__keyboard.vhd

vhdl编写的4X4键盘扫描程序

--------------------------------------------------------------------------------
-- Company: 
-- Engineer:
--
-- Create Date:    16:32:37 08/31/07
-- Design Name:    
-- Module Name:    keyboard - Behavioral
-- Project Name:   
-- Target Device:  
-- Tool versions:  
-- Description:
--
-- Dependencies:
-- 
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
-- 
--------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

---- Uncomment the following library declaration if instantiating
---- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity keyboard is
    Port ( KB_ROW : buffer 	std_logic_vector(3 downto 0);
           KB_COL : in	 	std_logic_vector(3 downto 0);
           KB_CLK	: in 		std_logic;
           KB_RST	: in 		std_logic;
           KB_VAL : out 	std_logic_vector(7 downto 0);
			  KB_VLD	: out 	std_logic;
           KB_BLL : out 	std_logic);
end keyboard;

architecture Behavioral of keyboard is

constant MAXSCAN1: std_logic_vector(3 downto 0):= X"4";
constant BELLDIV : std_logic_vector(4 downto 0):= "11111";

signal SCANTMP :std_logic_vector(7 downto 0);
signal SCANVAL :std_logic_vector(7 downto 0);
signal SCANCNT :std_logic_vector(3 downto 0);
signal BL_CNT :std_logic_vector(4 downto 0);
signal BL_FRQ  :std_logic;
signal BL_ENA  :std_logic;

begin

KB_BLL <= not(KB_CLK and BL_ENA);

process(KB_CLK,KB_RST)
begin
	if(KB_RST = '0') then
		SCANVAL <= X"FF";
		SCANCNT <= MAXSCAN1;
		BL_ENA  <= '0';
		KB_VAL <= X"FF";
		KB_ROW <= X"E";
		KB_VLD <= '0';
	 elsif(KB_CLK'event and KB_CLK = '1') then
	   case KB_ROW is
	      when X"E" => KB_ROW <= X"D";
	      when X"D" => KB_ROW <= X"B";
	      when X"B" => KB_ROW <= X"7";
	      when X"7" => KB_ROW <= X"F";
	      when X"F" => KB_ROW <= X"E";
	      when others=>KB_ROW <= X"E";
	 	end case;
	 	if(KB_ROW = X"F")     then 
			SCANTMP <= X"FF";
			if(SCANTMP = X"FF" or SCANTMP /= SCANVAL) then
				SCANVAL <= SCANTMP;
				SCANCNT <= MAXSCAN1;
            BL_ENA <= '0';
				KB_VLD <= '0';
    		else
				if(SCANCNT > X"1")	then 
			 	   SCANCNT <= SCANCNT-1;
					BL_ENA <= '1';
					KB_VLD <= '0';
				elsif(SCANCNT = X"1") then
					case SCANVAL is
						when X"EE" => KB_VAL<=X"55";
						when X"ED" => KB_VAL<=X"44";
						when X"EB" => KB_VAL<=X"42";
						when X"E7" => KB_VAL<=X"45";
						when X"DE" => KB_VAL<=X"39";
						when X"DD" => KB_VAL<=X"36";
						when X"DB" => KB_VAL<=X"33";
						when X"D7" => KB_VAL<=X"52";
						when X"BE" => KB_VAL<=X"38";
						when X"BD" => KB_VAL<=X"35";
						when X"BB" => KB_VAL<=X"32";
						when X"B7" => KB_VAL<=X"2E";
						when X"7E" => KB_VAL<=X"37";
						when X"7D" => KB_VAL<=X"34";
						when X"7B" => KB_VAL<=X"31";
						when X"77" => KB_VAL<=X"30";
						when others => KB_VAL<=X"67"; 
					end case;
					SCANCNT <= X"0";
					KB_VLD <= '1';
				else
					KB_VLD <= '0';				
				end if;
			end if;
	 	elsif(KB_COL /= X"F") then SCANTMP(3 downto 0)<=KB_ROW; SCANTMP(7 downto 4)<=KB_COL;
	 	else                       SCANTMP <= SCANTMP;
	 	end if;
	end if;
end process;

end Behavioral;