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# Ethernet 10/100+Modem 56
Using AT Commands

This section provides the following information:

- CountrySelect Utility
- Introduction to the Modem
- Modem Speed
- How to Use AT Commands
- Frequently Used AT Commands

## CountrySelect Utility

To complete the installation of Xircom utilities and online documentation, you must run SETUP.EXE from the Xircom compact disc, select "Install Software and Tools," follow the onscreen instructions, and then restart the system. After you restart and Windows reloads, run the Xircom CountrySelectTM to set the modem parameters for the country in which you are located.

To change the modem country setting when you travel to a new country, select Start, Programs, Xircom Utilities, CountrySelect. Select the COM port to which your Ethernet 10/100+Modem 56 is assigned. Then use the drop-down "Country" list box to select the country from which you want to use the modem. Click Save, then Exit. Use your communications software to make the modem call.

### Introduction to the Modem

Once the Ethernet 10/100+Modem 56 has been installed, using the instructions under Installation, most users will rely on a communications application program such as HyperTerminal to configure the modem and carry out communications and fax tasks. Interaction with the modem will usually be handled by the communications software.

However, some communications programs require the user to input certain types of modem commands. And some users prefer to configure the modem manually without the aid of their communication software's menus and prompts. Technical information is provided in this section to support both of those situations.

For help in solving problems that occur after the modem has been installed, see Troubleshooting.

### Modem Speeds and Protocols

Ethernet 10/100+Modem 56 models support both V.90 and K56flex standards for 56K data transmission. Downloading of information and E-mail from corporate networks or the Internet can occur at speeds of up to 56Kbps over standard phone lines. Data sent by the user to the network travels at the highest available V.34 rate (up to 33.6Kbps). In order to achieve 56Kbps download speeds, the modems at both ends of the connection must support the V.90 or K56flex standard. Otherwise a standard V.34 connection will be negotiated. Current U.S. Federal Communications Commission (FCC) regulations limit download speeds to 53Kbps.

Xircom modem firmware is designed to initially attempt to make a V.90 connection, and then fall back to K56flex if the computer being dialed does not support V.90. However, there are other factors that could affect your ability to achieve 56Kbps transmissions.

### How to Use AT Commands

Some communications programs require direct input of modem commands, and some users prefer to configure the modem manually without the aid of their communication software's menus and prompts. These operations are performed by typing alphanumeric commands on the screen while the modem is in command mode, using AT Commands and S-Registers.

For detailed reference information on the AT command language and related issues, see Modem AT Commands, S-Registers, and Result Codes.

#### Initialization Strings

The modem initialization string is an AT command line containing modem parameter settings. The Xircom modem is configured with a factory-default initialization string that can be restored at any time with the AT command AT&F. These settings may be suitable for some communications packages, while others may have custom requirements.

Modem operating modes

The Xircom modem has two operating states: command mode and online mode.

Command mode

The modem "wakes up" in command mode when it is powered on and modem software is loaded. Only in command mode does the modem accept and execute typed commands. The modem automatically switches from command to online mode when a connection is established with another modem.

Limitations of command mode

Command mode operations with most modems, including the Xircom modem, do not include sending or receiving files or faxes or logging on to a remote computer or network. Command mode can only be used to configure the modem and establish or break a connection. For all data communications and fax tasks you will also need appropriate equipment and applications software at both ends of the line.

Online mode

Online mode is the operating state the modem automatically switches to when a connection is established with another modem. If commands are typed in when the modem is in online mode and connected to another modem, they are not treated as commands but are sent as data to the other end of the connection. The exception is the "Escape" command (+++), which allows you to switch from online to command mode during a session with a remote modem without losing the connection.

The AT command set

The Xircom modem uses a Hayes and Microcom compatible command set for modem operations in command mode. This is an extended "AT" command set in which most command strings start with the letters AT and commands are executed by pressing the Enter key at the end of the command line. Use the command AT$ to see the complete set of available modem commands.

S-Registers

In conjunction with the AT command set, the modem also makes use of a series of programmable memory storage locations called S-Registers. These S-Registers contain values that govern the operation of the modem and the performance of many of the AT commands. For more information about S-Registers, their contents, function, and use, see S-Registers.

The Escape and ATO commands

The Escape command used with the Xircom modem is executed by typing three ASCII characters (default is "+++"). This command is used to return temporarily to command mode during connection to a remote modem.

The ASCII character is set with S-Register S2. The default is S2=43 (the + sign). Values 0-127 can be used. To disable this command, use an ASCII value greater than 127.

To return to online mode, type the command ATO (where O is the letter O), followed by Enter.

Fax commands

All fax operations require the use of fax software for configuration and execution of the appropriate fax and modem commands. This software switches the modem into fax mode, manages the fax process, and switches the modem back to its default data mode when the fax operation is complete.

See your fax software documentation for instructions on how to set up fax software and send or receive faxes.

#### Sending commands to the modem

AT commands can be executed only when the modem is in command mode. They are initiated by sending an attention code to alert the modem that commands are on the way. The AT attention code is followed by the appropriate command or commands, which can be in upper or lower case characters, or a combination of the two.

With two exceptions, all the commands issued to the modem must begin with AT and end with the Enter key. The exceptions are the Repeat command (A/), which executes as soon as you type /, and the Escape command +++, which executes as soon as three plus signs are typed.

Command parameters

Commands issued to the modem can be a single command such as AT&V or a sequence of commands such as AT &F S7=30 V1 X4 DT 1 213 555 2345. This line of characters is called the command line. The command line must be terminated by pressing the Enter key.

Commands can be up to 255 characters long, not counting the AT command prefix, any spaces used within the command line, any linefeed characters, or the terminating Enter key. Parentheses and hyphens are counted as command characters. Any attempt to create a command line of more than 255 characters in length results in an ERROR message. In this case the entire command line will be ignored by the modem.

Use the Backspace key (or the sequence Ctrl-H) to correct errors in typing the command string. You cannot delete the AT attention code. Press Ctrl-X to instruct the modem to ignore the entire command line and return to command mode. The modem responds by displaying OK without executing any of the command.

Command processing

The modem displays OK in response to commands it understands and can act upon, and ERROR in response to commands it does not understand or cannot execute. These command acknowledgment messages are called result codes. In addition to OK and ERROR, the modem can also respond with CONNECT, BUSY, NO CARRIER, RING, NO DIALTONE, and so on.

### Frequently Used Modem Commands

Below are some frequently-used AT commands. Using these sample commands, you can easily instruct the modem to dial and connect to another modem, to the Internet, or to a corporate network. Unless it is specifically stated otherwise, all the sample commands that follow must be preceded by the letters AT in all upper or all lower case and be executed by pressing the Enter key at the end of the command line.

Escape

+++ Escape. This command switches the modem's operating mode from online state to command state.

A response of OK after you have entered the +++ command from your communications program indicates that the modem is now in the command state and will accept AT commands. This command does not need to be preceded by the AT command prefix or terminated by Enter.

Dialing

The command that causes the modem to dial a number is the AT command ATDn. The n in this case represents a string of characters whose length is limited only by the capacity of the modem's command buffer. The command buffer can accommodate up to 255 characters in the dial string.

Handshaking

When you enter a Dial command and the modem successfully detects the distant modem's carrier signal, it attempts to negotiate a common data transmission rate and other transmission parameters based on the settings previously issued to both the sending and receiving modems. This negotiation, usually accompanied by a characteristic series of squeaks and squawks from the modem speaker, is called handshaking.

Dial modifiers

The Dial command has a variety of options, called dial modifiers, that are made up of specific letters and symbols and can be typed in any combination immediately following the Dial command. These dial modifiers allow you to control how a number is dialed.

For example, the command ATD P 9 W T 1 213 555 3456 instructs the modem to:

Go off-hook (pick up the phone) and detect dial tone

Pulse dial a 9

Wait for a second dial tone

Tone dial 12135553456 and wait for carrier detect

The P, W, and T are dial modifiers. For a complete list see AT Commands under the letter "D."

Another frequently-used dial modifier is the comma. The inclusion of a comma (,) in the command line causes the modem to pause briefly before processing the next character or symbol in the line.

For example, the command ATD 9, P 555-3333 could be used to dial a 9 using tones to get an external line through a PBX, pause long enough to get the external dialing tone and then pulse dial 555-3333.

The command ATDL redials the last number dialed.

Repeat

A/ Repeat. This command does not require the AT prefix and executes when / is typed. The Enter key is not required. A/ causes the modem to re-execute the command line currently stored in the command buffer, which is usually the last command line entered. This is useful for redialing telephone numbers that had previously returned a BUSY result code.

For example, if you entered the command ATD 9, P 1-804-555-3333 and the modem responded by displaying BUSY on your monitor screen, you do not have to retype the command string to redial. Simply type A/ and the modem will reprocess the entire command line.

Hang Up

ATH Hang Up. This command instructs the modem to go "on-hook" or to hang up. Typing ATH hangs up the modem and disconnects the telephone line.

Help

AT$ Help. This command displays a multi-screen summary of all the modem's commands.

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