What the OP wanted was advice on making his "thingie" work, not on how to change its hardware.

At the clock rate he said he was using, it should trivially work in any of a number of ways.

It seems that every time a query of this sort comes up, everybody tells him what OTHER hardware to use, rather than telling him how he might encourage what he wants to use to work. It's like telling the guy who asks the time of day how to build a clock. When you're done, he still doesn't know the time of day.

Now, I don't know why he wants to make the hardware he's chosen work as he wants, but he's the one who's chosen it. Sure, he could make something else work, but it doesn't solve his problem, which is making THIS hardware work. However terrible the 8255 may seem to some of you to be, there have been millions of them, if not tens of millions, successfully implemented, and there's no reason why this shouldn't be workable. The 8155/56 wouldn't work any better, and I mentioned it only because it might have been a bit easier from the hardware standpoint, had he chosen it instead. It's no better than the 8255, and, it, too, doesn't solve his problem, which is making an 805x work with an 8255 at an ultra-slow rate.

RE