kbd_alphanum.vhd

library ieee;
use ieee.std_logic_1164.all;

entity kbd_alphanum is
  port (
    clk : in std_logic;
    key_on : in std_logic_vector(2 downto 0);
    key_code : in std_logic_vector(47 downto 0);
    HEX1 : out std_logic_vector(3 downto 0); -- GFEDCBA
    HEX0 : out std_logic_vector(3 downto 0) -- GFEDCBA
  );
end kbd_alphanum;

architecture rtl of kbd_alphanum is
component bin2hex
	port (
		SW: IN STD_LOGIC_VECTOR(3 DOWNTO 0);
		light : IN STD_LOGIC;
		HEX0: OUT STD_LOGIC_VECTOR (6 DOWNTO 0)
	);
end component;

component ff_d
  port(
    D   : in std_logic;
    Clk : in std_logic;
	 Q   : out std_logic;
    Q_n : out std_logic;
	 Preset : in std_logic;
	 Clear  : in std_logic
  );
end component;

component ff_t
  port(
    T   : in std_logic;
    Clk : in std_logic;
	 Q   : out std_logic;
    Q_n : out std_logic;
	 Preset : in std_logic;
	 Clear  : in std_logic
  );
end component;

component code2ascii
	port (
		capital_en : in std_logic;
		key_code   : in std_logic_vector(15 downto 0);
		key_ascii  : out std_logic_vector(7 downto 0)
	);
end component;
  signal key_ascii : std_logic_vector (47 downto 0);
  signal key_shown : std_logic_vector (15 downto 0);
  signal shift_in, shift_out : std_logic;
  signal caps_in, caps_out   : std_logic;
  signal dp_on, capital_en, second_key : std_logic;

begin

	--Testa se a primeira tecla eh shift
	with key_code(15 downto 0) select shift_in <=
		'1' when x"0012",
		'1' when x"0059",
		'0' when others;

	--Testa se a primeira tecla eh caps
	with key_code(15 downto 0) select caps_in <=
		'1' when x"0058",
		'0' when others;
		
  -- Cria flipflop para o shift
  shift_flop : ff_d port map (
		shift_in,
		clk,
		shift_out,
		OPEN,
		'0', 
		'0'
  );
	
  --Cria flipflop para o caps
  caps_flop : ff_t port map (
		'1',
		caps_in,
		caps_out,
		OPEN,
		'0', 
		'0'
  );
  
  --Inverte o comportamento do shift se o caps estiver ativo
  capital_en <= caps_out xor shift_out;
 
  --Gera tradutores scan2ascii para as 3 teclas
  G1 : for i in 2 downto 0 generate		
		translate : code2ascii port map (
			capital_en,
			key_code(16*i + 15 downto 16*i),
			key_ascii(16*i + 7 downto 16*i)
		);
  end generate;
  
  --Se caps ou shift pressionados, aponta pra segunda tecla.
  second_key <= caps_in or shift_out;
  
  --Seleciona se a tecla a ser mostrada eh a segunda ou a primeira
  with second_key select key_shown <=
		key_ascii(15 downto 0) when '0',
		key_ascii(31 downto 16) when '1';
	
	--Define se o display deve ficar desligado caso nao haja uma representacao da tela em ascii
	with key_shown(7 downto 0) select dp_on <=
		'0' when x"00",
		'1' when others;
	
	--retorna o valor ascii
	HEX0 <= key_shown(3 downto 0);
	HEX1 <= key_shown(7 downto 4);
	
end rtl;