RS485 MODBUS Module 16O
User Manual
3. Communication configuration
3.1. Grounding and shielding
In most cases, IO modules will be installed in an enclosure along with other
devices which generate electromagnetic radiation. Examples of these devices are relays
and contactors, transformers, motor controllers etc. This electromagnetic radiation can
induce electrical noise into both power and signal lines, as well as direct radiation into
the module causing negative effects on the system. Appropriate grounding, shielding
and other protective steps should be taken at the installation stage to prevent these
effects. These protective steps include control cabinet grounding, module grounding,
cable shield grounding, protective elements for electromagnetic switching devices,
correct wiring as well as consideration of cable types and their cross sections.
3.2. Network Termination
Transmission line effects often present a problem on data communication
networks. These problems include reflections and signal attenuation.
To eliminate the presence of reflections from the end of the cable, the cable must
be terminated at both ends with a resistor across the line equal to its characteristic
impedance. Both ends must be terminated since the direction of propagation is bi-
directional. In the case of an RS485 twisted pair cable this termination is typically
120 Ω.
3.3. Setting Module ddress in RS485 Modbus Network
The following table shows how to set switch to determine the address of the
module. The module address is set with the switches in the range of 0 to 31. Addresses
From 32 to 255 can by set via RS485 or USB.
Adr SW5 SW4 SW3 SW2 SW1
0 OFF OFF OFF OFF OFF
1 OFF OFF OFF OFF ON
2 OFF OFF OFF ON OFF
3 OFF OFF OFF ON ON
4 OFF OFF ON OFF OFF
5 OFF OFF ON OFF ON
6 OFF OFF ON ON OFF
7 OFF OFF ON ON ON
8 OFF ON OFF OFF OFF
9 OFF ON OFF OFF ON
10 OFF ON OFF ON OFF
Adr SW5 SW4 SW3 SW2 SW1
11 OFF ON OFF ON ON
12 OFF ON ON OFF OFF
13 OFF ON ON OFF ON
14 OFF ON ON ON OFF
15 OFF ON ON ON ON
16 ON OFF OFF OFF OFF
17 ON OFF OFF OFF ON
18 ON OFF OFF ON OFF
19 ON OFF OFF ON ON
20 ON OFF ON OFF OFF
21 ON OFF ON OFF ON
Adr SW5 SW4 SW3 SW2 SW1
22 ON OFF ON ON OFF
23 ON OFF ON ON ON
24 ON ON OFF OFF OFF
25 ON ON OFF OFF ON
26 ON ON OFF ON OFF
27 ON ON OFF ON ON
28 ON ON ON OFF OFF
29 ON ON ON OFF ON
30 ON ON ON ON OFF
31 ON ON ON ON ON
Expansion Module– 16 digital outputs
User Manual Version 1. 6 / 16