I don't think you're going to get a DS3100 to drive a 14400 modem "reliably"
unless said modem is comfortable running at 19800bps.  Hey, if you want to
talk to a DZ11...

You might be able to pound the driver to do hardware flow control right,
but I'd still be surprised to see a 3100 talk to a serial port at 9600 while
doing anything else -- and unless the UART in your modem can handle 3% fuzz
in the inbound data rate, you're not going to get anywhere at 19.2, though as
I recall that goddamned DZ11-on-a-chip can sometimes, if you're lucky,
recieve okay at 19.2 -- but don't count on it.

Thor