AT+CGREG: Modes, parameters, and examples

AT+CGREG is an AT command for the GPRS registration status of the device. This article is a practical overview of how to use the command.

Overview

AT+CGREG=?

AT+CGREG=? is a test command that returns the list of supported network configurations.

AT+CGREG?

AT+CGREG? Is a read command for the GPRS registration status of the device. Receiving “registered” status from AT+CGREG? indicates that the device can access the internet.

Expected responses include +CGREG: <n>,5 and +CGREG: <n>,1.

• The n indicates the Unsolicited Result Code (URC) status,
• “5” indicates that the modem is registered to a network and is roaming, and
• “1” means the device is registered to the home network.

AT+CGREG=0

AT+CGREG=0 is a set command that disables the return of Unsolicited Response Codes (URCs) when network registration occurs.

In other words, there is no automated update on network registration.

AT+CGREG=1

AT+CGREG=1 is a set command that enables Unsolicited Response Codes (URCs) for the packet-switched network status.

Basically, this command tells the modem to respond when the network status changes, without having to manually check connectivity using AT+CGREG?.

AT+CGREG=2

AT+CGREG=2 is a set command that enables network registration and location information Unsolicited Result Codes (URCs).

+CREG vs +CGREG vs +CEREG

What are the differences between +CREG, +CGREG, and +CEREG?

• +CREG queries the registration to the circuit switched network, aka GSM networks.
• +CGREG and +CEREG query registration to the packet switched networks, aka networks which allow access to the internet.
• +CGREG queries the registration to GPRS network.
• +CEREG queries the registration to LTE or newer network technologies.

If you’re using modems with both GPRS and LTE technologies, use both AT+CGREG? and AT+CEREG?. The modem will report <n>,4 to the technology that is currently not active.

Defined values

<n> = Network registration unsolicited result code mode.

• 0 = Disable network registration unsolicited result code.
• 1 = Enable network registration unsolicited result code +CGREG: <stat>.
• 2 = Enable network registration and location information unsolicited result code +CGREG: <stat>[,<lac>,<ci>,<AcT>,<rac>].

<stat> = Current network registration status.

• 0 = Not registered and the modem is not currently searching for an operator to register to.
• 1 = Registered to the home network.
• 2 = Not registered, but the modem is currently trying to attach or is searching for an operator to register to.
• 3 = Registration denied.
• 4 = Unknown.
• 5 = Registered to a roaming network.
• 6 = Registered for “SMS only”, home network (applicable only when <Act> indicates E-UTRAN)
• 7 = Registered for “SMS only”, roaming (applicable only when <Act> indicates E-UTRAN) <lac> String type; two byte location area code in hexadecimal format (e.g. “00C3” equals 195 in decimal).

<lac> = Location area code.

String type; two byte location area code in hexadecimal format (e.g. “00C3” equals 195 in decimal).

<ci> = Cell ID

String type; four byte UTRAN/GERAN/E-UTRAN cell ID in hexadecimal format.

<AcT> = Access technology of the registered network.

• 0 = GSM
• 1 = GSM Compact
• 2 = UTRAN
• 3 = GSM w/EGPRS
• 4 = UTRAN w/HSDPA
• 5 = UTRAN w/HSUPA
• 6 = UTRAN w/HSDPA and HSUPA
• 7 = E-UTRAN
• 8 = EC-GSM-IoT (A/Gb mode)
• 9 = E-UTRAN (NB-S1 mode)

Interpreting this; 0 would typically be 2G connectivity, 7 is typically LTE (including LTE-M), and 9 is typically NB-IoT.

<rac> = Routing area code.

String type; one byte routing area code in hexadecimal format.

Notes

The information in this article is predominantly based on the SIMCOM 7020 series.