Subversion Repositories neo430

-- #################################################################################################
-- #  << NEO430 - Bootloader ROM >>                                                                #
-- # ********************************************************************************************* #
-- # This memory includes the in-place executable image of the NEO430 bootloader. See the          #
-- # processor's documentary to get more information.                                              #
-- # ********************************************************************************************* #
-- # BSD 3-Clause License                                                                          #
-- #                                                                                               #
-- # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #
-- #                                                                                               #
-- # Redistribution and use in source and binary forms, with or without modification, are          #
-- # permitted provided that the following conditions are met:                                     #
-- #                                                                                               #
-- # 1. Redistributions of source code must retain the above copyright notice, this list of        #
-- #    conditions and the following disclaimer.                                                   #
-- #                                                                                               #
-- # 2. Redistributions in binary 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.                                                            #
-- #                                                                                               #
-- # 3. Neither the name of the copyright holder nor the names of its 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    #
-- # COPYRIGHT HOLDER 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.                                                            #
-- # ********************************************************************************************* #
-- # The NEO430 Processor - https://github.com/stnolting/neo430                                    #
-- #################################################################################################
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
library neo430;
use neo430.neo430_package.all;
use neo430.neo430_bootloader_image.all; -- this file is generated by the image generator
 
entity neo430_boot_rom is
  port (
    clk_i  : in  std_ulogic; -- global clock line
    rden_i : in  std_ulogic; -- read enable
    addr_i : in  std_ulogic_vector(15 downto 0); -- address
    data_o : out std_ulogic_vector(15 downto 0)  -- data out
  );
end neo430_boot_rom;
 
architecture neo430_boot_rom_rtl of neo430_boot_rom is
 
  -- local types --
  type boot_img_t is array (0 to boot_size_c/2-1) of std_ulogic_vector(15 downto 0);
 
  -- init function --
  impure function init_boot_rom(init : bootloader_init_image_t) return boot_img_t is
    variable mem_v : boot_img_t;
  begin
    for i in 0 to boot_size_c/2-1 loop
      mem_v(i) := init(i);
    end loop; -- i
    return mem_v;
  end function init_boot_rom;
 
  -- local signals --
  signal acc_en : std_ulogic;
  signal rden   : std_ulogic;
  signal rdata  : std_ulogic_vector(15 downto 0);
  signal addr   : natural range 0 to boot_size_c/2-1;
 
  -- bootloader image --
  constant boot_img : boot_img_t := init_boot_rom(bootloader_init_image);
 
begin
 
  -- Access Control -----------------------------------------------------------
  -- -----------------------------------------------------------------------------
  acc_en <= '1' when (addr_i >= boot_base_c) and (addr_i < std_ulogic_vector(unsigned(boot_base_c) + boot_size_c)) else '0';
  addr <= to_integer(unsigned(addr_i(index_size_f(boot_size_c/2) downto 1))); -- word aligned
 
 
  -- Memory Access ------------------------------------------------------------
  -- -----------------------------------------------------------------------------
  mem_file_access: process(clk_i)
  begin
    -- check max size --
    if (boot_size_c > boot_max_size_c) then
      assert false report "Boot ROM size out of range! Max 2kB!" severity error;
    end if;
    if rising_edge(clk_i) then
      rden <= rden_i and acc_en;
      if (acc_en = '1') then -- reduce switching activity when not accessed
        rdata <= boot_img(addr);
      end if;
    end if;
  end process mem_file_access;
 
  -- output gate --
  data_o <= rdata when (rden = '1') else (others => '0');
 
 
end neo430_boot_rom_rtl;