Roger, I do not understand your post "the portpins are wired-and if you like" if anything they can be used in a negative wired or combination. I have used the '51 for more than 15 years and am definitely not in doubt about the ports. Yes, the pins default to ff and are thus input capable but I would NEVER rely on the default, who knows what else is going on in other areas of the code. I have many times seen a place in some code that writes e.g. 0x10 to a port in order to set a pin and then somewhere else an input on pin 2 fails. Re high impedance: yes P0 is open collector and thus a theoritical infinite impedance, but the remaining ports are not exactly low Z in their high state either.

Have fun,

Erik