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• Semantic Error (SEM1140): Constant variables cannot be assigned to VAR_IN_OUT parameters.

Semantic Error (SEM1140): Constant variables cannot be assigned to VAR_IN_OUT parameters.

In a code worksheet, another element than a variable is connected to a VAR_IN_OUT parameter ('Usage = InOut') of a function block. This is not allowed. Connect a non-constant variable to correct the error.

A formal parameter declared with 'Usage = InOut' is not a "real variable" but a reference to another variable. It can be compared to a pointer that points to the address of another variable.

This referenced variable is read and written by the FB. Writing, for example, a literal or a variable which is declared as CONSTANT is not possible. Thus, only writable variables are allowed at in/output parameters.