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/////////////////////////////////////////////////////////////////////

////                                                             ////

////  SBOX                                                       ////

////  The SBOX is essentially a 64x4 ROM                         ////

////                                                             ////

////  Author: Rudolf Usselmann                                   ////

////          rudi@asics.ws                                      ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

////                                                             ////

//// Copyright (C) 2001 Rudolf Usselmann                         ////

////                    rudi@asics.ws                            ////

////                                                             ////

//// This source file may be used and distributed without        ////

//// restriction provided that this copyright statement is not   ////

//// removed from the file and that any derivative work contains ////

//// the original copyright notice and the associated disclaimer.////

////                                                             ////

////     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////

//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////

//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////

//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      ////

//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         ////

//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    ////

//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   ////

//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        ////

//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  ////

//// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  ////

//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  ////

//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         ////

//// POSSIBILITY OF SUCH DAMAGE.                                 ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

module  sbox4(addr, dout);

input   [1:6] addr;

output  [1:4] dout;

reg     [1:4] dout;

always @(addr) begin

    case ({addr[1], addr[6], addr[2:5]})        //synopsys full_case parallel_case

         0:  dout =  7;

         1:  dout = 13;

         2:  dout = 14;

         3:  dout =  3;

         4:  dout =  0;

         5:  dout =  6;

         6:  dout =  9;

         7:  dout = 10;

         8:  dout =  1;

         9:  dout =  2;

        10:  dout =  8;

        11:  dout =  5;

        12:  dout = 11;

        13:  dout = 12;

        14:  dout =  4;

        15:  dout = 15;

        16:  dout = 13;

        17:  dout =  8;

        18:  dout = 11;

        19:  dout =  5;

        20:  dout =  6;

        21:  dout = 15;

        22:  dout =  0;

        23:  dout =  3;

        24:  dout =  4;

        25:  dout =  7;

        26:  dout =  2;

        27:  dout = 12;

        28:  dout =  1;

        29:  dout = 10;

        30:  dout = 14;

        31:  dout =  9;

        32:  dout = 10;

        33:  dout =  6;

        34:  dout =  9;

        35:  dout =  0;

        36:  dout = 12;

        37:  dout = 11;

        38:  dout =  7;

        39:  dout = 13;

        40:  dout = 15;

        41:  dout =  1;

        42:  dout =  3;

        43:  dout = 14;

        44:  dout =  5;

        45:  dout =  2;

        46:  dout =  8;

        47:  dout =  4;

        48:  dout =  3;

        49:  dout = 15;

        50:  dout =  0;

        51:  dout =  6;

        52:  dout = 10;

        53:  dout =  1;

        54:  dout = 13;

        55:  dout =  8;

        56:  dout =  9;

        57:  dout =  4;

        58:  dout =  5;

        59:  dout = 11;

        60:  dout = 12;

        61:  dout =  7;

        62:  dout =  2;

        63:  dout = 14;

    endcase

    end

endmodule