Ah, one of my pet projects at our carrier.....
It is EXTREMELY IMPORTANT to have a direct GPS feed to one's EGPWS. Even an FMS with GPS position input/feed will not provide maximum protection.
Do a search on this forum or read:
http://www.flightsafety.org/asw/aug0...g08_p18-20.pdf
This article was written by Mr. Don Bateman, a gentleman who all professional pilots owe a debt of gratitude....he is the person who invented GPWS and EGPWS.
Flight Safety Foundation 1997 AW&ST Award Citation for Bateman