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• Semantic Error (SEM1141): Read-only variables cannot be assigned to VAR_IN_OUT parameters.

Semantic Error (SEM1141): Read-only variables cannot be assigned to VAR_IN_OUT parameters.

In a code worksheet, a variable has been assigned to a VAR_IN_OUT parameter ('Usage = InOut') of a function block which is

This is not allowed. Replace this read-only variable by a variable which can be written by the FB.

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 a read-only variable, however, is not possible. Thus, only writeable variables are allowed at in/output parameters.

Further Info Also refer to the PLCnext Info Center which provides many information and practical user tips on the PLCnext Technology control platform and PLCnext Engineer.

Further Info Please refer to the user manual of the controller for further information on system variables.