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Chapter 3 - AT Commands
$SBn Serial Port Baud Rate
n = speed
Default: $SB57600
The $SB command sets the speed of the MT2834MR6’s serial port in both originate and
answer modes. Speed conversion allows you to set this serial port baud rate at a fixed
speed of up to 115,200 bps, regardless of the modem’s transmission speed setting.
For this command to work, the modem’s baud adjust feature must first be turned off with the
$BA0 command. When baud adjust is on, as soon as the modem receives its first AT
command, it automatically adjusts its serial port baud rate to match the speed of the
computer or terminal to which it is connected. However, in applications such as automatic
answer, the modem may not receive AT commands. In this case it is helpful to be able to
preset the serial port baud rate with the $SB command.
In addition to setting the modem’s serial port speed, this command sets the speed at which
the modem issues command mode responses (result codes).
The MT2834MR6 accepts AT commands at any speed, regardless of the speed preset by
the $SB command. If the modem receives a command at a speed different from the preset
speed, the modem switches its serial port baud rate to match the new command speed,
even though the baud rate value stored by the $SB command remains the same. This
provides you with a convenient way to switch the serial port speed while still making it easy
to automatically return to the original speed the next time the modem is powered up or
reset. $SB300 300 bps $SB1200 1200 bps
$SB2400 2400 bps $SB4800 4800 bps
$SB9600 9600 bps $SB19200 19,200 bps
$SB38400 38,400 bps $SB57600 57,600 bps
$SB115200 115,200 bps ( default)