i speak english little.
i can connect external modem to 8051

first you must read at command

exsample
atdt 3232222 atdt is construction
control modem call number 3232222

second you must read registor s0-s7
to set recive auto
thrid you must simulate cts rts and you can send data to serial port


this all example

this pc you use hyperterminal of windows98

and connect to com at modem connected
and type this

atdt2332232

and press enter
after you press enter you know.


i teach 8051 with c of keil6.10
and i employee to make hardware

http://go.to/c51