SA0038: Read access to output variable

Function	Determines output variables (VAR_OUTPUT) that are subject to read access within the POU.
Reason	The IEC-61131-3 standard prohibits reading an output within a function block. It indicates that the output is not only used as an output but also as a temporary variable for intermediate results. Such dual use should be avoided.
Importance	Low

Sample:

Function block FB_Sample:

FUNCTION_BLOCK FB_Sample
VAR_OUTPUT
    bOut    : BOOL;
    nOut    : INT;
END_VAR
VAR
    bLocal  : BOOL;
    nLocal  : INT;
END_VAR

Method FB_Sample.SampleMethod:

IF bOut THEN                     // => SA0038
    bLocal := (nOut > 100);      // => SA0038
    nLocal := nOut;              // => SA0038
    nLocal := 2*nOut;            // => SA0038
END_IF