It's not mentioned in my manual for the BOB rev. 4.4, that any of the port got specific inputs capabilities. all are connected through a diode and a TLP293-4 Optocoupler. Some Pins are configurable as NPN and PNP depends on the Jumper, so Anode and Cathode (LED) of the TLP293 input needs to be connected either +VSS or Gnd, depends on the jumper settings on Port3. 10,11,12,13,15. Maybe you got a different BOB?