Subversion Repositories tcp_ip_core_w_dhcp

----------------------------------------------------------------------------------
-- This program is free software; you can redistribute it and/or
-- modify it under the terms of the GNU General Public License
-- as published by the Free Software Foundation; either version 2
-- of the License, or (at your option) any later version.
--
-- This program 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, write to the Free Software
-- Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
-- 02111-1307, USA.
--
-- ©1997-2011 - X Engineering Software Systems Corp. (www.xess.com)
----------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------
-- Commonly-used functions and constants.
----------------------------------------------------------------------------------
 
 
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
 
package CommonPckg 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';
  constant HIZ  : std_logic := 'Z';
 
  -- Types of FPGA chips.
  constant SPARTAN2_G  : natural := 1;
  constant SPARTAN2E_G : natural := 2;
  constant SPARTAN3_G  : natural := 3;
 
  -- Convert a Boolean to a std_logic.
  function BooleanToStdLogic(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 IntSelect(s : in boolean; a : in integer; b : in integer) return integer;
 
  -- Select one of two reals based on a Boolean.
  function RealSelect(s : in boolean; a : in real; b : in real) return real;
 
  -- Convert a binary number to a graycode number.
  function BinaryToGray(b : in std_logic_vector) return std_logic_vector;
 
  -- Convert a graycode number to a binary number.
  function GrayToBinary(g : in std_logic_vector) return std_logic_vector;
 
  -- Find the maximum of two integers.
  function IntMax(a : in integer; b : in integer) return integer;
 
end package;
 
 
 
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
 
 
package body CommonPckg is
 
  -- Convert a Boolean to a std_logic.
  function BooleanToStdLogic(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 BooleanToStdLogic;
 
  -- 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 IntSelect(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 IntSelect;
 
  -- Select one of two reals based on a Boolean.
  function RealSelect(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 RealSelect;
 
  -- Convert a binary number to a graycode number.
  function BinaryToGray(b : in std_logic_vector) return std_logic_vector is
    variable g : std_logic_vector(b'range);
  begin
    for i in b'low to b'high-1 loop
      g(i) := b(i) xor b(i+1);
    end loop;
    g(b'high) := b(b'high);
    return g;
  end function BinaryToGray;
 
  -- Convert a graycode number to a binary number.
  function GrayToBinary(g : in std_logic_vector) return std_logic_vector is
    variable b : std_logic_vector(g'range);
  begin
    b(b'high) := g(b'high);
    for i in g'high-1 downto g'low loop
      b(i) := b(i+1) xor g(i);
    end loop;
    return b;
  end function GrayToBinary;
 
  -- Find the maximum of two integers.
  function IntMax(a : in integer; b : in integer) return integer is
  begin
    if a > b then
      return a;
    else
      return b;
    end if;
    return a;
  end function IntMax;
 
end package body;