architecture simple of comparator is
	quantity vin across p to m;
begin
	p1 : process
		constant vh : real := ABS(hys)/2.0;
		constant vl : real := -ABS(hys)/2.0;
	begin
		if vin’above(vh) then
			d <= '1' after td;
		elsif not vin’above(vl) then
			d <= '0' after td;
		end if;
		wait on vin'above(vh), vin'above(vl);
	end process;
end architecture simple;