Specifications

Chapter 11 – GPRS Commands
Multi-Tech Systems, Inc. AT Commands for EDGE Modems (S000371B) 147
11.5 AT+CGDATA Enter Data State
Description: The test command is used for requesting information on the supported layer 2 protocols to be
used between the TE and MT.
The write command causes the MT to perform all actions which are necessary to establish
communication between the TE and the network using one or more GPRS PDP types. This may
include performing a GPRS attach and one or more PDP context activations. Commands
following the AT+CGDATA command in the AT command line will not be processed by the MT.
If no <cid> is given or if there is no matching context definition, the MT will attempt to activate the
context with PDP type IP and all other context parameters set to their default values (see
AT+CGDCONT, AT+CGQREQ, AT+CGQMIN).
If the <L2P> parameter is omitted, the layer 2 protocol is unspecified and PPP will be used.
If the write command is successful, the MT issues the intermediate result code CONNECT and
enters V.250 online data state.
After data transfer is complete and the layer 2 protocol termination procedure has completed
successfully, the command state is reentered and the MT returns the final result code OK.
If the <L2P> parameter value is unacceptable to the MT, the MT returns ERROR or +CME
ERROR.
In the event of erroneous termination or a failure to start up, the command state is reentered and
the MT returns NO CARRIER, or if enabled +CME ERROR.
Test Command Syntax: AT+CGDATA=?
Response: +CGDATA: (list of supported <L2P>s)
OK
Write Command Syntax: AT+CGDATA=[<L2P>[, <cid>[, <cid>[,... ]]]]
Response: CONNECT
NO CARRIER
ERROR
+CME ERROR
Parameter Descriptions:
<L2P>
Layer 2 protocol to be used between the TE and MT.
“PPP“ layer 2 protocol PPP. Default.
<cid>
Parameter specifies a particular PDP context definition. The parameter is local to the TE-MT interface and is
used in other PDP context-related commands.
1...2
Notes:
• If the MT is in dedicated mode, write command returns “+CME ERROR: operation temporary not allowed”.
• It is possible to leave the GPRS data mode and enter the command mode by using the V.250 command +++.
By using the command AT+CGDATA again, the data mode is reentered. Which context is used to return to data
mode, depends on the supplied parameter <cid>.
If no <cid> is specified, this is equivalent to using the V.250 command ATO, which is usable for GPRS
connections too. In this case the first context will be used, which is active and already in data mode since it has
been activated.
It is possible to use AT+CGDATA to enter the data mode for a context, which is not yet in data mode since it has
been activated. With ATO this is not possible.
11.5.1 Automatic Deactivation of PDP Context During Dial-up PPP
When using the AT+CGDATA write command or ATD*99# or ATD*98# the MT issues the intermediate result
code CONNECT and enters V.250ter online data state. In V.250 online data state, first some LCP protocol
exchange between MT and TE is performed to set up the PPP link. After successfully establishing the PPP
link, the MT performs the PDP context activation procedure if the context is not already activated. As a
result, the MT is in a “PDP context activated” state within the PLMN, the PPP link is established on the
mobile side and the mobile is ready for IP data transfer.
If the TE wants to close the LCP link the MT may perform an LCP termination request procedure on PPP
level.
After this LCP termination procedure the MT deactivates the PDP context automatically and the MT returns
to V.250 command mode and issues the final result code NO CARRIER.
During the implicit PDP context deactivation procedure after LCP termination the TE may change into V.250
command state (e.g., by using +++ or by toggling DTR if AT&D is set to 1) before the result NO CARRIER
occurs.
In this case the application should not try to deactivate the PDP context by using the commands AT+CGACT
or ATH. If DTR is configured to disconnect data connections (AT&D2), then the application should not toggle
DTR during the implicit PDP context deactivation and before “NO CARRIER” is received.