|
SARA-R4/N4 series - AT Commands ManualUBX-17003787 - R09 2 General operationPage 16 of 3072 General operation2.1 Start up and initializationThe characteristics of the boot of the cellular device vary from module to module and are described in thecorresponding System Integration Manual; during this phase the module might be not responsive on the ATinterface until all necessary SW modules have been installed (e.g. USB drivers); monitoring of the greeting text,where supported, can help in detecting the successful end of the boot phase.A complete start up to be able to operate on the cellular network can take place only with a SIM card.If the SIM card has enabled the PIN check, some commands answer with "+CME ERROR: SIM PIN required"and most cellular functionalities are not started. After entering the required PIN via the +CPIN command, orif booting with a SIM with disabled PIN check, SIM initialization is carried out and a lot of SIM files are read:it is possible that some commands (e.g. phonebook AT commands) are affected by this preliminary phase,resulting in a temporary error response.2.1.1 Auto-registrationIf the +COPS parameter in the profiles or in NVM is left to its factory-programmed value 0 or set to 1,after SIM initialization, all u-blox modules will automatically perform PLMN selection and registration for circuitswitched/non EPS services as well as packet switched/EPS services. Auto-registration (sometimes called also"auto-COPS", not to be confused with automatic =0) will be triggered also at SIM insertion, for modulessupporting SIM hot insertion, or at SIM driver recovery, occurring when the communication with the SIM cardis re-established by the module after an unrecoverable error, caused e.g. by mechanical vibrations or electricalinterference. If no SIM is inserted in the module, the module will anyway select a cell of the cellular network andtry to maintain synchronization with it in limited service.The radio access technology selected by the module at start up is defined by the parameter ofthe +URAT command; afterwards the module will reselect the RAT based on the requirements of the cellularstandards it complies with and it is not possible to force it to remain in a given RAT unless it is locked on it via+URAT or on a specific cell via +UCELLLOCK (if supported).The user can retrieve the result of the auto-registration by polling the registration status commands (e.g.+CREG/+CGREG/+CEREG/+CIREG) or enabling their unsolicited notifications. If auto-COPS is running, at boottime or at SIM insertion, network service commands issued by the user might have a longer response time thanexpected; this is particularly visible when the module is switched on in a jammed condition, or with a roamingSIM card that shall perform several registration attempts before gaining access to a VPLMN. In case of failuresof the automatic registration whose cause cannot be retrieved via +CEER, it is suggested to disable auto-COPSstarting the module in +COPS:2 or in airplane mode +CFUN:4 and trigger registration with AT commands.2.1.2 Operational restrictionsOperational restrictions may derive from several settings: PIN required, SIM lock, invalidation of the IMEIor SIM credentials by the Mobile Network Operator (MNO) during the registration procedure, FDN enabled.Restrictions to access the network are also applied by the module in any one of these conditions:• In eCall only state (for all modules supporting the eCall feature)• In minimum functionality power modes (+CFUN: 0, +CFUN: 4, +CFUN: 19, +CFUN: 127), and even if themodule is restarted in +CFUN: 4 or +CFUN: 19 modes, because they are persistentIn case the module is in operational restricted state, it may reject all or specific service requests (e.g. operatorselection, connection establishment).2.2 AT commands types2.2.1 Action commandAn action command forces the DCE to print information text or execute a specific action for the command.A typical example of this command type is the provision of the factory-programmed settings of the DCE likemanufacturer name, firmware version, etc.
|
