1  FUNCTION_BLOCK LAG1

     2    VAR_INPUT

     3      RUN : BOOL ;     (* 1 = run, 0 = reset *)

     4      XIN : REAL ;     (* Input variable *)

     5      TAU : TIME ;     (* Filter time constant *)

     6      CYCLE : TIME ;   (* Sampling time interval *)

     7    END_VAR

     8    VAR_OUTPUT XOUT : REAL ; END_VAR  (* Filtered output *)

     9    VAR K : REAL ;     (* Smoothing constant, 0.0<=K<1.0 *)

    10    END_VAR

    11    IF RUN THEN XOUT := XOUT + K * (XIN - XOUT) ;

    12    ELSE XOUT := XIN ;

    13         K := TIME_TO_REAL(CYCLE) / TIME_TO_REAL(CYCLE + TAU) ;

    14    END_IF ;

    15  END_FUNCTION_BLOCK

    16