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PN 88300150
Note:
Do not be misled by the meaning of turning Baud Adjust "off", even though the term "Baud
Adjust" sounds like it should mean the same thing as "Speed Conversion". It actually means the opposite:
Turn Baud Adjust off to turn Speed Conversion on.
Turn Baud Adjust on to turn Speed Conversion off.
To turn Baud Adjust on (and Speed Conversion off), enter AT$BA1 and hit ENTER. The
modem will now match its RS232C speed to that of the computer, and will adjust its speed to
any changes in the computer's speed in the originate mode, or to the speed of the originating
modem when it's in the answer mode. With baud adjust on, the speed at which the modem
communicates over the phone line is always be the same as the speed at which it
communicates via its RS232C serial port.
$MB
Modem Baud Rate
The $MB command presets the MT2834MR's transmission baud rate for originate operations,
(i.e., the speed of the modem's transmissions over the telephone lines when originating a
call). With speed conversion, this transmission speed can be a different baud rate than the
serial port speed.
When the MT2834MR receives (answers) a call from another modem, it automatically
switches its phone line transmission baud rate to match the calling modem. However, if the
MT2834MR originates a call to another modem that is unable to connect at the baud rate of
the MT2834MR, the MT2834MR will automatically drop to a lower baud rate in an attempt to
match the speed of that modem. For example, if the MT2834MR is set for 33,600 bps and
calls another modem that has a top speed of 9600 bps, it will drop to 9600 bps.
To set the Modem Baud Rate, type AT$MBn, where n can be 75 (in ITU-T V.23 mode) 300,
1200, 2400, 4800, 9600, 14,400, 19,200, 24,000, 28,800, or 33,600 bps as listed below:
AT$MB75 = ITU-T V.23
AT$MB300 = 300 bps
AT$MB1200 = 1200 bps
AT$MB2400 = 2400 bps
AT$MB4800 = 4800 bps
AT$MB9600 = 9600 bps
AT$MB14400 = 14400 bps
AT$MB19200 = 19200 bps
AT$MB24000 = 24000 bps
AT$MB28800 = 28800 bps
AT$MB33600 = 33600 bps
The factory default setting is 33,600 bps.
If Baud Adjust is on ($BA1), speed conversion is off, as we discussed earlier. This means
that the $MB command is also ignored, since it is part of speed conversion.
$SB
Serial Port Baud Rate
The $SB command presets the speed of the MT2834MR's serial (RS232C) port, in both the
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
$BA command.
In addition to the MT2834MR's serial port speed being set by this command, the default
speed at which the modem issues Command mode responses (result codes) is also set.
The MT2834MR will accept AT commands at any speed, regardless of the speed preset by
the $SB command. If the modem receives such a command at a speed that is different than
the preset speed, the modem will switch its serial port baud rate to match the new AT
4/3/01
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