Hi Matt,

it looks like the standard development board,
with using an EEPROM instead of SRAM.

But I see nothing to do for the 74154 and an extra pin ?

I connected /WR of the upper 32kB to /WR of the 8031
and /OE with /PSEN and CE to A15 (/CE to GND).
The lower EEPROM must be connected with
/WR to VCC and /CE to A15 (CE to VCC).

So the upper 32kB are writeable with MOVX and
readable with MOVC.
And the lower 32kB data space are still available for
data SRAM and memory mapped I/O
(read, write with MOVX).

I know not, if the AT28C256 can be write protected.
If it can do, I suggest using this 3 byte sequence.
Otherwise data can be lost during power up or down.


Peter