Allen-Bradley 1756 Series, User Manual, Page: 43 / 136

Rockwell Automation Publication 1756-UM013B-EN-P - October 2019 43
Features Common to 1756 ControlLogix Digital Safety I/O Modules Chapter 2
Electronic Keying
Electronic Keying reduces the possibility that you use the wrong device in a
control system. It compares the device that is defined in your project to the
installed device. If keying fails, a fault occurs. These attributes are compared.
The following Electronic Keying options are available.
Carefully consider the implications of each keying option when selecting one.
More Information
For more detailed information on Electronic Keying, see Electronic Keying in
Logix 5000™ Control Systems Application Technique, publication
LOGIX-AT001.
Attribute Description
Vendor The device manufacturer.
Device Type The general type of the product, for example, digital I/O module.
Product Code The specific type of the product. The Product Code maps to a catalog number.
Major Revision A number that represents the functional capabilities of a device.
Minor Revision A number that represents behavior changes in the device.
Keying Option Description
Compatible
Module This is the default keying option. 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. With Compatible Module, you can typically replace a device with another device that
has the following characteristics:
• Same catalog number
• Same or higher Major Revision
• Minor Revision as follows:
– If the Major Revision is the same, the Minor Revision must be the same or higher.
– If the Major Revision is higher, the Minor Revision can be any number.
Exact Match Indicates that all keying attributes must match to establish communication. If any attribute
does not match precisely, communication with the device does not occur.
This is a suitable keying option for safety applications.
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.