Distech Controls ECLYPSE ECY-400 Series Installation Manual page 13

Figure 16: BACnet MS/TP Communications Wiring
When inserting multiple wires into a terminal-block connector, ensure to properly twist wires together prior to insertion.
Modbus RTU Communications Wiring
Ensure that you have at least a C1 Connectivity Pack to enable the Modbus functionality and use of RS-485 ports. See the controller's Spec
Sheet for more details.
This applies to both the on-board RS-485 port and any additional modules.
BACnet MS/TP and Modbus RTU communications are made by connecting directly to separate RS-485 ports. ECY-600 series controllers integrate up to
three RS-485 ports when equipped with one ECY-RS485 extension module allowing the controller to support more than one trunk or communication pro-
tocol at a time.
Furthermore, Modbus TCP devices can be integrated by connecting them to the controller's IP network.
The ECLYPSE User Guide provides extensive information and requirements to implement a Modbus RTU network. It contains information about network
topology, network and sub network wire length restrictions, cable type, device addressing, etc. It can be downloaded from our website. For optimal per-
formance, use Distech Controls 24 AWG (0.65 mm) stranded, twisted pair shielded cable or refer to the ECLYPSE User Guide for cable specification.
The Modbus RTU communication wire is polarity sensitive and the only acceptable topology is to daisy-chain the cable from one controller to the next.
The ECLYPSE Guide is available on the Distech Controls Documentation Portal.
As shown in the figure below:
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The first and last daisy-chained Modbus RTU devices must have their EOL resistors enabled / installed. All other devices must have
their EOL resistor disabled (default factory setting).
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The first and/or last daisy-chained Modbus RTU device must have their BIAS enabled. All other devices must have their BIAS disabled
(default factory setting). See the figure below. Note that the BIAS settings for Modbus RTU devices that do not have a specific setting to
enable / disable BIAS usually means that the BIAS is enabled when the EOL resistors are enabled.
£ When the Modbus RTU data bus is connected to a following device, twist data bus shields together.
£
Isolate all shields with electrical tape so there is no exposed metal that can touch ground or other conductors.
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The shield of the data bus must be connected to the electrical system ground at only one point – usually at one end of the bus as shown
below.
Connect no more than 50 devices to a Modbus RTU data bus.
Use the RS-485 port to connect to a trunk of Modbus RTU devices. RS-485 port terminal connectors are labeled such that NET+ is the same as + and
NET- is the same as -.
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