Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 12)

Chapter 2
I/O Scanner Concepts
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Quad density module: Discrete I/O module having 32 input or output
points.
I/O chassis: One of four different housings sized to hold either four, eight,
twelve, or sixteen discrete I/O modules.
Slot: Position in an I/O chassis the width of one discrete I/O module.
I/O group: An addressing concept representing 16 input bits (one input
image table word) and 16 output bits (one output image table word).
In hardware, an I/O group can represent one or two slots in an I/O chassis.
It has an address number.
Half–slot addressing: Addressing where an I/O group represents a half of
a slot.
One–slot addressing: Addressing where an I/O group represents one slot.
Two–slot addressing: Addressing where an I/O group represents two
slots.
I/O rack number: An addressing concept representing 8 I/O groups. An
I/O rack number can be distributed over one, two, three, or four I/O
chassis; or two rack numbers can be assigned to one I/O chassis, depending
on chassis size and your application requirements.
Module address: An address that defines the physical location of the
module in the I/O chassis by its I/O rack number and starting slot number.
I/O update: The scanner’s serial scan of all I/O chassis in the I/O
subsystem. This scan is asynchronous to scans between the scanner and
host processor.
Scan list: A list specifying the order in which I/O adapters are to be
scanned. It is specified by the host and sent to the scanner module as a
scanner management command. Although a maximum of 16 I/O adapters
is allowed, the scan list can specify a maximum of 64 I/O adapters. This is
done to allow the scanner to scan adapters more than once during its scan
cycle if more frequent updates are desired.
Block transfer: The transfer of data to or from an intelligent I/O module
up to 64 words at a time.
Scanner management request: A command from the host to the scanner
used to control and configure the scanner board.