Subversion Repositories open8_urisc

-- Copyright (c)2006, 2016, 2019 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

-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

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

--

-- VHDL Units :  o8_status_led

-- Description:  Provides a multi-state status LED controller

--

-- Register Map:

-- Offset  Bitfield Description                        Read/Write

--   0x00  -----AAA LED Mode (2:0)                     (RW)

--

-- LED Modes:

-- 0x00 - LED is fully off

-- 0x01 - LED is fully on

-- 0x02 - LED is dimmed to 50%

-- 0x03 - LED Toggles at 1Hz

-- 0x04 - LED fades in and out

--

-- Revision History

-- Author          Date     Change

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

-- Seth Henry      12/20/19 Design Start

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_status_led is

generic(

  Reset_Level           : std_logic;

  Address               : ADDRESS_TYPE

);

port(

  Clock                 : in  std_logic;

  Reset                 : in  std_logic;

  --

  Bus_Address           : in  ADDRESS_TYPE;

  Wr_Enable             : in  std_logic;

  Wr_Data               : in  DATA_TYPE;

  Rd_Enable             : in  std_logic;

  Rd_Data               : out DATA_TYPE;

  --

  LED_Out               : out std_logic

);

end entity;

architecture behave of o8_status_led is

  function ceil_log2 (x : in natural) return natural is

    variable retval     : natural;

  begin

    retval              := 1;

    while ((2**retval) - 1) < x loop

      retval            := retval + 1;

    end loop;

    return retval;

  end function;

  constant User_Addr    : std_logic_vector(15 downto 0)

                          := Address(15 downto 0);

  alias  Comp_Addr      is Bus_Address(15 downto 0);

  signal Addr_Match     : std_logic;

  signal Wr_En          : std_logic;

  signal Wr_Data_q      : std_logic_vector(2 downto 0);

  signal LED_Mode       : std_logic_vector(2 downto 0);

  signal Rd_En          : std_logic;

  signal Dim50Pct_Out   : std_logic;

  signal Half_Hz_Timer  : std_logic_vector(15 downto 0);

  constant HALF_HZ_PRD  : std_logic_vector(15 downto 0) :=

                           conv_std_logic_vector(500000,16);

  signal One_Hz_Out     : std_logic;

  constant TIMER_MSB    : integer range 9 to 20 := 18;

  signal Fade_Timer1    : std_logic_vector(TIMER_MSB downto 0);

  signal Fade_Timer2    : std_logic_vector(TIMER_MSB downto 0);

  signal Fade_Out       : std_logic;

begin

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

  io_reg: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

      Wr_En             <= '0';

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

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

      Rd_En             <= '0';

      Rd_Data           <= x"00";

    elsif( rising_edge( Clock ) )then

      Wr_En             <= Addr_Match and Wr_Enable;

      Wr_Data_q         <= Wr_Data(2 downto 0);

      if( Wr_En = '1' )then

        LED_Mode        <= Wr_Data_q;

      end if;

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

      Rd_En             <= Addr_Match and Rd_Enable;

      if( Rd_En = '1' )then

        Rd_Data         <= "00000" & LED_Mode;

      end if;

    end if;

  end process;

  Output_FF: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

      LED_Out           <= '0';

    elsif( rising_edge(Clock) )then

      LED_Out           <= '0';

      case( LED_Mode )is

        when "001" =>

          LED_Out       <= '1';

        when "010" =>

          LED_Out       <= Dim50Pct_Out;

        when "011" =>

          LED_Out       <= One_Hz_Out;

        when "100" =>

          LED_Out       <= Fade_out;

        when others => null;

      end case;

    end if;

  end process;

  Timer_proc: process( Clock, Reset )

  begin

    if( Reset = Reset_Level )then

      Dim50Pct_Out      <= '0';

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

      One_Hz_Out        <= '0';

      Fade_Timer1       <= (others => '0');

      Fade_Timer2       <= (others => '0');

      Fade_out          <= '0';

    elsif( rising_edge(Clock) )then

      Dim50Pct_Out      <= not Dim50Pct_Out;

      Half_Hz_Timer     <= Half_Hz_Timer - 1;

      if( Half_Hz_Timer = 0 )then

        Half_Hz_Timer   <= HALF_HZ_PRD;

        One_Hz_Out      <= not One_Hz_Out;

      end if;

      Fade_Timer1       <= Fade_Timer1 - 1;

      Fade_Timer2       <= Fade_Timer2 - 1;

      if( or_reduce(Fade_Timer2) = '0' )then

        Fade_Timer2(TIMER_MSB downto TIMER_MSB - 8) <= (others => '1');

        Fade_Timer2(TIMER_MSB - 9 downto 0 )        <= (others => '0');

      end if;

      Fade_out          <= Fade_Timer1(TIMER_MSB) xor Fade_Timer2(TIMER_MSB);

    end if;

  end process;

end architecture;