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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity bit_stripper is
generic(
INPUT_WIDTH : positive := 32;
OUTPUT_WIDTH : positive := 1;
CPS : positive := 2
);
port(
clock : in std_logic;
reset : in std_logic;
enable : in std_logic;
in_data : in std_logic_vector(INPUT_WIDTH-1 downto 0);
in_data_request : out std_logic;
in_data_valid : in std_logic;
out_data : out std_logic_vector(OUTPUT_WIDTH-1 downto 0);
out_data_request : in std_logic;
out_data_valid : out std_logic
);
end entity;
architecture arch of bit_stripper is
signal data_buffer : std_logic_vector( (INPUT_WIDTH + OUTPUT_WIDTH)-1 downto 0);
type stripper_fsm_t is (FLUSH,SHIFT_BUFFER,OUTPUT_DATA);
signal stripper_fsm : stripper_fsm_t;
constant THRESHOLD : positive := OUTPUT_WIDTH;
begin
rip_bit : process(clock,reset)
variable bit_count : natural range 0 to (INPUT_WIDTH + THRESHOLD + 1);
begin
if reset = '1' then
data_buffer <= (others =>'0');
bit_count := 0;
stripper_fsm <= FLUSH;
out_data <= (others => '0');
out_data_valid <= '0';
in_data_request <= '0';
elsif rising_edge(clock) then
out_data_valid <= '0';
in_data_request <= '0';
if enable = '0' then
stripper_fsm <= FLUSH;
end if;
case stripper_fsm is
when FLUSH =>
bit_count := 0;
data_buffer <= (others => '0');
if enable = '1' then
stripper_fsm <= SHIFT_BUFFER;
end if;
when SHIFT_BUFFER =>
--
case bit_count is
when 0 => data_buffer <= "0000" & in_data;
when 1 => data_buffer <= "000" & in_data & data_buffer(0);
when 2 => data_buffer <= "00" & in_data & data_buffer(1 downto 0);
when 3 => data_buffer <= '0' & in_data & data_buffer(2 downto 0);
when 4 => data_buffer <= in_data & data_buffer(3 downto 0);
when others => data_buffer <= "0000" & in_data;
end case;
bit_count := bit_count + INPUT_WIDTH;
stripper_fsm <= OUTPUT_DATA;
in_data_request <= '1';
when OUTPUT_DATA =>
if out_data_request = '1' then
out_data <= data_buffer(OUTPUT_WIDTH -1 downto 0);
out_data_valid <= '1';
--shift the data down
data_buffer <= (OUTPUT_WIDTH-1 downto 0 => '0') & data_buffer( (INPUT_WIDTH+OUTPUT_WIDTH)-1 downto OUTPUT_WIDTH);
bit_count := bit_count - OUTPUT_WIDTH;
end if;
if bit_count <= THRESHOLD then
stripper_fsm <= SHIFT_BUFFER;
end if;
end case;
end if;
end process;
end architecture;
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