UART-Transmitter-Reset

[Anfänger (Gast)]

Hallo,

ich habe hier in diesem Forum diesen UART-Transmitter gefunden.
Ich habe versucht es zum Laufen zu bringen. Es hängt sich aber aus 
irgendeinem grund auf, nachdem es einen Reset bekommen hat.
Könnt Ihr mir bitte helfen die Problemstelle zu finden?


UART-TRANSMITTER:

library ieee;
use ieee.std_logic_1164.all;

entity transmitter is
port (reset      : in  std_logic;                     -- asynch reset
      clk        : in  std_logic;                     -- clock 40 MHz
      data       : in  std_logic_vector(7 downto 0);  -- data input
      data_ready : in  std_logic;                     -- control signal
data ready
      tx_ready   : out std_logic;                     -- transmitter
ready for new data
      tx         : out std_logic);                    -- transmitter
output
end transmitter;

architecture behavior of transmitter is

-- internal signals
signal sending       : boolean;                       -- sending mode
signal sent          : boolean;                       -- sent mode
signal count_clk     : natural range 0 to 4167;       -- clock counter
for clock divider
signal count_bit     : natural range 0 to 10;         -- bit counter
signal enable        : std_logic;                     -- clock enable
for sending mode
signal tx_ready_int  : std_logic := '1';              -- initalized
to 1 for tx_ready = 1 on start
signal data_register : std_logic_vector(7 downto 0);  -- for storage of
data input to send

begin


-------------------------------------
-- load tx_ready with rx_ready_int --
-------------------------------------
tx_ready <= tx_ready_int;


--------------------------------------------------
-- clock divider for baudrate generation        --
-- sensitive to clock, asynch reset by received --
-- receiving mode: generate clock enable        --
-- for wished baudrate                          --
--------------------------------------------------
clock_divider : process (clk, sent) is
begin
if sent then
  count_clk <= 0;
elsif clk'event and clk = '1' then
    if sending then
      enable <= '0';
      if count_clk = 4167 then
        count_clk <= 0;
      elsif count_clk = 0 then
        enable <= '1';
        count_clk <= count_clk + 1;
      else
        count_clk <= count_clk + 1;
      end if;
    end if;
  end if;
end process clock_divider;


-----------------------------------------------------------
-- data storage of input data                            --
-- sensitive to clock, asynch reset by reset             --
-- storage data in internal register when data_ready = 1 --
-----------------------------------------------------------
data_storage : process (clk, reset, sent) is
begin
if reset = '1' or sent then
  data_register <= (others => '0');
  sending       <= false;
elsif clk'event and clk = '1' then
  if data_ready = '1' then
    if not sending then
      data_register <= data;
      sending       <= true;
    end if;
  end if;
end if;
end process data_storage;


-------------------------------------------------------
-- send storaged data                                --
-- sensitive to clock, asynch reset by reset         --
-- load tx with content of data register from 0 to 9 --
-- when sending complete : ready for new data        --
-------------------------------------------------------
data_send : process (clk, reset) is
begin
if reset = '1' then
  tx        <= '1';
  count_bit <= 0;
elsif clk'event and clk = '1' then
sent <= false;
  if enable = '1' then
    tx_ready_int <= '0';
    tx           <= '1';
    case count_bit is
      when 0  => tx        <= '0';
                 count_bit <= count_bit + 1;
      when 9  => tx        <= '1';
                 count_bit <= count_bit + 1;
      when 10 => tx            <= '1';
                 count_bit     <= 0;
                 sent          <= true;
                 tx_ready_int  <= '1';
      when others => count_bit <= count_bit + 1;
                     tx        <= data_register(count_bit - 1);
    end case;
  end if;
end if;
end process data_send;

end architecture behavior;



RESET: High->Low

library ieee;
use ieee.std_logic_1164.all;

entity cnt is
port ( clk:   in  STD_LOGIC;
       d :    out STD_LOGIC := '1');
end cnt;

architecture Behavioral of cnt is
signal count : integer range 0 to 100000 := 1;
begin
  process(clk)
  begin
    if rising_edge(clk)
      if count = 100000 then
        d <= '0';
      else
        count <= count + 1;
        d     <= '1';
      end if;
   end if;
  end process;
end Behavioral;

[Raini (Gast)]

Das signal "sent" wird synchron erzeugt und für einen asynchronen Reset 
in 2 Prozessen (data_storage,Clock_divider) verwendet. Da hätte ich ein 
wenig Bauchweh. Vllt. solltest du das "sent" in die synchrone Welt 
einbinden.
Sonst sehe ich spontan nichts.

Gruß
R