ExST assignment R=

If the operand of the reset assignment switches to TRUE, the assignment causes the variable to the left of the operator to be assigned a FALSE. The variable is reset.

Syntax:

<variable name> R= <operand name> ;

The variable and the operand have the data type BOOL.

Sample:

PROGRAM MAIN
VAR
    bOperand       : BOOL := FALSE;
    bResetVariable : BOOL := TRUE;
END_VAR

bResetVariable R= bOperand;

If the operand bOperand switches from FALSE to TRUE, the variable bResetVariable is assigned a FALSE. But then the variable keeps its state even if the operand keeps changing its state.

Multiple assignments

In the case of multiple assignments within a code line, the individual assignments are not processed from right to left, but all assignments refer to the operand at the end of the code line.

Sample:

FUNCTION F_Sample: BOOL
VAR_INPUT
    bIn : BOOL;
END_VAR

IF bIn = TRUE THEN
    F_Sample := TRUE;
    RETURN;
END_IF

PROGRAM MAIN
VAR
    bSetVariable   : BOOL;
    bResetVariable : BOOL := TRUE;
    bVar           : BOOL;
END_VAR

bSetVariable S= bResetVariable R= F_Sample(bIn := bVar);

bResetVariable receives the R= assignment of the return value of F_Sample. bSetVariable receives the S= assignment of the return value of F_Sample but not of bResetVariable.