93 lines
5.3 KiB
VHDL
93 lines
5.3 KiB
VHDL
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-- #################################################################################################
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-- # << NEORV32 - Processor-internal bootloader ROM (BOOTROM) >> #
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-- # ********************************************************************************************* #
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-- # BSD 3-Clause License #
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-- # #
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-- # The NEORV32 RISC-V Processor, https://github.com/stnolting/neorv32 #
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-- # Copyright (c) 2024, Stephan Nolting. All rights reserved. #
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-- # #
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-- # Redistribution and use in source and binary forms, with or without modification, are #
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-- # permitted provided that the following conditions are met: #
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-- # #
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-- # 1. Redistributions of source code must retain the above copyright notice, this list of #
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-- # conditions and the following disclaimer. #
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-- # #
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-- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of #
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-- # conditions and the following disclaimer in the documentation and/or other materials #
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-- # provided with the distribution. #
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-- # #
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-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to #
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-- # endorse or promote products derived from this software without specific prior written #
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-- # permission. #
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-- # #
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-- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS #
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-- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF #
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-- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE #
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-- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, #
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-- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
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-- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED #
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-- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING #
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-- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED #
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-- # OF THE POSSIBILITY OF SUCH DAMAGE. #
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-- #################################################################################################
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.numeric_std.all;
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library neorv32;
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use neorv32.neorv32_package.all;
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use neorv32.neorv32_bootloader_image.all; -- this file is generated by the image generator
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entity neorv32_boot_rom is
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port (
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clk_i : in std_ulogic; -- global clock line
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rstn_i : in std_ulogic; -- async reset, low-active
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bus_req_i : in bus_req_t; -- bus request
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bus_rsp_o : out bus_rsp_t -- bus response
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);
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end neorv32_boot_rom;
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architecture neorv32_boot_rom_rtl of neorv32_boot_rom is
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-- determine physical ROM size in bytes (expand to next power of two) --
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constant boot_rom_size_index_c : natural := index_size_f((bootloader_init_image'length)); -- address with (32-bit entries)
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constant boot_rom_size_c : natural range 0 to mem_boot_size_c := (2**boot_rom_size_index_c)*4; -- physical size in bytes
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-- ROM initialized with executable code --
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constant mem_rom_c : mem32_t(0 to boot_rom_size_c/4-1) := mem32_init_f(bootloader_init_image, boot_rom_size_c/4);
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-- local signals --
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signal rden : std_ulogic;
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signal rdata : std_ulogic_vector(31 downto 0);
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begin
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-- Memory Access --------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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mem_access: process(clk_i)
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begin
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if rising_edge(clk_i) then -- no reset to infer block RAM
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rdata <= mem_rom_c(to_integer(unsigned(bus_req_i.addr(boot_rom_size_index_c+1 downto 2))));
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end if;
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end process mem_access;
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-- Bus Feedback ---------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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bus_feedback: process(rstn_i, clk_i)
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begin
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if (rstn_i = '0') then
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rden <= '0';
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elsif rising_edge(clk_i) then
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rden <= bus_req_i.stb and (not bus_req_i.rw); -- read-only
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end if;
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end process bus_feedback;
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bus_rsp_o.data <= rdata when (rden = '1') else (others => '0'); -- output gate
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bus_rsp_o.ack <= rden;
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bus_rsp_o.err <= '0'; -- no access error possible
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end neorv32_boot_rom_rtl;
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