Subversion Repositories product_code_iterative_decoder

-- $Id: adder_08bit.vhdl,v 1.1.1.1 2005-11-15 01:52:30 arif_endro Exp $

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

-- Title       : 8 bit adder

-- Project     : 

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

-- File        : adder_08bit.vhdl

-- Author      : "Arif E. Nugroho" <arif_endro@yahoo.com>

-- Created     : 2005/11/01

-- Last update : 

-- Simulators  :

-- Synthesizers: 

-- Target      : 

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

-- Description : 8 bit signed adder

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-- Copyright (C) 2005 Arif Endro Nugroho

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

-- 

--      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 BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

-- IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

-- MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO

-- EVENT SHALL THE AUTHOR 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.

-- 

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

library IEEE;

use IEEE.std_logic_1164.all;

entity adder_08bit is

   port (

      addend_08bit  : in  bit_vector (07 downto 0);

      augend_08bit  : in  bit_vector (07 downto 0);

      adder08_output: out bit_vector (08 downto 0)

      );

end adder_08bit;

architecture structural of adder_08bit is

   component fulladder

      port (

      addend        : in   bit;

      augend        : in   bit;

      carry_in      : in   bit;

      sum           : out  bit;

      carry         : out  bit

      );

   end component;

signal c00 : bit;

signal c01 : bit;

signal c02 : bit;

signal c03 : bit;

signal c04 : bit;

signal c05 : bit;

signal c06 : bit;

signal c07 : bit;

signal c08 : bit;

signal over08 : bit;

signal adder08_output_int : bit_vector (08 downto 0);

begin

c00                     <= '0';

over08                  <= (addend_08bit (07) xor augend_08bit (07));

adder08_output_int (08) <= ((adder08_output_int (07) and over08) or

                           (c08 and (not (over08))));

adder08_output          <= adder08_output_int;

fa07 : fulladder

   port map (

      addend     => addend_08bit(07),

      augend     => augend_08bit(07),

      carry_in   => c07,

      sum        => adder08_output_int(07),

      carry      => c08

      );

fa06 : fulladder

   port map (

      addend     => addend_08bit(06),

      augend     => augend_08bit(06),

      carry_in   => c06,

      sum        => adder08_output_int(06),

      carry      => c07

      );

fa05 : fulladder

   port map (

      addend     => addend_08bit(05),

      augend     => augend_08bit(05),

      carry_in   => c05,

      sum        => adder08_output_int(05),

      carry      => c06

      );

fa04 : fulladder

   port map (

      addend     => addend_08bit(04),

      augend     => augend_08bit(04),

      carry_in   => c04,

      sum        => adder08_output_int(04),

      carry      => c05

      );

fa03 : fulladder

   port map (

      addend     => addend_08bit(03),

      augend     => augend_08bit(03),

      carry_in   => c03,

      sum        => adder08_output_int(03),

      carry      => c04

      );

fa02 : fulladder

   port map (

      addend     => addend_08bit(02),

      augend     => augend_08bit(02),

      carry_in   => c02,

      sum        => adder08_output_int(02),

      carry      => c03

      );

fa01 : fulladder

   port map (

      addend     => addend_08bit(01),

      augend     => augend_08bit(01),

      carry_in   => c01,

      sum        => adder08_output_int(01),

      carry      => c02

      );

fa00 : fulladder

   port map (

      addend     => addend_08bit(00),

      augend     => augend_08bit(00),

      carry_in   => c00,

      sum        => adder08_output_int(00),

      carry      => c01

      );

end structural;