B&B Electronics 3PCIOU4 - Manual - Manual (Page 42)

RS-422/485 Connections/Operation
36 Chapter 8 Document Number 3PCI-0712m
Figure 19. Termination and Bias Resistor Placement
Note: For more information on termination, biasing and how to
calculate resistor values download the RS-422/485 Application Note
from
www.bb-elec.com
2-Wire RS-485 Connections
The following diagram shows how to wire the DB-9 connector that will plug into your
MIport card for 2-wire RS-485 operation.
Figure 20. 2-Wire RS-485 Connections
2-Wire RS-485 Mode:
Your cables must bridge pins #1 & #3 and pins #2 & #9 in order to receive and transmit.
Connect from Pin #2 to Data B(+) of your devices and from pin #3 to Data A(-) of your
devices. Make sure your DIP switches are set, and that the driver Setting for RTS
Control is RS-485 Mode in the Device Manager, Port Settings, Advanced.
Note that the EIA RS-422 Specification labels data lines with an "A" and "B" designator.
Some RS-422 or RS-485 equipment uses a " " and "+" designator. In most cases, the
"A" line is the equivalent of the " " line and the "B" line is the equivalent of the "+" line.
Some device manufacturers may not follow the standard designation for RS-422 or RS-