keyboardhandler.vhd

描述：LED示范、按钮及开关、视频输出、键入、含Xilinx PicoBlaze微处理器的存储器模块

--Keyboard controller
--Reads the scan codes from the PS/2 keyboard and stores them in a FIFO buffer
--Based on the sample code available from the Digilent(R) Inc. website
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity KeyboardHandler is
	 generic ( buffer_size: positive := 32 );	  

    Port ( KEYBOARD_CLK : in std_logic;
           KEYBOARD_DATA : in std_logic;
           RESET : in std_logic;
           CLK : in std_logic; --Should be 50 MHz!

           FIRST_CHAR_INDEX : out std_logic_vector(7 downto 0);
           FIRST_FREE_INDEX : out std_logic_vector(7 downto 0);
           CHAR_INDEX : in std_logic_vector(7 downto 0);
           CHAR_DATA : out std_logic_vector(7 downto 0);

           READ_FIRST_CHAR : out std_logic_vector(7 downto 0);
			  READ_FIRST_CHAR_STROBE : in std_logic);
end KeyboardHandler;

architecture Behavioral of KeyboardHandler is
	type buff_array_type is array (buffer_size-1 downto 0) of std_logic_vector (7 downto 0);
				
	signal clkDiv : std_logic_vector (12 downto 0);			   
	signal pclk : std_logic;
	signal KDI, KCI : std_logic;
	signal DFF1, DFF2 : std_logic;
	signal shiftRegSig1: std_logic_vector(10 downto 0);
	signal shiftRegSig2: std_logic_vector(10 downto 1);
	
	signal CharBuffer: buff_array_type;
	signal FirstCharIndex, FirstFreeIndex: std_logic_vector (7 downto 0);

	signal buffer_map: std_logic_vector(7 downto 0);
begin	
	--Used to normalize the buffer counters when they are modified,
	--so that they remain in the domain 0..buffer_size - 1
 	buffer_map <= conv_std_logic_vector(buffer_size - 1, 8);

	--Divide the clock so that we can synchronize with the PS/2 clock
	CLKDivider: Process (CLK)
	begin
		if (CLK = '1' and CLK'Event) then 
			clkDiv <= clkDiv +1; 
		end if;	
	end Process;
	
	pclk <= clkDiv(3);

	FIRST_CHAR_INDEX <= FirstCharIndex;
	FIRST_FREE_INDEX <= FirstFreeIndex;

	process (CHAR_INDEX)
	begin
		CHAR_DATA <= CharBuffer( conv_integer(UNSIGNED(CHAR_INDEX)) );		
	end process;

	READ_FIRST_CHAR <= CharBuffer( conv_integer(UNSIGNED(FirstCharIndex - '1')) );

	--Buffer the keyboard data
	Process (pclk, RESET, KEYBOARD_CLK, KEYBOARD_DATA)
	begin
		if(RESET = '1') then
			DFF1 <= '0'; DFF2 <= '0'; KDI <= '0'; KCI <= '0';
		else												
			if (pclk = '1' and pclk'Event) then
				DFF1 <= KEYBOARD_DATA; KDI <= DFF1; DFF2 <= KEYBOARD_CLK; KCI <= DFF2;
			end if;
		end if;
	end process;

	--Shift Registers used to clock in scan codes from PS2--
	Process(KDI, KCI, RESET) --DFF2 carries KD and DFF4, and DFF4 carries KC
	begin																					  
		if (RESET = '1') then
			ShiftRegSig1 <= (others => '0');
			ShiftRegSig2 <= (others => '0');
		else
			if (KCI = '0' and KCI'Event) then
				ShiftRegSig1(10 downto 0) <= KDI & ShiftRegSig1(10 downto 1);
				ShiftRegSig2(10 downto 1) <= ShiftRegSig1(0) & ShiftRegSig2(10 downto 2);
			end if;
		end if;
	end process;
	
	--Reading out the scan code from the shift register and storing it
	--In the buffer when necessarry
	process(ShiftRegSig1, ShiftRegSig2, RESET, KCI)	
	begin
		if(RESET = '1')then		
			FirstFreeIndex <= (others => '0');
		else
			if(KCI'event and KCI = '1' and ShiftRegSig2(8 downto 1) = "11110000")then 				
				CharBuffer( conv_integer(UNSIGNED(FirstFreeIndex)) ) <= ShiftRegSig1(8 downto 1);				
				FirstFreeIndex <= (FirstFreeIndex + '1') AND buffer_map;
			end if;
		end if;
	end Process;

	--The read first available char process. It reads out the first available
	--char (scancode) from the FIFO buffer and increases the start counter
	--(actually this process only implements the second part, the first part
	--is done at the beginning)
	process (RESET, READ_FIRST_CHAR_STROBE)
	begin
		if (RESET = '1') then
			FirstCharIndex <= (others => '0');
		else
			if (READ_FIRST_CHAR_STROBE'event and READ_FIRST_CHAR_STROBE = '1') then
				if not (FirstFreeIndex = FirstCharIndex) then					
					FirstCharIndex <= (FirstCharIndex + '1') AND buffer_map;
				end if; 
			end if;			
		end if;
	end process;
end Behavioral;