Erik,

The classic "app-note" implementation of the i8255 doesn't use a decoder. It uses address lines as the chip selects to the i8255.

There are places, BTW, where the 8255 is still pretty cheap, and since the stopped making TTL and its scions a decade ago, when the chips are used up, they're gone forever.

A PALCE26CV12 will allow construction of an 8-bit output port with handshaking and interrupt generation, though. If you don't need the interrupt, a GAL22V10 will do the handshake and registers.

RE