Subversion Repositories openrisc_2011-10-31

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////  or1200_fpu_addsub                                           ////

////                                                              ////

////  This file is part of the OpenRISC 1200 project              ////

////  http://opencores.org/project,or1k                           ////

////                                                              ////

////  Description                                                 ////

////  addition/subtraction entity for the addition/subtraction    ////

////  unit                                                        ////

////                                                              ////

////  To Do:                                                      ////

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////                                                              ////

////  Author(s):                                                  ////

////      - Original design (FPU100) -                            ////

////        Jidan Al-eryani, jidan@gmx.net                        ////

////      - Conv. to Verilog and inclusion in OR1200 -            ////

////        Julius Baxter, julius@opencores.org                   ////

////                                                              ////

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

//

//  Copyright (C) 2006, 2010

//

//      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 or1200_fpu_addsub(

                 clk_i,

                 fpu_op_i,

                 fracta_i,

                 fractb_i,

                 signa_i,

                 signb_i,

                 fract_o,

                 sign_o);

   parameter FP_WIDTH = 32;

   parameter MUL_SERIAL = 0; // 0 for parallel multiplier, 1 for serial

   parameter MUL_COUNT = 11; //11 for parallel multiplier, 34 for serial

   parameter FRAC_WIDTH = 23;

   parameter EXP_WIDTH = 8;

   parameter ZERO_VECTOR = 31'd0;

   parameter INF = 31'b1111111100000000000000000000000;

   parameter QNAN = 31'b1111111110000000000000000000000;

   parameter SNAN = 31'b1111111100000000000000000000001;

   input clk_i;

   input fpu_op_i;

   input [FRAC_WIDTH+4:0] fracta_i;

   input [FRAC_WIDTH+4:0] fractb_i;

   input                  signa_i;

   input                  signb_i;

   output reg [FRAC_WIDTH+4:0] fract_o;

   output reg                  sign_o;

   wire [FRAC_WIDTH+4:0]       s_fracta_i;

   wire [FRAC_WIDTH+4:0]       s_fractb_i;

   wire [FRAC_WIDTH+4:0]       s_fract_o;

   wire                        s_signa_i, s_signb_i, s_sign_o;

   wire                        s_fpu_op_i;

   wire                        fracta_gt_fractb;

   wire                        s_addop;

   assign s_fracta_i = fracta_i;

   assign s_fractb_i = fractb_i;

   assign s_signa_i  = signa_i;

   assign s_signb_i  = signb_i;

   assign s_fpu_op_i = fpu_op_i;

   always @(posedge clk_i)

     begin

        fract_o <= s_fract_o;

        sign_o <= s_sign_o;

     end

   assign fracta_gt_fractb = s_fracta_i > s_fractb_i;

   // check if its a subtraction or an addition operation

   assign s_addop = ((s_signa_i ^ s_signb_i) & !s_fpu_op_i) |

                    ((s_signa_i ^~ s_signb_i) & s_fpu_op_i);

   // sign of result

   assign s_sign_o = ((s_fract_o == 28'd0) & !(s_signa_i & s_signb_i)) ? 0 :

                     (!s_signa_i & (!fracta_gt_fractb & (fpu_op_i^s_signb_i)))|

                     (s_signa_i & (fracta_gt_fractb | (fpu_op_i^s_signb_i)));

   // add/substract

   assign s_fract_o = s_addop ?

                      (fracta_gt_fractb ? s_fracta_i - s_fractb_i :

                       s_fractb_i - s_fracta_i) :

                      s_fracta_i + s_fractb_i;

endmodule // or1200_fpu_addsub