Rockwell Automation T7491 ICS Regent+Plus Mixed I/O Modules - Manual (Page 14)

Multiplexed I/O Module (T7491)
1 4
Industrial Control Services
Figure 9. The Mux Input Unit and Mux Output Unit Dialog
Boxes.
5) Edit each point:
Choose Edit from the Mux I/O Unit dialog box to define a
name and description for each point. In the Mux Input (or
Output) Point dialog box, enter names and values for each
of the point configuration fields described below.
The first I/O point on the first I/O Unit is unusable. Do not
enter a definition for this point. For example, if you
configure four, 64-point Input Units for a single MIU
processor, the first input unit has only 63 usable inputs.
Do not define the first input on the first input unit. The
remaining three input units may have 64 inputs defined. Important!