iSMA-B-MINI/MIX Modbus User Manual
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DMP262en | 1st Issue rev. 8 | 05/2022
page 22 of 107
4.4 RS485 Port
4.4.1 RS485 Communication Bus Connection
Figure 25. RS485 connection
4.4.2 RS485 Network Termination
Transmission line effects often present problems for data communication networks.
These problems include reflections and signal attenuation.
To eliminate the presence of reflections of signal from the end of the cable, the cable
must be terminated at both ends with a resistor across the line adequate to its
characteristic impedance. Both ends must be terminated since the propagation is
bidirectional. In case of an RS485 twisted pair cable this termination is typically 120
Ω.
4.5 Setting Module Address
To determine the address on the Modbus network, the module is equipped with two
rotary switches, S1 and S2, located on the top panel of the device.
It is possible to set the device address from 0 to 99.
The address is set with the following formula:
Address = S2
•
10 + S1
where S1 and S2 are the values of the switches.
For example:
Figure 26. Setting the address in a Modbus network