52 Connect Devices
WAGO-I/O-SYSTEM 750 XTR
750-652/040-000 Serial Interface RS-232/RS-485 XTR
Manual
Version 1.3.0
Figure 15: Bus Connection RS-485 Operating Mode with Biasing Network, Half-Duplex
With the use of the biasing resistors, it is guaranteed in this case that all receiver
inputs A have the voltage difference of more than 200 mV to the inputs B if no
transmitter is active. The oscillations of the receiver that can cause defective
reception are thus prevented.
Biasing network
Check the necessity of an external biasing network before start-up.
In modern devices with RS-485/RS-422 interface, this network is either already
integrated or the devices have an improved RS-485/RS-422 receiver. The output
of this receiver is in a defined state if the data line is short-circuited or not active.
7.2.4
DMX Operating Mode
In the DMX operating mode, the wiring is based on the RS-485 operating mode.
Twisted pair cables must be used for this operating mode. The ends of the cable
should be termina
ted with a terminal resistor (optimal value: 120 Ω).
