statetrans.vhd

电子打铃器 在max plus 2 下编译通过

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

ENTITY statetrans IS
	PORT(
		X		: IN	STD_LOGIC;
		sel: OUT STD_LOGIC_VECTOR(3 DOWNTO 0));
END statetrans;

ARCHITECTURE a OF statetrans IS
	ATTRIBUTE ENUM_ENCODING : string;
	TYPE state IS(s0,s1,s2,s3);
	ATTRIBUTE ENUM_ENCODING OF 
	State: TYPE is " 00 01 11 10";
	SIGNAL ps : state;
	SIGNAL ns : state;

BEGIN
	
	PROCESS (X)
	BEGIN
		IF X'event and X='1' THEN
		    ps<=ns;
		END IF;
		
	END PROCESS ;
	
	
	PROCESS (ps)
		BEGIN
			CASE ps IS
				WHEN s0 =>
				    ns<=s1;
										--