At Commands Protocol; At Commands Structure; Command Structure; Figure 7. At Commands Protocol - Motorola g20 Developer's Manual

Introduction to AT Commands
3.2

AT COMMANDS PROTOCOL

The figure below show a general messaging sequence of AT commands protocol between the terminal and the g20.
Terminal
N = 0,1,...,K
M = 0,1,...,L
The AT commands interface is basically a Modem Services Upon Request feature.
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 g20. 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 g20, "Indicator" messages are sent
asynchronously. Indicators can be between 0 to L.
The g20 can echo characters received from the terminal (commands) back to the DTE.
3.3

AT COMMANDS STRUCTURE

3.3.1

Command Structure

An AT command line may contain one or more commands. Delimiters are used to separate the commands from each other,
according to the following structure:
Prefix Command1
Each AT command has the "AT" prefix string.
Each AT command has the suffix is <CR>.
The delimiter is either a semicolon ";" or none (basic commands).
Each AT command has the following structure:
Token Mode
30
Command
Response
Results Code
Indications

Figure 7. AT Commands Protocol

Delimiter Command2
Arguments
Delimiter ... CommandN
g20
N
M
Suffix
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