alert.tdf

几个VHDL实现的源程序及其代码

SUBDESIGN alert
(
   clk,dain[6..0]		:INPUT;
   speak,lamp[2..0]		:OUTPUT;
)

VARIABLE
   s:	DFF;
   ss:	MACHINE OF BITS (lamp[2..0])
        WITH STATES(
              s0=B"000",
              s1=B"001",
 			  s2=B"010",
 			  s3=B"100");
BEGIN
   ss.clk=clk;

   IF(dain[]==0) THEN
      s.clk=clk;
      s.d=!s.q;
      speak=s.q;
      CASE ss IS
        WHEN s0 =>
				ss=s1;
		WHEN s1 =>
				ss=s2;	  			
		WHEN s2 =>
				ss=s3;
		WHEN s3 =>
				ss=s1;
		WHEN OTHERS =>
 				ss=s0;
	  END CASE;
   ELSE
      ss=s0;
      speak=GND;
   END IF;
END;