Rockwell Automation 6008-SV2R VMEbus remote I/O Scanner - Manual (Page 30)

3 Chapter
3Ć1
Addressing I/O
This chapter provides an overview of I/O addressing. This chapter also
explains the basics of how the scanner processes discrete I/O and
block-transfer data.
If you want to read about: go to page:
I/O addressing concept
3Ć1
choosing an addressing mode 3Ć3
addressing blockĆtransfer modules 3Ć6
assigning racks 3Ć7
Each terminal on an input or output module that can be wired to a field
device occupies a bit within the scanner’s input image table or output
image table.
I/O addressing maps the physical location of an I/O module terminal to a
bit location in the processor memory. I/O addressing is just a way to
segment memory:
Classification: Term: Relation to memory:
A specific terminal on an I/O module
terminal or
point
The density of an I/O module, i.e., 8Ćpoint, 16Ćpoint, 32Ćpoint,
directly relates to the amount of memory (bits) the module
occupies in memory. For example, a 16Ćpoint input module
occupies 16 bits in the input image table.
I/O terminals that when combined occupy 1 word in
the input image table and 1 word in the output
image table
I/O group 16 input bits = 1 word in the input image table
16 output bits = 1 word in the output image table
Combinations of bits or I/O groups I/O rack 128 input bits and 128 output bits
or
8 input words and 8 output words
or
8 I/O groups
Figure 3.1 shows the relationship between an I/O terminal and its location
in scanner memory.
Using This Chapter
I/O Addressing Concept