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use neorv32.neorv32_package.all;
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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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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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entity neorv32_boot_rom is
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generic (
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generic (
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BOOTROM_BASE : std_ulogic_vector(31 downto 0) := x"FFFF0000"; -- boot ROM base address
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BOOTROM_BASE : std_ulogic_vector(31 downto 0) := x"FFFF0000" -- boot ROM base address
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BOOTROM_SIZE : natural := 4*1024 -- processor-internal boot ROM memory size in bytes
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);
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);
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port (
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port (
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clk_i : in std_ulogic; -- global clock line
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clk_i : in std_ulogic; -- global clock line
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rden_i : in std_ulogic; -- read enable
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rden_i : in std_ulogic; -- read enable
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addr_i : in std_ulogic_vector(31 downto 0); -- address
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addr_i : in std_ulogic_vector(31 downto 0); -- address
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);
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);
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end neorv32_boot_rom;
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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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architecture neorv32_boot_rom_rtl of neorv32_boot_rom is
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-- local types --
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-- determine required ROM size in bytes (expand to next power of two) --
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type boot_img_t is array (0 to BOOTROM_SIZE/4-1) of std_ulogic_vector(31 downto 0);
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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 := (2**boot_rom_size_index_c)*4; -- size in bytes
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-- init function --
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-- impure function: returns NOT the same result every time it is evaluated with the same arguments since the source file might have changed
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-- IO space: module base address --
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impure function init_boot_rom(init : bootloader_init_image_t) return boot_img_t is
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constant hi_abb_c : natural := 31; -- high address boundary bit
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variable mem_v : boot_img_t;
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constant lo_abb_c : natural := index_size_f(boot_rom_max_size_c); -- low address boundary bit
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begin
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mem_v := (others => (others => '0'));
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for i in 0 to init'length-1 loop -- init only in range of source data array
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mem_v(i) := init(i);
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end loop; -- i
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return mem_v;
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end function init_boot_rom;
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-- local signals --
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-- local signals --
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signal acc_en : std_ulogic;
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signal acc_en : std_ulogic;
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signal rden : std_ulogic;
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signal rden : std_ulogic;
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signal rdata : std_ulogic_vector(31 downto 0);
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signal rdata : std_ulogic_vector(31 downto 0);
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signal addr : std_ulogic_vector(index_size_f(BOOTROM_SIZE/4)-1 downto 0);
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signal addr : std_ulogic_vector(boot_rom_size_index_c-1 downto 0);
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-- bootloader image --
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-- ROM - initialized with executable code --
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constant boot_img : boot_img_t := init_boot_rom(bootloader_init_image);
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constant mem_rom : 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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begin
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begin
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-- Sanity Checks --------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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assert false report "NEORV32 PROCESSOR CONFIG NOTE: Implementing internal bootloader ROM (" & natural'image(boot_rom_size_c) & " bytes)." severity note;
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assert not (boot_rom_size_c > boot_rom_max_size_c) report "NEORV32 PROCESSOR CONFIG ERROR! Boot ROM size out of range! Max "& natural'image(boot_rom_max_size_c) & " bytes." severity error;
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-- Access Control -------------------------------------------------------------------------
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-- Access Control -------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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acc_en <= '1' when (addr_i >= BOOTROM_BASE) and (addr_i < std_ulogic_vector(unsigned(BOOTROM_BASE) + BOOTROM_SIZE)) else '0';
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acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = BOOTROM_BASE(hi_abb_c downto lo_abb_c)) else '0';
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addr <= addr_i(index_size_f(BOOTROM_SIZE/4)+1 downto 2); -- word aligned
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addr <= addr_i(boot_rom_size_index_c+1 downto 2); -- word aligned
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-- Memory Access --------------------------------------------------------------------------
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-- Memory Access --------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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-- -------------------------------------------------------------------------------------------
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mem_file_access: process(clk_i)
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mem_file_access: process(clk_i)
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begin
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begin
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if rising_edge(clk_i) then
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if rising_edge(clk_i) then
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rden <= rden_i and acc_en;
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rden <= rden_i and acc_en;
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if (acc_en = '1') then -- reduce switching activity when not accessed
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if (acc_en = '1') then -- reduce switching activity when not accessed
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rdata <= boot_img(to_integer(unsigned(addr)));
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rdata <= mem_rom(to_integer(unsigned(addr)));
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end if;
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end if;
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end if;
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end if;
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end process mem_file_access;
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end process mem_file_access;
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-- output gate --
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-- output gate --
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