Hi Mr J. There must have been a confusion. I never say that buffering is a bad option. That will always work. All I say is that if you connect both pins togather, it will not harm!

The only assumption that if one of the device is faulty, is a rare assumption. Suppose one device is faulty. It might start driving the output, the other would still be in the input mode. Since the pins are pulled up, I don't think it will damage it instantaneously. I think the person using it will realize that before using it too much (which might damage it). I don't know the value of the internal pull-up. If it is enough to support a current which would flow if the pin is shorted to ground, it will not be damaged.

BTW I tried this thing. Things are not so easily damaged as it is perceived. I programmed the 89C52 to read the status of a port pin and light up an LED. I directly shorted that pin to ground. Di it for a minute or two. And did quite a number of runs. It didnot damage it.

Bottom line. If the Stefan wants to play safe, follow what Mr J said. Use a buffer. If you wanna live on the line like me,...you know what to do... :-)

Regards
Aman