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Siemens Simatic S7-400 User Manual

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RS 485 Repeater

10-2

S7-400, M7-400 Programmable Controllers Module Specifications

A5E00069467-07

10.1

Application and Characteristics

(6ES7972-0AA01-0XA0)

What is an RS 485 Repeater?

The RS 485 repeater amplifies data signals on bus lines and interconnects bus
segments.

Application of the RS 485 Repeater

You need an RS 485 repeater if:

more than 32 nodes are connected to the bus

bus segments are to be operated non-grounded on the bus, or

the maximum cable length of a segment is exceeded. (See table 10-1).

Table 10-1 Maximum Cable Length of a Segment

Baud Rate

Max. Cable Length of a Segment (in m)

9.6 to 187.5 kbaud

1000

500 kbaud

400

1.5 Mbaud

200

3 to 12 Mbaud

100

Rules

If you configure the bus with RS 485 repeaters:

Up to 9 RS 485 repeaters can be connected in series.

The maximum cable length between two nodes must not exceed the values in
Table 10-2.

Table 10-2 Maximum Cable Length between Two RS 485 Repeaters

Baud Rate

Maximum Length of Cable between 2 Nodes (in m) with

RS 485 Repeater (6ES7 972-0AA01-0XA0)

9.6 to 187.5 kbaud

10000

500 kbaud

4000

1.5 Mbaud

2000

3 to 12 Mbaud

1000

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