-----------------------------------------------------------------------------
--   File:  fir_rom_32tap_lowpass_300hz_50k.vhd
--   Coefficients for a 32 tap FIR circuit
--   4 sets (pages) of 32 12-bit signed numbers
--       page
--         0   one coefficient with a value of one
--         1   all coefficients have a value of one
--         2   Low pass filter, 300Hz cut-off, 50Khz sample rate
--         3   one coefficient with a hex value of FFF
--
--   Address bits 6 and 5, i.e. 6 downto 5, select the page.
--    L.Aamodt   rev2  05/13/21
-----------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity coef_rom is
   generic(
      ADDR_WIDTH: integer:=7;
      DATA_WIDTH:integer:=12
   );
   port(
      clk: in std_logic;
      addr_r: in std_logic_vector(ADDR_WIDTH-1 downto 0);
      dout: out std_logic_vector(DATA_WIDTH-1 downto 0)
   );
end coef_rom;

architecture beh_arch of coef_rom is
   type rom_type is array (0 to 2**ADDR_WIDTH-1)
        of std_logic_vector (DATA_WIDTH-1 downto 0);
   constant myROM: rom_type:=(                    -- 128 x 12bits
      x"001", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000",

      x"001", x"001", x"001", x"001", x"001", x"001", x"001", x"001",
      x"001", x"001", x"001", x"001", x"001", x"001", x"001", x"001",
      x"001", x"001", x"001", x"001", x"001", x"001", x"001", x"001",
      x"001", x"001", x"001", x"001", x"001", x"001", x"001", x"001",

      x"094", x"0C9", x"106", x"148", x"18F", x"1DA", x"226", x"273",
      x"2BE", x"306", x"347", x"381", x"3B2", x"3D7", x"3F1", x"3FE",
      x"3FE", x"3F1", x"3D7", x"3B2", x"381", x"347", x"306", x"2BE",
      x"273", x"226", x"1DA", x"18F", x"148", x"106", x"0C9", x"094",

      x"FFF", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000",
      x"000", x"000", x"000", x"000", x"000", x"000", x"000", x"000");

---------- A set of coefficients with sequencial values 0 to 31
-------    Useful in debugging to confirm correct coefficient selection
--      x"000", x"001", x"002", x"003", x"004", x"005", x"006", x"007",
--      x"008", x"009", x"00A", x"00B", x"00C", x"00D", x"00E", x"00F",
--      x"010", x"011", x"012", x"013", x"014", x"015", x"016", x"017",
--      x"018", x"019", x"01A", x"01B", x"01C", x"01D", x"01E", x"01F",		

begin
   process(clk)
   begin
     if (clk'event and clk = '1') then
        dout <= myROM(to_integer(unsigned(addr_r)));
     end if;
   end process;
end beh_arch;