-----------------------------------------------------------------
-- key.vhd
-- Christopher Kowalski
--
-- This code recieves the input from a AT keyboard.  This is usefull
-- for hooking up a PS2 keyboard to the Altera UP1 board.
-- Vector. 
-- The character entered on the keyboard must be read before another
-- is entered or the incorret value will be read.  This should be OK
-- is cases where the typist can not type faster then the clock rate
-- rate of the system, in this case arount 25 MHZ.
-- The start bit, stop bit, and parity bit are not stored.
-- 

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity key is
	port(keyboard,
		reset,
		keyclock	: in std_logic;
		scancode 	: out std_logic_vector(7 downto 0);
		gotcode		: out std_logic);
end key;

architecture behavioural of key is

	-- declare internal signals
		
begin

		
	scancoder : process (keyclock, reset) is

	-- process variable
	variable count:natural range 0 to 10;
	variable index:natural range 0 to 7;
	
	begin
		if reset = '1' then
			count:= 0;
			gotcode <= '0';
		elsif falling_edge(keyclock) then
			if count = 10 then
				count:= 0;
			elsif count = 9 then
				count:= (count +1);
				gotcode <= '1';
			elsif count = 0 then
				count:= (count + 1);
				gotcode <= '0';
			else
			index:= (count-1);
			scancode(index) <= keyboard;
			count:= (count + 1);

			end if;
		end if;

	end process scancoder;
end behavioural;