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--------------------------------------------------------------------

-- Company       : XESS Corp.

-- Engineer      : Dave Vanden Bout

-- Creation Date : 05/17/2005

-- Copyright     : 2005, XESS Corp

-- Tool Versions : WebPACK 6.3.03i

--

-- Description:

--    Miscellaneous VHDL constants and functions

--

-- Revision:

--    1.0.0

--

-- Additional Comments:

--    1.1.0:

--        Added int_select() and real_select functions.

--    1.0.0:

--        Initial release.

--

-- License:

--    This code can be freely distributed and modified as long as

--    this header is not removed.

--------------------------------------------------------------------

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

package common is

  constant YES                :    std_logic := '1';

  constant NO                 :    std_logic := '0';

  constant HI                 :    std_logic := '1';

  constant LO                 :    std_logic := '0';

  constant ONE                :    std_logic := '1';

  constant ZERO               :    std_logic := '0';

  -- convert a Boolean to a std_logic

  function boolean2stdlogic(b : in boolean) return std_logic;

  -- find the base-2 logarithm of a number

  function log2(v             : in natural) return natural;

  -- select one of two integers based on a Boolean

  function int_select(s       : in boolean; a : in integer; b : in integer) return integer;

  -- select one of two reals based on a Boolean

  function real_select(s      : in boolean; a : in real; b : in real) return real;

end package common;

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

package body common is

  -- convert a Boolean to a std_logic

  function boolean2stdlogic(b : in boolean) return std_logic is

    variable s                :    std_logic;

  begin

    if b then

      s := '1';

    else

      s := '0';

    end if;

    return s;

  end function boolean2stdlogic;

  -- find the base 2 logarithm of a number

  function log2(v : in natural) return natural is

    variable n    :    natural;

    variable logn :    natural;

  begin

    n      := 1;

    for i in 0 to 128 loop

      logn := i;

      exit when (n >= v);

      n    := n * 2;

    end loop;

    return logn;

  end function log2;

  -- select one of two integers based on a Boolean

  function int_select(s : in boolean; a : in integer; b : in integer) return integer is

  begin

    if s then

      return a;

    else

      return b;

    end if;

    return a;

  end function int_select;

  -- select one of two reals based on a Boolean

  function real_select(s : in boolean; a : in real; b : in real) return real is

  begin

    if s then

      return a;

    else

      return b;

    end if;

    return a;

  end function real_select;

end package body common;