Subversion Repositories open8_urisc

-- Copyright (c)2013, 2020 Jeremy Seth Henry

-- All rights reserved.

--

-- Redistribution and use in source and binary forms, with or without

-- modification, are permitted provided that the following conditions are met:

--     * Redistributions of source code must retain the above copyright

--       notice, this list of conditions and the following disclaimer.

--     * Redistributions in binary form must reproduce the above copyright

--       notice, this list of conditions and the following disclaimer in the

--       documentation and/or other materials provided with the distribution,

--       where applicable (as part of a user interface, debugging port, etc.)

--

-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY

-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

-- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY

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-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

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-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

--

-- VHDL Units :  o8_btn_int

-- Description:  Detects and reports when a user pushbutton is pressed with an

--                interrupt.

library ieee;

  use ieee.std_logic_1164.all;

  use ieee.std_logic_unsigned.all;

  use ieee.std_logic_arith.all;

  use ieee.std_logic_misc.all;

library work;

  use work.open8_pkg.all;

entity o8_btn_int is

generic(

  Num_Buttons           : integer range 1 to 8 := 8;

  Button_Level          : std_logic := '0';

  Address               : ADDRESS_TYPE := x"0000";

  Reset_Level           : std_logic := '1'

);

port(

  Clock                 : in  std_logic := '0';

  Reset                 : in  std_logic := '0';

  uSec_Tick             : in  std_logic := '0';

  --

  Bus_Address           : in  ADDRESS_TYPE := x"0000";

  Rd_Enable             : in  std_logic := '0';

  Rd_Data               : out DATA_TYPE;

  Interrupt             : out std_logic;

  --

  Button_In             : in  DATA_TYPE := x"00"

);

end entity;

architecture behave of o8_btn_int is

  constant User_Addr    : std_logic_vector(15 downto 0) := Address;

  alias  Comp_Addr      is Bus_Address(15 downto 0);

  signal Addr_Match     : std_logic;

  signal Rd_En          : std_logic;

  constant MSEC_DELAY   : std_logic_vector(9 downto 0) :=

                           conv_std_logic_vector(1000,10);

  signal mSec_Timer     : std_logic_vector(9 downto 0);

  signal mSec_Tick      : std_logic;

  signal Button_Pressed : DATA_TYPE := x"00";

  signal Button_CoS     : DATA_TYPE := x"00";

begin

  Addr_Match                 <= Rd_Enable when Comp_Addr = User_Addr else '0';

  io_reg: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

      Rd_En                  <= '0';

      Rd_Data                <= OPEN8_NULLBUS;

      Interrupt              <= '0';

    elsif( rising_edge( Clock ) )then

      Rd_En                  <= Addr_Match;

      Rd_Data                <= OPEN8_NULLBUS;

      if( Rd_En = '1' )then

        Rd_Data              <= Button_Pressed;

      end if;

      Interrupt              <= or_reduce(Button_CoS);

    end if;

  end process;

  mSec_proc: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

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

      mSec_Tick              <= '0';

    elsif( rising_edge(Clock) )then

      mSec_Timer             <= mSec_Timer - uSec_Tick;

      mSec_Tick              <= '0';

      if( mSec_Timer = 0 )then

        mSec_Timer           <= MSEC_DELAY;

        mSec_Tick            <= '1';

      end if;

    end if;

  end process;

Create_Debouncers: for i in 0 to Num_Buttons - 1 generate

  U_BTN : entity work.button_db

  generic map(

    Button_Level             => Button_Level,

    Reset_Level              => Reset_Level

  )

  port map(

    Clock                    => Clock,

    Reset                    => Reset,

    mSec_Tick                => mSec_Tick,

    --

    Button_In                => Button_In(i),

    --

    Button_Pressed           => Button_Pressed(i),

    Button_CoS               => Button_CoS(i)

  );

end generate;

end architecture;