-- DFF modelUSE WORK.ALL;entity DFF is   generic(constant TPHLRE:TIME:=10 ns;           constant TPLH:TIME:=12 ns;	   constant TPHL:TIME:=14 ns);   port (D, clk ,reset : in BIT;  	 Q :out BIT);end DFF;architecture BEH of DFF is beginP1: process(clk)variable Q_TEM:BIT:='0';	begin	if (clk'event and clk='1') then	  if (Q_TEM='0' and D='1') then 	    Q <=D after TPLH;	     elsif (Q_TEM='1' and D='0') then	      Q <= D after TPHL;	       else 	        Q <=D;           end if;           Q_TEM := D;	end if;    end process P1;end BEH;