Subversion Repositories hf-risc

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_ARITH.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

use ieee.std_logic_textio.all;

use std.textio.all;

entity boot_ram is

        generic(memory_file : string := "boot.txt";

                data_width: integer := 8;                       -- data width (fixed)

                address_width: integer := 12;                   -- address width

                bank: integer := 0);                                     -- memory bank (0,1,2,3)

        port(

        clk : in std_logic;                                     --clock

        addr : in std_logic_vector(address_width - 1 downto 2);         --address bus

        cs_n : in std_logic;                                    --chip select

        we_n : in std_logic;                                    --write enable

        data_i: in std_logic_vector(data_width - 1 downto 0);    --write data bus

        data_o: out std_logic_vector(data_width - 1 downto 0)    --read data bus

        );

end boot_ram;

architecture memory of boot_ram is

type ram is array(2 ** address_width - 1 downto 0) of std_logic_vector(data_width - 1 downto 0);

signal ram1 : ram := (others => (others => '0'));

begin

        process(clk)

                variable data : std_logic_vector(data_width*4 -1 downto 0);

                variable index : natural := 0;

                file load_file : text open read_mode is "boot.txt";

                variable hex_file_line : line;

        begin

                --Load in the ram executable image

                if index = 0 then

                        while not endfile(load_file) loop

                                readline(load_file, hex_file_line);

                                hread(hex_file_line, data);

                                ram1(conv_integer(index)) <= data(((bank+1)*data_width)-1 downto bank*data_width);

                                index := index + 1;

                        end loop;

                end if;

                if (clk'event and clk = '1') then

                        if(cs_n = '0') then

                                if(we_n = '0') then

                                        ram1(conv_integer(addr(address_width -1 downto 2))) <= data_i;

                                else

                                        data_o <= ram1(conv_integer(addr(address_width -1 downto 2)));

                                end if;

                        end if;

                end if;

        end process;

end memory;