Rockwell Automation Logix5000 Controllers I/O and Tag Data Programming Manual - Manual (Page 79)

Data access control Chapter 4
2. In the Parameter/Local Tag Properties dialog box, select the Constant
check box.
3. Click OK.
See Constant check box availability on page 80 for considerations.
Designate a constant in the Tag Editor
The Constant column in the Tag Editor lets you designate tags that cannot be
modified in the Logix Designer program. The Constant property applies to an
entire tag; all members of the tag take on the same setting. The Constant column
cells are blank for members of the constant tag.
An error message appears if you try to change the data type of a constant tag to a
data type that cannot be constant.
Follow these steps to add a constant value in the Tag Editor.
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