Subversion Repositories ecpu_alu

`timescale 1ns/1ps

module alu_barrel_shifter  (

                                x         ,

                                y         ,

                                z         ,

                                c         ,

                                direction

                              );

  parameter DWIDTH = 8;

  input       [DWIDTH-1:0]    x         ;

  input       [DWIDTH-1:0]    y         ;

  output      [DWIDTH-1:0]    z         ;

  output                      c         ;

  input                       direction ;

  reg         [DWIDTH-1:0]    z         ;

  reg                         c         ;

  reg         [DWIDTH-1:0]    y_tmp     ;

  initial

  begin

    c = 1'b0;

    y_tmp = 'd0; // initialise for simulation purposes

  end

  always @(x or y or direction)

  begin

    z = x;

    c = 0;

    for (y_tmp={{DWIDTH-3{1'b0}},y[2:0]}; y_tmp > 0; y_tmp = y_tmp - 1)

    begin

      `ifdef DEBUG_BARREL_SHIFTER

        $display ("[%0t] D%0d z=%0b", $time, y_tmp, z);

      `endif

       if (direction)

       begin

         z = {z[0], z[DWIDTH-1:1]};

         c = z[0]                 ;

       end

       else

       begin

         z = {z[DWIDTH-2:0], z[DWIDTH-1]} ;

         c = z[DWIDTH-2]                  ;

       end

    end

  end

endmodule