lib/derivative_st.txt
author Laurent Bessard
Tue, 11 Sep 2012 01:05:24 +0200
changeset 628 fe0d516fe291
parent 276 1679f514f38a
permissions -rwxr-xr-x
Fix bug in SFC generated code. Action state was declared in the list of variables to debug, but wasn't stored using structure with flags. This error had side effects that makes Beremiz debug crash.

(* 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