Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 314)

Addressing
Appendix A
AĆ7
that performs the opposite (complementary) function; an input module
complements an output module and vice-versa.
You can use an 8-point module with 16-point module in a 2-slot group;
however, it too must perform the opposite function. In this arrangement,
eight bits in the I/O image table are unused.
Assigning I/O Rack Numbers
When you select 2-slot addressing, each pair of slots (one I/O group) is
assigned to the corresponding pair of words in the input and output image
tables. You assign one I/O rack number to eight I/O groups (Figure A.5).
Figure A.5
I/O Table and Corresponding Hardware for One Assigned Rack Number
For 2Ćslot Addressing
Н Н Н
0
0
1
2
3
4
5
6
7
Word #
Output Image Table
When you select 2Ćslot addressing
each pair of slots is assigned an
input image table word and an
output image table word.
1 2 3 4 5 6 7
I O I O I O I O I O I O I O I O
0
1
2
3
4
5
6
7
Word #
Input Image Table