Siemens SIMATIC NET PROFIBUS User Manual download pdf (Page 4)

4

PROFIBUS topologies

Electrical network

SIMATIC NET offers a wide range of

PROFIBUS network components for

electrical and optical transmission

technology.

Electrical network

· The electrical network uses a shield-

ed, twisted pair cable. The RS 485

interface operates on voltage differ-

ences.

It is therefore less sensitive to

interference than a voltage or current

interface.

In PROFIBUS, the nodes are con-

nected to the bus by a bus terminal or

a bus connector (max. 32 nodes per

segment).

· The individual segments are

connected via repeaters.

· The transmission rate can be

adjusted in steps from 9.6 kbit/s

to 1.5 Mbit/s. For extremely

time-critical PROFIBUS-DP

applications, additional

transmission rates of 3, 6 and

12 Mbit/s are possible.

· The maximum segment length

depends on the transmission rate.

· The electrical network can be con-

figured as a bus or tree topology

(see Figure 6).

· For applications in the intrinsically

safe area, PROFIBUS-PA uses trans-

mission technology according to

IEC 61158-2. In this case, the trans-

mission rate is 31.25 kbit/s.

· The DP transmission method is

implemented by RS 485 (bit coding

by voltage difference signals)

according to IEC 61158-2 (bit coding

by current signals) by the network

components (DP/PA coupler or

DP/PA link)

Features:

· High-quality LAN cable

· Transmission method: RS 485

(according to EIA) or transmission

method IEC 61158-2 for the intrinsi-

cally safe area (PROFIBUS-PA)

· Bus topology with bus terminals

and bus connectors for connecting

the PROFIBUS nodes

· Simple, system-wide mounting and

grounding concept

· Simple installation.

Figure 6: Typical configuration electrical PROFIBUS network

PC

S7-400

ET 200S

Drive

ET 200X

PGOP 17 ET 200M

DP/PA-Link

Repeater

Intrinsically

safe area

Repeater

Bus calbe for PROFIBUS

Connecting cable

Bus terminal

Tap

ET 200X

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