ELECTRONIC KEYING FOR ALLEN BRADLEY PLCS
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Typically, PLC I/O Cards have major and minor revisions which indicate the functional features of the card.
The electronic keying settings in a project specify the allowable differences between the module revision configured in a project and the actual revision of the physical module.
There are three major electronic keying settings.
1. Exact Match: This setting means that the major and minor revision configured in the project must match the major and minor revision of the physical I/O device. This is used in instances where the firmware revision of the hardware has features integral to the project or in highly regulated environments.
2. Compatible Keying: This setting means that only the major revision of the configured module in the project and the actual device must match. The minor revision can be ignored.
3. Disable Keying: This setting means that both the major and minor revisions of the configured module do not need to match at all. This is commonly used in cases where maintenance staff might have spares for different modules and would want to be able to replace a module without project modification
Understanding the concept of electronic keying is important for maintenance staff and automation engineers to ensure maximum compliance and minimum downtime in production environments