Subversion Repositories modular_oscilloscope

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--| Modular Oscilloscope

--| UNSL - Argentine

--|

--| File: ctrl_data_skipper.vhd

--| Version: 0.12

--| Tested in: Actel A3PE1500

--|   Board: RVI Prototype Board + LP Data Conversion Daughter Board

--|-------------------------------------------------------------------------------------------------

--| Description:

--|   CONTROL - Data skipper

--|   It generates an enable signal for write acquisitions in memory.

--|   

--|-------------------------------------------------------------------------------------------------

--| File history:

--|   0.1   | jul-2009 | First testing

--|   0.11  | jul-2009 | Added input signal indicating when it's selected the first channel

--|   0.12  | jul-2009 | Optimized

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--| Copyright © 2009, Facundo Aguilera.

--|

--| This VHDL design file is an open design; you can redistribute it and/or

--| modify it and/or implement it after contacting the author.

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--==================================================================================================

-- TO DO

-- · ...

--==================================================================================================

library ieee;

use ieee.std_logic_1164.all;

use IEEE.NUMERIC_STD.ALL;

use ieee.math_real.all;

use work.ctrl_pkg.all;

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entity ctrl_data_skipper is

  generic(

    -- max losses = 2**(2**SELECTOR_WIDTH). (i.e., if SELECTOR_WIDTH = 5: 4.2950e+09)

    SELECTOR_WIDTH: integer := 5

  );

  port(

    -- enable output signal

    ack_O:            out  std_logic;

    -- sinal from wishbone interface

    ack_I, stb_I:     in  std_logic;

    -- selector from register, equation: losses = 2**(selector_I + 1) * enable_skipper_I

    selector_I:       in   std_logic_vector(SELECTOR_WIDTH-1 downto 0);

    -- enable from register 

    enable_skipper_I: in   std_logic;

    -- common signals

    reset_I, clk_I:   in   std_logic;

    first_channel_I:  in   std_logic

        );

end ctrl_entity data_skipper;

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architecture ARCH10 of ctrl_data_skipper is

  signal count:         std_logic_vector( integer(2**real(SELECTOR_WIDTH))-1 downto 0);

  signal decoded:       std_logic_vector( integer(2**real(SELECTOR_WIDTH))-1 downto 0);

  signal anded:         std_logic_vector( integer(2**real(SELECTOR_WIDTH))-1 downto 0);

  signal reset_count:   std_logic;

  signal match:         std_logic;

  signal enable_count:  std_logic;

begin

 U_COUNTER0: generic_counter

  generic map(

    OUTPUT_WIDTH => integer(2**real(SELECTOR_WIDTH)) -- Output width for counter.

  )

  port map(

    clk_I => clk_I,

    count_O => count,

    reset_I => reset_count,

    enable_I => enable_count

  );

  U_DECO0:  generic_decoder

  generic map(

    INPUT_WIDTH => SELECTOR_WIDTH

  )

  port map(

    enable_I => enable_skipper_I,

    data_I => selector_I,

    decoded_O => decoded

  );

  anded <= decoded and count;

  match <= '1' when anded = std_logic_vector(to_unsigned(0,integer(2**real(SELECTOR_WIDTH)))) else

           '0' ;

  reset_count <= reset_I;

  enable_count <= stb_I and ack_I and enable_skipper_I and first_channel_I;

  ack_O <= stb_I and ack_I and (match or not(enable_skipper_I)) and not(reset_I);

end architecture;