Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 321)

Addressing
Appendix A
AĆ14
Assigning I/O Rack Numbers
When you select 1/2-slot addressing, each slot corresponds to two I/O
groups. You still assign one rack number to eight groups; however, with
1/2-slot addressing this requires only four slots. Thus, in a single 16 slot
chassis, you now can have four I/O racks (Figure A.10).
Figure A.10
Assigning I/O rack Numbers with 1/2Ćslot Addressing
Н Н
НН
I/O Group No.
0Ć3 4Ć7 0Ć3 4Ć7 0Ć3 4Ć7 0Ć3 4Ć7
I/O Groups 0, 1
Rack 1 Rack 2 Rack 3 Rack 4
I/O Groups 2, 3
I/O Groups 6, 7
I/O Groups 4, 5
1771ĆA4B I/O Chassis using 1/2Ćslot addressing
Assigned Rack Numbers