasing Machine Safety

What if you could replace an IO device on a PROFINET network without using a computer?  Surprise, there is no ‘what-if’ here – you can do this now.  And there are no addressing switches to set either.  The network keeps running the whole time, too.

Here are the complete instructions for using this feature:

1. disconnect and remove the defective device
2. replace and reconnect the new device

There are a few caveats: the replacement device has to be the same as the device it’s replacing.  No surprise there; you can’t replace a drive with an IO block.  And since PROFINET uses names, not numbers, the replacement device has to have a blank name (which it will from the factory).

PROFINET by itself can’t deliver direct process connectivity. This is because Ethernet was never designed as a hazardous area network, nor does it have the ability to feed significant amounts of power to field devices like pressure transmitters. That’s what IEC 61158-2 is all about and conforming fieldbuses like PROFIBUS PA remain the only way to connect to field devices in process applications.

So how does PROFINET fit into the process environment? Well, that’s simple: PROFINET provides a high-speed, high-bandwidth, backbone for PROFIBUS PA (and other fieldbus networks) similar to the way that PROFIBUS DP does!

It differs slightly however by using a ‘proxy’ interface – a module that sits between PROFINET and the underlying bus. The data path via the proxy is fully transparent so instruments on the fieldbus appear directly connected to the PROFINET controller (or DCS) as remote IO. This makes configuration, maintenance and management of an automation system very simple from any part of the enterprise.

Proxies exist for PROFIBUS PA and for many other bus technologies including Foundation Fieldbus and WirelessHART.

The great advantage of the proxy approach is that existing field networks do not have to be replaced when upgrading a plant to PROFINET, so investments in skills and inventory are protected as the migration to Industrial Ethernet architectures occurs.

Moreover, the same PROFINET backbone can be used to connect other field devices typically found in process applications – for example drives and discrete IO. As most process plants are ‘hybrid’ i.e. they include both process and discrete automation elements, that means only one network – PROFINET – is needed to cover the entire plant.

Three key additional needs of process automation are also supported by PROFINET:

• Configuration in Run (CiR) – or the ability to make changes to an application program without stopping the controller.
• Time Sync / Time Stamping
• Scalable Redundancy – (PROFINET already has media redundancy, but needs to support system redundancy as well for process applications)

An Application Profile defining how these requirements are utulized has been published.  North American and European companies helped define these capabilities.

RECOMMENDED READING:  The Open to New Ways, PROFINET in Process Automation White Paper.

Designing and engineering a PROFINET project is straightforward, especially if you already have fieldbus experience. Migrating from fieldbus to Industrial Ethernet is particularly easy.

Even those who don’t have any experience should rapidly pick up the theory and practice of PROFINET. In this section we’ll talk you through the basics.  Our Resources will then give you all you need to understand what to do and how to do it.

Remember, PROFINET offers a modular approach to automation. That means it’s flexible and versatile. Not everything needs to be utilized so, ‘start slowly and build’.

Watch our Webinar: Completing A PROFINET Project

Ethernet is a highly scalable and versatile communications technology. It can be deployed in Line, Tree, Tree and Branch, Star and Ring architectures and both IO and peer-to-peer communications are possible.

Like office networks, PROFINET uses Ethernet switches to connect devices. PROFINET switches can be external infrastructure components and buying COTS (Commercial Off-The Shelf) is possible. However, the difficult environments of most manufacturing plants, plus the extra features that PROFINET can offer, mean that more sophisticated switches are the preferred solution. The following section on Selecting will give further details.

In addition, specialized ASIC-based switches are now being fitted into many end devices. Both 2 and 4 port versions are available. On-board 2-port switches allow easy ‘daisy-chaining’ of devices to enable bus-like line networks to be created. Design considerations here include taking into account accumulated switching delays. In linear networks 10 switches in a line is usually the desirable maximum.

If HMI traffic and data-intensive signals (e.g. vision) are required, it’s worth paying attention to overall bandwidth requirements. PROFINET’s ability to reserve bandwidth for particular functions means that limitations rarely occur. It also means that multiple-functionality can exist on a single network.

For high integrity systems, PROFINET supports ring topologies whereby, if a cable or device fails, then the system automatically segments itself into a ‘line’ topology to keep the rest of the system active.

RECOMMENDED READING: We offer a PROFINET Design Guideline that discusses best practices and steps when designing your network. Also included is a Load Calculation Tool that you can download.

To ensure the highest quality performance and to guarantee interoperability it is a mandatory requirement that all PROFINET products are certified, since only in that way can users have full confidence in their purchases. A list of products can be found in the Product Finder on the main PI website; NOTE: it is the responsibility of the manufacturer to maintain the listing of their products there! If a product cannot be found as such, it does not necessarily mean the product has not been certified. Check with the device manufacturer for a certificate.

For infrastructure devices such as switches, COTS (Commercial Off-The-Shelf) can be utilized. However, here is a list of the parameters that are important (and not important!) to PROFINET to guide you in making the right choice:

(*Why is Multicast an issue? Multicast is a default Ethernet mechanism used by some Industrial Ethernet protocols. It distributes every message to multiple receivers. This can quickly lead to ‘flooding’ of the network … and not just the automation network either as it will jeopardize the performance of any connected office Ethernet too! Therefore, in an Industrial Ethernet based on multicast messaging, all switches have to support a special feature called ‘IGMP Snooping’ which monitors what is happening and takes appropriate action to prevent ‘flooding’. This adds to costs. PROFINET uses only unicast messages and is not troubled by the requirement.)

Standard ‘best practice’ in cable installation and maintenance should be followed at all times. Here are a few additional factors that should be borne in mind:

• Remember that the environment you are planning for may be dirty, dusty, electrically noisy and generally unfriendly to data transmissions and infrastructure components of all types.
• Normal twisted pair cabling is suitable for PROFINET. TCP/IP has methods in place to resend telegrams when lost but the timing is not acceptable for industrial use! In other words, electrically noisy environments can easily interrupt your data flows and may cause control malfunctions. In these situations, always use Shielded Twisted Pair cabling.
• Grounding at both ends is best. However, it’s not always applicable due to ground loops.
• The need for shielding is independent of the protocol used. All Industrial Ethernets – and indeed fieldbuses – need protection in noisy environments. If you used shielded cable with DeviceNet or PROFIBUS, use shielded cable with PROFINET as well.
• Use PROFINET-rated cable.
• Always use rugged connectors too. Field installable RJ-45 types are available, as illustrated.

An excellent pair of publications, the PROFINET Installation Guide (Cabling and Assembly) and Installation Guide: Network Components are available, covering installation issues as a whole, including network components, network structures, wiring, plugs, cables and tips.

There are many resources that you can call on to help with commissioning.

• A PROFINET Commissioning Guideline is available, together with a separate Word file, which provides protocols and checklists for individual adaptations.
• Excellent engineering and test tools designed for use with Industrial Ethernet in general – and PROFINET in particular – are available from many sources. Such tools can investigate full Ethernet and PROFINET activity, provide detailed analysis of parameters such as delays and jitter, and time stamp frames for later assessment.
• General-purpose Ethernet tools include the Wireshark software analyzer which uses the Ethernet ports on a PC as the analyzer hardware. Wireshark is license free and acts as a sniffer to analyze the Ethernet traffic.

Standard Ethernet has a set of diagnostic tools and protocols that will be familiar to office-based technical personnel. These can be utilized in the industrial environment to provide detailed information about lower-level transport-oriented issues such as TCP, UDP and IP activity. They can also support statistical and connection analysis.

Standard Ethernet protocol tools

The use of familiar Ethernet protocols means that browser based access to individual devices is possible from any PC in any location – even over the internet. Many PROFINET devices incorporate a web server for this purpose. A browser can also read out information such as device status and configure a device either locally or from a remote site.

IT protocols familiar from the industrial world include SNMP (for managing components such as switches, and reading statistics and diagnostics). Again these can be used from anywhere in the network. Another familiar protocol is LLDP which is used for mapping network topologies for making device replacement easy.

PROFINET-specific tools

The PROFINET specifications also include a set of specific diagnostic tools which operate at the application layer level. These provide more advanced diagnostics capabilities in standardized formats. Some allow for remote monitoring of networks, and some are intended for on-site use.

Simple Device Replacement

Many devices can be replaced in the field without the need for configuration – no computer is required; you just take the new device out of the box and install it in place of a failed unit.

Click to enlarge

If you have PROFIBUS networks already installed, or if you’ve got PROFIBUS skills available in your plant then migrating from PROFIBUS to PROFINET will be quick and simple.

That’s because the Working Groups which developed PROFINET drew heavily on the experience of PROFIBUS.

For example, if you’re familiar with GSD files for engineering you’ll be familiar with the GSDML files used by PROFINET. Likewise, the diagnostic functions. Many of the PROFIBUS profiles – for example PROFIsafe and PROFIdrive – will also be familiar.

The migration process was also made simple, and not just by integrating the PROFIBUS and PROFINET protocols. That’s an easy step to take for sister technologies. More difficult is the integration of other protocols, especially from competing organizations. PROFINET achieves this through the use of the unique ‘proxy’ concept, which is covered in detail in this section. Proxies are part of the PROFINET specification and perform consistently across all protocols.

PROFINET is alone in being able to integrate many popular fieldbuses, making it the ideal way to move to Industrial Ethernet architectures.

Special Note: In addition to the proxy migration option, a wide range of gateway devices exists for connecting legacy protocols to PROFINET from various vendors.

A PROFINET ‘proxy’ is a black-box interface sitting between PROFINET and a sub-network such as PROFIBUS.

It differs from a conventional gateway device in that it maps the underlying protocol to PROFINET. This allows a controller on PROFINET to access devices on the sub-network with ease because all functions and services are directly available to PROFINET without further interpretation.

This means that investments in the skills, equipment, and software associated with the sub-network can be retained. No changes to automation systems at the fieldbus level are required; fieldbus networks can simply be connected into the PROFINET architecture and utilized as before.

Because of this, PROFINET can greatly assist in the expansion and deployment of distributed automation architectures. It also simplifies greater vertical integration, moving manufacturing closer to enterprise IT networks.

PROFINET is also highly scalable, and modular in concept so not every feature needs to be deployed at once. New users can start simply and build as required. Migration can happen in easy steps, allowing plant and personnel to build experience while improving productivity and profitability.

In the diagram (above) sub-networks such as PROFIBUS PA, HART, PROFIBUS DP , IO-Link and AS-Interface are shown connected to PROFINET via a single proxy. Alternative network structures are possible using different proxies. In addition, proxy definitions exist for many fieldbus protocols, including DeviceNet.

Remember, a ‘proxy’ is a special interface for connecting PROFINET to lower level networks such as PROFIBUS, INTERBUS, etc. A proxy differs from a standard gateway or bridge in that acts as a sub-network master and a PROFINET slave simultaneously. The underlying protocol is therefore mapped directly to PROFINET and the PROFINET controller ‘sees’ the sub-network as remote IO. Proxies are part of the PROFINET specification.

Proxy specifications also exist for DeviceNet.

Many of the design, engineering and deployment issues for PROFINET resemble those of PROFIBUS. However, there are capabilities that PROFINET offers that simply cannot be achieved with PROFIBUS.

PROFINET diagnostics leverage well-proven Ethernet diagnostics using easily available tools such as Internet browsers. Like PROFIBUS, the diagnostics are simple and faults can be identified down to channel, module and device level. Proven mechanisms like Simple Network Management Protocol (SNMP) allow Ethernet switches and other devices to be managed from any location.

• Simple device replacement: Just physically replace a device when it fails. There are NO switches to set and NO computer is needed.
• Device names, not numbers are used: Meaningful names can be allocated by the user which contributes to much simpler replacement procedures. The PLC assigns an IP address to the node.
• Standard wireless: familiar IEEE802.11 protocols are used.
• More topology options (see diagram top right): Ethernet offers many more topology options, including star, ring and tree structures which make it easier to design and commission according to the layout and functions of a plant, especially where redundancy, long distance and remote connections are needed.
• Shared Device/I-Device: One device can be accessed by more than one controller. This flexible assignment of modules to different controllers suits many applications, for example a single sensor that participates in a safety function and needs to communicate with a failsafe PLC. An IO-controller can also operate in a so-called i-Device mode, in which it combines the IO-Device functionality with an IO-Controller function on the same interface (see diagram bottom right).

Click to enlarge

PROFINET also offers much higher performance than PROFIBUS and other fieldbuses in terms of:

• Unlimited scalability
• Unlimited address space
• Larger message size (1440 bytes vs. 244)
• The possibility to coordinates more drive axes – with IRT updates in 1 ms range, with less than 1uSec jitter
• It’s faster too (see diagram above), which means more application potential and fewer interfaces

Click to enlarge

Content from this section can be found in The Easy Way to PROFINET White Paper. Another White Paper from the company (and PICC) HMS entitled Why It’s Time to Move to PROFINET is an excellent read.

PROFINET has core functionality that defines how data is transferred within a network. This relies on basic Ethernet standards such as TCP, UDP, DHCP, SNMP, LLDP, IP, and MRP. To this core functionality are added a set of options which deliver the full Industrial Ethernet experience. The basic industrial automation services are: TCP/UDP IP, for general data transfer; PROFINET real time (RT) for a broad range of IO applications including drives; and PROFINET isochronous real time (IRT), for advanced motion control.

The precise combination of functions used is up to the designer/developer and this provides considerable flexibility in device or system supply.  No matter what the application is, there is consultation available for every phase of the product design cycle.

PI & Member organizations offer support and consultation:

• Seminars, Workshops, Certification Classes
• Development Packages for PROFINET Field Devices and Controllers
• Fundamentals, Engineering, and Support
• Worldwide and local service from PI: at the PIC in Johnson City, TN or at the HMS Competence Center
• Test Labs can give up front guidance about the mandatory certification processes

Node Class

A PROFINET network is composed of different types of components.  Each performs different tasks and these device types are known as, and are described in four Node Classes.

• IO Devices – Input/Output devices are controlled by the IO Controller.  Examples include actuators, sensors, drives / motors, switches, solenoid & pneumatic valves, robots, protection & safety technology, and encoders.
• IO Controller – Controllers retrieve and process data from components or write to IO devices.  These can be PLCs or PACs.
• IO Supervisor – Supervisors will initiate parametrization or programming. They will typically read from, or write to, other IO devices and IO controllers on the network and integrate information vertically through the network.
• Network Components – Switches or access points for wireless communication are a few examples of Network Components.  Some network components can also be operated simultaneously as IO devices for enhanced network diagnostics.

Some PROFINET devices offer multifunction capability and can support more than one node class.

Interfaces

• Types of Interfaces – Options include: Copper wire (Ethernet cable for 100 Mbits/s, full duplex), Fiber Optics (FO), or Wireless (e.g. WLAN, Bluetooth)
• Number of Interfaces – Single Port or Multi Port

Communication Class

After determining the Node Class of the device, it is important to know where the device will be deployed so that it can effectively communicate with the necessary speed.

TCP/IP

• TCP/IP  and/or UDP/IP is used for configuration or parameter assignment.  It is a slightly slower type of communication, but because of its availability in PROFINET, this allows for simple Vertical Integration into MES/ERP systems.

RT – Real Time

• Real Time transmission can be used in almost every Node Class; but will be employed most by devices used generally in factory automation.  Typically these components update every 1 – 8 milliseconds.

IRT – Isochronous Real Time

• IRT data transmission is high-speed, high-performance, and deterministic.  Examples include motion control applications with update times of less than 1 millisecond.

Conformance Class

Furthermore, each Communication Class is part of a broader categorization of PROFINET devices.  These Conformance Classes incorporate other features, and manufacturers will define which functions will be supported by their device.  Then, the component is classified to help simplify its selection prior to usage, guarantee its properties, and ensure interoperability.

Incorporating PROFINET into your device means modularity and flexibility. Start simple and add functionality as required. There are features that some manufacturers will desire to be integrated, and others will not.

Some examples of these optional modules include:

• Fast Startup (FSU) – See the full description elsewhere on this page (look in the Table of Contents).
• Network Redundancy – This is used to help with management in networks with ring topologies.
• PROFIsafe – This is an Application Profile for the novel implementation of functional safety with less effort, cabling, and maintenance. Further information can be found under the PROFIsafe section.
• PROFIenergy – This is an Application Profile developed to save energy and reduce utility bills; it is built on top of the existing PROFINET protocol. PROFIenergy is discussed in depth in the Features section.

When choosing the format by which PROFINET will be integrated into a device, it is mainly dependent upon the eventual goals and applications of the component.  Different solutions exist for this; broadly they are:

Many of these products are supported with SDKs (software development kits). With each option there are multiple choices for consultation and engineering support, through vendors themselves and through the global PI Competence Center network.

Click to enlarge

Not all development environments are capable of handling every Conformance Class. Certain devices will require hardware and software that will enable it to perform in its desired application. For example, the requirements of Conformance Class C mean that devices have a Multi-Port interface, as shown below:

Additionally, Conformance Class C performance levels typically cannot be reached using a standard microcontroller (MCU):

Click to enlarge

Hardware and software design can pose special challenges and if you do not have in-house resources, you may need to find a supplier to help. A modular solution may well suit your needs if numbers are small. Flexibility is an additional benefit in these circumstances.  Maybe your volumes justify a special board design, or custom product.

The advantage of collaborating with an external technology or development partner when developing a PROFINET interface is that the device manufacturer can concentrate on its core areas of expertise.

Either way, there are plenty of resources available to help – contact PI North America for guidance. The PI member companies offer a wide range of services during the development phase.

Click to enlarge

Member companies of PI North America each bring expertise to certain phases of the design process. Contact information for these companies can be found in the next step. The chart below briefly outlines these areas of expertise:

Please find contact information for the above mentioned companies below.

Please click the logo or ‘Contact’ to be taken to the company’s website. Or, you may continue on to Certification Test below.

	Comtrol Corporation Contact
	Freescale Semiconductor, Inc. Contact
	Grid Connect Inc. Contact
	Hilscher North America, Inc. Contact
	HMS Industrial Networks, Inc. Contact
	Industrial Control Communications, Inc. Contact
	Innovasic Semiconductor Contact
	MESCO Engineering GmbH Contact
	Molex Contact
	Phoenix Contact Competence Center Contact
	Real Time Automation Contact
	PROFI Interface Center (PIC) (Siemens) Contact
	Softing North America Contact

Conformance testing and certification are mandatory for all PROFINET devices because that is the only way to guarantee interoperability. It is the primary factor in influencing customers to buy PROFINET products.

Prior to the Certification Test, a vendor ID must first be issued by PI (contact PI North America for help). It is recommended that a System Test is performed with PROFINET tools such as a PLC or ProfinetCommander before going into testing.

Certification is undertaken by an accredited PI Test Lab, and is carried out in accordance with established and proven procedures. The PI Lab for North America is the PROFI Interface Center, which offers device testing and further information on their website. Simultaneously, CE and/or UL certification is necessary and should be carried out independently.

The Test Lab tests for compliance with the PROFINET specification and any profiles involved, and also for interoperability with other PROFINET devices. Only when all test procedures are successfully undertaken will PI issue a formal Certificate for the device.

Accredited PI Test Labs are qualified to help mainly to certify devices but may also be able to advise on design issues and recommend adjustments to help ensure successful certification.

Once your device is certified, it is now ready for the market. Make sure your package is complete though: don’t forget sales literature and an easily found web presence. Make sure your sales force thoroughly understands the product. GSD files should be included in your package, or preferably made available over the internet.

You’ll have your own routes to market probably, but PI can offer help, including:

• A member-maintained on-line product database at www.profibus.com
• Electronic newsletters such as PROFINEWS with large distribution lists which can be used to promote your product widely and generate sales leads
• The opportunity to upload member press releases to the PI North America website

All of these services are free to members.

Your local Regional PI Association office (that’s PI North America in North America) will also be able to help by offering the chance to advertise and to exhibit at regional events. The advertising and exhibiting opportunities in North America are detailed here.

Most of these are excellent ways to meet new customers and to network with like-minded PROFINET people.

PI North America staff blog regularly about PROFIBUS and PROFINET, and there’s a Twitter feed at http://twitter.com/CHenning.