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Wendelstein 7-X is designed as a steady-state experiment to demonstrate the fusion reactor relevance of the advanced stellarator concept. The experiment's control and data acquisition will be performed by a distributed system of computers and programmable logic controllers (PLCs). Data of several systems have to be combined flexibly to control the machine, requiring a data exchange on a millisecond time scale between several connected units. A discharge can last up to half an hour, thus the connections may vary during a discharge. Hence it is desired to provide control relevant data, e.g. measurands, set points, interlock signals, cyclically via a bus system. The paper will analyse the special quality of control data streams and deduce the basic requirements for a real-time data bus. Ethernet is a candidate for the data bus since it is a widely used broad-band bus with a foreseeable potential for development. Because of its nondeterministic arbitration algorithm Ethernet is generally considered not to be suited for hard real-time applications. It is possible to circumvent this disadvantage of Ethernet either by using switching techniques or a software token to obtain a reliable base for hard real-time data transport.

Additional information

Authors: LAQUA H, Max-Planck-Institut für Plasmaphysik, Greifswald (DE);NIEDERMEYER H, Max-Planck-Institut für Plasmaphysik, Greifswald (DE);WILLMANN I, Max-Planck-Institut für Plasmaphysik, Greifswald (DE)
Bibliographic Reference: An article published in: IEEE Transactions on Nuclear Science, Volume 49, Issue 2 Part: 1, Apr. 2002, pp.478 -482
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