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.
Figure92: 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.
Figure93: 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 Using Repeaters to Extend the Data Bus).
BACnet MS/TP Communication Data Bus Fundamentals
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