MT3334HD8 User Guide
$MBn Modem Baud Rate
n = speed in bits per second Default: $MB33600
The $MB command sets a modem’s initial transmission speed for originate mode. In V.32 mode (9600 bps), it also sets the transmission speed for answer mode. With speed conversion on, this transmission speed can be different from the serial port speed.
When the modem answers a call from another modem, it automatically switches its transmission speed to match the calling modem. However, if the MT3334HD8 originates a call to another modem that is unable to connect at the transmission speed of the MT3334HD8, the MT3334HD8 will automatically drop to a lower speed in an attempt to match the speed of the other modem.
For example, if the MT3334HD8 is set for 14,400 bps and calls another modem that has a top speed of 2400 bps, it will drop to 2400 bps.
$MB75 | |
$MB300 | 300 bps |
$MB1200 | 1200 bps |
$MB2400 | 2400 bps |
$MB4800 | 4800 bps |
$MB7200 | 7200 bps |
$MB9600 | 9600 bps |
$MB12000 | 12,000 bps |
$MB14400 | 14,400 bps |
$MB16800 | 16,800 bps |
$MB19200 | 19,200 bps |
$MB28800 | 28,800 bps |
$MB33600 | 33,600 bps (factory default) |
Speed conversion must be on for this command to work. If baud adjust is on ($BA1), speed conversion is off and a modem baud rate command will be ignored.
The S48 register also can affect maximum transmission speed. See Chapter 4.
$SBn Serial Port Baud Rate
n = speed
Default: $SB57600
The $SB command sets the speed of the MT3334HD8’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 MT3334HD8 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.
34 | CommPlete Communications Server |
