14 Publication 1756-PM004C-EN-P - October 2009
Chapter 1 Communicate with I/O Modules
Electronic Keying
The electronic keying feature automatically compares the expected module, as
shown in the RSLogix 5000 I/O Configuration tree, to the physical module
before I/O communication begins. You can use electronic keying to help
prevent communication to a module that does not match the type and revision
expected.
For each module in the I/O Configuration tree, the user-selected keying
option determines if, and how, an electronic keying check is performed.
Typically, three keying options are available.
• Exact Match
• Compatible Keying
• Disable Keying
You must carefully consider the benefits and implications of each keying
option when selecting between them. For some specific module types, fewer
options are available.
Electronic keying is based on a set of attributes unique to each product
revision. When a Logix5000 controller begins communicating with a module,
this set of keying attributes is considered.
You can find revision information on the General tab of a module’s Properties
dialog box.
General Tab
Keying Attributes
Attribute Description
Vendor The manufacturer of the module, for example, Rockwell
Automation/Allen-Bradley.
Product Type The general type of the module, for example, communication
adapter, AC drive, or digital I/O.
Product Code The specific type of module, generally represented by its catalog
number, for example, 1756-IB16I.
Major Revision A number that represents the functional capabilities and data
exchange formats of the module. Typically, although not always, a
later, that is higher, Major Revision supports at least all of the data
formats supported by an earlier, that is lower, Major Revision of the
same catalog number and, possibly, additional ones.
Minor Revision A number that indicates the module’s specific firmware revision.
Minor Revisions typically do not impact data compatibility but may
indicate performance or behavior improvement.
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