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--| Modular Oscilloscope

--| UNSL - Argentine

--|

--| File: ctrl_output_manager.vhd

--| Version: 0.54

--| Tested in: Actel A3PE1500

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

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

--| Description:

--|   CONTROL - Output manager

--|   Reads a memory incrementaly under certain parameters.

--|   

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

--| File history:

--|   0.1   | jun-2009 | First testing

--|   0.2   | jul-2009 | Two levels internal buffer

--|   0.3   | jul-2009 | One level internal buffer and only one clock

--|   0.31  | jul-2009 | Internal WE signals

--|   0.5   | jul-2009 | Architecture completely renovated (reduced)

--|   0.54  | aug-2009 | New finish_O and init flag behavior

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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

-- · (NO) Speed up address_counter

-- · (OK) Full test of new architecture

-- · (OK) Fix default value of s_finish signal 

-- · General speed up

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

library ieee;

use ieee.std_logic_1164.all;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

use IEEE.NUMERIC_STD.ALL;

----------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------

entity ctrl_output_manager is

  generic(

    MEM_ADD_WIDTH: integer :=  14

  );

  port(

    ------------------------------------------------------------------------------------------------

    -- MASTER (to memory) 

    DAT_I_mem: in std_logic_vector (15 downto 0);

    --DAT_O_mem: out std_logic_vector (15 downto 0);

    ADR_O_mem: out std_logic_vector (MEM_ADD_WIDTH - 1  downto 0);

    CYC_O_mem: out std_logic;

    STB_O_mem: out std_logic;

    ACK_I_mem: in std_logic ;

    WE_O_mem:  out std_logic;

    ------------------------------------------------------------------------------------------------

    -- SLAVE (to I/O ports) 

    --DAT_I_port: in std_logic_vector (15 downto 0);

    DAT_O_port: out std_logic_vector (15 downto 0);

    --ADR_I_port: in std_logic_vector (7 downto 0); 

    CYC_I_port: in std_logic;

    STB_I_port: in std_logic;

    ACK_O_port: out std_logic ;

    WE_I_port:  in std_logic;

    ------------------------------------------------------------------------------------------------

    -- Common signals 

    RST_I: in std_logic;

    CLK_I: in std_logic;

    ------------------------------------------------------------------------------------------------

    -- Internal

    load_I:             in std_logic;

    -- load initial address

    enable_I:           in std_logic;

    -- continue reading from the actual address ('0' means pause, '1' means continue)

    initial_address_I:  in std_logic_vector (MEM_ADD_WIDTH - 1 downto 0);

    -- buffer starts and ends here 

    biggest_address_I:  in std_logic_vector (MEM_ADD_WIDTH - 1 downto 0);

    -- when the buffer arrives here, address is changed to 0 (buffer size)

    pause_address_I:    in std_logic_vector (MEM_ADD_WIDTH - 1 downto 0);

    -- address wich is being writed by control

    finish_O:           out std_logic

    -- it is set when communication ends and remains until next restart or actual address change                                                    

        );

end entity ctrl_output_manager;

----------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------

architecture ARCH22 of ctrl_output_manager is

  signal address_counter: std_logic_vector(MEM_ADD_WIDTH - 1  downto 0);

  signal enable_read: std_logic;

  signal enable_count: std_logic;

  signal enable_strobe: std_logic;

  signal s_finish: std_logic; -- register previous (and equal) to output

  signal init: std_logic;     -- register

  signal same_address: std_logic;

begin

  --------------------------------------------------------------------------------------------------

  -- Wishbone signals

  DAT_O_port <= DAT_I_mem;

  CYC_O_mem <= CYC_I_port;

  STB_O_mem <= STB_I_port and enable_read;

  ACK_O_port <= ACK_I_mem;

  ADR_O_mem <= address_counter;

  WE_O_mem <= '0' ;

  --------------------------------------------------------------------------------------------------

  -- Status signals  

  -- there is an init signal because in the first read, address_counter may be = to pause_address_I

  P_pause: process (CLK_I, RST_I, address_counter, pause_address_I)

  begin

    if CLK_I'event and CLK_I = '1' then

      if RST_I = '1' then

        same_address <= '0';

      elsif address_counter = pause_address_I then

        same_address <= '1';

      else

        same_address <= '0';

      end if;

    end if;

  end process;

  P_flags: process(CLK_I, RST_I, enable_I, enable_count, load_I)

  begin

    if CLK_I'event and CLK_I = '1' and CLK_I'LAST_VALUE = '0' then

      -- when enable is '0', finish_O must be 0 again

      if RST_I = '1' or enable_I = '0' then

        init <= '1';

        enable_strobe <= '0';

      elsif (load_I = '1' and enable_I = '1') then

        enable_strobe <= '1';

        init <= '1';

      elsif  enable_count = '1' then

        init <= '0';

      end if;

    end if;

  end process;

  enable_read <= '1'  when  WE_I_port = '0' and s_finish = '0' and

                            (same_address = '0' or init = '1') and enable_strobe = '1'

            else '0';

  enable_count <= CYC_I_port and STB_I_port and ACK_I_mem and enable_read;

  s_finish <= '1' when address_counter = initial_address_I and init = '0' else

              '0';

  finish_O <= s_finish;

  --------------------------------------------------------------------------------------------------

  -- Address counter

  P_count: process(CLK_I, RST_I, address_counter, enable_count, load_I)

  begin

    if CLK_I'event and CLK_I = '1' and CLK_I'LAST_VALUE = '0' then

      if RST_I = '1' then

        address_counter <= (others => '0');

      elsif load_I = '1' and enable_I = '1' then

        address_counter <= initial_address_I;

      elsif enable_count = '1' and address_counter >= biggest_address_I then

        address_counter <= (others => '0');

      elsif  enable_count = '1' then

        address_counter <= address_counter + 1;

      end if;

    end if;

  end process;

end architecture;