Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 42)

42 Publication 1756-UM009C-EN-P - December 2010
Chapter 3 ControlLogix Analog I/O Module Features
Disabled Keying
Disabled Keying indicates the keying attributes are not considered when
attempting to communicate with a module. Other attributes, such as data size
and format, are considered and must be acceptable before I/O
communication is established. With Disabled keying, I/O communication may
occur with a module other than the type specified in the I/O Configuration
tree with unpredictable results. We generally do not recommend using
Disabled keying.
If you use Disabled keying, you must take full responsibility for understanding
whether the module being used can fulfill the functional requirements of the
application.
ATTENTION
Be extremely cautious when using Disabled keying; if used
incorrectly, this option can lead to personal injury or death,
property damage, or economic loss.
EXAMPLE
In the following scenario, Disable keying prevents I/O
communication:
• The module configuration is for a 1756-IA16 digital input module.
The physical module is a 1756-IF16 analog input module. In this
case, communication is prevented because the analog
module rejects the data formats that the digital module
configuration requests.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IA16
Major Revision = 3
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Analog Input
Module
Catalog Number = 1756-IF16
Major Revision = 3
Minor Revision = 2
Communication is prevented