Compiler error C0041

Message: VAR_IN_OUT parameter '<parameter name>' of '<function name>' needs variable with write access as input

Possible error cause: The passed parameter is not a variable with write access (but a constant for example).

Error correction: Pass a VAR_IN_OUT parameter with write access to the function.

Example of the error:

PROGRAM PLC_PRG
VAR
	 i : INT;
	 x : INT;
END_VAR
i := Test(31415);

FUNCTION TEST : INT
VAR_IN_OUT
	in_out: INT;
END_VAR


--> C0041: VAR_IN_OUT' parameter 'in_out' of 'TEST' needs variable with write access as input

Error correction:

Example:
i := Test(x);