Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 315)

Addressing
Appendix A
AĆ8
The processor (by way of the adapter) addresses one I/O module slot as
one I/O group.
Each 1-slot I/O group is represented by a word in the input image table and
a word in the output image table. You have 16 input bits and 16 output bits
available for each slot. This lets you use any mix of 8 and 16-point I/O
modules in the I/O chassis in any order. Thirty-two-point modules must be
used in complementary arrangements.
You select 1-slot addressing by setting two switches in the I/O chassis
backplane switch assembly. See your scanner’s or adapter’s users’ manual
for the specific switches and their settings.
The physical address of each I/O group corresponds to an input and an
output image table word. The type of module you install (either 8-point or
16-point I/O) determines the number of bits in these words that are used.
Figure A.6 (on the next page) illustrates the 1-slot I/O group concept with
one 16-point I/O module. This module group uses an entire word of the
image table. You can use an 8-point I/O module with 1-slot addressing, but
the module uses only eight bits of the I/O image table word (8 bits in the
I/O image table are unused).
A.2.2
1ĆSlot Addressing