Subversion Repositories spi_boot

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

--

-- SD/MMC Bootloader

-- Sample client for loading an image to asynchronous SRAM

--

-- $Id: ram_loader.vhd 77 2009-04-01 19:53:14Z arniml $

--

-- Copyright (c) 2005, Arnim Laeuger (arniml@opencores.org)

--

-- All rights reserved, see COPYING.

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/projects.cgi/web/spi_boot/overview

--

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

library ieee;

use ieee.std_logic_1164.all;

entity ram_loader is

  port (

    -- Global Interface -------------------------------------------------------

    clk_i      : in    std_logic;

    reset_i    : in    std_logic;

    lamp_o     : out   std_logic;

    -- Config Interface -------------------------------------------------------

    cfg_clk_i  : in    std_logic;

    cfg_data_i : in    std_logic;

    start_o    : out   std_logic;

    mode_o     : out   std_logic;

    done_o     : out   std_logic;

    detached_i : in    std_logic;

    -- Asynchronous RAM Interface ---------------------------------------------

    ram_addr_o : out   std_logic_vector(15 downto 0);

    ram_data_b : out   std_logic_vector( 7 downto 0);

    ram_ce_no  : out   std_logic_vector( 3 downto 0);

    ram_oe_no  : out   std_logic;

    ram_we_no  : out   std_logic

  );

end ram_loader;

library ieee;

use ieee.numeric_std.all;

architecture rtl of ram_loader is

  signal addr_q     : unsigned(17 downto 0);

  signal inc_addr_s : boolean;

  signal shift_dat_q : std_logic_vector(7 downto 0);

  signal ser_dat_q   : std_logic_vector(7 downto 0);

  signal bit_q       : unsigned(2 downto 0);

  signal bit_ovfl_q  : boolean;

  type fsm_t is (IDLE,

                 WE_ON,

                 WE_OFF,

                 INC_ADDR1, INC_ADDR2,

                 FINISHED);

  signal fsm_s,

         fsm_q  : fsm_t;

  signal done_q          : std_logic;

  signal done_s          : boolean;

  signal mode_q,

         mode_s          : std_logic;

  signal ram_we_n_q,

         ram_we_n_s  : std_logic;

  signal ram_ce_n_q,

         ram_ce_n_s  : std_logic_vector(3 downto 0);

  type start_fsm_t is (WAIT_DETACH,

                       CHECK_NO_DONE,

                       WAIT_DONE);

  signal start_fsm_s,

         start_fsm_q  : start_fsm_t;

  signal start_s,

         start_q         : std_logic;

  signal enable_s,

         enable_q        : boolean;

begin

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

  -- Process seq

  --

  -- Purpose:

  --   Implements the sequential elements clocked with cfg_clk_i.

  --

  seq: process (cfg_clk_i, reset_i)

  begin

    if reset_i = '0' then

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

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

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

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

      bit_ovfl_q  <= false;

      fsm_q       <= IDLE;

      ram_we_n_q  <= '1';

      ram_ce_n_q  <= (others => '1');

      done_q      <= '0';

      mode_q      <= '0';

    elsif cfg_clk_i'event and cfg_clk_i = '1' then

      if inc_addr_s then

        addr_q <= addr_q + 1;

      end if;

      if enable_q then

        bit_q      <= bit_q + 1;

        bit_ovfl_q <= bit_q = 7;

        shift_dat_q(0) <= cfg_data_i;

        shift_dat_q(7 downto 1) <= shift_dat_q(6 downto 0);

      end if;

      -- update register when 8 serial bits have been shifted in

      if bit_ovfl_q then

        ser_dat_q <= shift_dat_q;

      end if;

      fsm_q <= fsm_s;

      ram_we_n_q <= ram_we_n_s;

      ram_ce_n_q <= ram_ce_n_s;

      -- done only settable once

      if done_s then

        done_q <= '1';

      end if;

      mode_q <= mode_s;

    end if;

  end process seq;

  --

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

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

  -- Process fsm

  --

  -- Purpose:

  --   Implements the combinational logic of the RAM loader FSM.

  --

  fsm: process (fsm_q,

                bit_ovfl_q,

                start_q,

                addr_q)

  begin

    -- default assignments

    inc_addr_s      <= false;

    ram_we_n_s      <= '1';

    done_s          <= false;

    fsm_s           <= IDLE;

    lamp_o          <= '1';

    mode_s          <= '0';

    case fsm_q is

      when IDLE =>

        lamp_o <= '0';

        if start_q = '1' then

          if bit_ovfl_q then

            fsm_s <= WE_ON;

          end if;

        end if;

      when WE_ON =>

        ram_we_n_s <= '0';

        fsm_s      <= WE_OFF;

      when WE_OFF =>

        fsm_s <= INC_ADDR1;

      when INC_ADDR1 =>

        fsm_s      <= INC_ADDR2;

      when INC_ADDR2 =>

        if addr_q = "001111111111111111" then  -- load only 64k

          fsm_s <= FINISHED;

          done_s <= true;

          mode_s <= '1';

        else

          inc_addr_s <= true;

          fsm_s      <= IDLE;

        end if;

      when FINISHED =>

        fsm_s  <= FINISHED;

        lamp_o <= '1';

        mode_s <= '1';

      when others =>

    end case;

  end process fsm;

  --

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

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

  -- Process ce_gen

  --

  -- Purpose:

  --   Generates the four CE signals for the external RAM chips.

  --

  ce_gen: process (addr_q)

  begin

    ram_ce_n_s <= (others => '1');

    ram_ce_n_s(to_integer(addr_q(17 downto 16))) <= '0';

  end process ce_gen;

  --

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

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

  -- Process start_seq

  --

  -- Purpose:

  --   Implements the sequential elements clocked with clk_i.

  --

  start_seq: process (clk_i, reset_i)

  begin

    if reset_i = '0' then

      start_fsm_q <= WAIT_DETACH;

      start_q     <= '0';

      enable_q    <= false;

    elsif clk_i'event and clk_i = '1' then

      start_fsm_q <= start_fsm_s;

      enable_q    <= enable_s;

      start_q     <= start_s;

    end if;

  end process start_seq;

  --

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

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

  -- Process start_comb

  --

  -- Purpose:

  --   Implements the combinational logic of the start FSM.

  --

  start_comb: process (start_fsm_q,

                       detached_i,

                       done_q,

                       enable_q,

                       start_q)

  begin

    -- default assignments

    start_fsm_s <= WAIT_DETACH;

    enable_s    <= enable_q;

    start_s     <= start_q;

    case start_fsm_q is

      -- Wait for detached_i to become '1'

      -- This state is entered/left twice:

      -- 1. after reset to start the data download

      -- 2. after data download to start the next configuration cycle

      when WAIT_DETACH =>

        if detached_i = '1' then

          start_fsm_s <= CHECK_NO_DONE;

          enable_s    <= true;

          start_s     <= '1';

        else

          start_fsm_s <= WAIT_DETACH;

        end if;

      -- Wait until done_q is '0'

      -- This ensures that the FSM stalls when it has started the configuration

      -- download. There must be no further action in this case.

      when CHECK_NO_DONE =>

        if done_q = '0' then

          start_fsm_s <= WAIT_DONE;

        else

          start_fsm_s <= CHECK_NO_DONE;

        end if;

      -- Wait until done_q is '1'

      -- done_q is the signal that the main FSM has finished its work. We

      -- need to start the configuration download.

      when WAIT_DONE =>

        if done_q = '1' then

          start_fsm_s <= WAIT_DETACH;

          enable_s    <= false;

          start_s     <= '0';

        else

          start_fsm_s <= WAIT_DONE;

        end if;

      when others =>

        null;

    end case;

  end process start_comb;

  --

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

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

  -- Output Mapping

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

  start_o    <= start_q;

  mode_o     <= mode_q;

  done_o     <=   done_q

                when start_q = '1' else

                  '1';

  ram_addr_o <= std_logic_vector(addr_q(15 downto 0));

  ram_data_b <= ser_dat_q;

  ram_oe_no  <= '1';

  ram_ce_no  <= ram_ce_n_q;

  ram_we_no  <= ram_we_n_q;

end rtl;