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--

-- Author: John Kent

-- Date  : April 2, 2004

-- Interface to John Clayton's PS2 keyboard

--

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

--

-- 7th Februaury 2007 - John Kent

-- Added Generics for Keyboard Timing

--

library ieee;

   use ieee.std_logic_1164.all;

   use IEEE.STD_LOGIC_ARITH.ALL;

   use IEEE.STD_LOGIC_UNSIGNED.ALL;

   use ieee.numeric_std.all;

entity keyboard is

  generic (

  KBD_Clock_Frequency : integer

  );

  port(

  clk             : in    std_logic;

  rst             : in    std_logic;

  cs              : in    std_logic;

  rw              : in    std_logic;

  addr            : in    std_logic;

  data_in         : in    std_logic_vector(7 downto 0);

  data_out        : out   std_logic_vector(7 downto 0);

  irq             : out   std_logic;

  kbd_clk         : inout std_logic;

  kbd_data        : inout std_logic

  );

end keyboard;

architecture rtl of keyboard is

constant Clock_Frequency_MHz : integer := KBD_Clock_Frequency / 1000000;

signal kbd_stat       : std_logic_vector(7 downto 0);

signal kbd_ctrl       : std_logic_vector(7 downto 6);

signal kbd_ascii_code : std_logic_vector(7 downto 0);

signal kbd_tx_data    : std_logic_vector(7 downto 0);

signal kbd_read       : std_logic;

signal kbd_write      : std_logic;

signal kbd_write_ack  : std_logic;

component ps2_keyboard_interface

  generic (

  Frequency_MHz    : integer := Clock_Frequency_MHz

  );

  port(

  clk             : in    std_logic;

  reset           : in    std_logic;

  ps2_clk         : inout std_logic;

  ps2_data        : inout std_logic;

  rx_extended     : out   std_logic;

  rx_released     : out   std_logic;

  rx_shift_key_on : out   std_logic;

--  rx_scan_code    : out   std_logic_vector(7 downto 0);

  rx_ascii        : out   std_logic_vector(7 downto 0);

  rx_data_ready   : out   std_logic;       -- rx_read_o

  rx_read         : in    std_logic;       -- rx_read_ack_i

  tx_data         : in    std_logic_vector(7 downto 0);

  tx_write        : in    std_logic;

  tx_write_ack    : out   std_logic;

  tx_error_no_keyboard_ack      : out  std_logic

  );

end component;

begin

my_ps2_keyboard_interface : ps2_keyboard_interface

  generic map (

  Frequency_MHz   => Clock_Frequency_MHz

  )

  port map(

  clk             => clk,

  reset           => rst,

  ps2_clk         => kbd_clk,

  ps2_data        => kbd_data,

  rx_extended     => kbd_stat(2),

  rx_released     => kbd_stat(3),

  rx_shift_key_on => kbd_stat(4),

  rx_ascii        => kbd_ascii_code,

  rx_data_ready   => kbd_stat(0),

  rx_read         => kbd_read,

  tx_data         => kbd_tx_data,

  tx_write        => kbd_write,

  tx_write_ack    => kbd_write_ack,

  tx_error_no_keyboard_ack      => kbd_stat(5)

  );

keyboard_strobe : process( clk, rst, cs, rw, kbd_stat  )

begin

        if( rst = '1' ) then

                kbd_read <= '0';

        elsif( clk'event and clk='0' ) then

                if( cs='1' and rw='1' and addr='1' ) then

                        kbd_read <= '1';

                elsif( kbd_stat(0)='1' ) then

                        kbd_read <= '0';

                else

                        kbd_read <= kbd_read;

                end if;

        end if;

end process;

--

-- read keyboard registers

--

keyboard_read : process( addr, kbd_ascii_code, kbd_stat )

begin

        if( addr = '1' ) then

                data_out <= kbd_ascii_code;

        else

                data_out <= kbd_stat;

   end if;

end process;

--

-- Write to keyboard register

--

keyboard_write : process( clk, rst, cs, rw, addr, data_in, kbd_tx_data,

                                                                         kbd_write, kbd_write_ack )

begin

        if(rst = '1' ) then

           kbd_ctrl   <= "00";

           kbd_tx_data <= "00000000";

                kbd_write  <= '0';

        elsif( clk'event and clk='0' ) then

                if( cs='1' and rw='0' ) then

                        if( addr='1' ) then

                                kbd_tx_data  <= data_in;

                                kbd_ctrl    <= kbd_ctrl;

                                kbd_write   <= '1';

                        else

                                kbd_tx_data  <= kbd_tx_data;

                                kbd_ctrl    <= data_in(7 downto 6);

                                kbd_write   <= kbd_write;

                        end if;

                elsif( kbd_write_ack='1' ) then

                        kbd_write <= '0';

                else

                        kbd_write <= kbd_write;

                end if;

                kbd_stat(1) <= not kbd_write;

        end if;

end process;

keyboard_interrupt : process( kbd_ctrl, kbd_stat )

begin

        kbd_stat(6)     <= kbd_ctrl(6);

        kbd_stat(7) <= kbd_ctrl(7) and kbd_stat(0);

        irq         <= kbd_stat(7);

end process;

end rtl;