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[/] [neorv32/] [trunk/] [rtl/] [core/] [neorv32_boot_rom.vhd] - Rev 32
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-- ################################################################################################# -- # << NEORV32 - Processor-internal bootloader ROM (BOOTROM) >> # -- # ********************************************************************************************* # -- # 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 NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # -- ################################################################################################# library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; library neorv32; use neorv32.neorv32_package.all; use neorv32.neorv32_bootloader_image.all; -- this file is generated by the image generator entity neorv32_boot_rom is generic ( BOOTROM_BASE : std_ulogic_vector(31 downto 0) := x"FFFF0000"; -- boot ROM base address BOOTROM_SIZE : natural := 4*1024 -- processor-internal boot ROM memory size in bytes ); port ( clk_i : in std_ulogic; -- global clock line rden_i : in std_ulogic; -- read enable addr_i : in std_ulogic_vector(31 downto 0); -- address data_o : out std_ulogic_vector(31 downto 0); -- data out ack_o : out std_ulogic -- transfer acknowledge ); end neorv32_boot_rom; architecture neorv32_boot_rom_rtl of neorv32_boot_rom is -- local types -- type boot_img_t is array (0 to BOOTROM_SIZE/4-1) of std_ulogic_vector(31 downto 0); -- init function -- -- impure function: returns NOT the same result every time it is evaluated with the same arguments since the source file might have changed impure function init_boot_rom(init : bootloader_init_image_t) return boot_img_t is variable mem_v : boot_img_t; begin mem_v := (others => (others => '0')); for i in 0 to init'length-1 loop -- init only in range of source data array 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(31 downto 0); signal addr : std_ulogic_vector(index_size_f(BOOTROM_SIZE/4)-1 downto 0); -- bootloader image -- constant boot_img : boot_img_t := init_boot_rom(bootloader_init_image); begin -- Access Control ------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- acc_en <= '1' when (addr_i >= BOOTROM_BASE) and (addr_i < std_ulogic_vector(unsigned(BOOTROM_BASE) + BOOTROM_SIZE)) else '0'; addr <= addr_i(index_size_f(BOOTROM_SIZE/4)+1 downto 2); -- word aligned -- Memory Access -------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- mem_file_access: process(clk_i) begin 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(to_integer(unsigned(addr))); end if; end if; end process mem_file_access; -- output gate -- data_o <= rdata when (rden = '1') else (others => '0'); ack_o <= rden; end neorv32_boot_rom_rtl;
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