Image Processing Reference
In-Depth Information
21
Real-Time Ethernet for
Automation Applications
. Introduction .........................................
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. StructureoftheIECStandardization .................
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. Real-TimeRequirements.............................
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User-Application Requirements
●
Performance Indicators of
the IEC Standard
. PracticalRealizations.................................
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Realization of the on Top of TCP/IP Protocols
●
Realization
of the on Top of Ethernet
●
Realizations of the “Modified
Ethernet”
. Summary:Conclusions...............................
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References .................................................
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Max Felser
Bern University of Applied Sciences
21.1 Introduction
International fieldbus standardization has always been a difficult endeavor. After a timely start in
and a few enthusiastic years of development, the quest for the one and only comprehensive
international fieldbus gradually became entangled in a web of company politics and marketing inter-
ests []. What followed was a protracted struggle inside European Committee for Electrotechnical
Standardization (CENELEC, see www.cenelec.org) and International Electrotechnical Commis-
sion (IEC, see www.iec.ch) committees that finally ended up in the complete abandonment of the
original idea. Instead of a single fieldbus, a collection of established systems was standardized.
In Europe, CENELEC adopted a series of multivolume standards compiled from specifications of
provenieldbussystems.Onaworldwidescale,IECdeinedamatrixofprotocolmodules,the
so-called types [], together with guidelines how to combine the various modules into actually
working fieldbus specifications []. With the adoption of the IEC standard [] on the mem-
orable date of December , , the fieldbus war seemed to be settled just in time for the new
millennium.
Atthesametime,intheoiceworld,weseethepenetrationofthenetworksbasedonEthernet
andTCP/IP.hecostsofthenetworkinfrastructureintheoiceworldaresteadilygoingdown,and
it is becoming possible to connect almost anything with everything, anywhere, with the help of the
Internet technology. But in the field of automation technology, dedicated fieldbuses are used. The
only barrier to access devices in the field of the automation world, from the Internet over a network
connection, is the ieldbuses. herefore, the question is why is it not possible to use Ethernet also in
the automation technology?
