At Command Interpreter - MTX -3G-JAVA-IoT User Manual

6. AT command interpreter

After a successful installation of the driver package, the physical USB interface of the modem is
represented in the operating system by two virtual interfaces, each assigned to a virtual COM port of
its own:
- Modem interface:
This interface is referred to as "Modem" if queried using the AT^SQPORT command. In the quick
reference tables it is named USB0-MDM.
The Modem interface is intended particularly for data transmission (UMTS or GPRS).
All URCs are normally issued on the Application interface. URCs related to data calls (RING, NO
CARRIER) as well as the "^SYSSTART" URC are issued on the Modem interface.
- Application interface:
This interface is referred to as "Application" if queried using the AT^SQPORT command. In the quick
reference tables it is named USB0-APP.
The Application interface is designed especially for controlling the IoT, i.e. for entering AT commands,
receiving URCs, or sending and receiving short messages. It cannot be used as a data interface for
UMTS, or GPRS.
Please note that URCs are normally indicated only on this interface, no matter whether the Modem
interface or the Application interface was used to send the AT commands to activate their
presentation. This URC management scheme is the default configuration recommended for a typical
MTX-IoT application.
Bear in mind that the Modem interface and the Application interface are handled by the same AT
command interpreter.
As a result, AT commands entered on both interfaces are not executed in parallel but sequentially, one
after the other. So, an AT command issued on one interface will be buffered on this interface to be
executed after the other interface has completed processing earlier AT command(s).
When a data connection is established over the Modem interface, the Application interface can be
used simultaneously for any control functions. This eliminates the need for the user to enter AT
commands, such as +++ and ATO, as well as switching back and forth between command and online
mode when working on one interface only.
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