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//=======================================================================

// Project Monophony

//   Wire-Frame 3D Graphics Accelerator IP Core

//

// File:

//   fm_3d_fcnv.v

//

// Abstract:

//   3D float conversion IEEE single floating point number to

//   22-bits floating point number

//

// Author:

//   Kenji Ishimaru (info.info.wf3d@gmail.com)

//

//======================================================================

//

// Copyright (c) 2015, Kenji Ishimaru

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

//  -Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

//  -Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER 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.

//

// Revision History

module fm_3d_fcnv (

  i_f32,

  o_f22

);

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

// I/O definition

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

    input  [31:0] i_f32;

    output [21:0] o_f22;

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

// assign

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

    assign o_f22 = f_f32_to_f22(i_f32);

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

// function

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

    function [21:0] f_f32_to_f22;

        input [31:0] f32;

        reg s;

        reg [7:0]  e8;

        reg [8:0]  e8d;  // width sign bit

        reg [4:0]  e5;

        reg [23:0] m23;

        reg [14:0] m15;

        reg        carry;

        reg        zf;

        begin

            s = f32[31];

            e8 = f32[30:23];

            zf = (e8 == 8'h00);

            m23 = f32[22:0];

            {carry,m15} = m23[22:8] + m23[7];

            e8d = e8 - 112 + carry;  // -127+15 + carry

            if (zf|e8d[8]) begin

                e5 = 5'h0;

            end else begin

                e5 = e8d[4:0];

            end

            f_f32_to_f22 = {s,e5,!(zf|e8d[8]),m15};

        end

    endfunction

endmodule