ExST assignment 'R='

When the operand of the Reset assignment switches to ‎TRUE‎, then ‎FALSE‎ is assigned to the variable to the left of the operator. The variable is reset.

‎<variable name> R= <operand name> ;‎

The variables and the operand have the data type ‎BOOL‎.

Example

VAR
	xOperand: BOOL := FALSE;
	xResetVariable: BOOL := TRUE;
END_VAR

xResetVariable R= xOperand;

When the operand ‎xOperand‎ switches from ‎FALSE‎ to ‎TRUE‎, then ‎FALSE‎ is also assigned to the variable ‎xResetVariable‎. But then the variable keeps its state, even if the operand continues to change its state.

Multiple assignments

NOTICE

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 operands at the end of the code line.

Example

FUNCTION funCompute : BOOL
VAR_INPUT
	xIn : BOOL;
END_VAR
IF xIn = TRUE THEN
	funCompute := TRUE;
	RETURN;
END_IF

PROGRAM PLC_PRG
VAR
	xSetVariable: BOOL;
	xResetVariable: BOOL := TRUE;
	xVar: BOOL;
END_VAR
xSetVariable S= xResetVariable R= funCompute(xIn := xVar);

‎xResetVariable‎ gets the ‎R=‎ assignment of the return value of ‎funCompute‎. ‎xSetVariable‎ gets the ‎S=‎ assignment of ht return value of ‎funCompute‎, but not from ‎xResetVariable‎.