Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 77)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
Configure the 1756-HSC Module 77
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.
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
.
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.
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.