In the low-level RS-485 communications, the "unit number" determines which GIO is the originator or recipient of each message, not the position of the GIO board in the RS-485 daisy chain. This unit number is configurable using a group of three (3) jumper posts on the top of the GIO board. The unit numbers can be arbitrarily assigned and do not have to be sequential, but they do have to be unique within a controller system.
Figure 29-11: Unit Number Jumper
The unit number also determines a keyword ("GIO_<unit_number>") that is specified to configure a GIO board as a node in a controller's Servo Network.
NOTE: At the software application level, the network node number and not the GIO board unit number determines how the GIO's digital input and output lines are addressed.
For more information on node numbers and configuring the controller, see the Hardware and Software Configuration section of this manual.
In Table 29-5, the interpretation of the Unit Number Jumpers (J7, J8, J9) is provided. As shipped from the factory, all of the jumpers are installed, which indicates GIO unit #1.
NOTE: The Unit Number Jumpers for the GIO are J7/J8/J9 whereas the GSB utilizes J8/J9/J10.