Specifications

Chapter 4 – Serial Interface Control Commands
Multi-Tech Systems, Inc. AT Commands for EDGE (E1) Modems (S000474A) 71
4.9.1 Autobauding
To take advantage of autobaud mode specific attention must be paid to the following requirements:
• Synchronization between TE and TA:
Ensure that TE and TA are correctly synchronized and the bit rate used by the TE is detected by the TA.
To allow the bit rate to be synchronized simply use an "AT" or "at" string. This is necessary when you start
up the ME while autobauding is enabled. It is recommended to wait 3 to 5 seconds before sending the first
AT character. Otherwise undefined characters might be returned.
• Restrictions on Autobauding Operation:
∗ If autobaud mode is enabled, then autobauding does not take effect immediately after the write
command AT+IPR=0 ends. Instead the old bit rate remains active. The autobaud mode is activated
with the next restart of the TA. This is indicated by any following AT+IPR read command which still
returns the old bit rate until the next restart.
Before you activate autobauding switch on the local echo with ATE1. To verify if autobauding has
become effective after restart first send only the characters "AT" or "at" and check that they are
echoed within 100ms. In some cases you may need to repeat this several times, until both characters
are properly echoed within 100ms.
Please note that after the successful synchronization between TE and TA the autobauding
mechanism of the TA is deactivated until next restart. So, while autobauding is enabled you will need
to restart the TA each time after changing the bit rate of the TE.
∗ The TA cannot distinguish between 1 and 2 stop bits. Therefore, 1 stop bit will be used by the TA.
∗ The command A/ cannot be used.
∗ Only the first "AT" or "at" after restart of the module can be detected (neither "At" nor "aT"). This
means that all the AT commands have to use the same bit rate and frame type.
• Autobauding and Bit Rate after Restart.
Unless the bit rate is determined, the following constraints apply:
∗ An incoming CSD call or a network initiated GPRS request cannot be accepted. This must be taken
into account when autobauding and autoanswer mode (ATS0 ≠’ 0) are enabled at the same time,
especially if SIM PIN 1 authentication is done automatically and the setting ATS0 ≠’ 0 is stored to the
user profile with AT&W.
∗ Until the bit rate is found, URCs generated after restart will be output at 115200 bps. This applies only
to user defined URCs, such as “+CREG”, “CCWA”, “^SCKS” etc. The URCs “^SYSSTART” and
“^SYSSTART AIRPLANE MODE”will not be indicated when autobauding is enabled.
Notes:
• To avoid any problems caused by undetermined bit rates in the direction from TA to TE we strongly
recommend to configure a fixed bit rate rather than autobauding.
• This command is not PIN protected.
• This command is supported in airplane mode.