PQ>    Ahhh, I see. Right. I need to access the DSP chip on my modem. But
I'm not at all familiar with your modem, or the DSP chip on it, but
generally speaking, you _don't_ access it.  Modems and their DSPs are
hardwired to do a specific thing, emulate a typical UART and do the
modem functions.
Of course, yours may be different.  As I said, I don't have any
experience with it.
PQ>to get from the developers if possible. The idea is that I would like to
PQ>make a Dos driver for the modem. To do this I would need to know how
PQ>one would normally access a serial port down to the IN's & OUT's and
PQ>How I would be able to emulate a serial port. Processing the questions
PQ>and outputting the answers, as if a 16550 Fifo.
  I'm really having problems understand the what and why of what
you are wanting to do.
At times, it sounds like you are wanting to totally replace the modem
code with your own, but at others, just simply write a DOS driver to
access the already existing modem & software.
Simply accessing it would be done the normal method.  You wouldn't have
to worry about how the DSP emulates the UART in its own software.
PQ>set the modem up, open the port, etc.. I have read the part of
PQ>Ralph Brown's Interrupt list about ports, but I soon lost the
That really isn't too relevant about serial I/O.  Although it can give
some register level details, there are too many other
programming details.
PQ>plot. Do I need to get hold of a technical specification of the chip?
No, you shouldn't need any real technical specs.  Well, beyond knowing
the layout of the UART registers and such.
Frankly, I don't know much about the low level details of serial I/O and
uarts.  That's what serial I/O libraries and canned routines, etc. are
for.  I think that all I have are either precompiled libraries or C
source.
If you have internet access, I'd suggest taking a look at the various C
source collections (like on Simtel, etc.).  You might also want to
browse at the free source for the HS/Link xfer protocol.  The author has
made it public.
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