Hi everyone - thanks for all the help :-)

From what I can see - since I am executing code from external flash I'm
going to have conflicts with writing data to Port 0 (I only ever want to
output to it) and getting the next instructions from flash?

ALE is connected to two latches (74HCT373s) one for RAM/FLASH access and
one for the 12bit DAC.

The chip-enable of the DAC-latch is ANDed with ALE and Y3 of my decoder.

If say I do something like (running in external flash) :

setb P1.1
setb P1.2
clr P1.3 ;; set Y3
mov dptr,dacvalue ;; place bottom byte of dacvalue into data latch
mov @dptr,a

will this not cause conflicts on Port0?

Is there a standard circuit layout for using external flash, ram, accessing
devices via Port0? (All pins on ports 1 & 3 are already in use).

I'm worried that our hardware as currently configured will not give me all
the access to devices I need.

(Maybe I should go back to using Motorola 68000/PowerPC chips!)

Kev