Subversion Repositories nanoblaze

--##############################################################################

--

--  scratchpad

--      The scratchpad as defined in version 3

--

--      This corresponds to a simple RAM.

--

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

--

--  Versions / Authors

--      1.0 Francois Corthay    first implementation

--

--  Provided under GNU LGPL licence: <http://www.gnu.org/copyleft/lesser.html>

--

--  by the electronics group of "HES-SO//Valais Wallis", in Switzerland:

--  <http://www.hevs.ch/en/rad-instituts/institut-systemes-industriels/>.

--

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

--

--  Hierarchy

--      Used by "nanoblaze/nanoProcessor".

--

--##############################################################################

LIBRARY ieee;

  USE ieee.std_logic_1164.all;

  USE ieee.numeric_std.all;

ENTITY scratchpad IS

  GENERIC(

    registerBitNb    : positive := 8;

    spadAddressBitNb : natural  := 4

  );

  PORT(

    reset   : IN  std_ulogic;

    clock   : IN  std_ulogic;

    addr    : IN  unsigned(spadAddressBitNb-1 DOWNTO 0);

    write   : IN  std_ulogic;

    dataIn  : IN  signed(registerBitNb-1 DOWNTO 0);

    dataOut : OUT signed(registerBitNb-1 DOWNTO 0 )

  );

END scratchpad ;

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

ARCHITECTURE RTL OF scratchpad IS

  subtype memoryWordType is signed(dataOut'range);

  type memoryArrayType is array (0 to 2**addr'length-1) of memoryWordType;

  signal memoryArray : memoryArrayType;

BEGIN

  process (clock)

  begin

    if rising_edge(clock) then

      if write = '1' then

        memoryArray(to_integer(addr)) <= dataIn;

      end if;

    end if;

  end process;

  dataOut <= memoryArray(to_integer(addr));

END ARCHITECTURE RTL;