Actually the time delay is probably from the moment that the empeg provides power to the RA line, and not when the serial port is opened. GPS units use an almanac and their known location to know which satellites should be visible, and if they don't have either, they have to wait until they hear an almanac broadcast from one of the satellites - this could easily take 15-20 minutes. Some receivers allow for an almanac to be loaded into them via software which would prevent this delay, although battery backup should prevent the almanac from being lost once acquired. It is possible that one of the other pins on the 'serial' port is actually a 3-5V memory line, but YMMV.