1 (*

     2  * (c) 26 Feb 2001 David Campbell

     3  *

     4  * Offered to the public under the terms of the GNU General Public License

     5  * as published by the Free Software Foundation; either version 2 of the

     6  * License, or (at your option) any later version.

     7  *

     8  * This program is distributed in the hope that it will be useful, but

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

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

    11  * Public License for more details.

    12  *

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

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

    15  *)

    16 

    17 (*

    18  * An IEC 61131-3 IL and ST compiler.

    19  *

    20  * Based on the

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

    22  *

    23  *)

    24 

    25 

    26 (*

    27  * This is part of the library conatining the functions

    28  * and function blocks defined in the standard.

    29  *

    30  * SR and RS function blocks

    31  * -------------------------

    32  *)

    33 

    34 

    35 FUNCTION_BLOCK SR

    36   VAR_INPUT

    37     S1 : BOOL;

    38     R  : BOOL;

    39   END_VAR

    40   VAR_OUTPUT

    41     Q1 : BOOL;

    42   END_VAR

    43   VAR

    44     Q_INTERNAL : BOOL;

    45   END_VAR

    46 

    47   Q_INTERNAL := S1 OR ( Q_INTERNAL AND (NOT R));

    48   Q1 := Q_INTERNAL;

    49 END_FUNCTION_BLOCK

    50 

    51 FUNCTION_BLOCK RS

    52   VAR_INPUT

    53     S : BOOL;

    54     R1 : BOOL;

    55   END_VAR

    56   VAR_OUTPUT

    57     Q1 : BOOL;

    58   END_VAR

    59   VAR

    60     Q_INTERNAL : BOOL;

    61   END_VAR

    62 

    63   Q_INTERNAL := (NOT R1) AND (S OR Q_INTERNAL);

    64   Q1 := Q_INTERNAL;

    65 END_FUNCTION_BLOCK