lib/derivative_st.txt
author mjsousa
Tue, 08 Apr 2014 14:35:31 +0100
changeset 889 5f380b99e95e
parent 276 1679f514f38a
permissions -rwxr-xr-x
Correctly handle structured variables that include FB and external FBs (example: FB1.FB2.extFB3.FB4.extFB5.extFB6.structvar.field1 := 42;) (this commit fixes only ST code. TODO: IL and SFC)

(* Following taken directly from the IEC 61131.3 draft standard *)

(*
 * An IEC 61131-3 IL and ST compiler.
 *
 * Based on the
 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
 *
 *)


 FUNCTION_BLOCK DERIVATIVE
   VAR_INPUT
     RUN : BOOL ;          (* 0 = reset                  *)
     XIN : REAL ;          (* Input to be differentiated *)
     CYCLE : TIME ;        (* Sampling period            *)
   END_VAR
   VAR_OUTPUT
     XOUT : REAL ;         (* Differentiated output      *)
   END_VAR
   VAR X1, X2, X3 : REAL ; END_VAR
   IF RUN THEN
      XOUT := (3.0 * (XIN - X3) + X1 - X2)
              / (10.0 * TIME_TO_REAL(CYCLE)) ;
      X3 := X2 ; X2 := X1 ; X1 := XIN ;
   ELSE XOUT := 0.0; X1 := XIN ; X2 := XIN ; X3 := XIN ;
   END_IF ;
 END_FUNCTION_BLOCK