Semantic Error (SEM1087): The variable '...' does not exist in '...'.

In an ST code worksheet, a function or function block is called with a formal parameter which does not exist in the called POU. The entire function/FB call is underlined in the code. Check all formal parameters and correct wrong spelling/parameters.

For user-defined FUs/FBs, this may be expected if the appropriate variable has not yet been declared with 'Usage' = 'Input' (IEC 61131-3 keyword VAR_INPUT) or 'Output' (VAR_OUTPUT) or if the formal parameter name has been changed meanwhile.