EDDL_FieldBus

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24 IEE Computing & Control Engineering | December/January 2004/05

EDDL tforsimplicitywithadvanced, full functionality

Digital fieldbusinstallationsuse

IMPROVEMENTS AND EXPANSIONCONTINUE FOR THE OPEN, ROBUSTGLOBAL STANDARD – EDDL.

024-031_CCE_DecJan0405_EJ 11/17/04 1:13 PM Page 24

EDDL technology

IEE Computing & Control Engineering | December/January 2004/05 25

When IEC 61804-2 Electronic DeviceDescription Language (EDDL) wasapproved as an international standardin March 2004, the EDD source filescreated using EDDL were already

deployed in millions of process industry field devices.EDDL is a text-based language for describing the digital

communication characteristics of intelligent fieldinstrumentation and equipment parameters – device status,diagnostic data, and configuration details – in an operatingsystem (OS) and human machine interface (HMI) neutralenvironment.

Initially developed in 1992 for use as part of the HART

Communication Protocol (HART, www.hartcomm.org),EDDL based-technologies continue to evolve. EDDL is beingenhanced to extend the concept of interoperability to theHMI and diagnostic data.

Today EDDL technologies form the engineering andoperating foundation on which all major digital fieldbusprotocols – FOUNDATION, HART, and Profibus – constructparametric and device descriptions. And, because EDDL isan open technology with international standard status, itcan be easily and effectively applied to any device and anyfieldbus protocol.

The EDDL technology enables a Host Systemmanufacturer to create a single engineering environmentthat can support any device, from any supplier, using anycommunications protocol, without the need for customsoftware drivers for each device type.

MATCHING NEEDSTechnologies and standards appear and disappear all thetime. Often, those who buy into the ‘technology de jour’have later been disappointed and incurred unnecessaryexpense to replace a ‘promising’ but unsupportedtechnology.

Today’s process industry users have become verycautious about buying ‘technology hype’, especially whenfaced with choosing a technology that must remain in placefor a decade or more.

When discussing digital field automation technologyarchitectures, users state their concerns a hundred differentways, but in the end, what users seek are assurances thetechnology platform they choose provides:� Freedom of choice in plant floor instrumentation and

equipment independent of the Host – valves,transmitters, motor starters, remote I/O, etc.;

� Consistency in how plant floor instrumentation andequipment is engineered;

� Flexibility and efficiency in how plant-floor data areshared throughout the enterprise;

� Ease of maintenance; and� Quantified proof that adopting manufacturers have long-

term commitments to expand and improve theunderlying technology.A seldom-mentioned, yet extremely important

realisation influencing a technology’s success is itsdependence on other technologies.

From a product manufacturer’s perspective, the lessdependent a technology’s architecture is on underlyingtechnologies, the better. Not only does such a design helpmanage risk, it frees up development resources to enhanceand improve product features – something end-users seekwhen evaluating similar products from differentmanufacturers.

Overall, the simple elegance, enhanced capabilities, andOS and HMI neutrality of EDDL technology provides ➔

technologyBy Martin Zielinski

From a product manufacturer’sperspective, the less dependenta technology’s architecture ison underlying technologies,the better

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solutions that address the engineering and operatingquestions, concerns, and needs of both end-users andmanufacturers.

EMPOWERING USERSFrequently, marketing literature and sales presentationsstate that end-users insist on a single engineeringenvironment to manage, commission, and configure anyfield device, from any manufacturer, to any fieldbusprotocol.

Similarly, the engineering environment is often the focusat industry and user group meetings in the form of a multi-part question, “During a Process Automation System’s(PAS) life-time, what percentage of time will/did it take to:1. Develop the initial database and control logic?2. Perform software maintenance and upgrades? and3. Make periodic engineering improvements and

enhancements”?Undoubtedly engineering, configuring, and managing

activities are important. Further, when those activities arecompared to the amount of time operators use the system,experienced users also ask, “How consistent can we makeour HMI systems so our operators can confidently andefficiently use them”?

Depending on the data source, it’s usually agreed that operations personnel use the PAS 70-85% ofthe time, with other activities sharing the remaining 15-30%.

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While engineering, installation, development, andimprovement activities are fundamental, it’s equallyimportant to understand how EDDL technology is beingenhanced to meet the daily needs of operators andmaintenance personnel.

OPERATOR INFORMATION AND INTERACTION EDDL technology creates source files containing onlycontent relevant to a specific manufacturer’s intelligent fieldinstrument or device. This is an important aspect of theEDDL technology design philosophy that insists that EDDfiles remain OS and HMI neutral.

For manufacturers of intelligent field instrumentationand equipment, this philosophy eliminates the need toexpend resources designing and writing software to supportoperator interfaces – specifying fonts, sizing windows,selecting colours, etc. – for different manufacturers HMIproducts and platforms.

For end-users, EDDL’s neutrality philosophy ensuresthat operators are provided information with a look and feelthat is consistent with other information being presentedon the same HMI.

Some might argue that content is more important thanconsistency; this may be correct for operating informationthat users access several times an hour. However, EDD filecontent provides access to ‘normal’ and ‘abnormal’operating information. EDD file content is about access toinformation contained in intelligent field devices andequipment, the sort of information that’s viewed byoperators during all sorts of process operations.

Because abnormal process operations occur infrequently– every few days, weeks, or months – presentationconsistency does become important. For example, most ofus have experienced the ‘use it or lose it’ softwarephenomenon; the one where we revisit a softwareapplication we once knew well, only to find we’ve forgottena lot of what we once knew.

That’s exactly what EDDL’s design philosophy avoids.Most people would agree that when faced with efficiently

EDDL puts special emphasis onensuring that both operators and maintenance technicians are comfortable using thetechnology to make criticaloperational decisions

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evaluating and acting on information, a familiarpresentation format provides users with considerableconfidence that they are making the correct decisions.

There’s no doubt that a technology for deploying digitalfield instrumentation or equipment should provideefficiencies in addressing the development of the initialdatabase and logic, aid maintenance, and supportenhancements. As previously noted, those functions areemployed about 15-30% of the time.

Most of the time the efficiency and effectiveness of thetechnology is being ‘realised’ by process operators andmaintenance technicians, thus the technology must do itswork in a way that makes these individuals comfortable.

Using a Foundation Fieldbus based temperaturetransmitter as an example, fig 1 shows the parameters asthey would appear on an HMI, if read directly from the

EDDL technology


EDD without any parametric organisation applied.Fig 2 shows how those same parameters could be

organised on the HMI by using the EDDL enhancements.In this case, the host system supplier has chosen to usedialog boxes with identifying tabs.

Fig 3 shows an alternate display organisation of theparameters using the exact same EDD. In this case, an‘explorer view’ of the temperature transmitter contents isshown. The enhancements to EDDL provide the HostSystem manufacturer with the flexibility to organise theparameters of a field device in the manner recommendedby its manufacturer, but consistent with the look and feelof the HMI.

EDDL technology is designed to address engineering,start-up and daily operations requirements, with specialemphasis on ensuring that operators and maintenance ➔

DEVICE DESCRIPTOR LANGUAGE (DDL) technology firstappeared in 1990 and because of its flexibility and reliability it hasbecome a significant technology in many industries includingtelecommunications, mainframe and personal computingapplications, and instrumentation and control.

The HART Communication Protocol (HART) first begin using DDLtechnology in 1992. HART’s advancement of the DDL technologyeventually lead to the development of the InternationalElectrotechnical Commission’s IEC 61804-2 standard, ElectronicDevice Description Language (EDDL).

Key elements that continue to make EDDL technology a secure,reliable workhorse for instrumentation and control applicationsinclude:Operating system independence – EDD files do not containspecific operating system commands or instructions, thus theyremain transportable and operating system independent.Consistency and uniformity – EDDL technology’s architecturesupports multiple protocols within the same host application and

requires no custom tools to maintain a common look and feel.Single Engineering Environment – EDDL technology enables aHost System manufacturer to create a single engineeringenvironment that can support any device, from any supplier, usingany communications protocol, without the need for custom softwaredrivers for each device type.Revision control – Device revision is used to identify the revisionlevel of a device. This permits manufacturers to improve an existingdevice’s implementation, such as adding support for additionalparameters or enhanced diagnostics.Testing and registration – Testing includes validating the syntax,dependencies, and other protocol and language rules using toolkitsand registering the EDD binary file with the appropriate fieldbusorganisation.International standard support – EDDL technology is aninternational standard approved by the International ElectrotechnicalCommission (IEC) and is available as standard number 61804-2. Italso makes use of ISO standards for language and country codes.

KEY FEATURES OF EDDL TECHNOLOGY

Fig 1 (far left): Parameters in a temperaturetransmitter read directly from the EDD without anyorganisation appliedFig 2 (centre left): Parameters in a temperaturetransmitter organised via the enhancements of EDDLand the look and feel of the HMIFig 3 (left): The same EDD as in Figure 2, but with adifferent look and feel as determined by the HMI



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technicians are comfortable using the technology to makecritical operational decisions.

ADDRESSING ENGINEERING REQUIREMENTSEDDL technology addresses the engineering requirementsof end-users and intelligent field device and equipmentmanufacturers. Though their reasons differ, the engineeringrequirements of both groups are similar, each seekingsolutions that:� Ensures operating system independency;� Supports multiple fieldbus protocols;� Avoids special, proprietary, or executable files for

different host system platforms;� Supports multiple country codes and international

languages;� Utilises standardised testing and validation procedures

and tools;� Efficient configuration entry;� Uses a robust, consistent, easy to identify revision

control methodology; and� Includes third-party testing and registration.

Besides meeting all of these engineering requirements,EDDL technology also has international standards statusas IEC 61804-2.

EDDL’s design philosophy provides end-users andintelligent field device product manufacturers a consistentand rich engineering environment.

MAINTENANCE AND UPGRADESWhen control and automation systems adopted ‘opensystem’ technologies, software maintenance, withmandatory and voluntary software upgrades, increaseddramatically. Today it’s not uncommon to install mandatorysoftware upgrades and/or OS security patches two or moretimes a month. However, EDDL’s neutrality to OS and HMItechnologies eliminate the need for end-users to worryabout what happens to EDD files as a result of softwareupgrades.

Everyone who’s upgraded a computer from Microsoft

Windows 98 to Windows 2000 and later to Windows XPappreciates the complexities of re-linking applications,re-loading device drivers, re-establishing networkcommunications, and dealing with incompatible executablefiles. EDDL technology does not install or create anyexecutable files in the HMI host application; thus EDDLbased technologies eliminate the need to re-link applicationsor communications, and incompatible EDD files simplydon’t exist.

One feature personal computer users have come toappreciate is the ‘plug-and-play’ technology known asUniversal Serial Bus (USB).

From a user’s perspective, USB appears quite simple and,regardless of the device manufacturer or device type that’sbeen plugged-in, what appears on the user’s screen isconsistent for Windows users and different, yet consistentfor Macintosh users.

Behind the scenes USB shares a lot of similarities withEDDL technology. Both use device description files and bothmake use of device descriptor services embedded in thehost platform that are designed to provide users with aconsistent information presentation format.

Similar to the efforts that produced USB, representativesof Fieldbus Foundation (FF), HART CommunicationFoundation (HCF), and Profibus Nutzerorganisation e.V.(PNO) met in Feb 2003 to extend the capabilities of the IEC61804-2, Electronic Device Description Language standard.

Fig 4: Example EDDL user presentation of radar levelgauge threshold calibration. In this example, a graphis used to present the echo waveform of a radar level

gauge in order to identify false echo areas andconfigure appropriate thresholds. Thanks to EDDL’s

uniformity design philosophy, information is presentedto users the same regardless of device manufacturer.

USB shares a lot of similarities withEDDL technology. Both make use ofdevice descriptor services embeddedin the host platform for consistentpresentation format.

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EDDL technology

Among EDDL’s extensions are improved device dataorganisation, graphical visualisation consistency, andsupport for persistent data storage.

The objective is to specify a common set ofenhancements, validate and then incorporate theenhancements into the EDDL technologies of the respectivefieldbus organisations. Later, when the IEC 61804-2 standardundergoes its required review and maintenance, theenhancements will be added to the International Standard.

From a system administrator’s perspective, thesimplicity, longevity, robustness, and OS and HMI platformneutrality of field devices conforming to IEC 61804-2simplifies software maintenance activities. For alreadyoverworked control system engineers/technicians,eliminating software maintenance worries is a welcomebenefit of deploying EDDL based fieldbus technologies.

For intelligent field device manufacturers, knowing thatEDD files are always OS and HMI neutral permits eachmanufacturer to release a new product when the product isready and not have to wait until the product completescompatibility testing with a variety of different HMImanufacturers and/or OS revisions.

PLATFORM AND PROTOCOL INDEPENDENCEEveryone is aware of the difficulties of getting devicesoftware drivers to work following a host platform OSupgrade. EDDL was specifically designed for the EDD fileto avoid this issue. The IEC 61804-2 standard is not only OSand HMI independent, but also fieldbus communicationprotocol neutral.

It’s this extended neutrality that allows devicemanufacturers to confidently develop a single EDD sourcefile for a given fieldbus based device and be assured it willsafely and consistently perform on a variety of hostapplication platforms.

From an end-user perspective, it’s equally reassuring toknow that a host workstation change from Unix to Linux orfrom Windows NT to Windows XP or a port to Windows CEdoes not require modification of the existing EDD files.

The way EDDL technology retains its platform andprotocol independence is really quite simple. Each EDD fileis uniquely numbered and contains only the descriptionsneeded by the host application. Any methods included inthe EDD file are interpreted by the host application using amethod interpreter, thus providing a safe area or ‘sandbox’where methods execute.

Security and reliability are also assured because theinstallation of an EDD file does not initiate installation ofWin32-based DLL (dynamic linking library), ActiveX, orsimilar executable software, thus avoiding the problemsassociated with incompatible versions, revised path names,and/or ‘file missing’ error messages.

EDDL technology is designed to encourage worldwideuse and includes support for multiple languages as definedby the International Organisation for Standardisation(ISO).

Under the EDDL architecture, developers write a singleEDD file that incorporates multiple language text strings,each conforming to ISO 639 for language codes, and ISO 3166for country codes. The EDD host application selects theappropriate language from the EDD file to display userinformation.

Avoiding host application conflicts and maintaining aconsistent look-and-feel is paramount for operator/users.To this end EDD files do not specify fonts, window sizes,colour, or other aspects of the host interface.

Because of the wide number of host application types –PAS with a rich graphic interface to a simple handheld unitwith a limited capability display – the host applicationgenerates the screens based on constructs provided by EDDfile content. This permits information contained in the EDDfiles to seamlessly integrate with a specific hostapplication’s capabilities.

For intelligent device manufacturers, the platform andcommunication protocol independence of the IEC 61804-2Electronic Device Description Language standard ensuresproven:� Specifications exist for defining the architecture of ➔

Fig 5: platform independence. EDDLtechnology permits manufacturers tocreate a single EDD file and use that fileon a wide variety of host platforms, eachwith a different operating system anddisplay capabilities.


FOR ADDITIONAL READINGReaders can visit the following websites to learn more about the useof EDDL technology and fieldbus protocols.� ARC Advisory Group www.arcweb.com� Fieldbus Foundation www.fieldbus.org� HART Communication Foundation www.hartcomm.org� International Electrotechnical Commission www.iec.ch� Profibus Nutzerorganisation e.V. www.profibus.com


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the application, syntax (form), semantics (meaning), anduser interface structure;

� Capabilities exist to implement a single version of aproduct-specific EDD file containing the device’sconfiguration, maintenance, and functionality; and

� Flexibility exists for deploying the same product, and itsassociated EDD file, on different fieldbus protocols.For end-users, knowing that manufacturers of IEC 61804-2

conforming devices are developing, testing, andmaintaining a minimum number of EDD files, providesadditional peace of mind when facing PAS upgrades,patches, and even operating system changes.

TESTING AND VALIDATIONAs an international standard, EDDL technology marks amajor advancement towards achieving interoperability ofintelligent field instrumentation incorporating differentfieldbus protocols.

EDD file testing is a multi-part activity. The intelligentfield device manufacturer conducts the first series of tests.The second series of tests is conducted by the appropriateprotocol organisation – Fieldbus Foundation (FF), HARTCommunication Foundation (HCF), or ProfibusNutzerorganisation e.V (PNO) – with each organisationapplying similar EDD file testing and registration

procedures.For example, after an intelligent field device

manufacturer creates an EDD source file for use with FFprotocol, the developer uses a tokeniser tool to validatethe syntax, dependencies, and other protocol andlanguage rules. Once all checks are verified andvalidated, the tokeniser tool generates an EDD binary filethat organises the information into a format accessibleby host HMI applications. Besides providing acompressed, easier to transfer file, the binary formatprovides protection against accidental changes using asimple text editor.

The manufacturer then submits the EDD binary file toFF for additional testing and registration.

Before FF registers the submitted EDD binary file it is

subjected to a series of tests using FF’s Interoperability TestKit (ITK).

The first test loads the EDD binary into a test system tovalidate correct identification information exists.

Next the file is subjected to multiple test cases to ensurethe EDD file content matches its device and follows protocolrules for maintaining interoperability between hosts anddevice.

Finally, FF logs the EDD file information, includingname, date, size, and the 32-bit cyclic redundancy checksumvalue. These become the files available for download fromthe Foundation’s website.

For end-users and intelligent field device manufacturers,the simple elegance of EDDL technology combined with thetesting and validation tools developed and maintained byeach fieldbus organisation provides an unprecedented levelof confidence that robust, protocol interoperable solutionsperform as designed and desired. It reflects over 10 years ofaccumulated experience.

EDDL ARCHITECTUREThe architecture of EDDL technology makes it easy to usemultiple communication protocols within the same HMIhost application, requires no custom tools for configuration,and maintains a common look and feel for operators andmaintenance technicians, regardless of the intelligent fieldinstrumentation or equipment being viewed. The EDDLtechnology enables a Host System manufacturer to createa single engineering environment that can support anydevice, from any supplier, using any communicationsprotocol, without the need for custom software drivers foreach the device type.

With HMI host systems ranging from large processautomation systems (PAS) with rich graphic displays, tosimple handheld devices with limited display capabilities,EDDL’s consistent look and feel philosophy represents agreat advantage when it comes to operator andmaintenance personnel user training.

Because EDDL technology was designed to eliminatethe need for special or proprietary files in host systems, asingle EDD file created for a full-featured PAS worksequally well in the handheld device.

This important design feature eliminates the expenseand burden for intelligent field instrument manufacturersto create, test, register, and maintain different files fordifferent HMI host systems, or a different OS for a differentrevision of the same host system.

For users, this feature of EDDL technology greatlysimplifies changing, adding, upgrading, and evolving HMIhost systems.

Verification that EDDL’s design philosophy worksoccurred in 2002 when Infraserv Hochst established a multi-



EDDL technology

vendor laboratory, incorporating six Foundation Fieldbushost systems and 42 field devices from 11 instrumentsuppliers.

Infraserv Hochst developed and applied a variety of teststo evaluate the interoperability of the Foundation Fieldbustechnology.

In its final report, delivered to the NAMUR GeneralAssembly in Lahnstein, Germany, Infraserv Hochst statedthat 100% of the EDD files worked correctly between eachhost system and the respective devices. Infraserv Hochst’stests further validate an important aspect of EDDLtechnology – that system-wide interoperability is bestachieved using a well-defined specification and rigoroustesting procedures.

EDDL EXTENSIONSIn February 2003, representatives of, FF, HCF, and PNO metin a collaborative project to extend the capabilities of theIEC 61804-2 standard.

The scope of the co-operative project is to add robustorganisation and graphical visualisation of device data aswell as support for persistent data storage (i.e., permanentdata storage) features to IEC 61804-2. Sophisticated deviceswith hundreds of configuration, calibration, and diagnosticparameters, such as control valves, radar level gauges, andvariable frequency drives, will greatly benefit from the newuser interface enhancements.

Once implemented, the new extensions will further unifythe HMI environment and eliminate the need for customconfiguration software packages.

Using familiar dialog boxes, text, dynamic variables,pictures, charts, and archived data are presented to usersin a consistent, familiar format. Graphs, such as controlvalve signatures, may incorporate pan/zoom functionalityfor inspecting specific detail. Additionally, EDDL extensionssupport user interaction with device content, such aspermitting adjusting filter values.

By providing a standard, platform-independent meansfor displaying graphical information, device suppliers usingEDDL technology can focus resources on increasingproduct features to better meet user requirements and knowthat developed solutions will be consistently delivered

across a variety of platforms and operating systems.One EDDL extension that end-users asked to be included

is the support for persistent data storage. This new featurepermits device manufacturers to instruct the hostapplication to store device or local data. Thisimplementation method relieves the intelligent devicemanufacturer of having to learn the underlying file systemnuances of different host applications; how data are storedis left up to the host application.

Persistent data storage enables a variety of newapplications using EDDL technology. For example, valvediagnostic software, developed using EDDL technology, canarchive valve signatures for later review by supportpersonnel.

The benefit of IEC 61804-2’s neutrality is again revealedwith the addition of the new EDDL extensions.

For example, an intelligent field instrumentationmanufacturer who previously developed products for useon the FF protocol isn’t required to begin using the newEDDL Tokeniser, Viewer, and Services tools until itsproducts begin using the new EDDL extensions.

In fact, for simple devices, EDD file developers maycontinue writing EDDL files the same way they do todayusing either the existing or a new tool.

For more complex devices, developers can use anexisting EDD file as the starting point to create the extendedEDD file. EDDL is being enhanced, but it is maintainingbackward compatibility with the millions of devices thathave been installed over the past 10 years.

Because an extended EDD file contains additional fielddevice information, PAS host systems must be updated witha new EDDL Host Services module. It is available from therespective fieldbus protocol organisation and can beprocured by all PAS suppliers. More importantly, the HostService Module provides backward compatibility for plantfloor devices using older EDD files.

This simple, yet eloquent ability to extend EDDL’stechnology without ‘touching’ existing EDD files providesend-users the much sought after peace of mind thatdeploying a new intelligent field instrument withextensions carries minimum risk.

THE STANDARDWith EDDL technology used by millions of installed fieldinstruments, EDDL is the process industry de facto standardfor ensuring that information about intelligent field devicesis consistently available for use by operators, engineers, andmaintenance technicians. And the beauty of it is, the EDDsource file created for instrument number one works rightalongside the EDD source file for instrument number 5 million, or 10 million, and so on – never once requiring anupgrade, revision, or patch of any kind. �

The beauty of EDD is, a source file created forinstrument number one worksright alongside the source file for instrument number 5 million– never once requiring anupgrade, revision, or patch of any kind

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With permission from IEE Computing and Control Magazine, Dec. 2004/Jan. 2005

Documents

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