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 Address 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 1.2
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