VHDL PROGRAM OF A74XX21_vhd

-- ============================================================================
-- 74XX21 Dual 4-Input AND Gates
--
-- Copyright (C),2004 Andrew John Jacobs.
--
-- This program is provided free of charge for educational purposes
--
-- Redistribution and use in binary form without modification, is permitted
-- provided that the above copyright notice, this list of conditions and the
-- following disclaimer in the documentation and/or other materials provided
-- with the distribution.
--
-- THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS '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 OR CONTRIBUTORS 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 A74XX21 is
 generic (
  tplh  : time := 0 ns;
  tphl  : time := 0 ns);
 port (
  a1   : in  std_logic;
  b1   : in  std_logic;
  c1   : in  std_logic;
  d1   : in  std_logic;
  a2   : in  std_logic;
  b2   : in  std_logic;
  c2   : in  std_logic;
  d2   : in  std_logic;
  o1   : out  std_logic;
  o2   : out  std_logic);
end entity;

-- ============================================================================

library ieee;
use ieee.std_logic_1164.all;

architecture dataflow of A74XX21 is
begin
 o1 <= '0' after tphl when (a1 and b1 and c1 and d1) = '0' else
    '1' after tplh;

 o2 <= '0' after tphl when (a2 and b2 and c2 and d2) = '0' else
    '1' after tplh;
end architecture;