Compiler Error C0178

Message: No external access to 'VAR_IN_OUT' parameter '<parameter name>' of '<object name>'

Possible error cause: An attempt is made to remotely access a 'VAR_IN_OUT' parameter.

Error correction: Do not remotely access 'VAR_IN_OUT' parameters.

PROGRAM PLC_PRG
VAR
    inst : FB;
    i : INT;
END_VAR
i := inst.in_out;

FUNCTION_BLOCK FB
VAR_IN_OUT
    in_out : INT;
END_VAR