input.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 input is
	port(keyIn:in std_logic;
		clk:in std_logic;
		keyOut:out std_logic);
end input;

architecture main of input is
	signal a,b,c,d:std_logic;
	begin
		a<=(not keyIn) nand b;
		b<=a nand (not c);
		keyOut<=c and (not d);
		process(clk)
		begin
			if(falling_edge(clk)) then
				c<=a;
				d<=c;
			end if;
		end process;
	end main;