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Message
From: jeanpaul.milani at amicweb.com<jeanpaul.milani@a...>
Date: Fri Apr 20 21:53:17 CEST 2007
Subject: [oc] White Noise generator
Hi
I'm approcing to realize a white noise generator
using a Lattice fpga and a pcm1793 dac @ 192KHz
I've found many solutions on the web but many of them
are too slice's expencive for me.
I've try with a lfsr using this code:
entity wgn is
port(
clk_24 : in std_logic;
rst : in std_logic;
en_192 : in std_logic;
wgn_out : out std_logic_vector (23 downto 0);
data_valid : out std_logic
);
end;
architecture rtl of wgn is
signal sh_reg : std_logic_vector(23 downto 0);
signal data_valid_int : std_logic;
begin
process(clk_24,rst)
begin
if rst = '1' then
wgn_out <= (others => '0');
sh_reg <= (others => '1');
data_valid_int <= '0';
data_valid <= '0';
elsif (clk_24'event and clk_24 = '1') then -- Rising edge for clk24
if en_192 = '1' then
sh_reg(sh_reg'high downto 1) <= sh_reg((sh_reg'high-1) downto 0);
sh_reg(0)<= sh_reg(23) xor sh_reg(7) xor sh_reg(2) xor sh_reg(1);
data_valid_int <= '1';
else
data_valid <= data_valid_int;
data_valid_int <= '0';
wgn_out <= sh_reg;
end if;
end if;
end process;
end rtl;
when i've try the machine i've notice that the power spectrum isn't flat
but it's quite gaussian with a peak @ 20KHz.
I hope someone can help me
thanks
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