A lot of questions are posted - almost daily - related to the 8255, apparently by 'newcomers' who have little or no experience with using this part. One of the most frequently given answers to any of these questions is: don't use it, it's old. In the FAQ "How do I interface an 8255 to an 8052", Steve Tyler gives a shiny example.

From the perspective of the poster, this may be the worst answer one could expect. It not only doesn't solve his or her problem, but also indicates the road back to the drawingboard: think again and change your design.

Two things come to my mind here. First of all, there are still a lot of suppliers that 'forget' to mention that this part is - or will in the near future become - obsolete, especially those that can be counted to the 'hobby' suppliers. Of course, it is up to the designer to determine if a particular part should be used or not, but making the right decision requires a good insight in end-of-life data. Most manufacturers make this data available on their web-sites, but sometimes it is hard to find. Similarly, a part that is not listed as being obsolete may still be awfully difficult to get: there's a lot of 74LS- series (for instance 4-bit counters, 4-bit comparators and even some buffers/drivers) that according to the books are still available, but in real life appear to be dead, at least at the moment one needs them.

Secondly, for low volume designs I don't see any real problem in using parts like the 8255. Again, they are still available from a number of sources and especially for newcomers are fun to play with so as to learn how to use I/O in general and in combination with the 8052 in particular. There's a lot of information to be found all over the internet on how to - and how not to - use it, which again makes it an ideal beginners device.

The point that I would like to make here is that a simple "don't use it" answer is a little short-sighted. It's good to point out that a particular part is not or less suitable for large volume designs, but that should be first line of the answer to the question and not the whole answer.