count4.vhd

实现了16*16点阵上的三色显示的弹球游戏

library ieee;
use ieee.std_logic_1164.all;
entity count4 is
	port(clk:in std_logic;
		--en:in std_logic;
		co:out std_logic;
		qcnt:buffer std_logic_vector(1 downto 0));
end count4;

architecture main of count4 is
	shared variable i:integer range 0 to 1:=0;
	signal count:std_logic_vector(1 downto 0):=(others =>'0');
	begin
		qcnt<=count;
		co<=qcnt(0) and qcnt(1);
		process(clk)
		begin
			if(rising_edge(clk)) then
				count(i)<=not count(i);
				i:=1-i;
				if(count(1)='1') and (count(0)='1')then
					i:=0;
					count<="00";
				end if;
			end if;
		end process;
	end main;