Subversion Repositories mips_enhanced

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

--  This file is a part of the GRLIB VHDL IP LIBRARY

--  Copyright (C) 2003, Gaisler Research

--

--  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 2 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, write to the Free Software

--  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

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

-- Entity:      ahbram

-- File:        ahbram.vhd

-- Author:      Jiri Gaisler - Gaisler Reserch

-- Description: AHB ram. 0-waitstate read, 0/1-waitstate write.

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

library ieee;

use ieee.std_logic_1164.all;

library grlib;

use grlib.amba.all;

use grlib.stdlib.all;

use grlib.devices.all;

library techmap;

use techmap.gencomp.all;

entity ahbram is

  generic (

    hindex  : integer := 0;

    haddr   : integer := 0;

    hmask   : integer := 16#fff#;

    tech    : integer := DEFMEMTECH;

    kbytes  : integer := 1);

  port (

    rst     : in  std_ulogic;

    clk     : in  std_ulogic;

    ahbsi   : in  ahb_slv_in_type;

    ahbso   : out ahb_slv_out_type

  );

end;

architecture rtl of ahbram is

constant abits : integer := log2(kbytes) + 8;

constant hconfig : ahb_config_type := (

  4 => ahb_membar(haddr, '1', '1', hmask),

  others => zero32);

type reg_type is record

  hwrite : std_ulogic;

  hready : std_ulogic;

  hsel   : std_ulogic;

  addr   : std_logic_vector(abits+1 downto 0);

  size   : std_logic_vector(1 downto 0);

end record;

signal r, c : reg_type;

signal ramsel : std_ulogic;

signal write : std_logic_vector(3 downto 0);

signal ramaddr  : std_logic_vector(abits-1 downto 0);

signal ramdata  : std_logic_vector(31 downto 0);

begin

  comb : process (ahbsi, r, rst, ramdata)

  variable bs : std_logic_vector(3 downto 0);

  variable v : reg_type;

  variable haddr  : std_logic_vector(abits-1 downto 0);

  begin

    v := r; v.hready := '1'; bs := (others => '0');

    if (r.hwrite or not r.hready) = '1' then haddr := r.addr(abits+1 downto 2);

    else

      haddr := ahbsi.haddr(abits+1 downto 2); bs := (others => '0');

    end if;

    if ahbsi.hready = '1' then

      v.hsel := ahbsi.hsel(hindex) and ahbsi.htrans(1);

      v.hwrite := ahbsi.hwrite and v.hsel;

      v.addr := ahbsi.haddr(abits+1 downto 0);

      v.size := ahbsi.hsize(1 downto 0);

    end if;

    if r.hwrite = '1' then

      case r.size(1 downto 0) is

      when "00" => bs (conv_integer(r.addr(1 downto 0))) := '1';

      when "01" => bs := r.addr(1) & r.addr(1) & not (r.addr(1) & r.addr(1));

      when others => bs := (others => '1');

      end case;

      v.hready := not (v.hsel and not ahbsi.hwrite);

      v.hwrite := v.hwrite and v.hready;

    end if;

    if rst = '0' then v.hwrite := '0'; v.hready := '1'; end if;

    write <= bs; ramsel <= v.hsel or r.hwrite; ahbso.hready <= r.hready;

    ramaddr <= haddr; c <= v; ahbso.hrdata <= ramdata;

  end process;

  ahbso.hresp   <= "00";

  ahbso.hsplit  <= (others => '0');

  ahbso.hirq    <= (others => '0');

  ahbso.hcache  <= '1';

  ahbso.hconfig <= hconfig;

  ahbso.hindex  <= hindex;

  ra : for i in 0 to 3 generate

    aram :  syncram generic map (tech, abits, 8) port map (

        clk, ramaddr, ahbsi.hwdata(i*8+7 downto i*8),

        ramdata(i*8+7 downto i*8), ramsel, write(3-i));

  end generate;

  reg : process (clk)

  begin

    if rising_edge(clk ) then r <= c; end if;

  end process;

-- pragma translate_off

    bootmsg : report_version

    generic map ("ahbram" & tost(hindex) &

    ": AHB SRAM Module rev 1, " & tost(kbytes) & " kbytes");

-- pragma translate_on

end;