Rockwell Automation 1756-HYD02 ControlLogix Hydraulic Servo Module - Manual (Page 45)

Publication 1756-UM525A-EN-P - June 2003 45
Using the 1756-HYD02 Module Features Chapter 4
General Tab
Exact Match
Exact Match keying requires all keying attributes, that is, Vendor, Product
Type, Product Code (catalog number), Major Revision, and Minor Revision, of
the physical module and the module created in the software to match precisely
in order to establish communication. If any attribute does not match precisely,
I/O communication is not permitted with the module or with modules
connected through it, as in the case of a communication module.
Use Exact Match keying when you need the system to verify that the module
revisions in use are exactly as specified in the project, such as for use in
highly-regulated industries. Exact Match keying is also necessary to enable
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.