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-- Copyright (c) 2011 Antonio de la Piedra

-- 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 3 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, see <http://www.gnu.org/licenses/>.

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity dual_mem is

  generic (ADDR_LENGTH : integer := 8;

           DATA_LENGTH : integer := 8;

           N_ADDR      : integer := 256);

  port (clk  : in std_logic;

        we   : in std_logic;

        a    : in std_logic_vector(ADDR_LENGTH - 1 downto 0);

        dpra : in std_logic_vector(ADDR_LENGTH - 1 downto 0);

        di   : in std_logic_vector(DATA_LENGTH - 1 downto 0);

        spo  : out std_logic_vector(DATA_LENGTH - 1 downto 0);

        dpo  : out std_logic_vector(DATA_LENGTH - 1 downto 0));

end dual_mem;

architecture rtl of dual_mem is

  type ram_type is array (N_ADDR - 1  downto 0)

        of std_logic_vector (DATA_LENGTH - 1 downto 0);

  signal RAM : ram_type;

  signal read_a : std_logic_vector(ADDR_LENGTH - 1 downto 0);

  signal read_dpra : std_logic_vector(ADDR_LENGTH - 1 downto 0);

  attribute ram_style: string;

  attribute ram_style of RAM: signal is "block";

begin

  process (clk)

  begin

    if rising_edge(clk) then

      if (we = '1') then

        RAM(conv_integer(a)) <= di;

      end if;

      read_a <= a;

      read_dpra <= dpra;

    end if;

  end process;

  spo <= RAM(conv_integer(read_a));

  dpo <= RAM(conv_integer(read_dpra));

end rtl;