Biasing The Modbus Rs-485 Device Network; Figure 12: Modbus Rs-485 Biasing Switch On The Protonode N34 (Left) And Protonode N35 (Right) - SMC Networks ProtoNode FPC-N34 Manual

3.2.4 Biasing the Modbus RS-485 Device Network

•
An RS-485 network with more than one device needs to have biasing to ensure proper
communication. The biasing only needs to be done on one device.
•
None of the ENVI's support biasing. The ProtoNode is required to bias the RS-485 network.
•
The ProtoNode has 510 Ohm resistors that can be used to set the biasing. The ProtoNode's
default positions from the factory for the Biasing jumpers are OFF.
•
The OFF position is when the 2 RED biasing jumpers straddle the 4 pins closest to the outside of
the board of the ProtoNode.
•
Only turn biasing ON:
o
IF the BMS cannot see more than one device connected to the ProtoNode
o
AND all the settings (Modbus COM settings, wiring, and DIP switches) have been
checked.
•
To turn biasing ON, move the 2 RED biasing jumpers to straddle the 4 pins closest to the inside
of the board of the ProtoNode.

Figure 12: Modbus RS-485 Biasing Switch on the ProtoNode N34 (left) and ProtoNode N35 (right)

(Figure 12)
RS-485 Bias
Switch
(off)
Page 17 of 50
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