Configuration Options With The Rs 485 Repeater; Setting Of The Terminating Resistor - Siemens SIMATIC S5 Manual

RS 485 repeaters: installing, connecting and operating
6.3

Configuration options with the RS 485 repeater

Overview
Terminating
resistor ON (in cir-
cuit) or OFF (not in
circuit)
Segment 1 and 2
terminated
Segment 1
Segment 2
Figure 6-3 Two bus segments connected to the RS 485 repeater (1)
6-6
This section discusses the configuration options offered by the RS 485
repeater:
Segment 1 and segment 2 terminating at the RS 485 repeater
Segment 1 terminating at the RS 485 repeater and segment 2 looped
through the RS 485 repeater,
and
Segment 1 and segment 2 looped through the RS 485 repeater.
Fig. 6-2 shows the position of the selector switch for the terminating resistor:
Terminating resistor
in circuit:
Figure 6-2

Setting of the terminating resistor

Fig. 6-3 shows the RS 485 repeater used to terminate two segments:
Segment 1
Terminating resistor
not in circuit:
Terminating resistor Terminating resistor
bus segment bus segment 1
on
R
Segment 2
Terminating resistor
bus segment 2
on
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a