1

(*

     2

 *  This file is part of matiec - a compiler for the programming

     3

 *  languages defined in IEC 61131-3

     4

 *

     5

 *  Copyright (C) 2011  Mario de Sousa (msousa@fe.up.pt)

     6

 *

     7

 * See COPYING and COPYING.LESSER files for copyright details.

     8

 * This library is free software; you can redistribute it and/or

     9

 * modify it under the terms of the GNU Lesser General Public

    10

 * License as published by the Free Software Foundation; either

    11

 * version 3 of the License, or (at your option) any later version.

    12

 *

    13

 * This library is distributed in the hope that it will be useful,

    14

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

    15

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    16

 * Lesser General Public License for more details.

    17

 * 

    18

 * You should have received a copy of the GNU Lesser General Public

    19

 * License along with this library; if not, write to the Free Software

    20

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307

    21

 * USA

    22

 *

    23

 * This code is made available on the understanding that it will not be

    24

 * used in safety-critical situations without a full and competent review.

    25

 *)

    26

    27

    28

    29

(*

    30

 * An IEC 61131-3 compiler.

    31

 *

    32

 * Based on the

    33

 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)

    34

 *

    35

 *)

    36

    37

    38

(*

    39

 * This is part of the library conatining the functions

    40

 * and function blocks defined in the standard.

    41

 *

    42

 * SR and RS function blocks

    43

 * -------------------------

    44

 *)

    45

    46

(* The standard defines the SR FB thus: 

    47

    48

                  +-----+

    49

S1----------------| >=1 |---Q1

    50

         +---+    |     |

    51

 R------O| & |----|     |

    52

 Q1------|   |    |     |

    53

         +---+    +-----+

    54

*)

    55

    56

FUNCTION_BLOCK SR

    57

  VAR_INPUT

    58

    S1, R : BOOL;

    59

  END_VAR

    60

  VAR_OUTPUT

    61

    Q1 : BOOL;

    62

  END_VAR

    63

  Q1 := S1 OR ((NOT R) AND Q1);

    64

END_FUNCTION_BLOCK

    65

    66

    67

(* The standard defines the RS FB thus: 

    68

                   +---+

    69

R1----------------O| & |---Q1

    70

        +-----+    |   |

    71

S-------| >=1 |----|   |

    72

Q1------|     |    |   |

    73

        +-----+    +---+

    74

*)

    75

    76

FUNCTION_BLOCK RS

    77

  VAR_INPUT

    78

    S, R1 : BOOL;

    79

  END_VAR

    80

  VAR_OUTPUT

    81

    Q1 : BOOL;

    82

  END_VAR

    83

  Q1 := (NOT R1) AND (S OR Q1);

    84

END_FUNCTION_BLOCK