Networking
5-21
AutomationSystem S7-400 Hardwareand Installation
A5E00850741-01
5.7 RS 485 Repeater / Diagnostics Repeater
Purpose of the Repeater
The RS 485 Repeater / Diagnostics Repeater amplifies data signals on bus cables
and couples bus segments.
Youneed an repeater when:
•More than 32 nodes are connected in the network,
•A grounded segment is to be connected to an ungrounded segment
•The maximum cable length of a segment is exceeded.
Description of the RS 485 Repeater
A detailed description and technical data of the RS 485 repeater can be found in
the Reference Manual Module Specifications, Chapter 10.
Assembly
Youcan install the repeater on a 35 mm standard profile rail.
Wiring the Power Supply Unit
Towire the power supply unit of the repeater, proceed as follows:
1. Openthe “M” and “PE” screws.
2. Stripthe 24 VDC power supply cable.
3. Terminatethe cable to “L+” and “M” or “PE”.
Terminal“M5.2”
Terminal“M5.2” should not be wired because it is only needed during maintenance.
Terminal“M5.2” is the reference ground you require when measuring the voltage
between terminals “A1” and “B1”.
Connecting the PROFIBUS-DP Bus Cable
For detailed information on hwo to connect the PROFIBUS DP bus cable to the
RS 485 repeater,refer to the SIMATIC NET Profibus Networks manual: