Fieldbus -- General

1. What is a fieldbus? Why would I need to use it, and how does it compare with other cabling technologies such as 4-20mA, Ethernet, FDDI, etc.

   The underlying concept behind the fieldbus is that it is a fully digital network standard designed to connect all the devices used in an area of automation. This concept includes the connection of field devices such as valve actuators, temperature transducers and variable speed drives, and also the connection of systems such as PLCs and supervisory PCs.

   The main advantages of a fieldbus compared with cabling technologies such as 4-20mA, Ethernet etc., are:

   • Digital technology provides for connection of multiple devices on a single cable and for transfer not only of control data (eg on/off) but also configuration, status and diagnostic data.
   • High noise immunity.
   • Lower cost and easy installation.

   For more information:

   • Download our “Why Fieldbus?” report (MS Word).
   • Download our “Why Fieldbus?” presentation (Powerpoint).

2. Why should I adopt Fieldbus now?

   The only reason for moving to any new technology is that of potential business benefits. The potential benefits of Fieldbus are now well-known. There are key factors in today’s marketplace that make it time to move now, and gain a competitive advantage:

   • The potential benefits are now clear.
   • Your competitors are moving forward.
   • Products and services are now available.
   • Fieldbus standards are settling.
   • You will take time to gain experience.
   • You can now assess the benefits and risks.

   For more information:

   • Download our “Why Now?” report (MS Word).
   • Download our “Why Now?” presentation (Powerpoint)
   .

3. What is the WorldFIP Fieldbus? Why would I need it?

   WorldFIP is the most advanced fieldbus available today and provides all the facilities expected of a fieldbus, plus some important additions:

   • Conforms to the IEC physical layer standard.
   • Provides for dual-media cabling which gives network security in the event of a cable failure.
   • Provides time-critical transfer of control data, at the same time as providing messaging services for configuration and diagnostic data without compromise to the time-critical transfer.

   For more information:

   • Download our “Why WorldFIP?” report (MS Word).
   • Download our “Why WorldFIP?” presentation (Powerpoint).

1. How does WorldFIP compare with other bus systems?
   • Protocol:
     WorldFIP protocol is unique in providing the ability to pass time-critical and message data easily on the same bus and without any disturbance to the time-critical data by the messages. Other bus systems cannot do this, or require additional application effort and/or a mixture of several solutions to achieve the same result.
   • Components:
     WorldFIP’s family of components is unique in allowing full implementation of a full-function fieldbus at the same cost level as lower-level buses which offer less functionality.
   • Organisation:
     WorldFIP organisation is unique, in that it has involved end-users in active participation from the very beginning, and still has an equal balance of users and vendors on its governing body. Most other fieldbus organisations are either dominated by vendors or are effectively dominated by a single vendor, even though they may claim “openness”.
   • Standards:
     WorldFIP is a European Standard -- but one that incorporates within itself the maximum amount of available international fieldbus standards. This gives security against change, and a promise of eventual compliance with the international standard when it is in place. Other buses which do not have the status of a standard cannot offer such security.

   WorldFIP therefore benefits all the players:

   • End Users and Contractors:
     By offering a standard solution which can support integration of the “Information Technology” world across the application and support time-critical plant control. As a standard WorldFIP can be supplied by many vendors.
   • Systems Integrators:
     The explicit support of time-critical and messaging data by the WorldFIP protocol makes systems design easier and makes the performance of the communications system predictable.
   • Product Vendors:
     WorldFIP allows the design of a single interface supporting products with added-value functions for parameter-setting and diagnostics at low cost.

2. What are the real issues involved in establishing genuine interoperability at product and system levels?
   • Efficient data handling -- absence of queues etc when passing data between levels in the control system hierarchy.
   • Single point/source configuration.
   • Single network diagnostics.

3. As a product manufacturer, I think that I might be able to use WorldFIP myself. But how do I set about deciding whether it really is the right solution for me?

   To decide whether WorldFIP is the right solution for you, look first at your requirements. If you find that:

   • Your products are used in situations where both control data and diagnostics or configuration transfer are required
   • Your products are used in applications requiring high-speed data transfer
   • You are concerned to ensure that your product conforms to International Standards
   • You are concerned to minimise the cost of the bus interface

   then WorldFIP is the network for you.

4. As a system integrator I can see the advantages of interoperability at fieldbus level. But why should I choose WorldFIP?

   There are two really important reasons:

   • Single Consistent Protocol:
     A typical industrial system may cover many levels of activity -- from simple “on/off” plant sensors and more complex plant instrumentation, to static power supplies for fixed-speed and variable-speed AC and DC motors, to I/O systems; and on upwards to PLCs, PCs and workstations; not forgetting the man-machine interface (MMI) screens and input panels for plant operators.
     Many fieldbus systems can cope with a part of this overall range of equipment. Some systems specialize in linking simple sensors and I/O that exchange data in small byte-size units; other systems are specially designed to handle more complex data-sets of 100 bytes or more in length.
     WorldFIP is different. It alone covers the whole range efficiently -- from simple byte-size data and messages right up to cell-bus data strings of 256 bytes and more. The whole range is covered by a single consistent protocol -- so you can link all the items of your system via a single bus system, with no need for the hidden costs and problems of interfaces and protocol-convertors that are necessary with other bus systems.
   • Compliance with International Standards:
     WorldFIP complies with the emerging IEC Fieldbus standard -- it already complies with the existing Physical Layer -- and WorldFIP is committed to converging 100% to this standard as it becomes complete. Fieldbus Foundation has made exactly the same commitment -- the difference is that WorldFIP has had real products and systems in service for years, proven and reliable, in hundreds of industrial applications all around the world.

   No other fieldbus system offers you both of these essential options. But in addition to these two main features, WorldFIP has also tackled many other vital issues which few other fieldbus systems address -- such as bus-redundancy, EMC resistance, and the ability to handle both deterministic data and random messages. All this makes WorldFIP the obvious choice for any professional system integrator.

1. What is WorldFIP’s position with regard to the eventual International Standard for fieldbus? Does it have a plan to migrate to this standard, when it eventually emerges?

   WorldFIP is committed, as part of its constitution, to work towards an international standard. To that end, WorldFIP members are active in all the relevant Standardisation Committees.

   WorldFIP is already a European Standard (EN50170 Part 3), and uses the IEC Fieldbus Physical Layer standard (IEC 1158-2), and also a subset of the ISO’s MMS messaging standard.

   The WorldFIP Data Link Layer has the functionality to support time-critical and message data as provided in the draft IEC Link Layer standard. Because of this, migration to the eventual IEC standard will be invisible to the user, merely requiring vendors to update their chip-sets. To enable vendors to do this, a development program is under way to develop a chip (FICOMP) that will operate both the WorldFIP and IEC protocols.

2. What is WorldFIP’s position with respect to Fieldbus Foundation?

   WorldFIP is a member of Fieldbus Foundation. We have a technology agreement with Fieldbus Foundation, and we are trying to encourage further convergence. WorldFIP has major experience and knowledge of the high-speed 1Mb/sec and 2.5Mb/sec Fieldbus, referred to by Fieldbus Foundation as H2.

   Fieldbus Foundation has focused so far upon the low-speed 31.25kb/sec bus, and are only now starting to work on H2 -- so there is a natural opportunity for us to work together.

   For more information:

   • Download our article “WorldFIP Position” (MS Word).

1. What is so good about the WorldFIP protocol?

   Read the answers to the next two questions -- about Reliability and High Availability. That will tell you some of the main technical reasons why WorldFIP is the best available fieldbus protocol. Add to this, that WorldFIP has been around for long enough to be thoroughly proven and tested in complex and demanding industrial applications all around the world.

2. Is WorldFIP a reliable bus system?

   WorldFIP is the most reliable fieldbus system you can buy. To give just two examples of this:

   • Redundancy:
     WorldFIP protocol supports dual-redundant bus operation -- so you can link PLC’s, I/O, controllers, MMI systems etc via a twin-bus and be certain that your system will be tolerant to cable-damage which would cause other bus systems to crash.
   • EMC Resistance:
     WorldFIP protocol was specially developed with EMC-tolerance in mind. By a combination of Frame-Check Sequence and Manchester Type 2 coding, the protocol ensures that integrity of data-transfer is so high that likelihood of an undetected error in transmission is less than 10-18. No other fieldbus system comes anywhere remotely close to this level of security. Finally, thanks to the ease of introducing optical/copper repeaters with WorldFIP, an optical section can be incorporated to reduce even further the risk of the whole network being contaminated from a single critical section.
     Where EMC resistance is concerned, WorldFIP is second to none -- it is intrinsically rugged, whilst competing solutions require additional precautions, which add to the number of components and reduce overall reliability without achieving real success.

   WorldFIP has been consistently chosen for power-station and refinery projects, and for high-reliability marine applications where safety and reliability are major consdierations.

3. Can I achieve high availability with WorldFIP?

   Yes -- because WorldFIP has two major advantages over other systems:

   • Reliability:
     For details, see the answer to the previous question.
   • Support for both Messaging and Data:
     WorldFIP protocol is designed to support both determinstic data-transfer and also random messaging. That means, you can build in the ability for your system to transmit random messages (eg alarm data, periodic reports, status messages) without upsetting its ability to transmit time-critical data exactly on time. WorldFIP will ensure that your fast control loops function correctly -- and you can send status/diagnostic messages down the same bus with no problem.

   How many other fieldbus systems offer you this? (Why not ask them and see for yourself?)

4. Is WorldFIP suitable for use in large and/or complex systems?

   It’s ideal for such systems -- see the answer to Question 4 in the section "Why Should I Choose WorldFIP" above.

5. Can I implement high-speed control loops using WorldFIP?

   No problem. WorldFIP supports true determinstic data-transfer, at rates up to 5Mb/sec. You can specify the data cycle with as much flexibility as you need, and tailor its length, refresh rate and other key parameters to match the requirements of your system.

6. Suppose I want access to lots of diagnostic information via my network?

   That’s OK. WorldFIP protocol supports transfer of time-critical deterministic data for control (both periodic and aperiodic data), and also random messaging (for status reports, alarm handling etc). The messaging feature can be used to transmit diagnostic data from your intelligent sensors, MMI system and other plant items -- with no risk of upsetting your time-critical control signals.

   For more information about this, you might like to look at the article on WorldFIP’s Application Layer, in Issue 4 of our newsletter. This describes in detail the way in which the WorldFIP protocol handles the time-allocation of these different types of information-transfer.

7. Is WorldFIP suitable for use in an environment where there is EMC interference?

   Yes, it’s specially designed with EMC in mind, and more cost-competitive than any other solution -- see the above answer to Question 2 in this section.

1. What is the purpose of the WorldFIP organisation? How does it work?

   WorldFIP is a registered non-profit organisation, which exists to promote the development and application of an open fieldbus, that is well placed to form the basis of the future International Standard.

   The WorldFIP Board is composed of a mixture of vendors, end-users and third-parties such as academic/research organisations, which helps to keep the evolution of WorldFIP on a path that will meet the declared aims.

   WorldFIP has National Promotional Groups and Technical Support Centres active in several countries, in addition to its HQ in France. These national centres, like the HQ, are funded from the contributions of members and are also non-profit-making organisations, which exist solely to support the members and users of WorldFIP around the world.

   The WorldFIP technical protocol is an open fieldbus (that is, non-proprietary and freely available to anyone). It is already fully evolved and tested, and has successfully passed all its proving stages in a wide range of industrial pilots and real applications. This has provided a stable base, free from the "growing pains" of some other competing bus systems, which have changed as they evolved because they did not consider future needs in their early development stage.

2. What is the point of me becoming a WorldFIP member?

   Whether user, manufacturer, systems integrator or consultant, you benefit as a WorldFIP member:

   • WorldFIP data, and training on principles and implementation. Details of current status and likely evolution of international standards, to aid you in planning development work.
   • Participate in WorldFIP Pilot Projects and evaluations.
   • Join working groups defining WorldFIP companion standards, to ensure these additional standards meet your own needs.
   • Introductions to other vendors and users who are members of WorldFIP, to new potential partners, and perhaps to an expansion of your market.
   • Priority access, at reduced rates, to WorldFIP components and tools, with documentation and help to apply them, saving you time and money.
   • Access to WorldFIP testing tools, to aid development and debugging.
   • Develop products compatible with those of other WorldFIP vendors: your products or systems will interwork with others and have wider market appeal.
   • Participate in international exhibitions and seminars on WorldFIP stands.
   • Access to the services of WorldFIP's Technical Centres.