Siemens Simatic S7-400 - Manual (Page 422)

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