beautypg.com

Star topologies with olms, Optical channels – Siemens SIMATIC NET PROFIBUS User Manual

Page 35

background image

Topologies of SIMATIC NET PROFIBUS Networks

2-9

PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000

Star Topologies with OLMs

Several optical link modules are grouped together to form a star coupler via a bus
connection of the RS-485 interfaces. This RS-485 connection allows the
attachment of further DTEs until the maximum permitted number of 32 bus
attachments per segment is reached.

PG

S7-400

OP 25

А

А

А

А

Terminating resistor activated

Star hub

А

А

А

1 FO cable

2 LAN cable for PROFIBUS

4 PROFIBUS 830-2 connecting cable

4

2

1

2

2

2

1

À

4

S7-400

À

Figure 2-4

Example of a Star Topology with OLMs

Optical Channels

The OLMs are connected to the star coupler by duplex fiber-optic cables.

Both DTEs and electrical bus segments can be connected to the OLMs attached
by the duplex fiber-optic cables. Depending on the requirements and the distance,
the duplex cables can be implemented with plastic, PCF or glass (OLM only)
fibers.