9XTend-PKG-U™ USB RF Modem User’s Guide
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2.3.5. Command Mode
To modify or read modem parameters, the modem must first enter into Command Mode (state in
which incoming characters are interpreted as commands). Two command types are supported:
• AT Commands
• Binary Commands
For modified parameter values to persist in the modem registry, changes must be saved to non-
volatile memory using the WR (Write) command. Otherwise, parameters are restored to previ-
ously saved values when the modem is powered off and then on again.
AT Command Mode
To Enter AT Command Mode:
Default AT Command Mode Sequence (for transition to Command Mode):
• No characters sent for one second [refer to the BT (Guard Time Before) Command]
• Input three plus characters (“+++”) within one second
[refer to the CC (Command Sequence Character) Command.]
• No characters sent for one second [refer to the AT (Guard Time After) Command.]
All of the parameter values in the sequence can be modified to reflect user preferences.
To Send AT Commands:
Figure 2-06. Syntax for sending AT Commands
To read a parameter value stored in the modem register, leave the parameter field blank.
The preceding example would change the modem’s Destination Address to "0x1F". To store the
new value to non-volatile (long term) memory, the Write (ATWR) command must subsequently be
sent before powering off the modem.
System Response. When a command is sent to the modem, the modem will parse and execute
the command. Upon successful execution of a command, the modem returns an “OK” message. If
execution of a command results in an error, the modem returns an “ERROR” message.
To Exit AT Command Mode:
For an example of programming the RF modem using AT Commands and descriptions of each config-
urable parameter, refer to the "RF Modem Configuration" chapter [p17].
1. Send the 3-character command sequence "+++" and observe guard times before and after
the command characters. [refer to ‘Default AT Command Mode Sequence’ below.] The ‘Ter-
minal’ tab (or other serial communications software) of the X-CTU Software can be used to
enter the sequence.
[OR]
2. Assert (low) the CONFIG
pin and turn the power going to the modem off and back on (or
pulse the SHDN
pin).
[If the modem is mounted to a Digi RS-232/485 Interface Board, the result can be achieved
by pressing the configuration switch down for 2 seconds.]
Send AT commands and parameters using the syntax shown below.
1. If no valid AT Commands are received within the time specified by CT (Command Mode
Timeout) Command, the modem automatically returns to Idle Mode.
[OR]
2. Send ATCN (Exit Command Mode) Command.
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