SA0170: Address of an output variable should not be used

Function	Determines code positions where the address of an output variable (VAR_OUTPUT, VAR_IN_OUT) of a function block is used.
Reason	It is not allowed to use the address of a function block output in the following way: By means of the ADR operator By means of REF=
Exception	No error is reported if the output variable is used within the same function block.
Importance	Medium

Sample:

Function block FB_Sample:

FUNCTION_BLOCK FB_Sample
VAR_INPUT
    nIn          : INT;
END_VAR
VAR_OUTPUT
    nOut         : INT;
END_VAR
VAR
    pFB          : POINTER TO FB_Sample;
    pINT         : POINTER TO INT;
END_VAR

IF pFB <> 0 THEN
    pINT := ADR(pFB^.nOut);                    // => SA0170
END_IF
 
nOut := nIn;
pINT := ADR(THIS^.nOut);                       // no error due to internal usage
pINT := ADR(nOut);                             // no error due to internal usage

Accesses within another function block, in this case in the MAIN program:

PROGRAM MAIN
VAR
    fbSample     : FB_Sample;
    pExternal    : POINTER TO INT;
    refExternal  : REFERENCE TO INT;
END_VAR

pExternal   := ADR(fbSample.nOut);             // => SA0170
refExternal REF= fbSample.nOut;                // => SA0170