Rs 485 Repeater - Siemens S7-400 Installation Manual

5.7

RS 485 Repeater

Purpose of the RS 485 Repeater
The RS 485 repeater enhances data signals on bus cables and links bus
segments.
You need an RS 485 repeater when:
• More than 32 nodes are connected in the network,
• A grounded segment is to be connected to an ungrounded segment, or
• 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
You can install the RS 485 repeater on a 35 mm standard profile rail.
Wiring the Power Supply Unit
To wire the power supply unit of the RS 485 repeater, proceed as follows:
1. Slacken the screw for "M" and "PE".
2. Strip the cable for the 24 VDC supply.
3. Connect the cable to terminals "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".
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Networking
5-23