SA0004: Multiple write access on output

Function	Determines outputs that are written at more than one position.
Reason	The maintainability suffers if an output is written in various places in the code. It is then unclear which write access is actually affecting the process. It is good practice to perform the calculation of the output variables in auxiliary variables and to assign the calculated value to a point at the end of the cycle.
Exception	No error is issued if an output variable is written in different branches of IF or CASE statements.
Importance	High
PLCopen rule	CP12

	This rule cannot be disabled via a pragma or attribute! For more information on attributes, see Pragmas and attributes.

Sample:

Global variable list:

VAR_GLOBAL
    bVar     AT%QX0.0 : BOOL;
    nSample  AT%QW5   : INT;
END_VAR

MAIN program:

PROGRAM MAIN
VAR
    nCondition        : INT;
END_VAR

IF nCondition < INT#0 THEN
    bVar    := TRUE;             // => SA0004
    nSample := INT#12;           // => SA0004 
END_IF
 
CASE nCondition OF
    INT#1:
        bVar := FALSE;           // => SA0004
 
    INT#2:
        nSample := INT#11;       // => SA0004 
 
ELSE
     bVar    := TRUE;            // => SA0004
     nSample := INT#9;           // => SA0004 
END_CASE