Subversion Repositories wf3d

//=======================================================================
// Project Monophony
//   Wire-Frame 3D Graphics Accelerator IP Core
//
// File:
//   floating point to integer conversion
//
// Abstract:
//   IP Core top module
//
// Author:
//   Kenji Ishimaru (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_f22_to_i (
  i_a,
  o_b
);
 
///////////////////////////////////////////
//  port definition
///////////////////////////////////////////
  input  [21:0] i_a;          // input s1, e5, f1.15
  output [15:0] o_b;          // 2's complement value
///////////////////////////////////////////
//  wire definition
///////////////////////////////////////////
  // intermidiate wire
  wire [4:0]  w_exp;
  wire [15:0] w_fraction;
  wire        w_s;
  wire [15:0] w_ui;
  wire [15:0] w_ui_2c;
///////////////////////////////////////////
//  assign statement
///////////////////////////////////////////
  assign w_s = i_a[21];
  assign w_exp  = i_a[20:16];
  assign w_fraction = i_a[15:0];
 
  assign w_ui = f_ftoi(w_exp, w_fraction);
  assign w_ui_2c = ~w_ui + 1'b1;
  assign o_b = (w_s) ?  w_ui_2c : w_ui;
///////////////////////////////////////////
//  function statement
///////////////////////////////////////////
    function [15:0] f_ftoi;
        input [4:0]  exp;
        input [15:0] frac;
        reg   [5:0]  ee;
        begin
            ee = exp - 4'd15;  // remove bias
            if (ee[5]) begin
                f_ftoi = 16'h0;
            end else begin
                case (ee[4:0])
                    5'd0:  f_ftoi = {15'b0,frac[15]};    // bias 0
                    5'd1:  f_ftoi = {14'b0,frac[15:14]};
                    5'd2:  f_ftoi = {13'b0,frac[15:13]};
                    5'd3:  f_ftoi = {12'b0,frac[15:12]};
                    5'd4:  f_ftoi = {11'b0,frac[15:11]};
                    5'd5:  f_ftoi = {10'b0,frac[15:10]};
                    5'd6:  f_ftoi = {9'b0,frac[15:9]};
                    5'd7:  f_ftoi = {8'b0,frac[15:8]};
                    5'd8:  f_ftoi = {7'b0,frac[15:7]};
                    5'd9:  f_ftoi = {6'b0,frac[15:6]};
                    5'd10: f_ftoi = {5'b0,frac[15:5]};
                    5'd11: f_ftoi = {4'b0,frac[15:4]};
                    5'd12: f_ftoi = {3'b0,frac[15:3]};
                    5'd13: f_ftoi = {2'b0,frac[15:2]};
                    5'd14: f_ftoi = {1'b0,frac[15:1]};
                    5'd15: f_ftoi = frac[15:0];
                    default: f_ftoi = 16'h0;
                endcase
            end
        end
    endfunction
 
endmodule