I am looking for a scan tool. I guess what I'm asking for is the basics. All I know is what OBD/OBD II is. What is protocol?

I want to be able to do the basic diagnostic. This is for entry level/home shop.

Is there such a scan tool that handles both OBD I and II?

__________________
'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R