3. AT COMMAND SET

This section describes the AT command set for Modem. Some of the AT commands described below may not be available in a given revision of Modem, depending on the build options your license includes. The default values stated are typical for a full featured Modem and may be different in reduced configurations. The command result code is always "OK" unless stated otherwise in the command description.

3.1. GENERAL AT COMMANDS

3.1.1. A/ - Re-execute Command

The A/ command command instructs the modem to re-execute the last AT command. It will repeat the command already in the command buffer. This command does not require AT prefix and does not have to be followed by the terminator character. This command is mostly used to redial the last number in case of a busy signal.

3.1.2. A> - Continuously Repeat Last Command

The A> command will continuously repeat the previous AT command until it returns success. This feature is typically used to redial a number automatically until a connection is established. Up to 10 redial attempts will be performed. The modem will only attempt to redial for the following responses:

• BUSY
• NO DIALTONE
• REORDER
• NO CARRIER (caused by expiration of S7 register)

3.1.3. AT$ - Help

This command, if enabled, prints a brief description of the basic AT commands.

3.1.4. AT= x - Write to Selected S-Register

This command writes the value x to the currently selected S-Register. An S-Register can be selected by using the ATSn command.

3.1.5. AT? - Read Selected S-Register

This command reads and displays the selected S-Register. An S-Register can be selected by using the ATSn command.

3.1.6. A - Answer

This command instructs Modem to go off-hook and answer an incoming call. After a successful connection the modem will go on-line in the answer mode. The execution of this command is affected by +FCLASS command settings. This command must be the last on the command line. All characters before the end of the line are discarded.

If +FCLASS=0 is selected, Modem will try to establish a data connection with the remote modem. Upon successful connection, Modem will go on-line and issue a CONNECT result code. If connection is not established within a time specified by S7 register, Modem will go on hook and issue a NO CARRIER result code. Any character sent to Modem after A command but before CONNECT result code will abort the connection.

If +FCLASS=1 is selected, Modem will go off-hook in V.21 answer mode. It will generate the V.25 answer tone followed by V.21 modulation as if +FTH=3 command were issued.

3.1.7. Bn - CCITT/Bell Mode

This command selects the modulation type used by Modem for 300 and 1200 bps connections.

3.1.8. Cn - Carrier Control

This command is included for compatibility only.

3.1.9. Dn - Dial

This command instructs Modem to go off-hook and dial the number specified by the dial string supplied as a command parameter. The execution of this command is affected by +FCLASS command settings.

If +FCLASS=0 is selected, Modem will try to establish data connection with the remote modem after the dialing is completed. If the dial string is empty, the modem will try to establish a data connection immediately. If a remote modem is not detected within the time specified by the S6 register, or if the connection is not established within a time specified by S7 register, Modem will go on-hook and return the NO CARRIER result code.

Any character sent to Modem after the command but before CONNECT result code will abort the connection.

If +FCLASS=1 is selected, Modem will go into fax V.21 receive mode after dialing. Any character sent to Modem after the command but before modem finished dialing will abort the connection.

3.1.10. En - Command Echo

This command controls the echoing of the characters in the command mode. The command parameter is written to bit 1 of S14 register.

3.1.11. Fn - Select Modulation (Compatibility only)

This command selects the modulation to be used during data connection. This command is enabled for compatibility only, and using N command and S37 register is the recommended way of selecting the desired modulation. The F command will change the settings of both the N command and the S37 register.

3.1.12. Hn - Disconnect and hook control

This command controls the modem's hook switch.

3.1.13. In - Modem Identification

This command reports information about the modem and current status.

3.1.14. Ln - Speaker Volume

This command instructs Modem to use specified speaker volume setting when speaker is on. The parameter of this command is stored in two least significant bits of register S22.

In some cases, the speaker volume may also be controlled by the PC audio subsystem. The computer's mixer program and the volume control on the external speakers (if any) may have an impact on the volume of the modem.

3.1.15. Mn - Speaker Control

This command controls the speaker of the modem. The parameter of this command is stored in bits 2 and 3 of register S22.

In some cases, the speaker volume may also be controlled by the PC audio subsystem. The computer's mixer program and the volume control on the external speakers (if any) may have an impact on the volume of the modem.

3.1.16. Nn - Automoding Control

This command controls automoding. The parameter of this command is stored in bit 1 of register S31. The behavior of this command depends on the value of S37.

3.1.17. On - Return to On-Line Data Mode

This command is only valid in on-line command mode. If the modem is off-line it will return ERROR result code.

3.1.18. P - Set Pulse Dialing as a default

This command instructs Modem to use pulse dialing as the default dialing method. This command sets bit 5 of S14 register.

The default dialing method can be overridden using dial modifiers (see D command).

3.1.19. Qn - Results Codes Control

The command controls the displaying of the result codes. The parameter of this command is stored in bit 2 of S14 register.

3.1.20. Sn - Access S-Register

This command is used to query or set S registers.

3.1.21. T - Set Tone Dial Default

This command instructs Modem to use tone dialing as the default dialing method. This command clears bit 5 of S14 register. The default dialing method can be overridden by dial modifiers (see D command).

3.1.22. Vn - Result Code Form

This command controls the format of the result codes returned by Modem.

3.1.23. Wn - Connect Result Code Control

This command controls the format of CONNECT messages. The parameter of this command is stored in bits 2 and 3 of register S31.

3.1.24. Xn - Extended Result Codes Control

This command selects which result codes will be used by Modem. The parameter of this command is stored in bits 4-6 of register S22.

The following table is a summary of supported result codes based on X command settings. A 'y' means result code is supported; a number indicates which (less explicit) report will be used instead.

3.1.25. Yn - Long Space Disconnect

This command controls the generation and response to long space disconnect. The parameter of this command is stored in bit 7 of S21.

When this feature is enabled, Modem will send a four-second BREAK when the user instructs the modem to disconnect. After the BREAK is sent, the modem will hang up.

In addition, if Modem receives a BREAK longer than 1600 ms from the remote modem, it will automatically hang up.

3.1.26. Zn - Reset

This command will force Modem to perform a soft reset. If nonvolatile memory is supported it will restore the profile according to the parameter of the command.

3.2. EXTENDED "AT&" COMMANDS

3.2.1. &$ - Help

This command, if enabled, prints a brief description of the extended AT& commands.

3.2.2. &Cn - DCD Option

This command informs Modem how to control DCD signal (V.24 circuit 109). The parameter of this command is stored in bit 5 of register S21.

3.2.3. &Dn - DTR Option

This command informs Modem how to treat DTR signal (V.24 circuit 108). The parameter of this command is stored in bits 3,4 of register S21.

3.2.4. &Fn - Restore Default Configuration

This command instructs Modem to restore the default ("factory") configuration.

Note: Modem has only one default configuration.

3.2.5. &Gn - Select Guard Tone

This command instructs Modem which if any guard tone should be used for V.22/V.22bis modulation. The parameters of this command is stored in bits 6 and 7 of register S23.

3.2.6. &Jn - Telephone Jack Control

This command is included only compatibility and performs no function except to load the S-register. The parameter value, if valid, is written to S21 bit 1.

3.2.7. &Kn - Flow Control

This command instructs Modem which flow control method to use. The parameter of this command is stored in bits 0-2 of register S39.

3.2.8. &Ln - Leased Line Selection

This command is provided for compatibility only. The parameter of this command is written to bit 2 of register S27.

3.2.9. &Mn - Mode Selection

This command is used for compatibility only. &Q commands should be used for mode control.

3.2.10. &Pn - Pulse Dialing Control (US Models only)

The parameter of this command is stored in bits 3,4 of register S28.

3.2.11. &Qn - Mode Selection

The parameter of this command is stored in bits 5-7 of register S28.

3.2.12. &Sn - DSR Option

The parameter of this command is stored in bit 6 of S21.

3.2.13. &Tn - Test and Diagnostics

The modem will perform selected test and diagnostic functions according to the parameter supplied. To terminate a test in progress, the escape sequence must be entered first, except for parameters 7 and 8. If S18 is non-zero, a test will terminate automatically after the time specified by S18 and display the OK message.

Note: For tests 3, 6, and 7, a connection between the two modems must first be established. Only V.22bis non error-corrected connection is suported for all tests.

3.2.14. &V - Display Current Configuration.

This command displays the current configuration of Modem. If nonvolatile memory is supported the stored profiles are displayed as well.

3.2.15. &Wn - Store Current Configuration

This command is only available for configurations supporting nonvolatile memory. It stores the current configuration to one of two stored configurations defined by the command parameter.

3.2.16. &Yn - Selects a Default Reset Profile

This command is only available for configurations supporting nonvolatile memory. It selects which one of two profiles to load after a reset.

3.2.17. &Zn=x - Store Telephone Number

This command is only available for configurations supporting nonvolatile memory. This command instructs Modem to store a telephone number in the directory. The number may contain up to 34 digits and up to 4 numbers can be stored.

3.2.18. &$ - Help

This command, if enabled, prints a brief description of the extended AT& commands.

3.3. EXTENDED "AT\" COMMANDS

3.3.1. \An - Select Maximum MNP Block Size

The modem will operate an MNP error corrected link using a maximum block size controlled by the parameter supplied. The parameter value, if valid, is written to S41 bits 5 and 6.

Result Codes:

3.3.2. \Bn - Transmit Break to Remote

Instructs the modem to send a BREAK signal to the remote modem. "n" specifies the number of 100 ms units The modem will transmit a break signal to the remote modem with a length in multiples of 100 ms according to parameter specified. If a number in excess of 100 is entered (10 seconds), 100 is used. The command works in conjunction with the \K command.

In error correction mode, the modem will signal a break through the active error correction protocol.

Result Codes:

Note: When the modem receives a break from the remote modem, break is passed to the DTE as follows: In non-error correction mode direct, the break length is passed; in non-error correction mode normal and in error correction mode, a 300 ms break is passed.

3.3.3. \Jn - DCE Rate Adjustment

This command controls whether the modem should force the maximum DCE speed to be less or equal DTE rate. The value is written to S27 bit 7.

3.3.4. \Kn - Break Control

This command controls the modem's reaction to a BREAK received from the DTE. This command also controls the action taken when the \Bn command is entered by the user. This parameter value is stored in S40 bits 3-5.

If the modem receives a BREAK from the DTE while in the on-line state, it will:

If the modem is in command mode (while connected to the remote modem), entering the \B command will instruct the modem to:

Result codes:

3.3.5. \Nn - Selects Operating Mode

This command controls the preferred error correcting mode to be negotiated in a subsequent data connection.

All other N values return ERROR. Modem does not implement direct mode.

3.4. EXTENDED "AT%" COMMANDS - ERROR DETECTION AND DATA COMPRESSION

3.4.1. %$ - Help

This command, if enabled, prints a brief description of the extended AT% commands.

3.4.2. %C - Enable/Disable Data Compression

Enables or disables data compression negotiation. The modem can only perform data compression on an error-corrected link. The parameter value, if valid, is written to S41 bits 0 and 1.

Note that HardModems typically support MNP5 with C1 and MNP5 or V.42bis with C3.

3.4.3. %Dn - Enable/Disable Doze mode

This command enables/disables doze mode feature. If modem is dozing %D0 will wake it up.

3.4.4. %En - Auto Fallback/Fallforward Control

This command instructs Modem whether to perform automatic fallback/fallforward if the line condition requires. This command controls only locally-generated requests for retrains or fallback/fallforward. (If the remote modem requests a retrain or fallback/fallforward, the local modem will automatically comply.)

The parameter value is stored in S41 bits 2 and 3.

3.4.5. %L - Line Signal Level

This command returns the received signal level in dBm. The value has an implicit minus sign.

3.4.6. %Q - Line Signal Quality

This command returns the line signal to noise ratio in dB.

3.4.7. %TT - PTT Testing utilities

This command facilitates testing of signal levels by providing continious signals regardless of whether the modem is connected or not. The signal is specified by the AT command paramter. Parameters to this command are interpreted as hexadecimal numbers.

The test is initiated upon receipt of a %TTn command, and is aborted when any keyboard character is entered. The modem will continiously transmit the tone or carrier accorind to parameter supplied.

3.4.8. %TFtdn - PTT Testing utilities for fax

This command is similar to %TT command(see above) but also prints reports on BER and recovery from impairments(like gain hits, phase hits, interruptions).

3.5. CALL WAITING COMMANDS

3.5.1. +CWT - Enable/Disable Call Waiting

3.5.2. +PCW - Enable/Disable Call Waiting

This command was added because of V.92 and partially overlaps the +CWT command.

Inquiries

Result Codes:

3.6. CALLER ID COMMANDS

3.6.1. #$ - Help

This command, if enabled, prints a brief description of the extended AT# commands.

3.6.2. #CIDn - Caller ID

This command enables or disables caller ID.

Inquiries

3.7. CALLER ID DATA FORMAT

Modem presents the data in the <tag> = <value> pair format as described in the table below. Spaces are present on both sides of the equal sign.

Notes:

1. Modem does not present any Caller ID information if it detects a checksum error in the Caller ID packet.
2. In the event of an unrecognized data tag, Modem will present the data in ASCII hex numbers following the MESG tag.

Example of Formatted Form Reporting

1. The following example illustrates a normal Caller ID message packet.

   RING
   
   DATE = 0622
   TIME = 1525
   NMBR = 4087744222
   NAME = S W MODEM
   
   RING
   
   RING
   

2. The following example illustrates the case where the tag of the packet is not recognized by Modem.

   RING
   
   MESG = 060342424231
   
   RING
   
   RING
   

Example of Unformatted Form Reporting

Modem presents all information and packet control information found in the message. However, it excludes the leading U's (channel seizure information) from the presentation. The packet is presented in ASCII printable hex numbers; with no spaces or line feeds inserted for between bytes or words of the packet. Modem does not detect the checksum of the packet.

RING

0412303332323234303539313435353132333435

RING

RING

3.8. DSVD COMMANDS

3.8.1. -SSE - Enable/Disable DSVD.

Enables or disables DSVD (digital simultaneous voice and data). The modem can only perform DSVD on V42 error-corrected link. The parameter value, if valid, is written to S49 bit 5.

Result Codes:

3.9. V.92 COMMANDS

3.9.1. +PMH - Enable/Disable Modem on Hold(MOH).

Enables/disables MOH. The parameter value, if valid, is written to S57 bit 1.

Inquiries

Result Codes:

3.9.2. +PMHT - Controls Modem On Hold(MOH) timeout

Sets the timeout(T1) for the MOH transaction. Since the server sets the value of this timeout the +PMHT command is irrelevant for the client.

Inquiries

Result Codes:

3.9.3. +PMHR - Initiate Modem On Hold(MOH)

Initate MOH transaction. If the MOH request is denied the modem will hang up.

Result Codes:

3.9.4. +PIG - PCM upstream ignore

Enable/Disable PCM upstream in V.92 connection.

Inquiries

Result Codes:

3.9.5. +PMHF - Hook flash.

Hook flash. The on-hook time is controled by S29.

3.9.6. +PQC - V.92 short Phase 1 and Phase 2 Control.

Enable/Disable short Phase 1 or Phase 2.

Inquiries

Result Codes:

3.9.7. +PSS - V.92 force long connect ignoring +PQC.

Forces the modem to use long connect sequences regardless of +PQC settings. Note: forcing short sequences is not implemented.

Inquiries

Result Codes:

3.10. PC 99 COMMANDS

3.10.1. #UD - Unimodem Diagnostics Command

This command produces output as described by the Microsoft Unimodem Diagnostics Command Specification.

#UD is an action command. It does not take parameters. It should be the last command in the command line. In response to this command, Modem will report one or more lines of information text in following format:

DIAG <token key=value [ [key=value [key=value] ]...>

Refer to Unimodem Diagnostics Command Specification for detailed description.

3.11. LOGGING COMMANDS

3.11.1. +TLOG - Enable/Disable logfile

On some platforms, Modem may be configured to collect connection log files.

If this feature is enabled, a user may specify the maximum size of the log and the name of the log where to store it.

3.12. AT COMMAND RESULT CODES

The Modem AT command handler responds to commands from the caller and to activity on the line via result codes. The possible result codes that Modem can send are listed below.

Two forms of each result code are available: long-form, "verbose" response when V1 is selected, and short-form, a data-like numeric response (included in parentheses following the long-form) when V0 is selected. The long-form code is preceded and terminated by the sequence <CR> <LF>. The short-form is terminated by <CR> only with no preceding sequence. If result messages are suppressed, nothing is returned to the caller.

3.12.1. OK (0)

The OK code is returned by the modem to acknowledge execution of a command line.

3.12.2. CONNECT (1)

Modem will send this result code upon connecting when the line speed is 300 bps and the modem has been instructed to report the line speed upon connecting, or the range of result code responses is restricted by the X command such that no speed reporting is allowed.

3.12.3. RING (2)

Modem sends this result code when incoming ringing is detected on the line as per the interface description.

3.12.4. NO CARRIER (3)

Modem sends this result code when attempting to establish a call if no ringback is detected within the period of time determined by register S7. It is also used when the modem auto-disconnects due to loss of carrier.

Under X0, if busy tone detection is enforced, this result code is used as a response to the detection of busy or reorder. Under X0, if dial tone detection is enforced or selected, this result code is used to indicate that dial tone has not been detected.

3.12.5. ERROR (4)

Modem returns this result code if the command line contains a syntax error or it is unable to execute a command contained in the command line. It is issued if a command does not exist or if the parameter supplied is outside the permitted range.

Under X0, X1, X2, and X3, this result is used instead of DELAYED and BLACKLISTED.

3.12.6. CONNECT 1200 (5)

For X1, X2, X3, and X4, Modem sends this result code when the line speed is 1200 bps and Modem has been instructed to report the line speed upon connecting.

3.12.7. NO DIALTONE (6)

For X2 and X4, Modem sends this result code if it has been instructed to wait for dial tone during dialing but none is received.

3.12.8. BUSY (7)

For X3 and X4, if busy tone detection is enforced, Modem sends this result code when attempting to originate a call if the busy signal is detected on the line.

3.12.9. DELAYED (24)

For X4, X5 the modem returns this result code when a call fails to connect and the number dialed is considered 'delayed' due to country blacklisting requirements.

3.12.10. BLACKLISTED (32)

For X4, X5 the modem returns this result code when a call fails to connect and the number dialed is considered 'blacklisted'.

3.12.11. FAX (33)

The modem returns this result code when a fax modem connection is established in a facsimile mode.

3.12.12. DATA (35)

The modem returns this result code when a data modem connection is established in a facsimile mode.

3.12.13. CONNECT n

where n is one of the following codes:

For X1, X2, X3, and X4, Modem sends this result code when the line speed is as indicated (in bps) and Modem has been instructed to report the line speed when connecting. These codes are also reported when the API-controlled virtual DTE speed is reported upon connection.

For X1, X2, X3, and X4, Modem returns this result code upon establishing a V.23 originate or answer connection when Modem has been instructed to report the line speed upon connection.

3.12.14. CARRIER n

where n is one of the following codes:

Modem sends one of these when the indicated data rate (in bps) has been detected on the line and carrier reporting has been enabled. (See S95 and Xn)

3.12.15. COMPRESSION: V.42 bis (67)

The COMPRESSION result is sent when Modem has connected in V.42 bis or MNP5 mode and COMPRESSION message reporting has been enabled. (See S95 and Xn.)

3.12.16. COMPRESSION: CLASS 5 (67)

See above.

3.12.17. COMPRESSION: NONE (69)

See above.

3.12.18. PROTOCOL: NONE (70)

The PROTOCOL result is sent to the DTE when Modem has connected without any form of error correction, LAPM correction, or MNP (ALT) correction, and the PROTOCOL message reporting has been enabled. (See S95 and Xn.)

3.12.19. PROTOCOL: LAPM (77)

See above.

3.12.20. PROTOCOL: ALT (77)

See above.