About Setting Built-In Eol Terminations; Only A Daisy-Chained Data Bus Topology Is Acceptable - Acuity Controls nLight ECLYPSE User Manual

Modbus RTU Communication Data Bus Fundamentals
Baud: Auto (Factory Default)
Typical Modbus RTU
Device
EOL ON
Figure 105: EOL Terminations Must be Enabled at Both the First and Last Device on the Data Bus
Devices with built-in EOL terminations are factory-set with the EOL termination disabled by default.
The BACnet/IP to MS/TP Adapter does not have EOL Termination (and Modbus RTU Data Bus biasing) capabilities to be used at the end of
a Modbus RTU data bus. Instead, use the BACnet/IP to MS/TP Router for this application.

About Setting Built-in EOL Terminations

ECLYPSE Controllers have built-in EOL terminations. These Controllers use jumpers or DIP switches to enable the EOL
resistors and biasing circuitry. These controllers have separate bias and EOL termination settings. This is useful in the fol-
lowing scenario: the ECLYPSE controller is located in the middle of the data bus and either one or both Modbus RTU de-
vices at the data bus ends do not have biasing or EOL terminations. In this situation, set the bias on the ECLYPSE con-
troller and set the EOL termination on the Modbus RTU devices at the end of the data bus. If a Modbus RTU device at the
end of the data bus does not have a built-in EOL termination, then add a 120 Ohm resistor across the device's terminals.
Figure 106: Typical ECLYPSE Controller with Separate EOL Termination and Bias Configuration Settings
Refer to the Modbus RTU device's Hardware Installation Guide for how to identify and set a device's built-in EOL termina-
tions.

Only a Daisy-Chained Data Bus Topology is Acceptable

Use a daisy-chained Modbus RTU data bus topology only. No other data bus topology is allowed.
Only linear, daisy-chained devices provide predictable data bus impedances required for reliable data bus operation.
Only a daisy-chained data bus topology should be specified during the planning stages of a project and implemented in the installation phase
of the project.
nLight ECLYPSE
Baud: Auto (Factory Default)
Typical Modbus RTU
Device
EOL OFF
Data Bus: Shielded Twisted Pair Cable
Baud: Auto (Factory Default)
Typical Modbus RTU
Device
EOL OFF
Baud: 38 400
Typical Modbus RTU
Device
EOL OFF
Baud: 38 400
ECLYPSE
EOL
ON
Electrical
System
Ground
112