User guide

Chapter 5 - AT Commands

Each command has a valid range of parameters. For example, &S can have only 0 or 1 as a parameter. Valid

commands always generate an OK result code, and a few generate an additional response such as a list of

parameters. An invalid command such as &S3, which has a parameter outside the valid range, generates an

ERROR result code. Most commands have a default parameter that is enabled when the modem is turned on or

reset with the ATZ or AT&F command. Factory defaults are stored in read-only memory (ROM) and cannot be

changed. User-defined defaults can be stored in nonvolatile random-access memory (NVRAM) and can be

changed or deleted at will.

Command Editing

Always begin a command with the letters AT. Enter the entire command string in upper or lower case, but do not

mix cases within the command string. The AT command is not executed until you press ENTER. Use the

BACKSPACE key to erase the previous command character. It will not erase the AT characters once they are

typed. If your keyboard has no BACKSPACE key, use CTRL+H. (You can change the character recognized by

the modem as BACKSPACE to any other ASCII character by changing register S5.)

Press CTRL+X to cancel an entire command that has been typed but not yet executed. This also clears the

command buffer. The effect is the same as backspacing the command, only quicker.

The modem stores characters entered in a command in its command buffer until they are executed by pressing

ENTER. The command buffer’s capacity is 40 characters. The attention characters (AT) do not count toward the

40-character command line maximum. You may use spaces for increased readability when typing a command.

Spaces are not stored in the command buffer, and they do not count towards the 40-character command line

maximum. Special characters, such as hyphens and parentheses, are not allowed.

If you exceed the 40-character limit or type invalid characters, the command buffer is automatically erased and

an ERROR message appears. Retype the command within the 40-character limit, using only the allowed

characters.

The commands in this chapter are organized by function. Abbreviated commands are listed on the next page by

function along with a short description and page numbers that refer to a more detailed description, immediately

following this list.

Topic Command Description

Dialing Action D Dial

H On-hook/off-hook

Dial Modifiers L, P, T, W Command accepted, but has no function

, Command accepted, but has no function

; Command accepted, but has no function

! $ @ ^ Command accepted, but has no function

Phone Number Memory &Z Store a phone number

DS Dial a stored number

Configuration Storage & Recall

&W Store configuration

&F Load factory default configuration

Z Reset modem

&Y Select stored configuration on power-up