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

-- Copyright (C) 2004 Arif Endro Nugroho

-- All rights reserved.

-- 

-- Redistribution and use in source and binary forms, with or without

-- modification, are permitted provided that the following conditions

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-- 1. Redistributions of source code must retain the above copyright

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-- 2. Redistributions in binary form must reproduce the above copyright

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-- 

-- THIS SOFTWARE IS PROVIDED BY ARIF ENDRO NUGROHO "AS IS" AND ANY EXPRESS

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-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

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

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity adder_15bit is

   port (

      addend_15bit  : in  bit_vector (14 downto 0);

      augend_15bit  : in  bit_vector (14 downto 0);

      adder15_output: out bit_vector (15 downto 0) -- 16 bit output

      );

end adder_15bit;

architecture structural of adder_15bit is

   component fulladder

      port (

      addend        : in   bit;

      augend        : in   bit;

      carry_in      : in   bit;

      sum           : out  bit;

      carry         : out  bit

      );

   end component;

-- internal signal

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 c09 : bit;

signal c10 : bit;

signal c11 : bit;

signal c12 : bit;

signal c13 : bit;

signal c14 : bit;

signal c15 : bit;

signal over15 : bit;

signal adder15_output_int : bit_vector (14 downto 0);

signal ov  : bit;

begin

c00                     <= '0';

over15                  <= (addend_15bit (14) xor augend_15bit (14));

ov                      <= ((adder15_output_int (14) and over15) or

                           (c15 and (not (over15))));

adder15_output(14 downto 00) <= adder15_output_int;

adder15_output(15)           <= ov;

fa14 : fulladder

   port map (

      addend     => addend_15bit(14),

      augend     => augend_15bit(14),

      carry_in   => c14,

      sum        => adder15_output_int(14),

      carry      => c15

      );

fa13 : fulladder

   port map (

      addend     => addend_15bit(13),

      augend     => augend_15bit(13),

      carry_in   => c13,

      sum        => adder15_output_int(13),

      carry      => c14

      );

fa12 : fulladder

   port map (

      addend     => addend_15bit(12),

      augend     => augend_15bit(12),

      carry_in   => c12,

      sum        => adder15_output_int(12),

      carry      => c13

      );

fa11 : fulladder

   port map (

      addend     => addend_15bit(11),

      augend     => augend_15bit(11),

      carry_in   => c11,

      sum        => adder15_output_int(11),

      carry      => c12

      );

fa10 : fulladder

   port map (

      addend     => addend_15bit(10),

      augend     => augend_15bit(10),

      carry_in   => c10,

      sum        => adder15_output_int(10),

      carry      => c11

      );

fa09 : fulladder

   port map (

      addend     => addend_15bit(09),

      augend     => augend_15bit(09),

      carry_in   => c09,

      sum        => adder15_output_int(09),

      carry      => c10

      );

fa08 : fulladder

   port map (

      addend     => addend_15bit(08),

      augend     => augend_15bit(08),

      carry_in   => c08,

      sum        => adder15_output_int(08),

      carry      => c09

      );

fa07 : fulladder

   port map (

      addend     => addend_15bit(07),

      augend     => augend_15bit(07),

      carry_in   => c07,

      sum        => adder15_output_int(07),

      carry      => c08

      );

fa06 : fulladder

   port map (

      addend     => addend_15bit(06),

      augend     => augend_15bit(06),

      carry_in   => c06,

      sum        => adder15_output_int(06),

      carry      => c07

      );

fa05 : fulladder

   port map (

      addend     => addend_15bit(05),

      augend     => augend_15bit(05),

      carry_in   => c05,

      sum        => adder15_output_int(05),

      carry      => c06

      );

fa04 : fulladder

   port map (

      addend     => addend_15bit(04),

      augend     => augend_15bit(04),

      carry_in   => c04,

      sum        => adder15_output_int(04),

      carry      => c05

      );

fa03 : fulladder

   port map (

      addend     => addend_15bit(03),

      augend     => augend_15bit(03),

      carry_in   => c03,

      sum        => adder15_output_int(03),

      carry      => c04

      );

fa02 : fulladder

   port map (

      addend     => addend_15bit(02),

      augend     => augend_15bit(02),

      carry_in   => c02,

      sum        => adder15_output_int(02),

      carry      => c03

      );

fa01 : fulladder

   port map (

      addend     => addend_15bit(01),

      augend     => augend_15bit(01),

      carry_in   => c01,

      sum        => adder15_output_int(01),

      carry      => c02

      );

fa00 : fulladder

   port map (

      addend     => addend_15bit(00),

      augend     => augend_15bit(00),

      carry_in   => c00,

      sum        => adder15_output_int(00),

      carry      => c01

      );

end structural;