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HUAWEI ME909u-521 LTE LGA Module
Application Guide
Overview
Issue 01 (2013-07-05)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
9
1.3 Basic AT Command Processing Principles
1.3.1 Ports
The ME909u-521 module provides three ports to interact with its host:
MODEM port: simulated using USB, for AT command interaction and
establishing data connection.
Port name: HUAWEI Mobile Connect-3G Modem
PCUI port: simulated using USB, for AT command interaction only.
Port name: HUAWEI Mobile Connect-3G PCUI Interface
ECM port: simulated using USB, for establishing communication connection.
Port name: CDC Ethernet Control Model (ECM)
The ME909u-521 also provides a port for debugging:
DIAG port: Simulated using USB, for DIAG (diagnostic) command interaction
(mainly used to debug modules at present).
Port name: HUAWEI Mobile Connect-3G Application Interface
A host controls a module using AT commands. If AT commands are unavailable, a
module can be deemed as unavailable.
1.3.2 AT Command Processing Mechanism
A module processes AT commands from the ports (MODEM, PCUI) in series. An AT
command can be processed when and only when the previous AT command
processing has been completed. If the module is processing an AT command, a new
AT command from the same port will be ignored and other commands from other
ports will be buffered until the current AT command is processed.
This rule also applies to COM ports converted from USB ports.
The processing of an AT command starts when the AT command is entered from the
TE, and ends when the UE (the module) returns all the results in response the
command.