Yes, of course you can have 256 bytes of some thing, using only port0, but how to avoid the latch?
Use the upper half of the address (OH, now I see where your 256 byte gap comes from). It might, indeed be better to keep the latch and use P0 only and then insert the P2Mirror as upper address, then you could use P2 as I/O. Anyhow, why does he worry about memory mapping, he has 32 pins.

Hilsen fra den anden side dammen

Erik