public int getInterval ()
    {
    	int	interval = getU8 (6);
	String	type = getType ();
	boolean	highspeed = iface.getDevice ().getSpeed () == "high";

	if (type == "iso" || highspeed) {
		if ((type == "bulk" || type == "control") && interval == 0)
			/* never NAKs */ ;
		else
			interval = 1 << (interval - 1);
	}
	interval *= highspeed ? 125 : 1000;
	return interval;
    }