Siemens SIMATIC NET PROFIBUS manual Line topology, Please note

3 Network Topologies 3.1 Line topology

3 Network Topologies

The following network topologies can be realized with the PROFIBUS OLM:

Point-to-point connections

Line topologies

Star topologies

Redundant optical rings

Combinations of these basic types are also possible. Lines with two optical fibers are used to create the fiber links for these network topologies.

If a malfunction – e.g. a break in a fiber line – makes a high degree of field bus network fail-safety necessary, the availability of the network can be increased using a redundant network configuration.

Please note:

Single terminals or entire PROFIBUS segments with max. 31 subscribers can be connected to the electrical interface of the PROFIBUS OLM.

In areas with a high EMC incidence, only lay optical fiber lines in order to exclude the possibility of EMC affecting the whole network.

Optically only OLMs of the same type can be connected together:

–OLM/P11 with OLM/P12

–OLM/G11 with OLM/G12 and OLM/G12 EEC

–OLM/G11-1300 with OLM/G12-1300

Optical ports which are connected by optical fiber must be set to the same operating mode.

Junctions between different OLM types are only possible via the RS485 interface.

OLM/G12-EEC can be used everywhere in those network topologies described below in which a OLM/G12 can also be used.

3.1 Line topology

Terminal unit /	Terminal unit /	Terminal unit /
bus segment	bus segment	bus segment

Terminal unit / bus segment

RS 485 bus line

Optical fiber

CH 1

OLM/P11

OLM/G11 (-1300)

CH 2
T	R

CH 1

OLM/P12

OLM/G12 (-1300)

CH 2		CH 3
T	R	T	R

CH 1

OLM/P12

OLM/G12 (-1300)

CH 2		CH 3
T	R	T	R

CH 1

OLM/P11

OLM/G11 (-1300)

CH 2
T	R

Fig. 2: Network structure in an optical line topology

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