fenping.vhd

上个用VHDL语言写的音乐程序,希望对大家能够有帮助

library ieee;
use ieee.std_logic_1164.all;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

entity fenping is
	PORT(
		 fin		: IN	STD_LOGIC;
		f2	: OUT	STD_LOGIC
		);
end;

architecture behv of fenping is
	SIGNAL  SET 	:   STD_LOGIC;
	SIGNAL 	QN		: 	STD_LOGIC_VECTOR(21 DOWNTO 0);	   
BEGIN
											
		PROCESS (fin)				-- *** COUNTER
		BEGIN
				IF SET = '1' THEN
					QN <= "0111111111111111111111";		-- Set Counter	
				ELSIF fin'event AND fin='1' THEN
					QN <= QN - 1;		-- COUNTER - 1 
				END IF;
		END PROCESS;			

		SET <= QN(21);
		f2 <= QN(20);				-- Result Output			

end behv;