Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 16)

Introduction
Chapter 1
1Ć6
We use the following terms to describe the various parts of your PLC-2/30
system.
Chassis — a hardware assembly used to house PC devices such as I/O
modules, adapter modules, processor modules, power supplies and some
processors (PLC-2/02, -2/16 and -2/17, for example).
I/O Group — The logical assignment of a specific input image table
word and its companion output image table word to a rack location. For
example: address 123 indicates an input module in rack 2, I/O group 3.
This applies to all addressing modes.
Rack — an I/O addressing unit that corresponds to 8 input image table
words and 8 output image table words (128 input and 128 output
terminals).
Rack Fault — 1) The condition that occurs because of a loss of
communication between the processor and remote I/O chassis; 2) any
diagnostic indicator that lights up to signal a rack fault.
Slot — 1) The physical location where each module is placed within
a chassis; 2) a part of the Rack-Group-Slot addressing information for
intelligent I/O modules.
Slot Addressing — a method of assigning one input and one output image
table word to two slots, one slot, or one-half of a slot. (Appendix A is an
in-depth discussion on this topic.)
Slot Pair — two adjacent slots that can share image table words. Slot pairs
are: slots 0 and 1, 2 and 3, 4 and 5, and 6 and 7. (See Appendix A)
These and other terms are defined in Programmable Controller Terms
(publication no. PCGI–7.2).
1.4
Terms Used in This Manual