http://www.innovationfirst.com/FIRST...sersManual.pdf
Each port, as said above, has 4 analog inputs (0-5V) and 4 digital inputs (on/off).
The pinouts for the ports start on page 14 in the link above. The function isn't set in stone, because it can be used for anything really. You just gotta program it different then.
If you run out of switches you can always start using analog inputs.... You'll just have two settings when you program it: 0 or 255.