Specifications

Chapter 1 – Introduction

Multi-Tech Systems, Inc. AT Commands for EDGE (E1) Modems (S000474A) 16

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; e.g., a URC is issued automatically when a certain event occurs. Hence, a 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.

A list of all URCs can be found in Section 20.7, 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 one second; i.e., the line changes to physical “Low”

level. This allows the TE to stay in power saving mode until an ME-related event requests service.

If several URCs occur coincidentally or in quick succession, each URC triggers the RING line

independently, although the line will not be activated between each URC. As a result, the RING line

may stay low for more than one second.

If an incoming call is answered within less than one second (with ATA or if auto answering is set to

ATSO=1, then 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.

For most of these messages, the ME needs to be configured whether or not to send a 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”, “^SYSSTART <text>”, “^SHUTDOWN”.

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>”, however, are not presented at all. For details please refer to Section 4.9.1, Autobauding. To avoid

problems we recommend to configure a fixed bit rate rather than using autobauding.

1.8 Errors and Messages

The command result codes “+CME ERROR: <err>” and “+CMS ERROR: <err>” indicate errors related to

mobile equipment or network functionality.

The format of <err> can be either numeric or verbose and is selectable via AT+CMEE.

A result error code terminates the execution of the command and prevents the execution of all remaining

commands that may follow on the same command line. If so, neither “ERROR” nor “OK” result codes are

returned for these commands. A 30 seconds timeout will deliver “ERROR” when the input of a command is

not complete.

Using the wrong command syntax may result in errors: For example, using the execute command syntax

although the command has no execute format, causes “ERROR” to be returned. Likewise, using the write

command syntax although the command has no write format causes “+CME ERROR: <err>” to be returned.