On Tue, Nov 12, 2002 at 07:38:00PM -0500, Thomas Miller wrote:
> Well, my z50 works with an external modem connected to the serial port.
> It also works with a pcmcia modem.  I don't understand why it would need
> anything much different to work with the internal modem.  Could you please
> explain to me in a little more detail what might need to be done to get
> the internal modem working?  

problem is, it's probably not a real modem. (i.e. it's not a serial device
in the normal sense, which handles all the translation of serial signals to
tones on the phone, on its own). it's probably a specialized DSP (Digital
Signal Processor - just like a sound card), which is programmed directly by
the driver running on the CPU. 

so you need to know exactly how to program this particular model of DSP
(which is eminently more complex than a serial driver).

building 'soft modems' this way makes the device less expensive, since
there's less physical hardware needed; and even tho it loads the CPU down
far more than a hardware modem would, CPU is cheap these days, so it's a
worthwhile tradeoff for most purposes.

on the downside; you need to have a great degree of access to the chip's
design, in order to get anything meaningful out of it. companies are
notoriously unwilling to give you this, unless you pay them lots of money
and promise not to tell anyone else.

Carl Soderstrom.
-- 
Systems Administrator
Real-Time Enterprises
www.real-time.com