Constant Attribute
The Constant attribute prohibits instructions from writing values to a variable. Setting the Constant at-
tribute will prevent any program from overwriting the variable.
The values of variables with a Constant attribute cannot be written from instructions after the initial val-
ue is set. If there is an instruction in a POU that attempts to write a value to a variable with the Con-
stant attribute, an error will occur when the program is built.
6-2-7
Function Block Instances
Function block instances are added to and displayed in the local variable table or the global variable
table as data types.
Additional Information
A function block instance is treated as a local variable of the program in which the instance is
created. As such, the instance is added to and displayed in the local variable table of the pro-
gram.
6-2-8
Restrictions on Variable Names and Other Safety Program-relat-
ed Names
The following table lists the restrictions on variable names and other safety program-related names.
6 Programming
6 - 17
NX-series Safety Control Unit User's Manual (Z930)
6-2 Variables
6
6-2-7 Function Block Instances
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