Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 269)

Rockwell Automation Publication 1715-UM001C-EN-P - March 2014 269
Electronic Keying Appendix B
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 can occur with a
module other than the type specified in the I/O Configuration tree with
unpredictable results. We generally do not recommend you use 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.
IMPORTANT Changing electronic keying selections online can cause the I/O communication connection to
the module to be disrupted and can result in a loss of data.
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
Cat. No. = 1756-IA16
Major Revision = 3
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Analog Input Module
Cat. No. = 1756-IF16
Major Revision = 3
Minor Revision = 2
Communication is prevented