Applications And Features (6Es7972-0Aa01-0Xa0) - Siemens SIMATIC S7-400 Reference Manual

RS 485 repeater

10.2 Applications and features (6ES7972-0AA01-0XA0)

10.2 Applications and features (6ES7972-0AA01-0XA0)
Application of the RS 485 repeater
The RS 485 repeater amplifies data signals on bus lines and couples bus segments. You need
an RS 485 repeater for the following situations:
● There are more than 32 nodes connected to the bus.
● Bus segments should be operated ungrounded on the bus.
● The maximum cable length of a segment is exceeded.
Table 10-1
9.6 to 187.5 Kbps
500 Kbps
1.5 Mbps
3 to 12 Mbps
Rules
The following applies if you configure the bus with RS 485 repeaters:
● No more than 9 RS 485 repeaters can be connected in series.
● The maximum cable length between two nodes with RS 485 repeater may not exceed the
values listed in the table below.
Table 10-2
9.6 to 187.5 Kbps
500 Kbps
1.5 Mbps
3 to 12 Mbps
388
Maximum cable length of a segment
Baud rate
Maximum cable length between two RS 485 repeaters
Baud rate
Max. cable length of a segment (in m)
1000
400
200
100
Max. cable length between 2 nodes (in m)
with the RS 485 repeater (6ES7 972-0AA01-0XA0)
10000
4000
2000
1000
Reference Manual, Ausgabe 11/2016, A5E00850736-08
S7-400 Automation System Module Data