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The end points, first and last controller on the string must
have a 120 ohm termination resistor.
All LMC341 DIWE controllers are grounded, the signal
ground is not needed as PE (Protective Earth) is used as
signal ground.
The following installation is not guaranteed to work!
Master
Controller
LMC341
DIWE
LMC341
DIWE
Modbus (RTU) via RS485
LMC341
DIWE
LMC341
DIWE
#1
#2
#3
#10
...
4.2. Communication recommen-
dations
The poll-interval setting in the master controller must be
considered. The processor of the LMC341 DIWE controller
can only handle a certain amount of requests per second.
Beyound this, request from the master controller will be
lost.
The data in the LMC341 DIWE controller don’t change very
rapidly so a poll interval of seconds will be sufficient for
the monitoring purpose.
4. How to ...
4.1. Connection samples
• The Modbus communication is connected using a
shielded, 2-wired, twisted pair cable (RS485).The two
signal wires must be in the same pair of wires.
• The connection can be multi-drop with up to 10
LMC341 DIWE controllers on the same communication
line. For larger installations or from building to building, a
RS-485 repeater with galvanic isolation must be used.
• The cable must be installed as a string, not a star.
• The LMC341 DIWE is always the client (slave unit).
One master controller and one LMC341 DIWE.
Master
Controller
LMC341
DIWE
Modbus (RTU) via RS485 (2-wire)
120 ohm
Termination
resistor
120 ohm
Termination
resistor
One master controller and several LMC341 DIWE.
Master
Controller
LMC341
DIWE
LMC341
DIWE
Modbus (RTU) via RS485 (2-wire)
LMC341
DIWE
LMC341
DIWE
120 ohm
Termination
resistor
120 ohm
Termination
resistor
#1
#2
#3
#10
...
