Siemens SIMATIC NET OLM12M Description And Operating Manual page 54

6ZB5530–3AB00–0BA0/01
4 Overview of Network Topologies
Using the SIMATIC NET optical link modules, all the network topologies set out in the PROFIBUS
Users Organization guideline "Optical Transmission Techniques for PROFIBUS" can be
implemented:
Point-to-point connection
Bus topology
Ring topology (single-fiber ring)
Star topology
Combinations of these basic types are also possible. It is also possible to combine one or more
electrical RS 485 bus segments with these network topologies.
Redundant optical rings are not supported by the OLM12M.
4.1 Bus Topology
The advantage of this topology is that large distances can be covered and that any number of
active bus nodes (masters) and passive bus nodes (slaves) can be connected to each optical link
module.
Mode settings: L=Line, I=Inactive
Figure 2: Optical Bus Structure
The individual SIMATIC NET OLM12M optical link modules are connected together in pairs by a
duplex FO cable.
All the optical channels connected to the optical bus structure are switched to the "Line" mode. The
optical channels at the start and end of the bus must be switched to the "Inactive" mode if they are
not used.
Individual DTEs or a complete PROFIBUS segment with a maximum of 31 nodes can be connected
to each optical link module via the electrical channel with its RS 485 interface.
With the monitoring function, the individual FO cable sections can be monitored by the optical link
modules connected to it.
If an optical link module drops out or if an FO cable breaks, the network is broken up into two
subnetworks. Problem-free operation is possible within these subnetworks.
Copyright Siemens AG 1997
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SIMATIC NET OLM12M