Subversion Repositories openrisc_2011-10-31

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

////                                                              ////

////  OR1200 FPU arith                                            ////

////                                                              ////

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

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

////                                                              ////

////  Description                                                 ////

////  Wrapper for floating point arithmetic units.                ////

////                                                              ////

////  To Do:                                                      ////

////   - lf.rem.s and lf.madd.s instruction support               ////

////                                                              ////

////  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_arith

  (

   clk_i,

   opa_i,

   opb_i,

   fpu_op_i,

   rmode_i,

   output_o,

   start_i,

   ready_o,

   ine_o,

   overflow_o,

   underflow_o,

   div_zero_o,

   inf_o,

   zero_o,

   qnan_o,

   snan_o

   );

   parameter FP_WIDTH = 32;

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

   parameter MUL_COUNT = 34; //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'b11111111_10000000000000000000000;

   parameter SNAN = 31'b11111111_00000000000000000000001;

   // fpu operations (fpu_op_i):

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

   // 000 = add, 

   // 001 = substract, 

   // 010 = multiply, 

   // 011 = divide,

   // 100 = square root - DISABLED - JPB

   // 101 = unused

   // 110 = unused

   // 111 = unused

   // Rounding Mode: 

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

   // 00 = round to nearest even (default), 

   // 01 = round to zero, 

   // 10 = round up, 

   // 11 = round down

   input  clk_i;

   input [FP_WIDTH-1:0] opa_i;

   input [FP_WIDTH-1:0] opb_i;

   input [2:0]           fpu_op_i;

   input [1:0]           rmode_i;

   input                start_i;

   output reg           ready_o;

   output reg [FP_WIDTH-1:0] output_o;

   output reg                ine_o;

   output reg                overflow_o;

   output reg                underflow_o;

   output reg                div_zero_o;

   output reg                inf_o;

   output reg                zero_o;

   output reg                qnan_o;

   output reg                snan_o;

   reg [FP_WIDTH-1:0]         s_opa_i;

   reg [FP_WIDTH-1:0]         s_opb_i;

   reg [2:0]                  s_fpu_op_i;

   reg [1:0]                  s_rmode_i;

   reg                       s_start_i;

   reg [5:0]                  s_count; // Max value of 64

   reg [FP_WIDTH-1:0]         s_output1;

   reg [FP_WIDTH-1:0]         s_output_o; // Comb

   reg                       s_ine_o;

   wire                      s_overflow_o,

                             s_underflow_o,

                             s_div_zero_o,

                             s_inf_o, s_zero_o, s_qnan_o, s_snan_o;

   wire                      s_infa, s_infb;

   parameter t_state_waiting = 0,

               t_state_busy = 1;

   reg                       s_state;

   //// ***Add/Substract units signals***

   wire [27:0]                prenorm_addsub_fracta_28_o;

   wire [27:0]                prenorm_addsub_fractb_28_o;

   wire [7:0]                 prenorm_addsub_exp_o;

   wire [27:0]                addsub_fract_o;

   wire                      addsub_sign_o;

   wire [31:0]                postnorm_addsub_output_o;

   wire                      postnorm_addsub_ine_o;

   //// ***Multiply units signals***

   wire [9:0]                 pre_norm_mul_exp_10;

   wire [23:0]                pre_norm_mul_fracta_24 ;

   wire [23:0]                pre_norm_mul_fractb_24 ;

   wire [47:0]                mul_fract_48;

   wire [47:0]                mul_24_fract_48;

   wire                      mul_24_sign;

   wire [47:0]                serial_mul_fract_48;

   wire                      serial_mul_sign;

   wire                      mul_sign;

   wire [31:0]                post_norm_mul_output   ;

   wire                      post_norm_mul_ine;

   //// ***Division units signals***

   wire [49:0]                pre_norm_div_dvdnd;

   wire [26:0]                pre_norm_div_dvsor;

   wire [EXP_WIDTH+1:0]      pre_norm_div_exp;

   wire [26:0]                serial_div_qutnt;

   wire [26:0]                serial_div_rmndr;

   wire                      serial_div_sign;

   wire                      serial_div_div_zero;

   wire [31:0]                post_norm_div_output;

   wire                      post_norm_div_ine;

   //// ***Square units***

   wire [51:0]                pre_norm_sqrt_fracta_o;

   wire [7:0]                 pre_norm_sqrt_exp_o;

   wire [25:0]                sqrt_sqr_o;

   wire                      sqrt_ine_o;

   wire [31:0]                post_norm_sqrt_output  ;

   wire                      post_norm_sqrt_ine_o;

   //***Add/Substract units***

   or1200_fpu_pre_norm_addsub fpu_prenorm_addsub

     (

      .clk_i(clk_i)  ,

      .opa_i(s_opa_i)  ,

      .opb_i(s_opb_i)  ,

      .fracta_28_o(prenorm_addsub_fracta_28_o)  ,

      .fractb_28_o(prenorm_addsub_fractb_28_o)  ,

      .exp_o(prenorm_addsub_exp_o) );

   or1200_fpu_addsub fpu_addsub

     (

            .clk_i(clk_i)  ,

            .fpu_op_i(s_fpu_op_i[0]),

            .fracta_i(prenorm_addsub_fracta_28_o)        ,

            .fractb_i(prenorm_addsub_fractb_28_o)        ,

            .signa_i( s_opa_i[31]),

            .signb_i( s_opb_i[31]),

            .fract_o(addsub_fract_o)  ,

            .sign_o(addsub_sign_o)  );

   or1200_fpu_post_norm_addsub fpu_postnorm_addsub

     (

      .clk_i(clk_i)  ,

      .opa_i(s_opa_i)  ,

      .opb_i(s_opb_i)  ,

      .fract_28_i(addsub_fract_o)  ,

      .exp_i(prenorm_addsub_exp_o)  ,

      .sign_i(addsub_sign_o)  ,

      .fpu_op_i(s_fpu_op_i[0]),

      .rmode_i(s_rmode_i)  ,

      .output_o(postnorm_addsub_output_o)  ,

      .ine_o(postnorm_addsub_ine_o)

      );

   //***Multiply units***

   or1200_fpu_pre_norm_mul fpu_pre_norm_mul

     (

      .clk_i(clk_i),

      .opa_i(s_opa_i),

      .opb_i(s_opb_i),

      .exp_10_o(pre_norm_mul_exp_10),

      .fracta_24_o(pre_norm_mul_fracta_24),

      .fractb_24_o(pre_norm_mul_fractb_24));

   /*

    mul_24 i_mul_24

    (

    .clk_i(clk_i)  ,

    .fracta_i(pre_norm_mul_fracta_24)  ,

    .fractb_i(pre_norm_mul_fractb_24)  ,

    .signa_i(s_opa_i[31]),

    .signb_i(s_opb_i[31]),

    .start_i(start_i)  ,

    .fract_o(mul_24_fract_48)  ,

    .sign_o(mul_24_sign)        ,

    .ready_o()  );

    */

   // Serial multiply is default and only one included here

   or1200_fpu_mul fpu_mul

     (

      .clk_i(clk_i)  ,

      .fracta_i(pre_norm_mul_fracta_24)  ,

      .fractb_i(pre_norm_mul_fractb_24)  ,

      .signa_i(s_opa_i[31]),

      .signb_i(s_opb_i[31]),

      .start_i(s_start_i)  ,

      .fract_o(serial_mul_fract_48)  ,

      .sign_o(serial_mul_sign)  ,

      .ready_o()

      );

   // Serial or parallel multiplier will be chosen depending on constant 

   // MUL_SERIAL

   assign mul_fract_48 = MUL_SERIAL ? serial_mul_fract_48 : mul_24_fract_48;

   assign mul_sign = MUL_SERIAL ? serial_mul_sign : mul_24_sign;

   or1200_fpu_post_norm_mul fpu_post_norm_mul

     (

      .clk_i(clk_i)  ,

      .opa_i(s_opa_i)  ,

      .opb_i(s_opb_i)  ,

      .exp_10_i(pre_norm_mul_exp_10)  ,

      .fract_48_i(mul_fract_48)  , // Parallel multiplier input

      .sign_i(mul_sign)  , // Parallel multiplier input

      .rmode_i(s_rmode_i)  ,

      .output_o(post_norm_mul_output)  ,

      .ine_o(post_norm_mul_ine)

      );

   ////***Division units***

   or1200_fpu_pre_norm_div fpu_pre_norm_div

     (

      .clk_i(clk_i)  ,

      .opa_i(s_opa_i)  ,

      .opb_i(s_opb_i)  ,

      .exp_10_o(pre_norm_div_exp)  ,

      .dvdnd_50_o(pre_norm_div_dvdnd)    ,

      .dvsor_27_o(pre_norm_div_dvsor)    );

   or1200_fpu_div fpu_div

     (

      .clk_i(clk_i) ,

      .dvdnd_i(pre_norm_div_dvdnd)  ,

      .dvsor_i(pre_norm_div_dvsor)  ,

      .sign_dvd_i(s_opa_i[31]),

      .sign_div_i(s_opb_i[31]),

      .start_i(s_start_i)  ,

      .ready_o()  ,

      .qutnt_o(serial_div_qutnt)  ,

      .rmndr_o(serial_div_rmndr)  ,

      .sign_o(serial_div_sign)  ,

      .div_zero_o(serial_div_div_zero)   );

   or1200_fpu_post_norm_div fpu_post_norm_div

     (

      .clk_i(clk_i)  ,

      .opa_i(s_opa_i)  ,

      .opb_i(s_opb_i)  ,

      .qutnt_i(serial_div_qutnt)        ,

      .rmndr_i(serial_div_rmndr)  ,

      .exp_10_i(pre_norm_div_exp)  ,

      .sign_i(serial_div_sign)   ,

      .rmode_i(s_rmode_i)       ,

      .output_o(post_norm_div_output)  ,

      .ine_o(post_norm_div_ine)  );

   //////////////////////////////////////////////////////////////////-

   // Input Registers

   always @(posedge clk_i)

     begin

        s_opa_i <= opa_i;

        s_opb_i <= opb_i;

        s_fpu_op_i <= fpu_op_i;

        s_rmode_i <= rmode_i;

        s_start_i <= start_i;

     end

   // Output registers

   always @(posedge clk_i)

     begin

        output_o <= s_output_o;

        ine_o <= s_ine_o;

        overflow_o <= s_overflow_o;

        underflow_o <= s_underflow_o;

        div_zero_o <= s_div_zero_o & !s_infa;

        inf_o <= s_inf_o;

        zero_o <= s_zero_o;

        qnan_o <= s_qnan_o;

        snan_o <= s_snan_o;

     end

   always @(posedge clk_i)

     begin

        if (s_start_i)  begin

           s_state <= t_state_busy;

           s_count <= 0;

        end

        else if (s_state == t_state_busy) begin

           // Ready cases

           if (((s_count == 6) & ((fpu_op_i==3'd0) | (fpu_op_i==3'd1))) |

               ((s_count==MUL_COUNT) & (fpu_op_i==3'd2)) |

               ((s_count==33) & (fpu_op_i==3'd3)))

             begin

                s_state <= t_state_waiting;

                ready_o <= 1;

                s_count <= 0;

             end

           else

             s_count <= s_count + 1;

        end // if (s_state == t_state_busy)

        else begin

           s_state <= t_state_waiting;

           ready_o <= 0;

        end // else: !if(s_state == t_state_busy)

     end // else: !if(s_start_i)

   //// Output Multiplexer

   always @(posedge clk_i)

     begin

        case(fpu_op_i)

          3'd0,

            3'd1: begin

               s_output1 <= postnorm_addsub_output_o;

               s_ine_o <= postnorm_addsub_ine_o;

            end

          3'd2: begin

             s_output1 <= post_norm_mul_output;

             s_ine_o <= post_norm_mul_ine;

          end

          3'd3: begin

             s_output1 <= post_norm_div_output;

             s_ine_o <= post_norm_div_ine;

          end

          //      3'd4: begin

          //            s_output1       <= post_norm_sqrt_output;

          //            s_ine_o         <= post_norm_sqrt_ine_o;

          //    end

          default: begin

             s_output1 <= 0;

             s_ine_o <= 0;

          end

        endcase // case (fpu_op_i)

     end // always @ (posedge clk_i)

   // Infinte exponent

   assign s_infa = &s_opa_i[30:23];

   assign s_infb = &s_opb_i[30:23];

   always @*

     begin

        if (s_rmode_i==2'd0 | s_div_zero_o | s_infa | s_infb | s_qnan_o |

            s_qnan_o) // Round to nearest even

          s_output_o = s_output1;

        else if (s_rmode_i==2'd1 & (&s_output1[30:23]))

          // In round-to-zero: the sum of two non-infinity operands is never 

          // infinity,even if an overflow occures

          s_output_o = {s_output1[31], 31'b1111111_01111111_11111111_11111111};

        else if (s_rmode_i==2'd2 & (&s_output1[31:23]))

          // In round-up: the sum of two non-infinity operands is never 

          // negative infinity,even if an overflow occures

          s_output_o = {32'b11111111_01111111_11111111_11111111};

        else if (s_rmode_i==2'd3) begin

           if (((s_fpu_op_i==3'd0) | (s_fpu_op_i==3'd1)) & s_zero_o &

               (s_opa_i[31] | (s_fpu_op_i[0] ^ s_opb_i[31])))

             // In round-down: a-a= -0

             s_output_o = {1'b1,s_output1[30:0]};

           else if (s_output1[31:23]==9'b0_11111111)

             s_output_o = 32'b01111111011111111111111111111111;

           else

             s_output_o = s_output1;

        end

        else

          s_output_o = s_output1;

     end // always @ *

   // Exception generation

   assign s_underflow_o = (s_output1[30:23]==8'h00) & s_ine_o;

   assign s_overflow_o = (s_output1[30:23]==8'hff) & s_ine_o;

   assign s_div_zero_o = serial_div_div_zero & fpu_op_i==3'd3;

   assign s_inf_o = s_output1[30:23]==8'hff & !(s_qnan_o | s_snan_o);

   assign s_zero_o = !(|s_output1[30:0]);

   assign s_qnan_o = s_output1[30:0]==QNAN;

   assign s_snan_o = s_output1[30:0]==SNAN;

endmodule // or1200_fpu_arith