8-2CHAPTER 8: CONTROLLING DATA RATES

Your software may use terms such as locked serial port (fixed rate) or autobaud (variable rate).

To allow your modem

Set the serial port

Command

rate as

 

 

 

To change its serial port rate to match the

Variable

AT&B0

connection rate.

 

 

 

 

 

To always communicate with an attached

Fixed

AT&B1 (Default)

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 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

Fixed for ARQ calls

AT&B2

you specify using your communications

 

 

software (for example, 38.4 Kbps) when

 

 

the Business Modem connects in ARQ

 

 

mode.

 

 

If the connection is not under error

and

 

 

 

control, the Business 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 Business Modem stores the rate of the command in NVRAM along with the current settings. The Business Modem checks 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.

Variable for non-ARQ calls when answering only.

See Chapter 13, Handshaking, Data Compression, and Error Control, for more information about ARQ

The serial port rate MUST be equal to or higher than the Connection rate (&Nn).

Page 66
Image 66
3Com 56K manual To allow your modem Set the serial port Command Rate as, AT&B0, AT&B2