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Code:
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 ps2_keyboard_interface is
generic (
CLK_FREQ_MHZ : integer
);
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 ps2_keyboard_interface;
-------------------------------------------------------------------------------
-- Architecture for ps2 keyboard interface
-------------------------------------------------------------------------------
architecture rtl of ps2_keyboard_interface is
-----------------------------------------------------------------------------
constant TOTAL_BITS : integer := 11;
constant EXTEND_CODE : integer := 16#E0#;
constant RELEASE_CODE : integer := 16#F0#;
constant LEFT_SHIFT : integer := 16#12#;
constant RIGHT_SHIFT : integer := 16#59#;
constant CTRL_CODE : integer := 16#14#;
constant CAPS_CODE : integer := 16#58#;
-- constants
-- The timer value can be up to (2^bits) inclusive.
-- Values for 49.152 MHz clock
--constant TIMER_60USEC_VALUE_PP : integer := 2950; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 12; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 186; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 8; -- Number of bits needed for timer
-- Values for 12.5 MHz Clock
--constant TIMER_60USEC_VALUE_PP : integer := 750; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 10; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 62; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 6; -- Number of bits needed for timer
-- Values for 25 MHz Clock
--constant TIMER_60USEC_VALUE_PP : integer := 1500; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 11; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 125; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 7; -- Number of bits needed for timer
-- Values for generic Clock up to 50 MHz
constant TIMER_60USEC_VALUE_PP : integer := CLK_FREQ_MHZ * 60; -- Number of sys_clks for 60usec.
constant TIMER_60USEC_BITS_PP : integer := 12; -- Number of bits needed for timer
constant TIMER_5USEC_VALUE_PP : integer := CLK_FREQ_MHZ * 5; -- Number of sys_clks for debounce
constant TIMER_5USEC_BITS_PP : integer := 8; -- Number of bits needed for timer
constant TRAP_SHIFT_KEYS_PP : integer := 1; -- Default: No shift key trap.
-- State encodings, provided as constants
-- for flexibility to the one instantiating the module.
-- In general, the default values need not be changed.
-- State "m1_rx_clk_l" has been chosen on purpose. Since the input
-- synchronizing flip-flops initially contain zero, it takes one clk
-- for them to update to reflect the actual (idle = high) status of
-- the I/O lines from the keyboard. Therefore, choosing 0 for m1_rx_clk_l
-- allows the state machine to transition to m1_rx_clk_h when the true
-- values of the input signals become present at the outputs of the
-- synchronizing flip-flops. This initial transition is harmless, and it
-- eliminates the need for a "reset" pulse before the interface can operate.
type m1_type is ( m1_rx_clk_h, m1_rx_clk_l,
m1_tx_wait_clk_h, m1_tx_force_clk_l,
m1_tx_clk_h, m1_tx_clk_l,
m1_tx_wait_keyboard_ack, m1_tx_done_recovery,
m1_tx_error_no_keyboard_ack, m1_tx_rising_edge_marker,
m1_tx_first_wait_clk_h, m1_tx_first_wait_clk_l, m1_tx_reset_timer,
m1_rx_falling_edge_marker, m1_rx_rising_edge_marker );
-- Internal signal declarations
signal timer_60usec_done : std_logic;
signal timer_5usec_done : std_logic;
signal extended : std_logic;
signal released : std_logic;
signal shift_key_on : std_logic;
signal ctrl_key_on : std_logic;
signal caps_key_on : std_logic;
-- NOTE: These two signals used to be one. They
-- were split into two signals because of
-- shift key trapping. With shift key
-- trapping, no event is generated externally,
-- but the "hold" data must still be cleared
-- anyway regardless, in preparation for the
-- next scan codes.
signal rx_output_event : std_logic; -- Used only to clear: hold_released, hold_extended
signal rx_output_strobe : std_logic; -- Used to produce the actual output.
signal tx_parity_bit : std_logic;
signal rx_shifting_done : std_logic;
signal tx_shifting_done : std_logic;
signal shift_key_plus_code: std_logic_vector(8 downto 0);
signal q : std_logic_vector(TOTAL_BITS-1 downto 0);
signal m1_state : m1_type;
signal m1_next_state : m1_type;
signal bit_count : std_logic_vector(3 downto 0);
signal enable_timer_60usec: std_logic;
signal enable_timer_5usec : std_logic;
signal timer_60usec_count : std_logic_vector(TIMER_60USEC_BITS_PP-1 downto 0);
signal timer_5usec_count : std_logic_vector(TIMER_5USEC_BITS_PP-1 downto 0);
signal ascii : std_logic_vector(7 downto 0); -- "REG" type only because a case statement is used.
signal left_shift_key : std_logic;
signal right_shift_key : std_logic;
signal hold_extended : std_logic; -- Holds prior value, cleared at rx_output_strobe
signal hold_released : std_logic; -- Holds prior value, cleared at rx_output_strobe
signal ps2_clk_s : std_logic; -- Synchronous version of this input
signal ps2_data_s : std_logic; -- Synchronous version of this input
signal ps2_clk_hi_z : std_logic; -- Without keyboard, high Z equals 1 due to pullups.
signal ps2_data_hi_z : std_logic; -- Without keyboard, high Z equals 1 due to pullups.
signal tx_write_ack_o : std_logic;
--
-- key lookup table
--
component keymap_rom
Port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (8 downto 0);
rdata : out std_logic_vector (7 downto 0);
wdata : in std_logic_vector (7 downto 0)
);
end component;
begin
my_key_map : keymap_rom
Port map (
clk => clk,
rst => reset,
cs => '1',
rw => '1',
addr => shift_key_plus_code,
rdata => ascii,
wdata => "00000000"
);
----------------------------------------------------------------------------
-- Module code
-- assign ps2_clk = ps2_clk_hi_z?1'bZ:1'b0;
-- assign ps2_data = ps2_data_hi_z?1'bZ:1'b0;
--
ps2_direction : process( ps2_clk_hi_z, ps2_data_hi_z )
begin
if( ps2_clk_hi_z = '1' ) then
ps2_clk <= 'Z';
else
ps2_clk <= '0';
end if;
if( ps2_data_hi_z = '1' ) then
ps2_data <= 'Z';
else
ps2_data <= '0';
end if;
end process;
-- Input "synchronizing" logic -- synchronizes the inputs to the state
-- machine clock, thus avoiding errors related to
-- spurious state machine transitions.
ps2_synch : process(clk, ps2_clk, ps2_data)
begin
if falling_edge(clk) then
ps2_clk_s <= ps2_clk;
ps2_data_s <= ps2_data;
end if;
end process;
-- State register
m1_state_register : process( clk, reset, m1_state )
begin
if falling_edge(clk) then
if (reset = '1') then
m1_state <= m1_rx_clk_h;
else
m1_state <= m1_next_state;
end if;
end if;
end process;
m1_state_logic : process( m1_state, q,
tx_shifting_done, tx_write,
ps2_clk_s, ps2_data_s,
timer_60usec_done, timer_5usec_done )
begin
-- Output signals default to this value, unless changed in a state condition.
ps2_clk_hi_z <= '1';
ps2_data_hi_z <= '1';
tx_error_no_keyboard_ack <= '0';
enable_timer_60usec <= '0';
enable_timer_5usec <= '0';
case (m1_state) is
when m1_rx_clk_h =>
enable_timer_60usec <= '1';
if (tx_write = '1') then
m1_next_state <= m1_tx_reset_timer;
elsif (ps2_clk_s = '0') then
m1_next_state <= m1_rx_falling_edge_marker;
else
m1_next_state <= m1_rx_clk_h;
end if;
when m1_rx_falling_edge_marker =>
enable_timer_60usec <= '0';
m1_next_state <= m1_rx_clk_l;
when m1_rx_clk_l =>
enable_timer_60usec <= '1';
if (tx_write = '1') then
m1_next_state <= m1_tx_reset_timer;
elsif (ps2_clk_s = '1') then
m1_next_state <= m1_rx_rising_edge_marker;
else
m1_next_state <= m1_rx_clk_l;
end if;
when m1_rx_rising_edge_marker =>
enable_timer_60usec <= '0';
m1_next_state <= m1_rx_clk_h;
when m1_tx_reset_timer =>
enable_timer_60usec <= '0';
m1_next_state <= m1_tx_force_clk_l;
when m1_tx_force_clk_l =>
enable_timer_60usec <= '1';
ps2_clk_hi_z <= '0'; -- Force the ps2_clk line low.
if (timer_60usec_done = '1') then
m1_next_state <= m1_tx_first_wait_clk_h;
else
m1_next_state <= m1_tx_force_clk_l;
end if;
when m1_tx_first_wait_clk_h =>
enable_timer_5usec <= '1';
ps2_data_hi_z <= '0'; -- Start bit.
if (ps2_clk_s = '0') and (timer_5usec_done = '1') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_first_wait_clk_h;
end if;
-- This state must be included because the device might possibly
-- delay for up to 10 milliseconds before beginning its clock pulses.
-- During that waiting time, we cannot drive the data (q[0]) because it
-- is possibly 1, which would cause the keyboard to abort its receive
-- and the expected clocks would then never be generated.
when m1_tx_first_wait_clk_l =>
ps2_data_hi_z <= '0';
if (ps2_clk_s = '0') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_first_wait_clk_l;
end if;
when m1_tx_wait_clk_h =>
enable_timer_5usec <= '1';
ps2_data_hi_z <= q(0);
if (ps2_clk_s = '1') and (timer_5usec_done = '1') then
m1_next_state <= m1_tx_rising_edge_marker;
else
m1_next_state <= m1_tx_wait_clk_h;
end if;
when m1_tx_rising_edge_marker =>
ps2_data_hi_z <= q(0);
m1_next_state <= m1_tx_clk_h;
when m1_tx_clk_h =>
ps2_data_hi_z <= q(0);
if (tx_shifting_done = '1') then
m1_next_state <= m1_tx_wait_keyboard_ack;
elsif (ps2_clk_s = '0') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_clk_h;
end if;
when m1_tx_clk_l =>
ps2_data_hi_z <= q(0);
if (ps2_clk_s = '1') then
m1_next_state <= m1_tx_wait_clk_h;
else
m1_next_state <= m1_tx_clk_l;
end if;
when m1_tx_wait_keyboard_ack =>
if (ps2_clk_s = '0') and (ps2_data_s = '1') then
m1_next_state <= m1_tx_error_no_keyboard_ack;
elsif (ps2_clk_s = '0') and (ps2_data_s = '0') then
m1_next_state <= m1_tx_done_recovery;
else
m1_next_state <= m1_tx_wait_keyboard_ack;
end if;
when m1_tx_done_recovery =>
if (ps2_clk_s = '1') and (ps2_data_s = '1') then
m1_next_state <= m1_rx_clk_h;
else
m1_next_state <= m1_tx_done_recovery;
end if;
when m1_tx_error_no_keyboard_ack =>
tx_error_no_keyboard_ack <= '1';
if (ps2_clk_s = '1') and (ps2_data_s ='1') then
m1_next_state <= m1_rx_clk_h;
else
m1_next_state <= m1_tx_error_no_keyboard_ack;
end if;
when others =>
m1_next_state <= m1_rx_clk_h;
end case;
end process;
-- This is the bit counter
bit_counter: process(clk, reset, m1_state, bit_count )
begin
if falling_edge(clk) then
if ( reset = '1' ) or
( rx_shifting_done = '1' ) or
(m1_state = m1_tx_wait_keyboard_ack) then -- After tx is done.
bit_count <= "0000"; -- normal reset
elsif (timer_60usec_done = '1' ) and
(m1_state = m1_rx_clk_h) and
(ps2_clk_s = '1') then
bit_count <= "0000"; -- rx watchdog timer reset
elsif (m1_state = m1_rx_falling_edge_marker) or -- increment for rx
(m1_state = m1_tx_rising_edge_marker) then -- increment for tx
bit_count <= bit_count + 1;
end if;
end if;
end process;
assign: process( bit_count, tx_write, tx_write_ack_o, m1_state )
begin
if (bit_count = TOTAL_BITS) then
rx_shifting_done <= '1';
else
rx_shifting_done <= '0';
end if;
if (bit_count = (TOTAL_BITS-1)) then
tx_shifting_done <= '1';
else
tx_shifting_done <= '0';
end if;
-- This is the signal which enables loading of the shift register.
-- It also indicates "ack" to the device writing to the transmitter.
if ((tx_write = '1') and (m1_state = m1_rx_clk_h)) or
((tx_write = '1') and (m1_state = m1_rx_clk_l)) then
tx_write_ack_o <= '1';
else
tx_write_ack_o <= '0';
end if;
tx_write_ack <= tx_write_ack_o;
end process;
-- This is the ODD parity bit for the transmitted word.
-- assign tx_parity_bit = ~^tx_data;
--
tx_parity_bit <= not( tx_data(7) xor tx_data(6) xor tx_data(5) xor tx_data(4) xor
tx_data(3) xor tx_data(2) xor tx_data(1) xor tx_data(0) );
-- This is the shift register
q_shift : process(clk, tx_write_ack_o, tx_parity_bit, tx_data,
m1_state, q, ps2_data_s, rx_shifting_done )
begin
if falling_edge(clk) then
if (reset = '1') then
q <= "00000000000";
elsif (tx_write_ack_o = '1') then
q <= "1" & tx_parity_bit & tx_data & "0";
elsif ( (m1_state = m1_rx_falling_edge_marker) or
(m1_state = m1_tx_rising_edge_marker) ) then
q <= ps2_data_s & q((TOTAL_BITS-1) downto 1);
end if;
end if;
-- Create the signals which indicate special scan codes received.
-- These are the "unlatched versions."
if (q(8 downto 1) = EXTEND_CODE) and (rx_shifting_done = '1') then
extended <= '1';
else
extended <= '0';
end if;
if (q(8 downto 1) = RELEASE_CODE) and (rx_shifting_done = '1') then
released <= '1';
else
released <= '0';
end if;
end process;
-- This is the 60usec timer counter
timer60usec: process(clk, enable_timer_60usec, timer_60usec_count)
begin
if falling_edge(clk) then
if (enable_timer_60usec = '0') then
timer_60usec_count <= (others => '0');
elsif (timer_60usec_done = '0') then
timer_60usec_count <= timer_60usec_count + 1;
end if;
end if;
if (timer_60usec_count = (TIMER_60USEC_VALUE_PP - 1)) then
timer_60usec_done <= '1';
else
timer_60usec_done <= '0';
end if;
end process;
-- This is the 5usec timer counter
timer5usec : process(clk, enable_timer_5usec, timer_5usec_count )
begin
if falling_edge(clk) then
if (enable_timer_5usec = '0') then
timer_5usec_count <= (others => '0');
elsif (timer_5usec_done = '0') then
timer_5usec_count <= timer_5usec_count + 1;
end if;
end if;
if( timer_5usec_count = (TIMER_5USEC_VALUE_PP - 1)) then
timer_5usec_done <= '1';
else
timer_5usec_done <= '0';
end if;
end process;
-- Store the special scan code status bits
-- Not the final output, but an intermediate storage place,
-- until the entire set of output data can be assembled.
special_scan : process(clk, reset, rx_output_event, rx_shifting_done, extended, released )
begin
if falling_edge(clk) then
if (reset = '1') or (rx_output_event = '1') then
hold_extended <= '0';
hold_released <= '0';
else
if (rx_shifting_done = '1') and (extended = '1') then
hold_extended <= '1';
end if;
if (rx_shifting_done = '1') and (released = '1') then
hold_released <= '1';
end if;
end if;
end if;
end process;
-- These bits contain the status of the two shift keys
left_shift_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
left_shift_key <= '0';
elsif (q(8 downto 1) = LEFT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '0') then
left_shift_key <= '1';
elsif (q(8 downto 1) = LEFT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '1') then
left_shift_key <= '0';
end if;
end if;
end process;
right_shift_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
right_shift_key <= '0';
elsif (q(8 downto 1) = RIGHT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '0') then
right_shift_key <= '1';
elsif (q(8 downto 1) = RIGHT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '1') then
right_shift_key <= '0';
end if;
end if;
end process;
shift_key_on <= left_shift_key or right_shift_key;
rx_shift_key_on <= shift_key_on;
--
-- Control keys
--
ctrl_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
ctrl_key_on <= '0';
elsif (q(8 downto 1) = CTRL_CODE) and
(rx_shifting_done = '1') and
(hold_released = '0') then
ctrl_key_on <= '1';
elsif (q(8 downto 1) = CTRL_CODE) and
(rx_shifting_done = '1') and
(hold_released = '1') then
ctrl_key_on <= '0';
end if;
end if;
end process;
--
-- Caps lock
--
caps_proc : process(clk, reset, q, rx_shifting_done, hold_released, caps_key_on )
begin
if falling_edge(clk) then
if (reset = '1') then
caps_key_on <= '0';
elsif (q(8 downto 1) = CAPS_CODE) and
(rx_shifting_done = '1') and
(hold_released = '0') then
caps_key_on <= not caps_key_on;
end if;
end if;
end process;
-- Output the special scan code flags, the scan code and the ascii
special_scan_proc : process(clk, reset,
hold_extended, hold_released,
q, ascii, ctrl_key_on )
begin
if falling_edge(clk) then
if (reset = '1') then
rx_extended <= '0';
rx_released <= '0';
-- rx_scan_code <= "00000000";
rx_ascii <= "00000000";
elsif (rx_output_strobe = '1') then
rx_extended <= hold_extended;
rx_released <= hold_released;
-- rx_scan_code <= q(8 downto 1);
elsif ctrl_key_on = '1' then
rx_ascii <= ascii and x"1f";
else
rx_ascii <= ascii;
end if;
end if;
end process;
-- Store the final rx output data only when all extend and release codes
-- are received and the next (actual key) scan code is also ready.
-- (the presence of rx_extended or rx_released refers to the
-- the current latest scan code received, not the previously latched flags.)
rx_output_proc : process( clk, reset,
rx_shifting_done, rx_output_strobe,
extended, released,
q, ascii, rx_read )
begin
if (rx_shifting_done = '1') and (extended = '0') and (released = '0') then
rx_output_event <= '1';
else
rx_output_event <= '0';
end if;
if falling_edge(clk) then
if reset = '1' then
rx_output_strobe <= '0';
elsif (rx_shifting_done = '1') and
(rx_output_strobe = '0') and
(extended = '0') and
(released = '0') and
(hold_released = '0' ) and
(ascii /= x"00" ) then
-- ((TRAP_SHIFT_KEYS_PP = 0) or
-- ( (q(8 downto 1) /= RIGHT_SHIFT) and
-- (q(8 downto 1) /= LEFT_SHIFT) and
-- (q(8 downto 1) /= CTRL_CODE) ) )then
rx_output_strobe <= '1';
elsif rx_read = '1' then
rx_output_strobe <= '0';
end if;
end if;
rx_data_ready <= rx_output_strobe;
end process;
-- This part translates the scan code into an ASCII value...
-- Only the ASCII codes which I considered important have been included.
-- if you want more, just add the appropriate case statement lines...
-- (You will need to know the keyboard scan codes you wish to assign.)
-- The entries are listed in ascending order of ASCII value.
shift_key_plus_code <= shift_key_on & caps_key_on & q(7 downto 1);
--shift_map : process( shift_key_plus_code )
--begin
-- case shift_key_plus_code is
-- when x"066" => ascii <= x"08"; -- Backspace ("backspace" key)
-- when x"166" => ascii <= x"08"; -- Backspace ("backspace" key)
-- when x"00d" => ascii <= x"09"; -- Horizontal Tab
-- when x"10d" => ascii <= x"09"; -- Horizontal Tab
-- when x"05a" => ascii <= x"0d"; -- Carriage return ("enter" key)
-- when x"15a" => ascii <= x"0d"; -- Carriage return ("enter" key)
-- when x"076" => ascii <= x"1b"; -- Escape ("esc" key)
-- when x"176" => ascii <= x"1b"; -- Escape ("esc" key)
-- when x"029" => ascii <= x"20"; -- Space
-- when x"129" => ascii <= x"20"; -- Space
-- when x"116" => ascii <= x"21"; -- !
-- when x"152" => ascii <= x"22"; -- "
-- when x"126" => ascii <= x"23"; -- #
-- when x"125" => ascii <= x"24"; -- $
-- when x"12e" => ascii <= x"25"; --
-- when x"13d" => ascii <= x"26"; --
-- when x"052" => ascii <= x"27"; --
-- when x"146" => ascii <= x"28"; --
-- when x"145" => ascii <= x"29"; --
-- when x"13e" => ascii <= x"2a"; -- *
-- when x"155" => ascii <= x"2b"; -- +
-- when x"041" => ascii <= x"2c"; -- ,
-- when x"04e" => ascii <= x"2d"; -- -
-- when x"049" => ascii <= x"2e"; -- .
-- when x"04a" => ascii <= x"2f"; -- /
-- when x"045" => ascii <= x"30"; -- 0
-- when x"016" => ascii <= x"31"; -- 1
-- when x"01e" => ascii <= x"32"; -- 2
-- when x"026" => ascii <= x"33"; -- 3
-- when x"025" => ascii <= x"34"; -- 4
-- when x"02e" => ascii <= x"35"; -- 5
-- when x"036" => ascii <= x"36"; -- 6
-- when x"03d" => ascii <= x"37"; -- 7
-- when x"03e" => ascii <= x"38"; -- 8
-- when x"046" => ascii <= x"39"; -- 9
-- when x"14c" => ascii <= x"3a"; -- :
-- when x"04c" => ascii <= x"3b"; -- ;
-- when x"141" => ascii <= x"3c"; -- <
-- when x"055" => ascii <= x"3d"; -- =
-- when x"149" => ascii <= x"3e"; -- >
-- when x"14a" => ascii <= x"3f"; -- ?
-- when x"11e" => ascii <= x"40"; -- @
-- when x"11c" => ascii <= x"41"; -- A
-- when x"132" => ascii <= x"42"; -- B
-- when x"121" => ascii <= x"43"; -- C
-- when x"123" => ascii <= x"44"; -- D
-- when x"124" => ascii <= x"45"; -- E
-- when x"12b" => ascii <= x"46"; -- F
-- when x"134" => ascii <= x"47"; -- G
-- when x"133" => ascii <= x"48"; -- H
-- when x"143" => ascii <= x"49"; -- I
-- when x"13b" => ascii <= x"4a"; -- J
-- when x"142" => ascii <= x"4b"; -- K
-- when x"14b" => ascii <= x"4c"; -- L
-- when x"13a" => ascii <= x"4d"; -- M
-- when x"131" => ascii <= x"4e"; -- N
-- when x"144" => ascii <= x"4f"; -- O
-- when x"14d" => ascii <= x"50"; -- P
-- when x"115" => ascii <= x"51"; -- Q
-- when x"12d" => ascii <= x"52"; -- R
-- when x"11b" => ascii <= x"53"; -- S
-- when x"12c" => ascii <= x"54"; -- T
-- when x"13c" => ascii <= x"55"; -- U
-- when x"12a" => ascii <= x"56"; -- V
-- when x"11d" => ascii <= x"57"; -- W
-- when x"122" => ascii <= x"58"; -- X
-- when x"135" => ascii <= x"59"; -- Y
-- when x"11a" => ascii <= x"5a"; -- Z
-- when x"054" => ascii <= x"5b"; -- [
-- when x"05d" => ascii <= x"5c"; -- \
-- when x"05b" => ascii <= x"5d"; -- ]
-- when x"136" => ascii <= x"5e"; -- ^
-- when x"14e" => ascii <= x"5f"; -- _
-- when x"00e" => ascii <= x"60"; -- `
-- when x"01c" => ascii <= x"61"; -- a
-- when x"032" => ascii <= x"62"; -- b
-- when x"021" => ascii <= x"63"; -- c
-- when x"023" => ascii <= x"64"; -- d
-- when x"024" => ascii <= x"65"; -- e
-- when x"02b" => ascii <= x"66"; -- f
-- when x"034" => ascii <= x"67"; -- g
-- when x"033" => ascii <= x"68"; -- h
-- when x"043" => ascii <= x"69"; -- i
-- when x"03b" => ascii <= x"6a"; -- j
-- when x"042" => ascii <= x"6b"; -- k
-- when x"04b" => ascii <= x"6c"; -- l
-- when x"03a" => ascii <= x"6d"; -- m
-- when x"031" => ascii <= x"6e"; -- n
-- when x"044" => ascii <= x"6f"; -- o
-- when x"04d" => ascii <= x"70"; -- p
-- when x"015" => ascii <= x"71"; -- q
-- when x"02d" => ascii <= x"72"; -- r
-- when x"01b" => ascii <= x"73"; -- s
-- when x"02c" => ascii <= x"74"; -- t
-- when x"03c" => ascii <= x"75"; -- u
-- when x"02a" => ascii <= x"76"; -- v
-- when x"01d" => ascii <= x"77"; -- w
-- when x"022" => ascii <= x"78"; -- x
-- when x"035" => ascii <= x"79"; -- y
-- when x"01a" => ascii <= x"7a"; -- z
-- when x"154" => ascii <= x"7b"; -- {
-- when x"15d" => ascii <= x"7c"; -- |
-- when x"15b" => ascii <= x"7d"; -- }
-- when x"10e" => ascii <= x"7e"; -- ~
-- when x"071" => ascii <= x"7f"; -- (Delete OR DEL on numeric keypad)
-- when x"171" => ascii <= x"7f"; -- (Delete OR DEL on numeric keypad)
-- when others => ascii <= x"ff"; -- 0xff used for unlisted characters.
-- end case;
--end process;
end rtl;
Code:
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 ps2_keyboard_interface is
generic (
CLK_FREQ_MHZ : integer
);
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 ps2_keyboard_interface;
-------------------------------------------------------------------------------
-- Architecture for ps2 keyboard interface
-------------------------------------------------------------------------------
architecture rtl of ps2_keyboard_interface is
-----------------------------------------------------------------------------
constant TOTAL_BITS : integer := 11;
constant EXTEND_CODE : integer := 16#E0#;
constant RELEASE_CODE : integer := 16#F0#;
constant LEFT_SHIFT : integer := 16#12#;
constant RIGHT_SHIFT : integer := 16#59#;
constant CTRL_CODE : integer := 16#14#;
constant CAPS_CODE : integer := 16#58#;
-- constants
-- The timer value can be up to (2^bits) inclusive.
-- Values for 49.152 MHz clock
--constant TIMER_60USEC_VALUE_PP : integer := 2950; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 12; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 186; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 8; -- Number of bits needed for timer
-- Values for 12.5 MHz Clock
--constant TIMER_60USEC_VALUE_PP : integer := 750; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 10; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 62; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 6; -- Number of bits needed for timer
-- Values for 25 MHz Clock
--constant TIMER_60USEC_VALUE_PP : integer := 1500; -- Number of sys_clks for 60usec.
--constant TIMER_60USEC_BITS_PP : integer := 11; -- Number of bits needed for timer
--constant TIMER_5USEC_VALUE_PP : integer := 125; -- Number of sys_clks for debounce
--constant TIMER_5USEC_BITS_PP : integer := 7; -- Number of bits needed for timer
-- Values for generic Clock up to 50 MHz
constant TIMER_60USEC_VALUE_PP : integer := CLK_FREQ_MHZ * 60; -- Number of sys_clks for 60usec.
constant TIMER_60USEC_BITS_PP : integer := 12; -- Number of bits needed for timer
constant TIMER_5USEC_VALUE_PP : integer := CLK_FREQ_MHZ * 5; -- Number of sys_clks for debounce
constant TIMER_5USEC_BITS_PP : integer := 8; -- Number of bits needed for timer
constant TRAP_SHIFT_KEYS_PP : integer := 1; -- Default: No shift key trap.
-- State encodings, provided as constants
-- for flexibility to the one instantiating the module.
-- In general, the default values need not be changed.
-- State "m1_rx_clk_l" has been chosen on purpose. Since the input
-- synchronizing flip-flops initially contain zero, it takes one clk
-- for them to update to reflect the actual (idle = high) status of
-- the I/O lines from the keyboard. Therefore, choosing 0 for m1_rx_clk_l
-- allows the state machine to transition to m1_rx_clk_h when the true
-- values of the input signals become present at the outputs of the
-- synchronizing flip-flops. This initial transition is harmless, and it
-- eliminates the need for a "reset" pulse before the interface can operate.
type m1_type is ( m1_rx_clk_h, m1_rx_clk_l,
m1_tx_wait_clk_h, m1_tx_force_clk_l,
m1_tx_clk_h, m1_tx_clk_l,
m1_tx_wait_keyboard_ack, m1_tx_done_recovery,
m1_tx_error_no_keyboard_ack, m1_tx_rising_edge_marker,
m1_tx_first_wait_clk_h, m1_tx_first_wait_clk_l, m1_tx_reset_timer,
m1_rx_falling_edge_marker, m1_rx_rising_edge_marker );
-- Internal signal declarations
signal timer_60usec_done : std_logic;
signal timer_5usec_done : std_logic;
signal extended : std_logic;
signal released : std_logic;
signal shift_key_on : std_logic;
signal ctrl_key_on : std_logic;
signal caps_key_on : std_logic;
-- NOTE: These two signals used to be one. They
-- were split into two signals because of
-- shift key trapping. With shift key
-- trapping, no event is generated externally,
-- but the "hold" data must still be cleared
-- anyway regardless, in preparation for the
-- next scan codes.
signal rx_output_event : std_logic; -- Used only to clear: hold_released, hold_extended
signal rx_output_strobe : std_logic; -- Used to produce the actual output.
signal tx_parity_bit : std_logic;
signal rx_shifting_done : std_logic;
signal tx_shifting_done : std_logic;
signal shift_key_plus_code: std_logic_vector(8 downto 0);
signal q : std_logic_vector(TOTAL_BITS-1 downto 0);
signal m1_state : m1_type;
signal m1_next_state : m1_type;
signal bit_count : std_logic_vector(3 downto 0);
signal enable_timer_60usec: std_logic;
signal enable_timer_5usec : std_logic;
signal timer_60usec_count : std_logic_vector(TIMER_60USEC_BITS_PP-1 downto 0);
signal timer_5usec_count : std_logic_vector(TIMER_5USEC_BITS_PP-1 downto 0);
signal ascii : std_logic_vector(7 downto 0); -- "REG" type only because a case statement is used.
signal left_shift_key : std_logic;
signal right_shift_key : std_logic;
signal hold_extended : std_logic; -- Holds prior value, cleared at rx_output_strobe
signal hold_released : std_logic; -- Holds prior value, cleared at rx_output_strobe
signal ps2_clk_s : std_logic; -- Synchronous version of this input
signal ps2_data_s : std_logic; -- Synchronous version of this input
signal ps2_clk_hi_z : std_logic; -- Without keyboard, high Z equals 1 due to pullups.
signal ps2_data_hi_z : std_logic; -- Without keyboard, high Z equals 1 due to pullups.
signal tx_write_ack_o : std_logic;
--
-- key lookup table
--
component keymap_rom
Port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (8 downto 0);
rdata : out std_logic_vector (7 downto 0);
wdata : in std_logic_vector (7 downto 0)
);
end component;
begin
my_key_map : keymap_rom
Port map (
clk => clk,
rst => reset,
cs => '1',
rw => '1',
addr => shift_key_plus_code,
rdata => ascii,
wdata => "00000000"
);
----------------------------------------------------------------------------
-- Module code
-- assign ps2_clk = ps2_clk_hi_z?1'bZ:1'b0;
-- assign ps2_data = ps2_data_hi_z?1'bZ:1'b0;
--
ps2_direction : process( ps2_clk_hi_z, ps2_data_hi_z )
begin
if( ps2_clk_hi_z = '1' ) then
ps2_clk <= 'Z';
else
ps2_clk <= '0';
end if;
if( ps2_data_hi_z = '1' ) then
ps2_data <= 'Z';
else
ps2_data <= '0';
end if;
end process;
-- Input "synchronizing" logic -- synchronizes the inputs to the state
-- machine clock, thus avoiding errors related to
-- spurious state machine transitions.
ps2_synch : process(clk, ps2_clk, ps2_data)
begin
if falling_edge(clk) then
ps2_clk_s <= ps2_clk;
ps2_data_s <= ps2_data;
end if;
end process;
-- State register
m1_state_register : process( clk, reset, m1_state )
begin
if falling_edge(clk) then
if (reset = '1') then
m1_state <= m1_rx_clk_h;
else
m1_state <= m1_next_state;
end if;
end if;
end process;
m1_state_logic : process( m1_state, q,
tx_shifting_done, tx_write,
ps2_clk_s, ps2_data_s,
timer_60usec_done, timer_5usec_done )
begin
-- Output signals default to this value, unless changed in a state condition.
ps2_clk_hi_z <= '1';
ps2_data_hi_z <= '1';
tx_error_no_keyboard_ack <= '0';
enable_timer_60usec <= '0';
enable_timer_5usec <= '0';
case (m1_state) is
when m1_rx_clk_h =>
enable_timer_60usec <= '1';
if (tx_write = '1') then
m1_next_state <= m1_tx_reset_timer;
elsif (ps2_clk_s = '0') then
m1_next_state <= m1_rx_falling_edge_marker;
else
m1_next_state <= m1_rx_clk_h;
end if;
when m1_rx_falling_edge_marker =>
enable_timer_60usec <= '0';
m1_next_state <= m1_rx_clk_l;
when m1_rx_clk_l =>
enable_timer_60usec <= '1';
if (tx_write = '1') then
m1_next_state <= m1_tx_reset_timer;
elsif (ps2_clk_s = '1') then
m1_next_state <= m1_rx_rising_edge_marker;
else
m1_next_state <= m1_rx_clk_l;
end if;
when m1_rx_rising_edge_marker =>
enable_timer_60usec <= '0';
m1_next_state <= m1_rx_clk_h;
when m1_tx_reset_timer =>
enable_timer_60usec <= '0';
m1_next_state <= m1_tx_force_clk_l;
when m1_tx_force_clk_l =>
enable_timer_60usec <= '1';
ps2_clk_hi_z <= '0'; -- Force the ps2_clk line low.
if (timer_60usec_done = '1') then
m1_next_state <= m1_tx_first_wait_clk_h;
else
m1_next_state <= m1_tx_force_clk_l;
end if;
when m1_tx_first_wait_clk_h =>
enable_timer_5usec <= '1';
ps2_data_hi_z <= '0'; -- Start bit.
if (ps2_clk_s = '0') and (timer_5usec_done = '1') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_first_wait_clk_h;
end if;
-- This state must be included because the device might possibly
-- delay for up to 10 milliseconds before beginning its clock pulses.
-- During that waiting time, we cannot drive the data (q[0]) because it
-- is possibly 1, which would cause the keyboard to abort its receive
-- and the expected clocks would then never be generated.
when m1_tx_first_wait_clk_l =>
ps2_data_hi_z <= '0';
if (ps2_clk_s = '0') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_first_wait_clk_l;
end if;
when m1_tx_wait_clk_h =>
enable_timer_5usec <= '1';
ps2_data_hi_z <= q(0);
if (ps2_clk_s = '1') and (timer_5usec_done = '1') then
m1_next_state <= m1_tx_rising_edge_marker;
else
m1_next_state <= m1_tx_wait_clk_h;
end if;
when m1_tx_rising_edge_marker =>
ps2_data_hi_z <= q(0);
m1_next_state <= m1_tx_clk_h;
when m1_tx_clk_h =>
ps2_data_hi_z <= q(0);
if (tx_shifting_done = '1') then
m1_next_state <= m1_tx_wait_keyboard_ack;
elsif (ps2_clk_s = '0') then
m1_next_state <= m1_tx_clk_l;
else
m1_next_state <= m1_tx_clk_h;
end if;
when m1_tx_clk_l =>
ps2_data_hi_z <= q(0);
if (ps2_clk_s = '1') then
m1_next_state <= m1_tx_wait_clk_h;
else
m1_next_state <= m1_tx_clk_l;
end if;
when m1_tx_wait_keyboard_ack =>
if (ps2_clk_s = '0') and (ps2_data_s = '1') then
m1_next_state <= m1_tx_error_no_keyboard_ack;
elsif (ps2_clk_s = '0') and (ps2_data_s = '0') then
m1_next_state <= m1_tx_done_recovery;
else
m1_next_state <= m1_tx_wait_keyboard_ack;
end if;
when m1_tx_done_recovery =>
if (ps2_clk_s = '1') and (ps2_data_s = '1') then
m1_next_state <= m1_rx_clk_h;
else
m1_next_state <= m1_tx_done_recovery;
end if;
when m1_tx_error_no_keyboard_ack =>
tx_error_no_keyboard_ack <= '1';
if (ps2_clk_s = '1') and (ps2_data_s ='1') then
m1_next_state <= m1_rx_clk_h;
else
m1_next_state <= m1_tx_error_no_keyboard_ack;
end if;
when others =>
m1_next_state <= m1_rx_clk_h;
end case;
end process;
-- This is the bit counter
bit_counter: process(clk, reset, m1_state, bit_count )
begin
if falling_edge(clk) then
if ( reset = '1' ) or
( rx_shifting_done = '1' ) or
(m1_state = m1_tx_wait_keyboard_ack) then -- After tx is done.
bit_count <= "0000"; -- normal reset
elsif (timer_60usec_done = '1' ) and
(m1_state = m1_rx_clk_h) and
(ps2_clk_s = '1') then
bit_count <= "0000"; -- rx watchdog timer reset
elsif (m1_state = m1_rx_falling_edge_marker) or -- increment for rx
(m1_state = m1_tx_rising_edge_marker) then -- increment for tx
bit_count <= bit_count + 1;
end if;
end if;
end process;
assign: process( bit_count, tx_write, tx_write_ack_o, m1_state )
begin
if (bit_count = TOTAL_BITS) then
rx_shifting_done <= '1';
else
rx_shifting_done <= '0';
end if;
if (bit_count = (TOTAL_BITS-1)) then
tx_shifting_done <= '1';
else
tx_shifting_done <= '0';
end if;
-- This is the signal which enables loading of the shift register.
-- It also indicates "ack" to the device writing to the transmitter.
if ((tx_write = '1') and (m1_state = m1_rx_clk_h)) or
((tx_write = '1') and (m1_state = m1_rx_clk_l)) then
tx_write_ack_o <= '1';
else
tx_write_ack_o <= '0';
end if;
tx_write_ack <= tx_write_ack_o;
end process;
-- This is the ODD parity bit for the transmitted word.
-- assign tx_parity_bit = ~^tx_data;
--
tx_parity_bit <= not( tx_data(7) xor tx_data(6) xor tx_data(5) xor tx_data(4) xor
tx_data(3) xor tx_data(2) xor tx_data(1) xor tx_data(0) );
-- This is the shift register
q_shift : process(clk, tx_write_ack_o, tx_parity_bit, tx_data,
m1_state, q, ps2_data_s, rx_shifting_done )
begin
if falling_edge(clk) then
if (reset = '1') then
q <= "00000000000";
elsif (tx_write_ack_o = '1') then
q <= "1" & tx_parity_bit & tx_data & "0";
elsif ( (m1_state = m1_rx_falling_edge_marker) or
(m1_state = m1_tx_rising_edge_marker) ) then
q <= ps2_data_s & q((TOTAL_BITS-1) downto 1);
end if;
end if;
-- Create the signals which indicate special scan codes received.
-- These are the "unlatched versions."
if (q(8 downto 1) = EXTEND_CODE) and (rx_shifting_done = '1') then
extended <= '1';
else
extended <= '0';
end if;
if (q(8 downto 1) = RELEASE_CODE) and (rx_shifting_done = '1') then
released <= '1';
else
released <= '0';
end if;
end process;
-- This is the 60usec timer counter
timer60usec: process(clk, enable_timer_60usec, timer_60usec_count)
begin
if falling_edge(clk) then
if (enable_timer_60usec = '0') then
timer_60usec_count <= (others => '0');
elsif (timer_60usec_done = '0') then
timer_60usec_count <= timer_60usec_count + 1;
end if;
end if;
if (timer_60usec_count = (TIMER_60USEC_VALUE_PP - 1)) then
timer_60usec_done <= '1';
else
timer_60usec_done <= '0';
end if;
end process;
-- This is the 5usec timer counter
timer5usec : process(clk, enable_timer_5usec, timer_5usec_count )
begin
if falling_edge(clk) then
if (enable_timer_5usec = '0') then
timer_5usec_count <= (others => '0');
elsif (timer_5usec_done = '0') then
timer_5usec_count <= timer_5usec_count + 1;
end if;
end if;
if( timer_5usec_count = (TIMER_5USEC_VALUE_PP - 1)) then
timer_5usec_done <= '1';
else
timer_5usec_done <= '0';
end if;
end process;
-- Store the special scan code status bits
-- Not the final output, but an intermediate storage place,
-- until the entire set of output data can be assembled.
special_scan : process(clk, reset, rx_output_event, rx_shifting_done, extended, released )
begin
if falling_edge(clk) then
if (reset = '1') or (rx_output_event = '1') then
hold_extended <= '0';
hold_released <= '0';
else
if (rx_shifting_done = '1') and (extended = '1') then
hold_extended <= '1';
end if;
if (rx_shifting_done = '1') and (released = '1') then
hold_released <= '1';
end if;
end if;
end if;
end process;
-- These bits contain the status of the two shift keys
left_shift_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
left_shift_key <= '0';
elsif (q(8 downto 1) = LEFT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '0') then
left_shift_key <= '1';
elsif (q(8 downto 1) = LEFT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '1') then
left_shift_key <= '0';
end if;
end if;
end process;
right_shift_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
right_shift_key <= '0';
elsif (q(8 downto 1) = RIGHT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '0') then
right_shift_key <= '1';
elsif (q(8 downto 1) = RIGHT_SHIFT) and
(rx_shifting_done = '1') and
(hold_released = '1') then
right_shift_key <= '0';
end if;
end if;
end process;
shift_key_on <= left_shift_key or right_shift_key;
rx_shift_key_on <= shift_key_on;
--
-- Control keys
--
ctrl_proc : process(clk, reset, q, rx_shifting_done, hold_released )
begin
if falling_edge(clk) then
if (reset = '1') then
ctrl_key_on <= '0';
elsif (q(8 downto 1) = CTRL_CODE) and
(rx_shifting_done = '1') and
(hold_released = '0') then
ctrl_key_on <= '1';
elsif (q(8 downto 1) = CTRL_CODE) and
(rx_shifting_done = '1') and
(hold_released = '1') then
ctrl_key_on <= '0';
end if;
end if;
end process;
--
-- Caps lock
--
caps_proc : process(clk, reset, q, rx_shifting_done, hold_released, caps_key_on )
begin
if falling_edge(clk) then
if (reset = '1') then
caps_key_on <= '0';
elsif (q(8 downto 1) = CAPS_CODE) and
(rx_shifting_done = '1') and
(hold_released = '0') then
caps_key_on <= not caps_key_on;
end if;
end if;
end process;
-- Output the special scan code flags, the scan code and the ascii
special_scan_proc : process(clk, reset,
hold_extended, hold_released,
q, ascii, ctrl_key_on )
begin
if falling_edge(clk) then
if (reset = '1') then
rx_extended <= '0';
rx_released <= '0';
-- rx_scan_code <= "00000000";
rx_ascii <= "00000000";
elsif (rx_output_strobe = '1') then
rx_extended <= hold_extended;
rx_released <= hold_released;
-- rx_scan_code <= q(8 downto 1);
elsif ctrl_key_on = '1' then
rx_ascii <= ascii and x"1f";
else
rx_ascii <= ascii;
end if;
end if;
end process;
-- Store the final rx output data only when all extend and release codes
-- are received and the next (actual key) scan code is also ready.
-- (the presence of rx_extended or rx_released refers to the
-- the current latest scan code received, not the previously latched flags.)
rx_output_proc : process( clk, reset,
rx_shifting_done, rx_output_strobe,
extended, released,
q, ascii, rx_read )
begin
if (rx_shifting_done = '1') and (extended = '0') and (released = '0') then
rx_output_event <= '1';
else
rx_output_event <= '0';
end if;
if falling_edge(clk) then
if reset = '1' then
rx_output_strobe <= '0';
elsif (rx_shifting_done = '1') and
(rx_output_strobe = '0') and
(extended = '0') and
(released = '0') and
(hold_released = '0' ) and
(ascii /= x"00" ) then
-- ((TRAP_SHIFT_KEYS_PP = 0) or
-- ( (q(8 downto 1) /= RIGHT_SHIFT) and
-- (q(8 downto 1) /= LEFT_SHIFT) and
-- (q(8 downto 1) /= CTRL_CODE) ) )then
rx_output_strobe <= '1';
elsif rx_read = '1' then
rx_output_strobe <= '0';
end if;
end if;
rx_data_ready <= rx_output_strobe;
end process;
-- This part translates the scan code into an ASCII value...
-- Only the ASCII codes which I considered important have been included.
-- if you want more, just add the appropriate case statement lines...
-- (You will need to know the keyboard scan codes you wish to assign.)
-- The entries are listed in ascending order of ASCII value.
shift_key_plus_code <= shift_key_on & caps_key_on & q(7 downto 1);
--shift_map : process( shift_key_plus_code )
--begin
-- case shift_key_plus_code is
-- when x"066" => ascii <= x"08"; -- Backspace ("backspace" key)
-- when x"166" => ascii <= x"08"; -- Backspace ("backspace" key)
-- when x"00d" => ascii <= x"09"; -- Horizontal Tab
-- when x"10d" => ascii <= x"09"; -- Horizontal Tab
-- when x"05a" => ascii <= x"0d"; -- Carriage return ("enter" key)
-- when x"15a" => ascii <= x"0d"; -- Carriage return ("enter" key)
-- when x"076" => ascii <= x"1b"; -- Escape ("esc" key)
-- when x"176" => ascii <= x"1b"; -- Escape ("esc" key)
-- when x"029" => ascii <= x"20"; -- Space
-- when x"129" => ascii <= x"20"; -- Space
-- when x"116" => ascii <= x"21"; -- !
-- when x"152" => ascii <= x"22"; -- "
-- when x"126" => ascii <= x"23"; -- #
-- when x"125" => ascii <= x"24"; -- $
-- when x"12e" => ascii <= x"25"; --
-- when x"13d" => ascii <= x"26"; --
-- when x"052" => ascii <= x"27"; --
-- when x"146" => ascii <= x"28"; --
-- when x"145" => ascii <= x"29"; --
-- when x"13e" => ascii <= x"2a"; -- *
-- when x"155" => ascii <= x"2b"; -- +
-- when x"041" => ascii <= x"2c"; -- ,
-- when x"04e" => ascii <= x"2d"; -- -
-- when x"049" => ascii <= x"2e"; -- .
-- when x"04a" => ascii <= x"2f"; -- /
-- when x"045" => ascii <= x"30"; -- 0
-- when x"016" => ascii <= x"31"; -- 1
-- when x"01e" => ascii <= x"32"; -- 2
-- when x"026" => ascii <= x"33"; -- 3
-- when x"025" => ascii <= x"34"; -- 4
-- when x"02e" => ascii <= x"35"; -- 5
-- when x"036" => ascii <= x"36"; -- 6
-- when x"03d" => ascii <= x"37"; -- 7
-- when x"03e" => ascii <= x"38"; -- 8
-- when x"046" => ascii <= x"39"; -- 9
-- when x"14c" => ascii <= x"3a"; -- :
-- when x"04c" => ascii <= x"3b"; -- ;
-- when x"141" => ascii <= x"3c"; -- <
-- when x"055" => ascii <= x"3d"; -- =
-- when x"149" => ascii <= x"3e"; -- >
-- when x"14a" => ascii <= x"3f"; -- ?
-- when x"11e" => ascii <= x"40"; -- @
-- when x"11c" => ascii <= x"41"; -- A
-- when x"132" => ascii <= x"42"; -- B
-- when x"121" => ascii <= x"43"; -- C
-- when x"123" => ascii <= x"44"; -- D
-- when x"124" => ascii <= x"45"; -- E
-- when x"12b" => ascii <= x"46"; -- F
-- when x"134" => ascii <= x"47"; -- G
-- when x"133" => ascii <= x"48"; -- H
-- when x"143" => ascii <= x"49"; -- I
-- when x"13b" => ascii <= x"4a"; -- J
-- when x"142" => ascii <= x"4b"; -- K
-- when x"14b" => ascii <= x"4c"; -- L
-- when x"13a" => ascii <= x"4d"; -- M
-- when x"131" => ascii <= x"4e"; -- N
-- when x"144" => ascii <= x"4f"; -- O
-- when x"14d" => ascii <= x"50"; -- P
-- when x"115" => ascii <= x"51"; -- Q
-- when x"12d" => ascii <= x"52"; -- R
-- when x"11b" => ascii <= x"53"; -- S
-- when x"12c" => ascii <= x"54"; -- T
-- when x"13c" => ascii <= x"55"; -- U
-- when x"12a" => ascii <= x"56"; -- V
-- when x"11d" => ascii <= x"57"; -- W
-- when x"122" => ascii <= x"58"; -- X
-- when x"135" => ascii <= x"59"; -- Y
-- when x"11a" => ascii <= x"5a"; -- Z
-- when x"054" => ascii <= x"5b"; -- [
-- when x"05d" => ascii <= x"5c"; -- \
-- when x"05b" => ascii <= x"5d"; -- ]
-- when x"136" => ascii <= x"5e"; -- ^
-- when x"14e" => ascii <= x"5f"; -- _
-- when x"00e" => ascii <= x"60"; -- `
-- when x"01c" => ascii <= x"61"; -- a
-- when x"032" => ascii <= x"62"; -- b
-- when x"021" => ascii <= x"63"; -- c
-- when x"023" => ascii <= x"64"; -- d
-- when x"024" => ascii <= x"65"; -- e
-- when x"02b" => ascii <= x"66"; -- f
-- when x"034" => ascii <= x"67"; -- g
-- when x"033" => ascii <= x"68"; -- h
-- when x"043" => ascii <= x"69"; -- i
-- when x"03b" => ascii <= x"6a"; -- j
-- when x"042" => ascii <= x"6b"; -- k
-- when x"04b" => ascii <= x"6c"; -- l
-- when x"03a" => ascii <= x"6d"; -- m
-- when x"031" => ascii <= x"6e"; -- n
-- when x"044" => ascii <= x"6f"; -- o
-- when x"04d" => ascii <= x"70"; -- p
-- when x"015" => ascii <= x"71"; -- q
-- when x"02d" => ascii <= x"72"; -- r
-- when x"01b" => ascii <= x"73"; -- s
-- when x"02c" => ascii <= x"74"; -- t
-- when x"03c" => ascii <= x"75"; -- u
-- when x"02a" => ascii <= x"76"; -- v
-- when x"01d" => ascii <= x"77"; -- w
-- when x"022" => ascii <= x"78"; -- x
-- when x"035" => ascii <= x"79"; -- y
-- when x"01a" => ascii <= x"7a"; -- z
-- when x"154" => ascii <= x"7b"; -- {
-- when x"15d" => ascii <= x"7c"; -- |
-- when x"15b" => ascii <= x"7d"; -- }
-- when x"10e" => ascii <= x"7e"; -- ~
-- when x"071" => ascii <= x"7f"; -- (Delete OR DEL on numeric keypad)
-- when x"171" => ascii <= x"7f"; -- (Delete OR DEL on numeric keypad)
-- when others => ascii <= x"ff"; -- 0xff used for unlisted characters.
-- end case;
--end process;
end rtl;
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