The Ethernet Fieldbus

The Ethernet Fieldbus

ETG_Broschuere_09_2009_RZ.qxd 02.10.2009 14:30 Uhr Seite 1

2 EtherCAT Technology Group

© EtherCAT Technology Group. We reserve the right to make technical changes.

■ Content

03 Why EtherCAT?

4 User and Vendor Statements


8 EtherCAT – Technical Introduction and Overview

18 Implementation Aspects| Master| Slave

22 Conformance and Interoperability

24 Safety over EtherCAT

26 Why do companies choose EtherCAT?

28 Contact


3EtherCAT Technology Group

■ It’s faster| The fastest system available,

with outstanding synchronization features | Performance widely independent of topology| No underlying sub-system required any more| Meets today’s and tomorrow’s requirements

■ It’s cost effective| Meets or even undercuts fieldbus cost levels| No special master cards required –

on-board MAC or low cost standard NIC is fine| Highly integrated Slave Controllers for

lower interface costs| No active infrastructure components required

■ It’s easy to implement| Real-time protocol handling in hardware| Device application determines μC performance –

not the fieldbus protocol| Simple I/O slaves do not require μC at all| Universal slave interface modules available| Evaluation kits and stacks for master

and slave available

■ It’s easy to use| No manual address setting| No switch or router configuration| Auto configuration features| Diagnosis with exact localization

■ It’s flexible topology| All topologies supported: line, tree, star, ring| No node, switch or hub cascading issues| Up to 65,535 nodes per segment| Redundancy, Hot Connect, Hot Swap options

■ It’s versatile| master-slave, slave-slave and

master-master communication| Cyclic and acyclic services for process data

and parameter data| Suitable for centralized and distributed control

architectures| Machine control, robotics, embedded systems,

building automation, transport systems, …

■ It’s Industrial Ethernet| Standard Ethernet frames used| Supports all Internet technologies| HTTP, FTP, TCP/IP – without degrading

the real-time behavior| Simplifies vertical integration

■ It’s Safety on Ethernet| Functional Safety and standard application

with one network| Safety Protocol according to international

safety standard IEC 61508| Suitable for safety I/O and safety drives| Routable via gateways and fieldbus systems

■ It’s open| Open Technology, fully disclosed| Supported by the worlds largest Industrial

Ethernet Organization| EtherCAT is IEC, ISO and SEMI standard| Supports well established device profiles

■ It’s well proven| Deployed in series applications since 2003| Wide range of applications| Implemented on variety of controllers and

operating systems| Large product selection

© EtherCAT Technology Group. All rights reserved.

■ Why EtherCAT?


■ Martin Rostan, Head of TechnologyMarketing, Beckhoff Automation GmbH,and Executive Director,EtherCAT Technology Group:

“The strong growth of the EtherCAT Technology Groupreflects the tremendous worldwide interest in this exiting technology. Manufacturers and end users rec-

ognize the benefits: future-proof performance, flexible network topology, simpleconfiguration, and low costs. Nevertheless, while the number of members is animportant criterion for the success of a technology organization, it is not the cru-cial one. Acceptance of the technology resulting in product developments and ap-plications is even more important. Here too, EtherCAT is setting standards.”

■ Kenichi Karigane,General Manager,Drive Systems Division,Product Marketing & SalesEngineering Center,Hitachi IES Co., Ltd.:

EtherCAT is being adopted also inJapan: major industrial machinery manufacturers are introducingEtherCAT into their machines. With more EtherCAT based ma-chines made available on the market the potential of EtherCAT ap-plications will even further increase. We at Hitachi IES were quickoff the mark in releasing our large capacity AC servo system withEtherCAT and will further enhance our line-up of EtherCAT prod-ucts since EtherCAT has superiority of quality to other motion con-trol bus systems with regards to speed, cost performance andopenness.

“Omron has selected EtherCAT as Machine control network dedicatedmainly for its new motion & field de-vices bus system since it provides a

unique combination of performance, ease of use and topologyfreedom. Omron believes in open architectures, and has thereforealso decided to support and promote EtherCAT in Japan and in theAsian Market. Our first EtherCAT products are motion controllerand PLC master units together with servo motors, inverters, visionsensors and field I/Os.”

■ Dieter Hess, ManagingDirector, 3S Smart SoftwareSolutions GmbH:

“3S decided to implement EtherCAT asthe first real-time Ethernet protocol,since EtherCAT utilizes the maximumperformance of Ethernet. For us as a

software manufacturer, the fact that the master implementationis independent of special plug-in cards is particularly attractive.The software can be based on the universally available standardEthernet controller. The openness of the system and active sup-port of Beckhoff for ETG are further significant factors.”

■ Shinya Yamasaki,Senior General Manager, Control Devices Division HQ, Omron:

■ Dr. Peter Heidrich, R&D Manager,Baumüller GmbH, and ETG Board Member:

“Baumüller decided to use EtherCAT due to the signif-icant benefits it can offer, particularly in terms of price/performance ratio and availability. This decisionwas underlined through our active collaboration inthe ETG executive committee. We continue to be con-

vinced that the decision for EtherCAT was the right one. As soon as EtherCAT SlaveControllers became available, Baumüller started producing connections for thebmaXX 4400 system in August 2004. ETG has demonstrated that, due to the uni-versality of the EtherCAT technology, EtherCAT-based systems can be developedand realized very quickly.”

■ Erich Hutflesz, Manager Control Systems,Schuler SMG, and ETG Board Member:

“EtherCAT enables us to realize fast drive and hydrau-lic controls for all applications currently used in theSchuler Group. Another crucial factor is that, due toEtherCAT’s performance, we still have enough poten-tial for solving complex control tasks in future without

speed problems. Apart from the functional features of a technology, availabilityof a wide range of components is very significant for users of automation devices.The fact that so shortly after ETG was established so many member companieswere already presenting EtherCAT products and that further products are inpreparation is clear evidence for the success of this technology. The main factordetermining user acceptance continues to be simple and effective handling ofthe EtherCAT system in terms of configuration and diagnosis.”



■ User and Vendor Statements


“We implemented EtherCAT in a few applica-tions and find especially exciting that this pro-tocol allows us to have very high update rateswhich allows extremely cost efficient close loopcontrol to be implemented by SW means with

virtually no specialized HW added. Availability of EtherCAT enabled field-bus scanners, digital motion amplifiers as well as fast I/O allows for usingslim controller PC with just one Ethernet port instead of multiple PC slots.Introducing EtherCAT hence does not require abandoning all well estab-lished fieldbus systems right away but provides a smooth migration path.”

■ Norbert Hauser,VP Marketing,Kontron AG:

“EtherCAT is currently the most successful Ethernet-based fieldbus. This is also visible inthe strongly growing number of members ofrenowned companies. A major advantage of

EtherCAT is its openness, high performance and the excellent price-per-formance ratio. Kontron‘s embedded computing customers have identi-fied the advantages of EtherCAT for their business. Therefore, Kontron,one of the leading companies in the Embedded Computing market, hasdecided to offer the embedded portfolio also with EtherCAT.”

■ Thomas Porath,System Architect General X-Ray,Philips Medical Systems:

“We believe that EtherCAT is the righttechnology for the next step towards a sys-tem control architecture that enables us tofurther reduce costs and allows for new in-

novations, which the current architecture is not suitable to serve for. Theperformance of EtherCAT will allow us to implement hard real-time, safe-ty, and control-functions on one single cable, while simultaneously offer-ing flexible topologies, which will reduce cable-costs significantly.Not only performance, but also international standardization and world-wide acceptance are important features of EtherCAT. Our changeover toEtherCAT is simplified through the use of CANopen device profiles and theavailability of gateways and converters, since we are not able to convertall of our subsystems and components in one big step.”

■ Chris Choi,Director of Technology, Husky Injection Molding Systems Ltd.:

“The design of EtherCAT assures its cost effec-tiveness by the use of long-lasting low cost PCand Ethernet components. This steers engi-neering and investment decisions towards its

intensive use. In injection molding, a control cycle in the range of mS is anindustrial norm. EtherCAT has proven itself as the most effective industri-al Ethernet protocol to achieve high performance control for injectionmolding with a control cycle down to the 100 μS range. This has resultedin an improved reaction time which brings great benefits: enabling offerof products with productivity surpassed the status quo; and producingmolded parts at higher precision and better quality. We are confident thatEtherCAT is a right technology to support our product innovation.”

■ Pat Boland, Managing Director,ANCA Pty Ltd.:

“ANCA’s interest in EtherCAT as the stan-dard fieldbus in our CNC machines hasbeen driven by three main features. Firstlythere is the practically unlimited band-width offered by EtherCAT which gives our

designers freedom to imagine, scalability and long product lifetime. Sec-ondly the two physical layers give the option of choosing low cost, elec-trically rugged and widely available hardware components. Finally thesoftware only master allows easy use of high reliability, relatively low costindustrial motherboards as system controllers.”



■ Hans Beckhoff,Managing Director,Beckhoff Automation GmbH:

“Naturally, EtherCAT is particularly suitablefor fast PC-based controls. The master re-quires no plug-in card and can be imple-mented on any existing Ethernet controller

using a very simple interface. EtherCAT is therefore also well suited tosmall and medium control technology, where it opens up new areas ofapplication for distributed control. Therefore EtherCAT is the commu-nication backbone of Beckhoff system architecture and we are very pleased about the worldwide success of this technology.”

■ Dmitry Dzilno, Director of Engineering,Controls Group, Applied Materials Inc.:


product guides, issue press releases and articles, promoteEtherCAT via its website and organize joint fair and exhibi-tion booths.

Benefits of membership■ EtherCAT device vendors are encouraged to join ETG sothat they get access to development products and imple-mentation support as well as their own EtherCAT vendorID and the Conformance Test Tool. EtherCAT users supportthe technology and its adaptation to their industry by joining the ETG.■ Members are eligible to participate in working groupsand thus influence on future enhancements of the EtherCAT technology specifications.■ ETG represent the member’s interest in internationalstandardization committees such as IEC and ISO.■ ETG members have access to the members-only part ofthe EtherCAT website, which provides specifications, a de-velopers forum, the EtherCAT Knowledge Base and otherup-to-date information regarding the technology.

Everyone should be able to use and implement EtherCAT.The EtherCAT Technology Group stands for this philosophy.The ETG is a forum for end users from different sectors, andfor machine manufacturers and suppliers of powerful con-trol technology with the aim of supporting and promotingEtherCAT technology. The wide range of industry sectorsthat are represented ensures that EtherCAT is optimallyprepared for a large number of applications. With theirqualified feedback, the system partners ensure simple in-tegration of the hardware and software components in allrequired device classes.

The ETG Technical Committee meets frequently to re-view the technology. Working Groups look after topics likedevice profile integration, safety, wiring, standardization orconformance and certification.

In Training Classes and Seminars the ETG provides de-tailed information about the technology. Plug Fests help toprovide interoperability and implementation support andcomplement the conformance test and certificationprocess. The ETG Offices answer technical inquiries re-garding EtherCAT, provide marketing assistance, publish



■ EtherCAT Technology Group

ETG-Team



The Management Board of the International Electrotech-nical Commission (IEC) approved the Liaison of the EtherCAT Technology Group with the IEC Committees forDigital Communication: The ETG is official standardizationpartner organization.

International StandardizationThe EtherCAT specification is an international IEC and ISOstandard: EtherCAT is part of the international fieldbusstandard IEC 61158 (Digital data communication for meas-urement and control – Fieldbus for use in industrial con-trol systems). In part 2 of IEC 61784 profiles for specific EtherCAT device classes are defined. The new part 3 of thisstandard includes the Safety over EtherCAT specification,and the new edition of part 5 covers the EtherCAT networkinstallation. ISO 15745 deals with device description as-pects.

The IEC 61800-7 is particularly important for MotionControl applications. The integration of EtherCAT in thisstandard makes it a standardized communication technol-ogy for the SERCOS™ and CANopen™ drive profiles.

Also SEMI (Semiconductor Equipment and MaterialsInternational) has approved EtherCAT for their applicationsby accepting the EtherCAT SEMI standard E54.20. The lead-ing standards organizations thus respond to the growinginterest of the industry in the fastest Industrial Ethernetsolution.

Membership DevelopmentFounded in 2003, the EtherCAT Technology Group grew sofast that it became the worlds largest Industrial Ethernetorganization. With over 1000 member companies from allover the world and still growing, the ETG is a strong inter-national community. ETG Offices in Europe, Asia and NorthAmerica provide support and members services. The cur-rent membership list can be found on the EtherCAT web-site.

How to join the ETGETG headquarters provides all necessary information in-cluding ETG by-laws and application form on request:[email protected]



fieldbus systems in the past. The main requirements forthis type of application are high real-time capability, suit-ability for small data quantities, and naturally cost-effec-tiveness. EtherCAT meets these requirements and at thesame time makes internet technologies available at theI/O level.

With EtherCAT the controller can update the inputand/or output information at the time when the data isneeded. The I/O response time contains all hardware rele-vant delays (IPC, EtherCAT and I/O system) from the physi-cal input signal to the physical reaction on the output.With response times down to below 100 μs this offers aperformance to the PLC level that has been available up tonow only within servo drives with a digital signal proces-sor (DSP), (see Fig. 1).

■ Ethernet and real-time capabilityThere are many different approaches that try and providereal-time capability for Ethernet: for example, the CS-MA/CD media access procedure is disabled via higher level

■ IntroductionFieldbuses have become an integrated component of au-tomation technology. They have been tried and tested andare now widely established. It was fieldbus technologythat enabled the wide-scale application of PC-based con-trol systems. While the performance of controller CPUs –particularly for IPCs – is increasing rapidly, conventionalfieldbus systems tend to represent “bottlenecks” that lim-it the performance control systems can achieve. An addi-tional factor is the layered control architecture consistingof several subordinate (usually cyclic) systems: the actualcontrol task, the fieldbus system and perhaps local expan-sion buses within the I/O system or simply the localfirmware cycle in the peripheral device. Reaction times aretypically 3–5 times higher than the controller cycle time –an unsatisfactory solution.

Above the fieldbus system level, i.e. for networkingcontrollers, Ethernet has already been the state of the artfor some time. What is relatively new is its application atthe drive or I/O level, i.e. in areas that were dominated by



■ Technical Introduction and Overview

This section provides an in-depth introduction into EtherCAT, the Ethernet-based fieldbus system.EtherCAT sets new performance standards. Handling is straightforward and similar to a fieldbus, thanksto flexible topology and simple configuration. Moreover, since EtherCAT can be implemented very cost-effectively, the system enables fieldbuses to be used in applications where fieldbus networking was not an option in the past.

■ Figure 1: Ultra short cycle times with I/O response time < 100 μs

Polling/Timeslicing

0102030405060708090

100

2-5%

BroadcastMaster➝Slave

20-30%

EtherCAT

80-97%

At 4 Byte user dataper note

From 2 Bituser dataper note

■ Figure 2: Comparison of Bandwidth Utilisation


Ethernet Header ECAT HDR Datagram 1 Datagram 2 Datagram 3 Ethernet

Logical Process ImageTask 1




protocol layers and replaced by the time slice procedure orpolling; other propositions use special switches that dis-tribute Ethernet packets in a precisely controlled timelymanner. Whilst these solutions may be able to transportdata packets more or less quickly and accurately to theconnected Ethernet nodes, the times required for the redi-rection to the outputs or drive controllers and for readingthe input data strongly depend on the implementation.

If individual Ethernet frames are used for each device,the usable data rate is very low in principle: The shortestEthernet frame is 84 bytes long (incl. inter-packet gap IPG).If, for example, a drive cyclically sends 4 bytes of actual val-ue and status information and accordingly receives 4 bytesof command value and control word information, at 100 %bus load (i.e. with infinitely short response time of thedrive) a usable data rate of only 4/84 = 4.8 % is achieved. Atan average response time of 10 μs, the rate drops to 1.9 %.These limitations apply to all real-time Ethernet approach-es that send an Ethernet frame to each device (or expect aframe from each device), irrespective of the protocols usedwithin the Ethernet frame.

■ EtherCAT operating principleEtherCAT technology overcomes these inherent limitationsof other Ethernet solutions: On the one hand the Ethernetpacket is no longer received then interpreted and processdata then copied at every device, but the EtherCAT slavedevices read the data addressed to them while the frame


passes through the node. Similarly, input data is insertedwhile the telegram passes through (see Fig. 3). The framesare only delayed by a few nanoseconds. The frame send bythe master is passed through to the next device until itreaches the end of the segment (or branch). The last devicedetects an open port and therefore sends the frame backto the master.

On the other hand, an EtherCAT frame comprises thedata of many devices both in send and receive directionwithin one Ethernet frame. The usable data rate increasesto over 90 %. The full-duplex features of 100BASE-TX arefully utilized, so that effective data rates of > 100 Mb/s(> 90 % of 2 x 100 Mb/s) can be achieved (see Fig. 2).

The EtherCAT master uses standard Ethernet MediumAccess Controllers (MACs) without extra communicationprocessors. Thus an EtherCAT master can be implementedon any equipment controller that provides an Ethernet in-terface, independently of the operating system or applica-tion environment.

The EtherCAT slave uses an EtherCAT Slave Controller(ESC) for processing the data “on-the-fly”. Thus the per-formance of the network is not determined by the micro-controller performance of the slave but is handled com-plete in hardware. A process data interface (PDI) to theslave‘s application offers a Dual-Port-RAM for data ex-change.

■ Figure 3: Process data is inserted in datagram


EtherCAT TelegramECATEthernet Header

DA SA Type Frame HDR Datagram 1 Datagram 2 -- Datagram n

(6)Ethertype 88A4h

(6) (2/4) (2) (10+n+2) (10+m+2) (10+k+2)

Ethernet

Pad. FCS

(0…32) (4)

EthernetHeader

IP Header UDP Header ECAT HDR EtherCAT Telegram

Ethertype 0800hUDP-Port: 88A4h

(20) (8)

Ethernet



■ ProtocolEtherCAT only uses standard frames according to IEEE802.3 – the frames are not shortened. EtherCAT frames canthus be sent from any Ethernet controller (master), andstandard tools (e.g. monitor) can be used.

The EtherCAT device protocol is optimized for processdata and is transported directly within the Ethernet framethanks to a special EtherType. It may consist of severalEtherCAT datagrams, each serving a particular memoryarea within the 4 gigabyte address space. For small I/O de-vices the EtherCAT Slave Controller also supports bitwisemapping. The bits of an input device can be inserted indi-vidually anywhere within the logical address space. If anEtherCAT datagram is sent that reads a certain process im-age area the input terminal inserts its data at the rightplace within the data area. This is done by the FieldbusMemory Management Unit (FMMU) within the ESC. So thedata sequence becomes independent of the physical orderof the Ethernet terminals in the network; addressing canbe in any order. Broadcast, Multicast and communicationbetween slaves are possible. Direct Ethernet frame trans-fer is used in cases where maximum performance is re-quired and the EtherCAT components are operated in thesame subnet as the controller.

However, EtherCAT applications are not limited to asingle subnet: EtherCAT UDP packages the EtherCAT proto-col into UDP/IP datagrams (see Fig. 4). This enables anycontrol with Ethernet protocol stack to address EtherCAT

■ Figure 4: EtherCAT: Standard Frames according to IEEE 802.3 [3]

systems. Even communication across routers into othersubnets is possible. In this variant, system performance ob-viously depends on the real-time characteristics of the con-trol and its Ethernet protocol implementation. The re-sponse times of the EtherCAT network itself are hardly re-stricted at all: once inside an EtherCAT segment the UDPprotocol does not have to be processed any more.

To access the local memory of the devices for examplefor configuration either the position of the devices in thesegment can be addressed or the device is addressed via anassigned node address.This means: No manual address ad-justment on the devices is needed!

The position addressing is used for the boot-up of thenetwork. The master can identify each device in the seg-ment (Vendor-ID, product code, etc.) and can read in thelink status of the device‘s ports. Therefore the complete in-formation about all devices and about the topology isavailable and can be compared to an expected configura-tion. Additionally, the master assigns the node address toall devices.

This node address is used afterwards and addresses thedevices reliably even if one or more devices are not con-nected (e.g. Hot Connect groups) and therefore the posi-tion in the segment is not the same.

In addition to the EtherCAT device protocol using dataexchange according to the master/slave principle, theEtherCAT automation protocol makes it also very suitablefor communication between controllers (e.g. master/mas-


■ Figure 5: Flexible Topology: Line, Tree or Star



Wiring flexibility is further maximized through thechoice of different cables. Flexible and inexpensive stan-dard Ethernet cables transfer the signals in 100BASE-TXmode. The Power over EtherCAT-option (compatible withIEEE 802.3af) allows one to connect e.g. sensors using a sin-gle cable. Fibre Optics (100BASE-FX or Plastic Optical Fibres)complement the system for special applications. The com-plete choice of Ethernet wiring – such as different opticalfibers and copper cables – can be used in combination withswitches or media converters.

The Fast Ethernet physics (100BASE-TX) enables a cablelength of 100 m between two devices. Since up to 65,535devices can be connected, the size of the network is almostunlimited.

The Ethernet protocol according to IEEE 802.3 remainsintact right up to the individual device; no sub-bus is re-quired. In order to meet the requirements of a modular de-vice like an electronic terminal block, the physical layer inthe coupling device can be converted from twisted pair oroptical fiber to LVDS (alternative Ethernet physical layer,standardized in [4,5]). A modular device can thus be ex-tended very cost-efficiently. Subsequent conversion fromthe backplane physical layer LVDS to the 100BASE-TX phys-ical layer is possible at any time – as usual with Ethernet.

ter). Pushed and polled process data exchange and a vari-ety of services for parameterization, diagnosis and remotecontrol cover a wide range of requirements. The data inter-faces of the device protocol and the automation protocolare identical.

For slave-to-slave communication, two mechanismsare available. Upstream devices can communicate todownstream devices within the same cycle – and thus ex-tremely fast. Since this method is topology-dependent, it isparticularly suitable for slave-to-slave communication re-lationships given by machine design – e.g. in printing orpackaging applications. For freely configurable slave-to-slave communication, the second mechanism applies: thedata is relayed by the master. Here, two cycles are needed,but due to the extraordinary performance of EtherCAT thisis still faster than any other approach.

■ TopologyLine, tree or star: EtherCAT supports almost any topology(see Fig. 5). The bus or line structure known from the field-buses thus also becomes available for Ethernet, withoutthe quantity limitations implied by cascaded switches orhubs.

Particularly useful for system wiring is the combina-tion of line and branches or stubs: the required interfacesexist on many devices (e.g. on I/O modules); no additionalswitches are required. Naturally, the classic Ethernet startopology can also be used.


sssss s

sΔt

M■ Figure 6: Synchronicity and Simultaneousness: Scope view of two

distributed devices with 300 nodes and 120m of cable between them



would lead to large step changes in the computed velocity.Since by using the distributed clocks the sampling is notbased on the communication jitter, very precise velocitymeasurements are achieved. It is orders of magnitude bet-ter than that of measuring techniques based on jitter-freecommunication. However, high-resolution distributedclocks are not only used for synchronization, but can alsoprovide accurate information about the local timing of thedata acquisition. With EtherCAT, timestamp data types areintroduced as a logical extension. The high resolution sys-tem time is linked to the measured value, which is madepossible by the large bandwidth offered by Ethernet. Thisfeature is not only very useful for any measurement appli-cation, but also enables very precise reaction times inde-pendent of the control cycle. External synchronization, e.g.across the plant, is then based on IEEE 1588.

■ PerformanceEtherCAT reaches new dimensions in network perform-ance. Thanks to hardware integration in the slave and di-rect memory access to the network controller in the mas-ter, the complete protocol processing takes place withinhardware and is thus fully independent of the run-time ofprotocol stacks, CPU performance or software implemen-tation. The update time for 1,000 I/Os is only 30 μs – in-cluding I/O cycle time (see Table 1). Up to 1486 bytes ofprocess data can be exchanged with a single Ethernetframe – this is equivalent to almost 12,000 digital inputsand outputs. The transfer of this data quantity only takes

■ Distributed clocksAccurate synchronization is particularly important in caseswhere spatially distributed processes require simultane-ous actions. This may be the case, for example, in applica-tions where several servo axes carry out coordinated move-ments simultaneously.

The most powerful approach for synchronization is theaccurate alignment of distributed clocks, as described forexample in the IEEE 1588 standard [6]. In contrast to fullysynchronous communication, where synchronization qual-ity suffers immediately in the event of a communicationfault, distributed aligned clocks have a high degree of tol-erance versus possible fault-related delays within the com-munication system.

With EtherCAT, the synchronization of the devices isfully based on a pure hardware machine. Since the com-munication utilizes a logical (and thanks to full-duplex FastEthernet also physical) ring structure, a timestamp can besampled within each device for the incoming and the re-turning frame. With these timestamps the master can de-termine the propagation delay offset to the individualslave clocks simply and accurately (see Fig. 7). The distrib-uted clocks are adjusted based on this value, which meansthat a very precise network-wide time base with a jitter ofsignificantly less then 1 microsecond is available (see Fig. 6). This is very important e.g. for motion control, wheretypically velocities are calculated from sequentially meas-ured positions. Particularly with very short sampling times,even a small temporal jitter in the position measurement

■ Figure 7: Setting the individual clocks of each device to the network-wide time base.



consistency with the specified configuration. The topologyshould also match the configuration. Due to the built-intopology recognition down to the individual terminals,this verification can not only take place during systemstart-up, automatic reading in of the network is also possi-ble (configuration up-load).

Bit faults during the transfer are reliably detectedthrough evaluation of the CRC checksum: The 32 bit CRCpolynomial has a minimum hamming distance of 4. Apartfrom broken wire detection and localization, the protocol,physical layer and topology of the EtherCAT system enableindividual quality monitoring of each individual transmis-sion segment. The automatic evaluation of the associatederror counters enables precise localization of critical net-work sections. Gradual or changing sources of error such asEMI influences, defective connectors or cable damage aredetected and located, even if they do not yet overstrain theself healing capacity of the network.

■ High availabilityIncreasing demands in terms of system availability arecatered for with optional cable redundancy that enablesdevices to be exchanged without having to shut down thenetwork. Adding redundancy is very inexpensive: the onlyadditional hardware is another standard Ethernet port (nospecial card or interface) in the master device and the sin-gle cable that turns the line topology into the ring (see Fig. 8). Switchover in case of device or cable failure onlytakes one cycle, so even demanding motion control appli-


150 μs. The communication with 100 servo axes is also ex-tremely fast: every 100 μs, all axes are provided with com-mand values and control data and report their actual posi-tion and status. The distributed clock technique enablesthe axes to be synchronized with a deviation of signifi-cantly less than 1 microsecond. And even at this pace, thereis more than sufficient bandwidth for asynchronous com-munications such as TCP/IP, parameter download or diag-nostic data upload.

The extremely high performance of the EtherCAT tech-nology enables control concepts that could not be realizedwith classic fieldbus systems. With EtherCAT, a communi-cation technology is available that matches the superiorcomputing capacity of modern Industrial PCs. The bus sys-tem is no longer the bottleneck of the control concept. Dis-tributed I/Os are recorded faster than is possible with mostlocal I/O interfaces. The EtherCAT technology principle isscalable and not bound to the baud rate of 100 Mbaud –extension to Gbit Ethernet is possible.

■ DiagnosisExperience with fieldbus systems shows that availabilityand commissioning times crucially depend on the diag-nostic capability. Only faults that are detected quickly andaccurately and located unambiguously can be rectifiedquickly. Therefore, special attention was paid to exemplarydiagnostic features during the development of EtherCAT.During commissioning, the actual configuration of thenodes (e.g. drives or I/O terminals) should be checked for

■ Table 1: EtherCAT Performance Overview

Process Data Update Time

256 distributed digital I/O 11 μs = 0,01 ms

1000 distributed digital I/O 30 μs

200 analog I/O (16 bit) 50μs ↔ 20 kHz

100 Servo Axis, with 8 Bytes 100 μs

input and output data each

1 Fieldbus Master-Gateway 150 μs

(1486 Bytes Input and

1486 Bytes Output Data)

■ Figure 8: Low cost cable redundancy with standard slaves


■ Figure 9: Decentralized Fieldbus Interfaces

cations survive a cable failure without problems. EtherCATalso supports redundant masters with hot standby func-tionality. Since the EtherCAT Slave Controllers immediatelyreturn the frame automatically if an interruption is en-countered, failure of a device does not necessarily lead tothe complete network being shut down. Drag chain appli-cations, for example, can thus be specifically configured asstubs in order to be prepared for cable break or use cableredundancy right away.

■ SafetyConventionally, safety functions are realized separatelyfrom the automation network, either via hardware or us-ing dedicated safety bus systems. Safety over EtherCAT en-ables safety-related communication and control communi-cation on the same network. The safety protocol is basedon the application layer of EtherCAT, without influencingthe lower layers. It is certified according to IEC 61508 andmeets the requirements of Safety Integrity Level (SIL) 3.Thedata length is variable, making the protocol equally suit-able for safe I/O data and for safe drive technology. Thereare no restrictions regarding the communication mediumor the transfer rate. Like other EtherCAT data, the safety da-ta can be routed without requiring safety routers or gate-ways. First fully certified products featuring Safety overEtherCAT are available since 2005. ETG also developed aSafety Drive Profile which provides a uniform data inter-face to the safety functionalities of drives and thus simpli-fies the setup and configuration.



■ EtherCAT instead of PCIWith increasing miniaturization of the PC components, thephysical size of Industrial PCs is increasingly determined bythe number of required slots. The bandwidth of Fast Ether-net, together with the process data width of the EtherCATcommunication hardware enables new directions: classicinterfaces that are conventionally located in the IPC aretransferred to intelligent EtherCAT interface terminals (seeFig. 9). Apart from the decentralized I/Os, drives and con-trol units, complex systems such as fieldbus masters, fastserial interfaces, gateways and other communication in-terfaces can be addressed.

Even further Ethernet devices without restriction onprotocol variants can be connected via decentralizedswitchport devices. The central IPC becomes smaller andtherefore more cost-effective. One Ethernet interface issufficient for the complete communication with the pe-riphery (see Fig. 10).

■ Device profilesThe device profiles describe the application parametersand the functional behavior of the devices including thedevice class-specific state machines. For many device class-es, fieldbus technology already offers reliable device pro-files, for example for I/O devices, drives or valves. Users arefamiliar with these profiles and the associated parametersand tools. No EtherCAT-specific device profiles have there-fore been developed for these device classes. Instead, sim-ple interfaces for existing device profiles are being offered


PDOMapping

ATMDT

FileAccess

Mailbox

EtherCAT Slave Controller

Physical Layer

IDN

CANopenApplication

HTTP,FTP, ...

File system,Bootloader

Process Data

Object Dictionary

SDOIP

TCP

Ethernet

Service Channel

Process Data

UDP

FoE EoE SoE CoE CoE/SoE

IEC61800-7-204Application(SERCOS)

■ Figure 11: Several Device Profiles and Protocols

can co-exist side by side



(see Fig. 11). This greatly assists users and device manufac-turers alike during the migration from the existing fieldbusto EtherCAT. At the same time the EtherCAT specificationkeeps it simple because all the protocols are optional. Thedevice manufacturer only has to implement the protocolthat the device application needs.

■ CAN application protocol over EtherCAT (CoE)CANopen™ device and application profiles are available fora wide range of device classes and applications, rangingfrom I/O components, drives, encoders, proportional valvesand hydraulic controllers to application profiles for plasticor textile machinery, for example. EtherCAT can provide thesame communication mechanisms as the familiarCANopen [7] mechanisms: object dictionary, PDO (processdata objects) and SDO (service data objects) – even the net-work management is comparable. EtherCAT can thus beimplemented with minimum effort on devices equippedwith CANopen. Large parts of the CANopen firmware canbe reused. Objects can optionally be expanded in order toaccount for the larger bandwidth offered by EtherCAT.

■ Servo drive profile according to IEC 61800-7-204 (SERCOS)

SERCOS interface™ is acknowledged as a high-perform-ance real-time communication interface, particularly formotion control applications. The SERCOS profile for servodrives and the communication technology are covered bythe IEC 61800-7-204 standard. The mapping of this profile

to EtherCAT (SoE) is specified in part 304 [8]. The servicechannel, and therefore access to all parameters and func-tions residing in the drive, is based on the EtherCAT mail-box. Here too, the focus is on compatibility with the exist-ing protocol (access to value, attribute, name, units, etc. ofthe IDNs) and expandability with regard to data lengthlimitation. The process data, with SERCOS in the form of ATand MDT data, are transferred using EtherCAT device pro-tocol mechanisms. The mapping is similar to the SERCOSmapping. The EtherCAT slave state machine can also be mapped easily to the phases of the SERCOS protocol.EtherCAT provides advanced real-time Ethernet technolo-gy for this device profile, which is particularly widespreadin CNC applications. Optionally, the command position,speed or torque can be transferred. Depending on the im-plementation, it is even possible to continue using thesame configuration tools for the drives.

■ Ethernet over EtherCAT (EoE)The EtherCAT technology is not only fully Ethernet-com-patible, but also characterized by particular openness “bydesign”: the protocol tolerates other Ethernet-based serv-ices and protocols on the same physical network – usuallyeven with minimum loss of performance. There is no re-striction on the type of Ethernet device that can be con-nected within the EtherCAT segment via a switchport. TheEthernet frames are tunneled via the EtherCAT protocol,which is the standard approach for internet applications(e.g. VPN, PPPoE (DSL), etc.). The EtherCAT network is fully

■ Figure 10: EtherCAT leads to smaller Controllers


virtual Ethernet SwitchFunctionality

virtual MAC AddressIP Address

■ Figure 12: Transparent for all Ethernet Protocols

transparent for the Ethernet device, and the real-timecharacteristics are not impaired (see Fig. 12).

The master acts like a layer 2 switch that redirects theframes to the respective devices according to the addressinformation. All internet technologies can therefore alsobe used in the EtherCAT environment: integrated web serv-er, e-mail, FTP transfer, etc.

■ File Access over EtherCAT (FoE)This very simple protocol similar to TFTP enables access toany data structure in the device. Standardized firmwareupload to devices is therefore possible, irrespective ofwhether or not they support TCP/IP.

■ Infrastructure costsSince no hubs and switches are required for EtherCAT, costsassociated with these devices including power supply, in-stallation, etc. are avoided. Standard Ethernet cables andstandard low cost connectors are used, if the environmen-tal conditions permit this. For environments requiring in-creased protection sealed connectors according to IECstandards are specified.



■ Literature[1] EtherCAT Technology Group, http://www.ethercat.org

[2] IEC 61158-3/4/5/6-12, Industrial communication

networks – Fieldbus specifications – Part 3-12: Data-link layer

service definition – Part 4-12: Data-link layer protocol

specification – Part 5-12: Application layer service definition –

Part 6-12: Application layer protocol specification – Type 12

elements (EtherCAT)

[3] IEEE 802.3: Carrier Sense Multiple Access with Collision

Detection (CSMA/CD) Access Method and Physical Layer

Specifications.

[4] IEEE 802.3ae: CSMA/CD Access Method and Physical

Layer Specifications: Media Access Control (MAC) Parameters,

Physical Layers, and Management Parameters for 10 GB/s

Operation.

[5] ANSI/TIA/EIA-644-A, Electrical Characteristics of Low

Voltage Differential Signaling (LVDS) Interface Circuits

[6] IEEE 1588: IEEE Standard for a Precision Clock

Synchronization Protocol for Networked Measurement

and Control Systems

[7] EN 50325-4: Industrial communications subsystem based on

ISO 11898 (CAN) for controller-device interfaces.

Part 4: CANopen.

[8] IEC 61800-7-301/304, Adjustable speed electrical

power drive systems – Part 7-301: Generic interface and use

of profiles for power drive systems – Mapping of profile

type 1 to network technologies – Part 7-304: Generic interface

and use of profiles for power drive systems – Mapping of

profile type 4 to network technologies

[9] SEMI E54.20: “Standard for Sensor/Actuator Network

Communications for EtherCAT”. http://www.semi.org

[10] IEC 61784-2, Industrial communication networks –

Profiles – Part 2: Additional fieldbus profiles for real-time

networks based on ISO/IEC 8802-3

[11] IEC 61784-3 Industrial communication networks –

Profiles – Part 3: Functional safety fieldbuses

[12] IEC 61784-5 Industrial communication networks –

Profiles – Part 5: Installation of fieldbuses


■ Figure 13: Versatile network architecture


■ SummaryEtherCAT is characterized by outstanding performance,very simple wiring and openness for other protocols.EtherCAT sets new standards where conventional field-bus systems reach their limits: 1,000 I/Os in 30 μs, op-tionally twisted pair cable or optical fiber and, thanksto Ethernet and Internet technologies, optimum verti-cal integration. With EtherCAT, the costly Ethernet startopology can be replaced with a simple line structure –no expensive infrastructure components are required.Where other real-time Ethernet approaches requirespecial interface hardware in the controller, for EtherCAT masters the on-board Ethernet port is suffi-cient. EtherCAT is versatile: master-to-slave, slave-to-slave and master-to-master communication is sup-ported (see Fig. 13). Safety over EtherCAT is available.EtherCAT makes Ethernet down to the I/O level techni-cally feasible and economically sensible. Full Ethernetcompatibility, internet technologies even in very sim-ple devices, maximum utilization of the large band-width offered by Ethernet, outstanding real-time char-acteristics at low costs are outstanding features of thisnetwork.



18


■ EtherCAT MasterEtherCAT communicates a maximum of 1,486 bytes of dis-tributed process data with just one Ethernet frame. Unlikeother solutions where the master device in each networkcycle has to process, send and receive frames for each node,EtherCAT systems typically only need one or two framesper cycle for the entire communication with all nodes.Therefore EtherCAT masters do not require a dedicatedcommunication processor. The master functionality putshardly any load on the host CPU which can handle this taskeasily besides processing the application program. Imple-mentation of an EtherCAT master can be very easy, partic-ularly for small and medium-sized control systems and forclearly defined applications. For example a PLC with a sin-gle process image: if it does not exceed the 1,486 bytes,cyclic sending of a single Ethernet frame with the cycletime of the PLC is sufficient. Since the header does notchange at run-time, all which is required is a constantheader to be added to the process image and the result tobe transferred to the Ethernet controller.

The process image is already sorted, since with EtherCAT mapping does not occur in the master, but in theslaves – the peripheral devices insert their data at the re-spective locations in the passing frame. This further un-burdens the host CPU. It was found that an EtherCAT mas-ter entirely implemented in software on the host CPU usesless of its processing power than much slower fieldbus sys-tems implemented with active plug-in cards – even servic-ing the DPRAM of the active card puts more load on thehost.

System configuration tools – available from severalmanufacturers – provide the network and device parame-ters including the corresponding boot-up sequence in astandardized XML format.

The EtherCAT technology was developed with very low cost devices in mind, like I/O terminals, sensors,and embedded controllers. EtherCAT only uses standard Ethernet frames according to IEEE 802.3.These frames are sent by the master device; the slave devices extract and/or insert data on the fly.Thus EtherCAT uses standard Ethernet MACs, where they really make sense: in the master device.And EtherCAT Slave Controllers are used, where such dedicated chips really make sense: in the slave device, where they handle the process data protocol in hardware and provide maximum real-time performance regardless of the local processing power or software quality.

■ Implementation Aspects

■ Master

Since EtherCAT uses standard Ethernet frames accord-ing to IEEE 802.3, any commercially available Ethernetmonitoring tool can be used for monitoring EtherCAT com-munication. In addition, an EtherCAT parser is part of theWireshark distribution. A Microsoft network monitor plug-in is also available for processing and displaying recordedEtherCAT data traffic.

■ Master implementation servicesEtherCAT masters have been implemented on a wide rangeof RTOS, including but not limited to: eCos, INtime, MI-CROWARE OS-9, On Time RTOS-32, Proconos OS, Real-TimeJava, RT Kernel, RT Linux, RTCX Quadros, RTAI Linux, PikeOS,Linux with RT-Preempt, QNX, VxWin + CeWin, VxWorks,Windows CE, Windows XP/XPE with CoDeSys SP RTE, Win-dows XP/XPE with TwinCAT RT extension and XENOMAILinux. Master stacks are available as open or shared sourceprojects, as sample code and as commercial software. Im-plementation services are also available from a variety ofvendors and for a variety of hardware platforms. Informa-tion about this fast growing offering can be found in theProduct Guide of the EtherCAT website [1].

■ Master sample codeAnother possibility to implement an EtherCAT master is to use sample code which is available for a nominal fee.The software is supplied as source code and comprises all EtherCAT master functions, including Ethernet overEtherCAT. All the developer has to do is adapt the code,which was created for Windows environments, to the tar-get hardware and the RTOS used. This has been done suc-cessfully for a number of systems.


Device Description(XML)

Control Task

HDR Process Data

Process ImageDescription (XML)

SystemConfiguration Tool

NetworkDescription incl.Boot-Up (XML)

EtherCAT Master

Standard Ethernet MAC

constant Header completely sorted(mapped) process data

WorkingCounter:constant

Padding Bytesand CRCgenerated byEthernetController (MAC)

Ethernet

FrameHDRFrameHDRDA SA Type Frame

HDREtherCATHDR

Data CTR Pad. FCS

Ethernet Header ECAT EtherCAT Datagram

(6) (6) (2) (2) (10) (0…1486) (2) (0…32) (4)

■ Master-Implementation with one Process Image

19

■ EtherCAT in embedded systems In an embedded environment an EtherCAT Master imple-mentation has to fit some special requirements, which areoften conflicting. On one hand, a specific environment re-stricts hard- and software properties, and on the otherhand, the application requirements have to be fulfilled.

The hardware environment includes a broad variationof micro controllers (8, 16 or 32 bit) with different con-straints concerning endianness and alignment limitations,which a master needs to address. There is also a broad vari-ation of different MAC chips used where a master has toface different data access methods (DMA access, IO access,Dual Port RAM access). A special objective in an embeddedenvironment is often the lack of a hard disk drive and ofcourse the limited resources like Memory, CPU or bus band-width (when accessing the MAC). Another objective a mas-ter should meet is a broad variety of different operatingsystems or in some cases even no operating system at all.If the same master software implementation shall run onmultiple of such different systems, the main requirementsto the software are portability and footprint.

Besides these different environments a system design-er has to consider which application requirements are tofulfill. These requirements are defined by the maximumnumber of slaves to be used, what kind of slaves are usedwith respect to the required slave protocols (e.g. EoE, CoE,FoE, SoE) and how much data has to be transferred pertime period (cyclic/acyclic data volume and bus cycle rate).


■ Structure of Master Sample Code

What also has to be considered is whether the used busconfiguration is static or dynamic. When using EtherCAT ascommunication technology between multiple embeddedsystems, there is often a special operating mode usedwhich is either the standard logical process data exchangeor a point-to-point type communication, whereslave stations are polled by acyclic commands and thecyclic part is only used to keep the system operational.

The main task for deciding which master solution touse is to clearly define how to face those conflicting re-quirements. The different options are to develop an ownmaster solution, to adapt the master sample code to theembedded environment or to purchase a commerciallyavailable master solution.

The benefit of EtherCAT in an embedded environmentis the possibility to have a scalable master by using oromitting some features or special protocols to meet theenvironment concerning memory and CPU. This is possiblebecause a master stack does not require a special hard-ware but can be implemented in software. EtherCAT pre-serves space in your control unit because no additional in-terface devices are needed. Furthermore it reduces powerconsumption because only an Ethernet MAC is needed andno additional active I/O cards. On mass products the cost isalways a matter of desire; here EtherCAT saves money be-cause standard MAC hardware (consumer market) can beused.


20


Slave Evaluation Kit (Altera/EBV)■ Slave

■ Slave Hardware: EtherCAT Slave Controller with Host CPU ■ Slave Hardware: EtherCAT Slave Controller with direct I/O

EtherCAT Interface with FPGA (IDAM) Slave Evaluation Kit (Hilscher)

■ Slave implementation servicesSeveral vendors offer slave implementation services in-cluding hardware and software integration. The variousEtherCAT Slave Controllers are supported by correspondingevaluation kits. The Slave Evaluation Kit makes all the in-terfaces of the controller easily accessible. Since withEtherCAT powerful communication processors are unnec-essary, the kit shown above contains an 8 bit μC which op-tionally can be used as host CPU. The kit comes with slavehost software – the equivalent to a protocol stack – insource code, and a reference master software package. Im-plementation workshops are held frequently.

■ Slave architectureA cost-effective EtherCAT slave controller is used in theslave devices. With EtherCAT the slave does not need a mi-crocontroller at all. Simple devices that get by with an I/Ointerface can be implemented only with the ESC and theunderlying PHY, magnetics and the RJ45 connector. Theprocess data interface (PDI) to the slave application is a 32-bit I/O interface. This slave without configurable parame-ters needs no software or mailbox protocol. The EtherCATState Machine is handled in the ESC. The boot-up informa-tion for the ESC comes out of the EEPROM that also sup-ports the identity information of the slave. More complexslaves that are configurable have a host CPU on board. ThisCPU is connected to the ESC with an 8-bit or 16-bit parallelinterface or via a serial connection (SPI). The performanceof the host CPU is determined by the slave application –the EtherCAT protocol software can be run additionally.TheEtherCAT stack manages the EtherCAT state machine andthe communication protocol: This means in general theCoE protocol and for supporting firmware download FoE.Optional the EoE protocol can be implemented.

EtherCAT MACMII

EEPROM

MIIEtherCAT MAC

Auto-Forwarderwith Loop Back

RegistersSYNC-Manager, FMMU

Process DataDual Port Memory

Mailbox

Host CPU

Process Data Service Data TCP/IP (optional)

HTTP,FTP, … RAM for TCP/IP

and complexApplications

Application Mapping

non volatile Data

EtherCATSlave

Controller

RJ45

Traf

o

PHY

RJ45

Traf

o

PHY

EtherCAT MACMII

EEPROM

MIIEtherCAT MAC

Auto-Forwarderwith Loop Back

RegistersSYNC-Manager, FMMU

Process DataDual Port Memory

Service Datanon volatile Data

EtherCATSlave

Controller

RJ45

Traf

o

PHY

RJ45

Traf

o

PHY

I/O Application

8 I/O8 I/O8 I/O8 I/O


■ EtherCAT Slave Controller overviewName ET1100 ET1200 ET18xx netX 5 netX 100 netX 500 netX 50Type ASIC ASIC Configurable IP Core ASIC ASIC ASIC ASICHW Supplier Beckhoff Beckhoff Altera/Xilinx Hilscher Hilscher Hilscher HilscherPackage BGA128 QFN48 FPGA dependent BGA201 BGA345 BGA345 PBGA324

0,8mm pitch 0,5mm pitch 0,8mm pitch 1mm pitch 1mm pitch 1mm pitchSize 10 x 10 mm 7 x 7 mm FPGA dependent 13 x 13 mm 22 x 22 mm 22 x 22 mm 19 x 19 mmμC Interface serial/parallel serial* serial/parallel serial (SPI), μC bus μC bus μC bus

(8|16bit) parallel (8|16bit)*" AVALON®/OPB®* (8/16/32, async) (internal, 32Bit) (internal, 32Bit) (internal, 32Bit)

Digital I/O 8-32* 8-16* 8-32* 16 - - -General Purpose I/O 0-32* 0-12* 0-128* - 16 16 32DPRAM 8 kByte 1 kByte 1...60 kByte* 6 kByte 256/400 Byte 256/400 Byte 6 kByte

(Mailbox/ (Mailbox/Process Data) Process Data)

SyncManager Entities 8 4 0…8* 8 4 4 8FMMU Entities 8 3 0…8* 8 3 3 8Distributed Clock Support yes yes yes* yes yes yes yesNo. of Ports 2–4(MII/EBUS)* 2–3 2 (MII/RMII) 2 x MII 2 (100BaseTX) 2 (100BaseTX) 2 (100BaseTX)

(EBUS/max. 1 x MII)*

Specials Routable with Various licence Multi Protocol Multi Protocol Multi Protocol Multi Protocol standard PCB models are Support Support, Support, Support,

available. A wide Integrated PHYs, Integrated PHYs, Integrated PHYs,range of Xilinx Integrated μC Integrated μC Integrated μCand Altera FPGAs (ARM9-200MHz) (ARM9-200MHz) (ARM9-200MHz)is supported.

*configurable

21


Slave Evaluation Kit (Beckhoff) Slave Evaluation Kit from Beckhoff

■ EtherCAT Slave ControllerSeveral Manufacturers provide EtherCAT Slave Controllers.Slave controller functionality can also be implementedvery cost effectively on FPGAs, for which binary code aswell as IP cores are available as buy-out license. The slavecontrollers typically feature an internal DPRAM and offer arange of interfaces for accessing this application memory:

■ The serial SPI (serial peripheral interface) is intendedparticularly for devices with small process data quanti-ty, such as analog I/O modules, sensors, encoders orsimple drives. This interface is typically used with 8 bitcontrollers, such as Microchip PIC, dsPIC, Intel 80C51,etc.

■ The parallel 8/16-bit microcontroller interface corre-sponds to conventional interfaces for fieldbus con-trollers with DPRAM interface. It is particularly suitablefor more complex devices with larger data volume.Controllers typically using this interface are e.g. Infi-neon 80C16x, Intel 80x86, Hitachi SH1, ST10, ARM or TITMS320 series.

■ The 32-bit parallel I/O interface is suitable for the con-nection of up to 32 digital inputs/outputs, but also forsimple sensors or actuators operating with 32 data bits.Such devices do not need a host CPU at all.

Latest information on the choice of EtherCAT Slave Con-trollers can be found on the EtherCAT website.




In order to achieve both, the ETG initially started with apragmatic approach: the Plug Fests. In addition to these in-teroperability meetings there is the Conformance Test Tool(CTT). For product certification official EtherCAT Test Cen-ters (ETC) have been established.

■ Plug FestPlug Fests – typically these are two-day events – are meet-ings where master and slave device suppliers gather to testand improve interoperability, to share implementation tipsand tricks and clarify questions regarding the technology.The Plug Fests have established themselves as pragmaticand effective means to achieve interoperable EtherCATproducts. They are typically attended by 20 or more devicevendors, representing 50+ different products. ETG organiz-es EtherCAT Plug Fests in Europe, Asia and North America.

■ Conformance Test Tool The Conformance Test Tool allows one to check protocolcompliance. Besides a standard PC with a standard Ether-net adapter, the MS Windows based Conformance Test Tooldoes not require any special hardware. The EtherCATframes to stimulate the Device under Test (DuT) are sentand received via a standard Ethernet port. The tool readsthe test cases from an XML file, so that test enhancementscan be generated without modifications to the test toolsoftware itself. Test results and comments are shown in atest logger. The tool also tests the EtherCAT Slave Informa-tion (ESI) file. CiA402 tests for example allow one to check

Conformance and interoperability are very important factors for the success of a communication techno-logy. Therefore the EtherCAT Technology Group is taking these topics very seriously. Conformance of thetechnology implementation with the specifications is the prerequisite of interoperability, which meansthat devices of different manufacturers co-operate within the same networked application.

■ Conformance and Interoperability

conformity of EtherCAT drives supporting the CiA402 driveprofile: easy set up, identical behaviour and correct supportof cyclic synchronous operation modes are part of thesetests.

To meet minimum conformance requirements a device hasto pass the protocol test using the Conformance Test Toolat the time of its first release to the market. Of course ven-dors are encouraged to keep up with the latest version ofthe Conformance Test Tool and also fix issues which onlyhave been revealed after the initial release of their device.The Conformance Test Tool is licensed on a subscription ba-sis, in order to ensure long term availability of resources formaintenance, support and enhancement. EtherCAT devicevendors have to maintain a valid subscription of the tool.The test cases are developed and maintained by the ETGWorking Group Conformance.

■ Working Group Conformance The Technical Committee of the ETG established the Work-ing Group Conformance, which defines the test proceduresand in particular works on continuously enhancing and im-proving the tests. The main goal of the working group is toreach complete test coverage in the future.The Working Group Conformance meets regularly, either inface-to-face or web meetings.




■ EtherCAT Test Center The ETG has accredited official EtherCAT Test Centers (ETC)in Nuremberg, Germany, and Kyoto, Japan. Further testcenters in Europe, Asia and North America are intended.ETCs do not only perform the official EtherCAT Confor-mance Test, but also provide qualified feedback and imple-mentation support for ETG members. Furthermore, ETCsprovide facilities for the interoperability test.

■ EtherCAT Conformance TestThe EtherCAT Conformance Test covers a ConformanceTest, Interoperability Test and Physical Layer Test carriedout by an ETC. Using the Conformance Test Tool already en-sures a high degree of conformity. However, since test toolresults of tests carried out in the R&D lab are not checkedby an independent body the EtherCAT Conformance Test isexecuted by the ETC, too. Vendors who want a Confor-mance Certificate submit their devices for testing at an of-ficial EtherCAT Test Center of their choice.Test Agenda of the EtherCAT Conformance Test:| EtherCAT Protocol (Conformance Test)

– ESI, SII (EEPROM), EtherCAT State Machine,Mailbox Communication and Services

| Indicator Specification| Marking Rules| CiA402 Drive Profile (if supported)| Interoperability Test

■ Interoperability TestThis test is performed using a network with a diverse com-bination of EtherCAT devices. Such networks are main-tained and constantly enhanced at the EtherCAT Test Cen-ter.

■ Conformance Certificate If a device passes the official EtherCAT Conformance Test atan EtherCAT Test Center, ETG issues the Conformance Cer-tificate. Devices for which a Conformance Certificate hasbeen issued are EtherCAT Conformance tested products.They may carry the official EtherCAT Conformance TestedLogo and they are marked accordingly in the EtherCATProduct Guide. EtherCAT users are encouraged to includethe availability of the conformance test mark in their ven-dor and device selection process.

More information about Conformance is available athttp://www.ethercat.org/en/conformance.html


M M M M M

PLC

StandardI/O

Safety/standard I/O

Safety/standard I/O

Safetydrives

Safety logic

Standard fieldbus

M M M M M

StandardI/O

Safetyoutputs

Standarddrives

PLC

Safetyinputs

Safety logic

Fieldbus

Relay logic



■ Safety fieldbus systemIntelligent safety solutions in the automation componentsand communication systems enable integration of safetytechnology into the machine design.

One of the key factors enabling this kind of integrationis the transfer of safety-related and standard communica-tion on the same fieldbus. The solution for EtherCAT is theSafety over EtherCAT protocol.

The benefits:| Single communication system for control and

safety information| Seamless integration of the safety concept into the

machine design| Outstanding diagnostic options for the

safety functions| Flexible extension options| No performance limitations in terms of real-time

and determinism| No separate development tools for standard and

safety application| Simple handling and transparent safety functions

■ Technology RequirementsThe basic principles for testing and certification of bus sys-tems for transferring safety-related messages are specifiedin the international IEC 61784-3 standard.

In the interest of realizing safe data communication over EtherCAT, the Safety over EtherCAT protocol has been disclosed within the EtherCAT Technology Group. Safety over EtherCAT meets the requirementsof IEC 61508 SIL 3 and enables the transfer of safe and non-safe information on the same communicationsystem without limitations with regard to transfer speed and cycle time.

■ Safety over EtherCAT

The following errors for such a network have to be as-sumed: corruption, repetition, interchanging, loss, delay, in-sertion, masquerading and invalid addressing of mes-sages. A safety protocol must be able to handle all these er-rors via suitable measures, i.e. they must be detected ac-cording to the required safety category.

The following features were crucial in the development ofthe Safety over EtherCAT protocol:| Compliance with Safety Integrity Level SIL 3 of

IEC 61508| Safe and non-safe information on the same

communication system| Independence of the protocol from the transfer

system and medium| The length of the safe process data is not restricted

by the protocol| Very short frame lengths are possible| No limitations with regard to transfer speed

and cycle time

The Safety over EtherCAT protocol has been assessed byGerman Technical Inspection Agency (TÜV). It is certified asa protocol for transferring process data between Safetyover EtherCAT devices up to SIL 3 according to IEC 61508.The implementation of the Safety over EtherCAT protocolin a device must meet the requirements of the safety tar-get. The associated product-specific requirements must betaken into account.

■ Safety fieldbus systems enable simple and flexible machine concepts ■ Safety over EtherCAT Frame


Maschine | A Maschine | B Maschine | C

#1 #2 #3

#1 #2 #3

Ethernet

Safety-over-EtherCAT Safety-over-EtherCAT


vices detects a communication error, it changes to resetstate, thereby resetting the connection.

■ Application ExampleThe safety and functionality of a safety communicationprotocol can only be proven through implementation in aproduct. Devices with Safety over EtherCAT have beenavailable since 2005. EtherCAT is therefore one of the firstIndustrial Ethernet real-time communication systems sup-porting a safe protocol.

Applications utilize the benefits of the technology.Scalable safety-related input and output components canbe used in the system; additional inputs or outputs can beextended flexibly using safety and non-safety devices asrequired.

Even the safety logic can be embedded within the net-work.The control PLC then remains a standard device with-out safety extension and the safety logic is processed with-in a safety device in the network segment. This saves costsand enables scaling of the safety logic within the system.Only the messages between the Safety over EtherCAT mas-ter and the corresponding safety slave devices are routedvia the standard PLC. Of course the classical safety PLC ar-chitecture is supported by Safety over EtherCAT as well.

With the black channel approach even the concatena-tion of machine parts is possible. The Safety over EtherCATFrames are routed via the standard communication pathon the Process Control level.


Any communication path can be used, including fieldbussystems, Ethernet or similar transfer systems, optical fibrecables, copper cables, or even radio links.

■ Implementation aspectEtherCAT is used as a single-channel communication sys-tem for transferring safe and non-safe information. Thetransport medium is regarded as a “black channel” and notincluded in safety considerations. A safety frame contain-ing the safe process data and the required data backup isincluded in the EtherCAT process data. This “container” isanalyzed in the devices at the safety application level. Thecommunication remains single-channel.

Via suitable procedures, the frame is designed suchthat a minimum container length of 6 bytes is sufficientfor transferring all error detection information, includingone byte of safe process data. Incidentally, the protocoldoes not impose any limits regarding the length of safeprocess data. This means that safety components with alarge amount of safe process data are also supported.

During start-up of a Safety over EtherCAT connection, astate machine is processed both in the master and in theslave. Here again, the focus was on a simple structure in or-der to make implementation as simple as possible. Statetransitions are initiated by the master and acknowledgedby the slave.

The “data” state is the normal operating state for ex-changing safety input and output data. If one of the de-

■ Black channel approach allows concatenation of machine parts ■ Safety over EtherCAT hardware architecture ■ Simple state machine for a

master/slave connection


26 EtherCAT Technology Group26 EtherCAT Technology Group


■ Why do companies choose EtherCAT?

■ Flexible TopologyThe machine structure determines the topology - not thebus system. Since no switches or hubs are needed, they donot limit the network structure. There are almost no re-strictions given by the EtherCAT technology: line, tree, star,drop lines - everything is possible.

The automatic link detection gives the possibility tosupport hot-swap functionality of machine parts. The(dis-)connection of the parts can be managed by the busmanager or can be handled automatically by the slavedevices.

With a simple extra cable to a second (standard) Ether-net port on the EtherCAT master, a very simple and cost ef-fective network redundancy is possible.

EtherCAT is also ideal for widely distributed applica-tions: Up to 100 m between two nodes on copper cables andup to 2 km on standard fiber-optic cables are supported.

Application examples:■ Baggage conveyor systems■ Bridge absorption system■ Snow blower control■ Automated warehousing■ Printing machines■ Hydraulic/electric presses■ Woodworking machines

■ High PerformanceEtherCAT is the fastest Industrial Ethernet technology withoutstanding synchronization features. It is used in all ap-plications with short cycle times like Motion Control appli-cations as well as for measurement applications withmany I/O signals.

Simply the use of EtherCAT allows one to increase thecontrol performance up to 20%, often even more. This per-formance is then available for the user application. The in-creased accuracy and productivity of the machine leads tolower costs and higher profits. EtherCAT meets today's andtomorrow's requirements!

Application examples:■ Robotics■ Machine tool applications■ CNC functionality■ Packaging machines■ Injection molding■ Engine test beds■ Measurement applications■ Ultra fast metal cutting■ Blow molding machinery■ Semiconductor + FPD manufacturing

Photo: BMW AG


27EtherCAT Technology Group 27EtherCAT Technology Group


■ Ease of UseThe configuration and maintenance of a machine is a deci-sive factor for the life cycle costs. With EtherCAT, thesetasks are significantly simplified. The configuration andthe topology of a machine can be scanned after installa-tion and can be compared to an expected configuration.

If a device has a failure or detects errors on the com-munication systems, the outstanding diagnostic featuresgive an exact localization of the error source and thereforeallow a fast trouble shooting.

Again the performance of EtherCAT is decisive: There isno need for network "tuning", as known for standard field-bus systems. If additional information is needed from a de-vice, it can be added to the cyclic transfer (nearly) withoutlimitations by the network bandwidth.

Application examples:■ Standard PLC applications■ Automotive factory automation with short MTTR

(Mean time to repair)■ Intra-machine communication with expected hard-

ware configuration■ Modular machines■ Welding machines■ Edge banding machines

■ Low CostEtherCAT meets or even undercuts fieldbus cost levels.There is no special master card required on the master side– on-board MAC or low cost standard NIC are sufficient. Forthe slave side, highly integrated slave controllers guaran-tee low interface costs. Furthermore, between the masterand the slave standard Ethernet cables can be used. No ac-tive infrastructure components are required and thereforeno costs for buying, configuration, installation and main-tenance of these devices are necessary.

Application examples:■ Embedded systems■ Frequency inverters■ Sensors■ Mass flow controller■ Encoder■ RFID reader



www.ethercat.org

■ Contact:

ETG Headquarters

Ostendstraße 196

90482 Nuremberg

Germany

Phone: +49 (911) 5 40 5620

Fax: +49 (911) 5 40 5629

Email: [email protected]

ETG Office North America

Volente, Texas, USA

Phone: +1-877-ETHERCAT

Fax: +1 (512) 535 1437


ETG Office China

Beijing, P. R. China

Phone: +86 (10) 66 21 7688

Fax: +86 (10) 66 21 0992


ETG Office Japan

Tokyo, Japan

Phone: +81 (3) 5825 5333

Fax: +81 (3) 5825 8550


ETG Office Korea

Seoul, Korea

Phone: +82 (2) 21 07 32 40

Fax: +82 (2) 21 07 39 69


EtherCAT®, Safety over EtherCAT™, are trademarks or registered trademarks.Other designations used in this publication may be trademarks whose use by third parties for their own purposes could violate the rights of the owners.


The Ethernet Fieldbus

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