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

BACnet MS/TP Communication Data Bus Fundamentals

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 controller is located in the middle of the data bus and either one or both controllers at the data bus
ends do not have biasing or EOL terminations. In this situation, set the bias on the controller and set the EOL termination
on the controllers at the end of the data bus. If a controller at the end of the data bus does not have a built-in EOL termina-
tion, then add a 120 Ohm resistor across the device's terminals as shown at the left side of the previous figure.
Figure 92: Typical Controller with Separate EOL Termination and Bias Configuration Settings
Refer to the controller's Hardware Installation Guide for how to identify and set a controller's built-in EOL terminations.

Only a Daisy-Chained Data Bus Topology is Acceptable

Use a daisy-chained BACnet MS/TP data bus topology only. No other data bus topology is allowed.

MS/ TP Data Bus Segment
Figure 93: Typical BACnet MS/TP LAN Topology Showing How Devices are Daisy-Chained Together to Form One Data Bus Segment
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.
A spur is only permitted when it is connected to the data bus through a repeater (see
nLight ECLYPSE
1
BIAS+
BMS
EOL
ECLYPSE Controller
ON
EOL Internally Set
Segment 1
Central Plant Air Handling Controllers
ON
2 3
OFF
EOL BIAS-
Maximum of 32 nodes and 1200 meters.
EOL
ON
EOL Internally Set to ON
Using Repeaters to Extend the Data Bus).
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