Siemens SIMATIC NET PROFIBUS Instrukcje Operacyjne Pobierz pdf (Strona 14)

Network Topologies

3.1 Linear (bus) Topology

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

8 Operating Instructions, 01/2013, C79000-G8976-C270-03

3.1 Linear (bus) Topology

Figure 3-1 Network structure in a linear (bus) optical topology

* If OLM / P22 or OLM / G22 are used, an additional DTE or bus segment

can be connected to Ch 0.

In a linear or bus structure, the single PROFIBUS OLMs are connected by two-fiber cables.

At the beginning and at the end of a line, modules with one optical channel are adequate, in-

between modules with two optical channels are necessary.

If single point-to-point connections are required, they can be implemented with modules with

one optical channel each.

The bus topology can be implemented with and without fiber-optic link monitoring. Fiber-optic

link monitoring is recommended in homogeneous OLM networks (factory default).

Please note that to ensure correct operation, the following conditions must be kept to when

configuring the network:

 The parameter MIN TSDR, described in the PROFIBUS standard EN 50170 /2/, must be

set to a value ≥ 11 on all DTEs. This is usually the case but should be checked if

permanent communication problems occur.

 Choose bus node addresses as low as possible when configuring your network, to reduce

master timeouts that may occur due to disruptions.

You will find information on changing the setting in the documentation supplied by the

manufacturer of your DTE.

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Siemens SIMATIC NET PROFIBUS Instrukcje Operacyjne Strona 14