What about WHERE you get the 8255? What about the performance limitations? Lots of instructors haven't yet learned that the 8255 was obsolete and no longer manufactured over 15 years ago and hasn't become more available since then. There are still many of them available, often as surplus, or as defective floor sweepings, or otherwise rejected components.

First of all, however, in answer to your question, no pin on any device of this type can be both input and output at the same time.

If you want to know why some people think the 8255 a poor choice, I'm sure there are lots of opinions available here, though I'd also guess that most are from people who have no real experience with these very flexible and useful devices. Unfortunately, they don't drive much, and take up lots of space. You can do the same job somewhat better if you build your own ports using TTL-workalike CMOS logic. An exact replica of the 8255 with all its options would be a big job, but since most applications don't require all the functions, you can probably manage this by making the configuration choices ahead of time.

If you need lots of current and lots of bits, I'd recommend you look for a datasheet for the 74BCT2424, which is no longer made but which, IIRC, could sink 64mA and would demultiplex into a 32-bit path from a 16-bit path. Two of these could be driven from a synthesized 16-bit path, and provide the signals to which I think you refer. It's up to you, of course, since you could also accomplish the same thing with a CPLD.

RE