3 AT Commands
$Rn Retransmit Count
n = 0 or 1 Default: $R0
If errors are received during a reliable connection, the modem
$R0 causes the modem to disconnect if the same block of data is
$R1 causes the modem to disable the retransmit counter, so that the modem keeps trying to send data and will not abort, no matter how many times the same block is resent. Type AT$R0 to disconnect the modem if all attempts to
Speed Conversion Commands
Speed conversion allows the MT3334HD8 to communicate at a fixed speed through the serial port while communicating at an independent speed over the online communications link.
Speed conversion is necessary for data compression, since data compression requires data to be sent from the computer to the modem at a rate up to four times faster than the modem’s transmission speed.
Speed conversion is also useful for an auto answer modem connected to a computer that does not have auto baud capability, since the computer must be set at a fixed baud rate regardless of the speed at which the modem communicates over the phone line.
$BAn Baud Adjust
n = 0 or 1 Default: $BA0
Even though the term “baud adjust” sounds like it should mean the same thing as “speed conversion,” it actually means the opposite. Turning baud adjust off turns speed conversion on; turning baud adjust on turns speed conversion off.
When baud adjust is on, the modem matches its
When speed conversion is on, the modem does not adjust its speed at the serial port to match its transmission speed. Serial port speed and transmission speed can therefore be set independently. Speed conversion is necessary for a high speed modem that is connected to a limited speed serial port.
$BA0 turns baud adjust off and speed conversion on.
$BA1 turns baud adjust on and speed conversion off.
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