Technical data

Topologies of SIMATIC NET PROFIBUS networks

2.1 Topologies of RS485 networks

PROFIBUS Network Manual

26 System Manual, Edition 04/2009, C79000-G8976-C124-03

Connecting segments using RS485 repeaters

By using RS485 repeaters, segments can be interconnected. The RS485 repeater amplifies

the data signals on the bus cables. You require an RS485 repeater when you want to attach

more than 32 nodes to a network or when the permitted segment length is exceeded. A

maximum of 9 repeaters can be used between any two nodes. Both bus and tree structures

can be implemented.

The following figure shows a typical topology using RS485 technology with 3 segments and

2 repeaters.

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

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Spur line

S7-400

S7-300S7-300

OP 25

RS 485

Repeater

RS 485

Repeater

OP 25

Figure 2-1 Topology with RS-485 technology

① Terminating resistor activated

② PG connected for maintenance via spur line (6ES7 901-4BD00-0XA0)

Increasing the overall span of a network by using repeaters can lead to longer transmission

times that may need to be taken into account when

configuring the network (Page 41).

2.1.2 Components for transmission speeds up to 1.5 Mbps

All SIMATIC NET bus attachment components can be used for transmission speeds up to

1.5 Mbps.