Siemens SIMATIC NET PROFIBUS - Manual (Page 405)

3.1 Line topology
9
3 Network Topologies
Version 1.0 8/00
3 Network Topologies
The following network topologies can be realized with the PROFIBUS OLM:
Ⅲ
Point-to-point connections
Ⅲ Line topologies
Ⅲ
Star topologies
Ⅲ
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:
Ⅲ
Single terminals or entire PROFIBUS segments with max. 31 subscribers can be connected to the electrical
interface of the PROFIBUS OLM.
Ⅲ In areas with a high EMC incidence, only lay optical fiber lines in order to exclude the possibility of EMC
affecting the whole network.
Ⅲ
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
Ⅲ Optical ports which are connected by optical fiber must be set to the same operating mode.
Ⅲ
Junctions between different OLM types are only possible via the RS485 interface.
Ⅲ
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
Fig. 2: Network structure in an optical line topology
CH 2
T R
CH 2
T R
CH 3
T R
OLM/P11
OLM/G11 (-1300)
OLM/P12
OLM/G12 (-1300)
CH 1 CH 1
Terminal unit /
bus segment
CH 2
T R
OLM/P11
OLM/G11 (-1300)
CH 1
Terminal unit /
bus segment
Terminal unit /
bus segment
CH 2
T R
CH 3
T R
OLM/P12
OLM/G12 (-1300)
CH 1
Terminal unit /
bus segment
RS 485 bus line
Optical fiber