Siemens Simatic M7-400 Reference Manual page 422

RS 485 Repeater
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
9.6 to 187.5 kbaud
500 kbaud
1.5 Mbaud
3 to 12 Mbaud
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
9.6 to 187.5 kbaud
500 kbaud
1.5 Mbaud
3 to 12 Mbaud
10-2
Max. Cable Length of a Segment (in m)
Maximum Length of Cable between 2 Nodes (in m) with
RS 485 Repeater (6ES7 972-0AA01-0XA0)
10000
S7-400, M7-400 Programmable Controllers Module Specifications
1000
400
200
100
4000
2000
1000
A5E00069467-07