3Com Courier Reference page 74

10-2 C 10: C
HAPTER ONTROLLING DATA RATES
Your software may use terms such as locked serial port (fixed rate) or
autobaud (variable rate).
To allow your modem
To change its serial port rate to match the
connection rate.
To always communicate with an attached
device at the rate at which you have set
the terminal or software, regardless of
the connection rate.
For the greatest throughput, set the serial
port to 230400, 115200, 57600, or
38400 bps for high-speed calls, and to at
least 9600 bps for 2400-bps calls.
To shift its serial port rate to a rate that
you specify using your communications
software (for example, 38.4 Kbps) when
the Courier V.Everything modem
connects in ARQ mode.
If the connection is not under error
control, the Courier V.Everything modem
behaves as if it was set to &B0 and
switches its serial port rates to match the
connection rate of each call.
To implement this feature, first set your
software to the desired rate. Then send
AT&B2&W to the modem.
The Courier V.Everything modem stores
the rate of the command in NVRA
along with the current settings. The
Courier V.Everything mode
NVRAM for the specified serial port rate
each time it makes an ARQ connection.
When saving subsequent configurations
to NVRAM, be sure your software is set to
your selected serial port rate so the
correct rate is maintained.
The serial port rate MUST be equal to or higher than the Connection rate
(&Nn).
Set the serial port
rate as
Variable
Fixed
Fixed for ARQ calls
and
Variable for non-ARQ calls when
answering only.
See Chapter 13, Handshaking, Data
Compression, and Error Control, for
more information about ARQ
checks
Command
AT&B0
AT&B1 (Default)
AT&B2