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

42 Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
Chapter 3 Common Module Features
Compatible Keying
Compatible Keying indicates that the module determines whether to accept or
reject communication. Different module families, communication adapters, and
module types implement the compatibility check differently based on the family
capabilities and on prior knowledge of compatible products.
Compatible Keying is the default setting. Compatible Keying allows the physical
module to accept the key of the module configured in the software, provided that
the configured module is one the physical module is capable of emulating. The
exact level of emulation required is product and revision specific.
With Compatible Keying, you can replace a module of a certain Major Revision
with one of the same catalog number and the same or later, that is higher, Major
Revision. In some cases, the selection makes it possible to use a replacement that
is a different catalog number than the original. For example, you can replace a
1756-CNBR module with a 1756-CN2R module.
Release notes for individual modules indicate the specific compatibility details.
EXAMPLE In the following scenario, Exact Match keying prevents I/O
communication.
The module configuration is for a 1756-IB16D module with module revision
3.1. The physical module is a 1756-IB16D module with module revision 3.2. In
this case, communication is prevented because the Minor Revision of the
module does not match precisely.
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 = 3
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 prevented