Rockwell Automation Logix5000 Controllers I/O and Tag Data Programming Manual - Manual (Page 16)

Chapter 1 Communicate with I/O modules
Important: Changing Electronic Keying parameters online interrupts connections to the device and any devices that are
connected through the device. Connections from other controllers can also be broken.
If an I/O connection to a device is interrupted, the result can be a loss of data.
Electronic Keying is based on a set of attributes unique to each product revision.
When a Logix5000 controller begins communicating with a device, the following
attributes are considered.
Attribute Description
Vendor The device manufacturer, for example, Rockwell Automation/Allen-Bradley.
Product Type The general type of the device, for example, communication adapter, AC drive, or digital I/O
module.
Product Code The specific type of device. The Product Code maps to a catalog number.
The Product Code differentiates the product from other products of the same Device Type under
the indicated Vendor.
Major Revision A number that represents the functional capabilities of a device. Typically, a Major Revision is
backwards compatible with a lower Major Revision.
Minor Revision A number that represents behavior changes in the device, for example, anomaly corrections. This
number does not represent the functional capabilities of a device.
Exact Match
Exact Match indicates that all keying attributes of the device that is defined in the
project must match the attributes of the installed device to establish
communication.
If any attribute does not match precisely, communication with the device does not
occur.
Compatible Module
Compatible Module indicates that the device determines whether to accept or
reject communication.
Compatible Module lets the installed device accept the key of the device that is
defined in the project when the installed device can emulate the defined device.
The exact level of emulation that is required is product and revision specific
With Compatible Module, you can typically replace a device of a certain Major
Revision with another device that has the following characteristics:
16 Rockwell Automation Publication 1756-PM004E-EN-P - October 2014