Blinky LEDs, Knight-Rider style.

knight_rider.vhdl

--
-- Copyright (C) 2013 Chris McClelland
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU Lesser General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU Lesser General Public License for more details.
--
-- You should have received a copy of the GNU Lesser General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
--
library ieee;

use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity knight_rider is
	port(
		clk_in   : in  std_logic;
		leds_out : out std_logic_vector(4 downto 0)
	);
end entity;

architecture rtl of knight_rider is
	signal count      : unsigned(2 downto 0) := (others => '0');
	signal count_next : unsigned(2 downto 0);
begin
	-- Infer registers
	process(clk_in)
	begin
		if ( rising_edge(clk_in) ) then
			count <= count_next;
		end if;
	end process;

	-- Next state logic
	count_next <= count + 1;

	with to_integer(count) select leds_out <=
		"10000" when 0,
		"01000" when 1,
		"00100" when 2,
		"00010" when 3,
		"00001" when 4,
		"00010" when 5,
		"00100" when 6,
		"01000" when others;	
end architecture;