The first thing a teacher has to do is to answer the quesiton before him. A preacher, OTOH, takes every opportunity to promote his own point of view, irresepective of whether anyone wants to hear it.

Unfortunately, the REAL teachers out there use textbooks, and textbooks often show old technology. That's probably where much of the student-interest in the i8255 orginates. In all the discussion, pro or con, regarding the i8255, I've not seen one line that refers to the timing requirements. Clearly, if one is to attach the thing as a memory-mapped peripheral, it has to be done with consideration of the timing requirements. If it's to be attached via I/O then all bets are off, of course, but it's hard for most 805x's to violate the timing requirements. Now, it's not impossible, especially with the really fast parts.

Note that you didn't address the matter of WHAT an 8 MHz CPU is vs WHAT a 12 MHz CPU is and how that relates to interfacing an 8255 to either one.

The datasheet I'm looking at shows that, for the faster (-5) version, a 300 ns read or write pulse is required. ISTR that the MCU in question has no difficulty in producing that width or more. You'll have to look at setup and hold times to figure out whether THIS MCU will provide the necessary pulse widths, setup times, and hold times.

If we're trying to teach folks something, shouldn't we focus on the details like the timing, rather than preaching about brand names?

RE