Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 267)

Rockwell Automation Publication 1715-UM001C-EN-P - March 2014 267
Electronic Keying Appendix B
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.
When a module is created, the module developers consider the module’s
development history to implement capabilities that emulate those of the previous
module. However, the developers cannot know future developments. Because of
this, when a system is configured, we recommend that you configure your module
by using the earliest, that is, lowest, revision of the physical module that you use
in the system. By doing this, you can avoid the case of a physical module rejecting
the keying request because it is an earlier revision than the one configured in the
software.
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.