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_version

-- Description:  Provides 2 read-only values, which are set at compile time

--

-- Register Map:

-- Offset  Bitfield Description                        Read/Write

--   0x00  AAAAAAAA Minor Version                         (RO)

--   0x01  AAAAAAAA Major Version                         (RO)

--

-- Revision History

-- Author          Date     Change

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

-- Seth Henry      10/21/20 Initial design

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_version is

generic(

  Minor_Version              : DATA_TYPE := x"00";

  Major_Version              : DATA_TYPE := x"00";

  Address                    : ADDRESS_TYPE

);

port(

  Open8_Bus                  : in  OPEN8_BUS_TYPE;

  Rd_Data                    : out DATA_TYPE

);

end entity;

architecture behave of o8_version is

  alias Clock                is Open8_Bus.Clock;

  alias Reset                is Open8_Bus.Reset;

  constant User_Addr         : std_logic_vector(15 downto 1)

                               := Address(15 downto 1);

  alias  Comp_Addr           is Open8_Bus.Address(15 downto 1);

  signal Addr_Match          : std_logic;

  alias  Reg_Sel_d           is Open8_Bus.Address(0);

  signal Reg_Sel_q           : std_logic := '0';

  signal Rd_En_d             : std_logic := '0';

  signal Rd_En_q             : std_logic := '0';

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

      Reg_Sel_q              <= '0';

      Rd_En_q                <= '0';

      Rd_Data                <= OPEN8_NULLBUS;

    elsif( rising_edge( Clock ) )then

      Reg_Sel_q              <= Reg_Sel_d;

      Rd_Data                <= OPEN8_NULLBUS;

      Rd_En_q                <= Rd_En_d;

      if( Rd_En_q = '1' )then

        if( Reg_Sel_q = '0')then

          Rd_Data            <= Minor_Version;

        else

          Rd_Data            <= Major_Version;

        end if;

      end if;

    end if;

  end process;

end architecture;