BGS2T AT Command Set
1.7 Unsolicited Result Code Presentation
BGS2T_ATC_V01.301 Page 28 of 554 1/31/12
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1.7 Unsolicited Result Code Presentation
URC stands for Unsolicited Result Code and is a report message issued by the ME without being requested by
the TE, i.e. an URC is issued automatically when a certain event occurs. Hence, an URC is not issued as part of
the response related to an executed AT command.
Typical events leading to URCs are incoming calls ("RING"), waiting calls, received short messages, changes in
temperature, network registration etc.
For most of these messages, the ME needs to be configured whether or not to send a URC. Descriptions of these
URCs are provided with the associated AT command. URCs which are not user definable are described in Sec-
tion 1.7.1, Common URCs. A summary of all URCs can be found in Section 19.7, Summary of Unsolicited
Result Codes (URC).
To announce a pending URC transmission the ME will do the following:
• The ME activates its RING line (logic "1") for 1 second, i.e. the RING line changes to the physical "Low" level.
This allows the TE to stay in power saving mode until a ME related event requests service.
If several URCs occur coincidently or in quick succession each URC triggers the RING line independently,
although the line will not be deactivated between each URC. As a result, the RING line may stay low for more
than 1 second.
If an incoming call is answered within less than 1 second (with ATA or if autoanswering is set to ATS0=1) than
the RING line will be deactivated earlier.
The "^SHUTDOWN" URC will not activate the RING line.
• If the AT command interface is busy a "BREAK" will be sent immediately but the URC will not be issued until
the line is free. This may happen if the URC is pending in the following cases:
- During the processing of an AT command (i.e. the time after the TE echoes back the first character "A" of
an AT command just sent by itself until the ME responds with "OK" or "ERROR").
- During a data call.
Please note that AT command settings may be necessary to enable in-band signaling, e.g. refer to AT+CMER
or AT+CNMI.
It is strongly recommended to use the multiplex mode to map logical communication channels onto the serial line
of the BGS2T, for details refer to [3] and AT command AT+CMUX. Doing so it is possible to use one channel to
still process URCs while having a data call active on another.
For most of these messages, the ME needs to be configured whether or not to send an URC. Depending on the
AT command, the URC presentation mode can be saved to the user defined profile (see AT&W), or needs to be
activated every time you reboot the ME. Several URCs are not user definable, such as "^SYSSTART", "^SYS-
START <text>", "^SHUTDOWN" and the Fax Class 2 URCs listed in Section 12.1, FAX parameters.
If autobauding is enabled (as factory default mode or set with AT+IPR=0), URCs generated after restart will be
output with 57600 bps until the ME has detected the current bit rate. The URCs "^SYSSTART", "^SYSSTART
<text>", howeve
r, are not presented at all. For details please refer to Section 4.7.1, Autobauding. To avoid prob-
lems we recommend to configure a fixed bit rate rather than using autobauding.
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