MC55 AT Command Set
4.7 AT+IPR s
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MC55_ATC_V01.05 Page 98 of 469 2/10/04
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4.7.1 Autobauding
To take advantage of autobaud mode specific attention must be paid to the f ollowing requirements:
• Synchronization between DTE and DCE
Ensure that DTE and DCE are correctly synchronized and the bitrate used by the DTE is detected by the DCE
(ME). To allow the bitrate to be synchronized simply use an "AT" or "at" string. This is necessary
- after you have activated autobauding
- when you start up the GSM engine while autobauding is enabled. It is recommen ded to wait 3 to 5 seconds
before sending the first AT character. Otherwise undefined characters migh t be returned.
• Autobauding and autoanswer mode
If you want to use autobauding and autoanswer at the same time, you can easily enable the DTE-DCE syn-
chronization, when you activate autobauding first and then con figure the autoanswer mode (ATS0 not equal
to 0).
The most recently detected baudrate cannot be stored when the GSM engine is powered down. After restart,
the ME will therefore use 57600bps by default, until the first AT character was tran smitted and the baudrate
was correctly detected (e.g. to send URCs). This should be taken into account when ATS0 is stored to the
user profile (see AT&W) and the ME is restarted if set to autobauding.
• Restrictions on autobauding operation
- The serial interface has to be operated at 8 data bits, no parity and 1 stop bit (this is the factory setting).
- The command A/ cannot be used.
- Only the strings "AT" or "at" can be detected (neither "At" nor "aT").
- The URCs "^SYSSTART", "^SYSSTART ALARM MODE" and "^SYSSTART CHARGE-ONLY MODE" are
not indicated when you start up the ME while autobauding is enabled. This is due to the fact that the new
bitrate is not detected unless DTE and DCE are correctly synchronized as d escribed above.
- Any other URC that may be issued before the ME detects the new bitrate (by receiving the firs t AT com-
mand string) will be sent at the previous bitrate (57600bps after power up).
- It is not recommended to switch to autobauding from a bitrate that cannot be de tected by the the autobaud
mechanism (e.g. 300bps). Responses to AT+IPR=0 and any commands o n the same line might be cor-
rupted.
- When entering several AT commands on the same line, conside r the requirements described above.
• Autobauding and bitrate after restart
The most recently detected bitrate cannot be stored when the ME is powered down (with AT^SMSO). There-
fore, the ME will use 57600 bps by default, until the first AT character was transmitted and the bitrate was
correctly detected.
For example, URCs generated after restart will be output with 57600 bps. The same applies to auto -answer
calls if SIM PIN1 authentication is done automatically and autoanswer mode (see ATS0) is enabled in the user
profile stored with AT&W.
• Autobauding and multiplex mode
If autobauding is active you cannot switch to multiplex mode (see AT+CMUX ).