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`timescale 1ns / 1ps

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

//        __

//   \\__/ o\    (C) 2006-2017  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch<remove>@finitron.ca

//       ||

//

//      fd2s.v

//    - convert floating point double to single

//

//

// This source file is free software: you can redistribute it and/or modify 

// it under the terms of the GNU Lesser General Public License as published 

// by the Free Software Foundation, either version 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file is distributed in the hope that it will be useful,      

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

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            

// GNU General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//                                                                          

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

module fd2s(a, o);

input [63:0] a;

output reg [31:0] o;

wire signi;

wire [10:0] expi;

wire [51:0] mani;

wire xinf;

wire xz;

wire vz;

fpDecomp #(64) u1 (.i(a), .sgn(signi), .exp(expi), .man(mani), .xinf(xinf), .xz(xz), .vz(vz) );

wire [11:0] exp = expi - 11'h896;   // 1023-127 (difference of the bias)

always @*

begin

o[31] <= signi;         // sign out = sign in, easy

o[22:0] <= a[51:29];

if (xinf)

    o[30:23] <= 8'hFF;

else if (vz)

    o[30:23] <= 8'h00;

else if (xz)

    o[30:23] <= 8'h00;

else begin

    if (exp[11]) begin  // exponent is too low - set number to zero

        o[30:23] <= 8'h00;

        o[22:0] <= 23'h000000;

    end

    else if (|exp[10:8]) begin  // exponent is too high - set number to infinity

        o[30:23] <= 8'hFF;

        o[22:0] <= 23'h000000;

    end

    else    // exponent in range

        o[30:23] <= exp[7:0];

end

end

endmodule