Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 61)

4Ć3
4.2 Dividing I/O into Racks
I/O modules are installed in a chassis, but you must group the I/O
points logically into an I/O rack, which is the principal I/O addressing
unit. An I/O rack is composed of 128 inputs and 128 outputs or 8
input words and 8 output words.
Use this section to help you divide your I/O points into racks. This
section describes:
D AllenĆBradley's I/O addressing concept
D how to address blockĆtransfer modules
D how to determine your remote I/O racks
4.2.1 AllenĆBradley's I/O Addressing Concept
Since the purpose of the PC3000 Remote I/O scanner is to read
inputs and control outputs of field devices such as switches, valves,
and thermocouples, these inputs and outputs must occupy a
location in the scanner module's memory so that they can be
addressed in your control program. Each terminal on an input or
output module that can be wired to a field device occupies a bit
within the PC3000's memory. The part of memory that houses I/O
addresses is the input image table and the output image table.
I/O addressing maps the physical location of an I/O module terminal
to a bit location in the PC3000's memory. I/O addressing is a
method of segmenting the PC3000's memory. See Table 4.1 for
information about how memory is mapped into an I/O address.