RS-485 bias switches - Facility Explorer - LIT-12014353 - FX-SC9BASE-0 - FX90 Supervisory Controller - 14.x

FX90 Supervisory Controller Installation Guide

Product
Controls > Supervisory Controls > FX90 Supervisory Controller
Document type
Installation Guide
Document number
LIT-12014353
Version
14.x
Revision date
2024-03-18
Product status
Active
Each RS-485 port has an adjacent 3-position biasing switch with the following settings:
  • BIA: The default middle switch. The controller provides RS-485 biasing without a termination resistor.
  • END: The controller provides both RS-485 biasing and a termination resistor.
  • MID: The controller does not provide RS-485 biasing or termination resistor.

RS-485 biasing can improve communications because this eliminates indeterminate idle states.

Note: FX-PC controllers implement biasing. When you use RS-485 for BACnet MS/TP with FX-PC controllers, use the MID position with FX-PC controllers at the ends of the trunks with their EOLs set. An all FX-PC controller trunk does not require the BIA position. For more information, refer to the FX-PC Series Controllers MS/TP Communications Bus Technical Bulletin (LIT-12011670).