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).