(*
 *  This file is part of matiec - a compiler for the programming
 *  languages defined in IEC 61131-3
 *
 *  Copyright (C) 2011  Mario de Sousa (msousa@fe.up.pt)
 *
 * See COPYING and COPYING.LESSER files for copyright details.
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 * USA
 *
 * This code is made available on the understanding that it will not be
 * used in safety-critical situations without a full and competent review.
 *)



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


(*
 * This is part of the library conatining the functions
 * and function blocks defined in the standard.
 *
 * SR and RS function blocks
 * -------------------------
 *)

(* The standard defines the SR FB thus: 

                  +-----+
S1----------------| >=1 |---Q1
         +---+    |     |
 R------O| & |----|     |
 Q1------|   |    |     |
         +---+    +-----+
*)

FUNCTION_BLOCK SR
  VAR_INPUT
    S1, R : BOOL;
  END_VAR
  VAR_OUTPUT
    Q1 : BOOL;
  END_VAR
  Q1 := S1 OR ((NOT R) AND Q1);
END_FUNCTION_BLOCK


(* The standard defines the RS FB thus: 
                   +---+
R1----------------O| & |---Q1
        +-----+    |   |
S-------| >=1 |----|   |
Q1------|     |    |   |
        +-----+    +---+
*)

FUNCTION_BLOCK RS
  VAR_INPUT
    S, R1 : BOOL;
  END_VAR
  VAR_OUTPUT
    Q1 : BOOL;
  END_VAR
  Q1 := (NOT R1) AND (S OR Q1);
END_FUNCTION_BLOCK