provided that it can be made to work!

Though I can't wire a 250-ic circuit from memory any more, some folks think I still work pretty much as well as I did when I was quite a bit younger. I'm still here, though, while the 8155 and 8255 aren't as avaiable.

If I were to fire up my old S-100-bus computer to run payroll & accounting, it would print the checks, issue the invoices, etc, just as it did in the late '70's. In fact, if anything, though it wouldn't have the (appearance over substance) "cool" displays, it would do the stuff it's supposed to do as well as the latest Windows stuff does, only in less time.

Likewise, if what the 8255, or the 8155/56 worked adequately back then, it would still work adequately now.

I've yet to see even one "solution" that replaces an 8255 or, for that matter, an 8155, that does better than the original. What do think that tells the "young whippersnappers" who are learning the trade now?

As for the 8155, the app-notes used the nRD and nWR lines as labelled, and used an address line for nM/IO and for nCS. That required no external logic.

BTW, the EDIF standard, which came out in the late '70's, makes "special" characters illegal in signal names, so people who used EDIF quickly learned to use a leading 'n' to identify active-low signals. Slash, asterisk, and exclamation point were all illegal under EDIF.

RE