AnnexF/derivative_st.txt
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     1  FUNCTION_BLOCK DERIVATIVE
       
     2    VAR_INPUT
       
     3      RUN : BOOL ;          (* 0 = reset                  *)
       
     4      XIN : REAL ;          (* Input to be differentiated *)
       
     5      CYCLE : TIME ;        (* Sampling period            *)
       
     6    END_VAR
       
     7    VAR_OUTPUT
       
     8      XOUT : REAL ;         (* Differentiated output      *)
       
     9    END_VAR
       
    10    VAR X1, X2, X3 : REAL ; END_VAR
       
    11    IF RUN THEN
       
    12       XOUT := (3.0 * (XIN - X3) + X1 - X2)
       
    13               / (10.0 * TIME_TO_REAL(CYCLE)) ;
       
    14       X3 := X2 ; X2 := X1 ; X1 := XIN ;
       
    15    ELSE XOUT := 0.0; X1 := XIN ; X2 := XIN ; X3 := XIN ;
       
    16    END_IF ;
       
    17  END_FUNCTION_BLOCK
       
    18