Rockwell Automation 1757-FFLDC4 FOUNDATION Fieldbus System User Manual - Manual (Page 98)

98 Rockwell Automation Publication 1757-UM012A-EN-P - July 2011
Chapter 5 Create an RSLogix 5000 Software Project
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 that is being used can fulfill the functional requirements of
the application.
EXAMPLE In the following scenario, Compatible keying allows I/O communication:
The module configuration is for a 1756-IB16D module with module revision 2.1. The physical module is a 1756-IB16D
module with module revision 3.2. In this case, communication is allowed because the major revision of the physical
module is higher than expected and the module determines that it is compatible with the prior major revision.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 2
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 3
Minor Revision = 2
Communication is allowed.
IMPORTANT Changing electronic keying selections online may cause the I/O
communication connection to the module to be disrupted and may 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.