Network Topology - Danfoss MCX-RTU User Manual

User Guide | MCX-RTU Rooftop

Network Topology

© Danfoss | ADAP-KOOL® | 2018.11
The network cable must be EIA485 rated. The cable is connected from controller to control-
ler, and no branches (stars) are allowed on the cable. If the cable length exceeds 1200 meters
(1312 yards) a repeater must be inserted. One repeater must be added for every 32 controllers.
If the data communication cable runs through an electrically noisy environment which impairs
the data signal, one or more repeaters must be added to stabilize the signal. When configuring
Modbus devices on the control bus, the highest device address that can be used is 120 (max 120
Modbus control devices in total). The wires are looped from device to device and must observe
polarity. A is connected to A and B is connected to B. The shield must be connected and com-
plete a path from the device, all controllers, any repeaters finally landed on the ground/shield
terminal at the AK-SM 800. The shield must not be connected to earth ground except at the AK-
SM 800. At the AK-SM 800 the shield must be attached to the shield terminal and then extended
to an external earth ground. See AK-SM 800 User Guide for system 485 wiring instructions.
The maximum number of MCX-RTU is dependent on which AK-SM 800 is used.
The AK-SM 880 (080Z4008 and 080Z4009) may use a maximum of 45 MCX-RTU controllers.
The AK-SM 820 (080Z4004) may use a maximum of 10 MCX-RTU controllers.
The AK-SM 800 User Manual can be found at:
http://food-retail.danfoss.com/knowledge-center/software/ak-sm-800/
Be sure to configure the Modbus repeater AKA 222 (code#084B2240) to the correct baud rate.
MCX-RTU baud rate must be set to 38.4 K when used with the AK-SM 800. MCX-RTU cannot be
on the same 485 bus with SLVs.
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