> > Not fair ! ;-)  I was just busy thinking about/doing the same, on a
> > somewhat smaller scale (no keypad, no LCD. no MAX232. Requests received
> > thru RS232), using 24Cxx I2C-memory (8 to 32 (64 ?) KByte variants).

Its one of those 'very obvious' things... ;-)
It has so many applications.

> >> First, I plan to implement a very scaled down version of the DOS FAT
> system
> >> in the NVRAM.  Master file table, FAT, sectors, and no subdirectories.
> >> The user will not be aware of the storage scheme. I want to use it to
> >> facilitate memory reuse as data blocks are added, changed, or deleted.
> > Another way to link "sectors" together could ne done by adding a pointer to
>
> > ?each data-block telling where the next "sector" is.
> > By the way : with 2 (or 4) MB of space a Directory-structure would be
> handy...

That of course depends on the lookup method and even more on the size of the
individual files.
What kinda storage hardware did you have in mind for larger amounts of data
space?
A flash rom would do, but requires some extra logic for pin multiplexing...
And another issue is 'deleting' files... can a flash rom be *partially* wiped?
(in the end of course you'd get into defragmenting issues, but that's not
really a prob)

> > Warning !  DOS Standard way's to communicate thru RS-232 ("TYPE {text} >
> > COMx" or "COPY {file} COMx") do not use handshake ...  And you will need it
>
> > (I think) when up-loading something to your device.  So, the first thing to
>
> > do is to load & install a "driver" for it ....

Many terminal programs have an ASCII upload feature that allows for
configurable delays between two chars, and at the end of a line. That'd solve
that prob.
Personally, I'd be tempted to implement Xmodem/CRC. Code-wise it's peanuts,
provided you can store the data temporarily while you're receiving... it
requires 128 bytes plus a few working regs. Some PICs have enough internal RAM,
otherwise you'd need to look for something external. No big deal.
At least Xmodem is reasonably reliable, if chars get lost or scrambled the prog
will notice it.

Tell you what, if someone offers nice suggestions to the above issues, I'll
write & publish the Xmodem code!
Fair deal ;-)

Regards, Arjen.