AT Commands Protocol
2-2 G24-L AT Commands Reference Manual April 15, 2008
General System Abbreviations
The basic system configuration contains a modem and a terminal.
The G24-L is the modem and may be referred to as the DCE, the phone, the mobile or the radio.
The terminal may be referred to as the DTE or the TE.
AT Commands Protocol
The figure below shows a general messaging sequence of AT commands protocol between the
terminal and the G24-L.
Figure 2-1: AT Commands Protocol
The AT commands interface is basically a Modem Services Upon Request.
Communication (almost) always begins from the terminal side. This means that any service
should be requested from the terminal. Thus a request is called a "command".
Each command must be answered by a "results code" from the G24-L. The results code reports
the command status to the terminal.
Some commands may include several "Response" requests (between 0 to K) to send data back to
the terminal.
Some commands may initiate a mode in which, when specified events are generated in the
G24-L, "Indicator" messages are sent asynchronously. Indicators can be between 0 to L.
The G24-L can echo characters received from the terminal (commands) back to the terminal.
Command
Terminal
G24-L
N
M
Response
Results Code
Indications
N=0,1,...,
K
M=0,1,...,
L
