Subversion Repositories scarts

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

-- This file is part of SCARTS.

-- 

-- SCARTS 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.

-- 

-- SCARTS 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 SCARTS.  If not, see <http://www.gnu.org/licenses/>.

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

use work.scarts_core_pkg.all;

use work.scarts_pkg.all;

entity scarts_iram is

  generic (

    CONF : scarts_conf_type);

  port (

    wclk        : in  std_ulogic;

    rclk        : in  std_ulogic;

    hold        : in  std_ulogic;

    wdata       : in  INSTR;

    waddr       : in  std_logic_vector(CONF.instr_ram_size-1 downto 0);

    wen         : in  std_ulogic;

    raddr       : in  std_logic_vector(CONF.instr_ram_size-1 downto 0);

    rdata       : out INSTR);

end scarts_iram;

architecture behaviour of scarts_iram is

  constant NWORDS : integer  := 2**CONF.instr_ram_size;

  type ram_array is array (0 to NWORDS-1) of INSTR;

  signal ram : ram_array := (others => NOP);

  signal enable    : std_ulogic;

  signal data_int       : INSTR;

begin

  enable <= not hold;

  process(wclk)

  begin

    if rising_edge(wclk) then

      if (enable = '1') then

        if wen = '1' then

          ram(to_integer(unsigned(waddr))) <= wdata;

        end if;

      end if;

    end if;

  end process;

  process(rclk)

  begin

    if rising_edge(rclk) then

      if (enable = '1') then

        data_int <= (others => '0');

        data_int <= ram(to_integer(unsigned(raddr)));

      end if;

    end if;

  end process;

  -- little-endianness used for storing instructions in memory

  -- => swap bytes

  rdata(15 downto 8) <= data_int(7 downto 0);

  rdata(7 downto 0) <= data_int(15 downto 8);

end behaviour;