Industrial Communication Guide

2.5.4. FIELDBUS AND ETHERNET

Ethernet Ethernet is a technology originally developed for office communica- tion, i.e. for the exchange of data in PC-based local data networks (LANs); it consists of a number of software and hardware compo- nents. Ethernet allows much higher transfer rates of up to 400 Giga- bit/s. A number of PLC manufacturers have extended basic Ethernet technology in order to meet various industrial requirements. This has resulted in the existence of a number of manufacturer-specific Eth- ernet systems. Examples are the real-time capability or the topology.

While network topologies can theoretically take on any form, each network technology has specific properties and limitations in terms of the potential network topologies that can be used. These can gen- erally be distinguished according to communication networks based on fieldbus or Ethernet. Fieldbus A fieldbus establishes the connection between sensors, actuators and control computer. Several devices can be connected to a field- bus and send their messages via the same line. In this case, it must be specified who is allowed to exchange information and when. Vir- tually every PLC manufacturer has designed their own fieldbus. For this reason, there are numerous technologies that are different from each other. For example, the maximum cable length, the data rate or in the range of functions.

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