Subversion Repositories open8_urisc

-- Copyright (c)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

-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

-- (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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--

-- VHDL Units :  o8_switch_if

-- Description:  Based on the Debounce_Enable bit, either detects and reports

--                when a user pushbutton is pressed with an interrupt or

--                simply makes the switch status available.

--

-- Register Map:

-- Offset  Bitfield Description                        Read/Write

--   0x00  AAAAAAAA Current Switch State                 (RW)

--

-- Revision History

-- Author          Date     Change

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

-- Seth Henry      01/22/20 Re-write of original with separate debouncer

-- Seth Henry      04/16/20 Modified to use Open8 bus record

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_switch_if is

generic(

  Debounce_Enables           : DATA_TYPE := x"00";

  Switch_Levels              : DATA_TYPE := x"00";

  Address                    : ADDRESS_TYPE := x"0000"

);

port(

  Open8_Bus                  : in  OPEN8_BUS_TYPE;

  Rd_Data                    : out DATA_TYPE;

  Interrupt                  : out std_logic;

  --

  Switch_In                  : in  DATA_TYPE := x"00"

);

end entity;

architecture behave of o8_switch_if is

  alias Clock                is Open8_Bus.Clock;

  alias Reset                is Open8_Bus.Reset;

  alias uSec_Tick            is Open8_Bus.uSec_Tick;

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

  alias  Comp_Addr           is Open8_Bus.Address(15 downto 0);

  signal Addr_Match          : std_logic := '0';

  signal Rd_En_d             : std_logic := '0';

  signal Rd_En_q             : std_logic := '0';

  constant MSEC_DELAY        : std_logic_vector(9 downto 0) :=

                                conv_std_logic_vector(1000,10);

  signal mSec_Timer          : std_logic_vector(9 downto 0) := (others => '0');

  signal mSec_Tick           : std_logic := '0';

  signal Button_Pressed      : DATA_TYPE := x"00";

  signal Button_CoS          : DATA_TYPE := x"00";

begin

  Addr_Match                 <= '1' when Comp_Addr = User_Addr else '0';

  Rd_En_d                    <= Addr_Match and Open8_Bus.Rd_En;

  io_reg: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

      Rd_En_q                <= '0';

      Rd_Data                <= OPEN8_NULLBUS;

      Interrupt              <= '0';

    elsif( rising_edge( Clock ) )then

      Rd_En_q                <= Rd_En_d;

      Rd_Data                <= OPEN8_NULLBUS;

      if( Rd_En_q = '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 7 generate

Debouncer_Enabled: if( Debounce_Enables(i) = '1' )generate

  U_BTN : entity work.button_db

  generic map(

    Button_Level             => Switch_Levels(i),

    Reset_Level              => Reset_Level

  )

  port map(

    Clock                    => Clock,

    Reset                    => Reset,

    mSec_Tick                => mSec_Tick,

    --

    Button_In                => Switch_In(i),

    --

    Button_Pressed           => Button_Pressed(i),

    Button_CoS               => Button_CoS(i)

  );

end generate;

Debouncer_Disabled: if( Debounce_Enables(i) = '0' )generate

  Button_Pressed(i)          <= Switch_In(i);

  Button_CoS(i)              <= '0';

end generate;

end generate;

end architecture;