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Modem AT Commands
With the exception of the "Special Commands" described at the beginning of the Command Reference, all commands must be preceded by the AT attention code (or command prefix) and terminated by pressing the Enter key.
The modem responds with the result code OK, which means it understands and can execute the command, or with ERROR, which means that the modem does not understand the command or that the command is invalid. A complete list of result codes appears later in this topic.
The modem must be in command mode when any command other than the online escape sequence is entered. Commands entered when the modem is in online mode are treated as data and transmitted as such to the modem at the other end of the line.
For modem script files to be used with popular communications packages, see the directory \SCRIPTS and the file SCRIPTS.TXT on the Xircom diskette or in the download package.
Special Commands:
+++ Online Escape Sequence
The escape sequence is used to switch to command mode from online mode during a session with a remote modem. Type three "plus signs." The escape sequence is not preceded by the AT command prefix, nor does it require the Enter key to execute.
The setting of S-Register S2 determines the ASCII character used. S2=43 is the default (the "+" sign). Any values from 0-127 are valid. To disable the command, set S2 to a value greater than 127. Use the ATO ("AT" and letter "oh") command to return to online mode.
Insert a pause before and after the escape sequence to prevent misinterpretation of the escape sequence as data. Use S-Register S12 to set the length of the pause.
A/ Repeat Last Command
The A/ command causes the modem to repeat the last command string. The command executes as soon as / (forward slash) is typed. It does not require the AT command line prefix, nor does it need to be followed by Enter.
AT Command Reference:
A Answer
Typing ATA causes the modem to go off-hook and respond to an incoming call by generating a carrier signal and starting the handshaking process. This command must be the only one or the final command in the command line.
If the handshaking process is successful, a connection is established and the normal CONNECT message is displayed. If the carrier signal is not detected within the time specified by the S7-Register, a NO CARRIER result code is displayed.
Bn Select Communications Standard
The ATBn command selects the communication standard (ITU or Bell) to be used by the modem, as follows: B0 .... Use ITU V.22 at 1200bps. B0 selects ITU V.22 at 1200bps
....... and ITU V.21 at 300bps.
B1 .... Use Bell 212A at 1200bps. B1 selects Bell 212A at 1200bps and Bell 103J at 300bps.
B2 .... Unselect V.23 reverse channel.
B3 .... Select V.23 reverse channel.
B15 ... Selects V.21 when the modem is at 300bps (same as B0).
B16 ... Selects Bell103J when the modem is at 300bps (same as B1).
The ATB1 and ATB16 parameter settings are not available in some countries. Defaults are country-specific.
Break (Escape) command
See "Special Commands" at the beginning of this Command Reference section.
Cn Carrier Control
The ATCn command, where n is 1, guarantees backward compatibility with communications software that issues the C1 command. C0 is not supported; it may set some modems to "receive only mode."
C0 .... Transmit carrier always off (not supported).
C1 .... Normal transmit carrier switching.
Dn Dial A Telephone Number
The ATDn command is used to dial a telephone number. The n represents a dial string consisting of dial digits/characters and dial modifiers (see below) and must not exceed 40 characters. Spaces, hyphens, and parentheses can be used for clarity, but are ignored by the modem.
The Dial command can be used for either pulse (rotary) or tone dialing. The dial digits/characters are 0 - 9 A B C D # *.
The characters A B C D and the symbols # and * represent specific tone pairs and can be used only when tone dialing. These characters and symbols are ignored when pulse dialing is used. Some countries restrict or prohibit the use of some of these characters.
Dial Modifiers
Dial modifiers are recognized by the modem only when they are part of a dial string following the ATD command. Possible dial modifiers are as follows:
L Redial Last Number
Redials the last number if used as first character following ATD; otherwise, it is ignored.
P Pulse Dialing Method
The P modifier is used with the Dial command to instruct the modem to pulse dial the telephone number that follows.
S=n Dial a Stored Telephone Number
The S modifier instructs the modem to dial a number that had been previously stored by the use of the AT&Zn=x command. The command to dial a stored telephone number is ATDS=n, where n represents telephone number storage location 0 or 1. For example, ATD P S=1 pulse dials the telephone number written to telephone number storage location 1.
, Delay Processing the Next Character
When the comma (,) modifier is included as part of the dial string following the ATD command, the modem pauses before processing the next character in the dial string. The duration of the pause is dictated by the contents of S8-Register. The comma (,) modifier is frequently inserted after the digit (usually 9) used to obtain an outside line from a Private Branch.
Exchange (PBX) to allow sufficient time for the dial tone to occur before the modem dials the telephone number. The W modifier can be used in place of the comma.
Some countries place restrictions on the amount of time a modem may delay during dialing.
T Tone Dialing Method
The T modifier is used with the Dial command to instruct the modem to tone dial the telephone number that follows. See also the ATT command.
W Wait for Second Dial Tone
The W modifier instructs the modem to wait for a dial tone before processing the remaining characters in the dial string.
! Hook Flash
The exclamation point (!) modifier serves as a switch hook (or hook flash) signal. This hook causes the modem to hang up (go on-hook) for about 0.5 seconds then return to off-hook (the actual duration of the hook flash varies in different countries).
@ Wait for Quiet Answer
The "At" symbol (@) modifier in a dial string instructs the modem to wait for five seconds of silence after dialing the number. If silence is not detected, the modem sends a NO ANSWER result code to the user.
; Return to Command Mode after Dialing
The semicolon (;) dial modifier can be used only at the end of a command line, immediately preceding the Enter, and instructs the modem to return to the command mode immediately after dialing and without breaking the connection with the distant modem.
^ Disable Data Calling Tone Transmission
The caret (^) modifier in a dial string disables data calling tone for the current call (calling tone is automatically enabled in many countries). This modifier is not available in all countries.
$ Credit Card Tone Detect
The dollar ($) modifier in a dial string instructs the modem to wait for a credit card "bong" tone before processing the remaining characters in the dial string.
En Echo Command
The ATEn command, where n represents 0 or 1, determines if the commands you issue through the keyboard to the modem in command mode are displayed (echoed) on your computer's monitor screen.
E0 .... Disable echo to the computer E1 .... Enable echo to the computer (default)
If the commands you type are not displayed on your monitor screen, your software is set to expect character echo from the remote system. You can remedy this by typing in the command ATE1. If the commands you type are displayed on your monitor with the characters duplicated, LLIIKKEETTHHIISS, type in the ATE0 command.
Fn Online Data Character Echo command
Ths ATFn command determines whether the modem will echo data from the DTE. This modem does not support the F0 version of the command. To ensure backward compatibility, the modem will accept F1.
F0 .... Online data character echo enabled (not supported; ....... returns ERROR)
F1 .... Online data character echo disabled
Hn Switch Hook Options
The ATHn command hangs up the modem or prepares it for dialing.
ATH0 .... Causes the modem to go on-hook (default).
ATH1 .... Causes the modem to go off-hook (this command is ......... restricted in some countries).
In Request ID Information
The ATI command has various options, which are used to instruct the modem to provide specific information about itself.
I0 .... Displays modem controller firmware revision (same as I3)
I1 .... Calculates ROM checksum and displays it on the DTE (for ....... example, 12AB)
I2 .... Performs a ROM check and calculates and verifies the ....... checksum displaying OK or ERROR.
I3 .... Displays modem firmware revision information
I12 ... Returns country code (for example, North America)
Ln Monitor Speaker Volume
The ATLn command, where n represents 0, 1, 2, or 3, is listed here for backward compatibility reference only. The volume of the monitor speaker is controlled by the laptop computer, not by the modem.
Mn Speaker On/Off Selection
The ATMn command, where n represents 0, 1, 2, or 3, enables or disables the transmission of sound signals from the modem to the computer speaker (Sound production also requires that the computer speaker be enabled).
M0 .... Speaker always off.
M1 .... Speaker on until data carrier is detected
M2 .... Speaker always on when modem is off-hook
M3 .... Speaker off as digits are dialed, then on after dialing
....... until data carrier is detected
Nn Negotiation of Handshaking Options
The ATNn command, where n represents 0 or 1, determines whether or not the sending modem performs a negotiated handshake when the speed of the answering modem is different from that of the sending modem.
N0 .... When originating or answering, handshake only at the
....... communication standard specified by the contents of
....... S37-Register and the ATBn command option selected.
N1 .... When originating or answering, handshake only at the
....... communication standard specified by the contents of
....... S37-Register and the ATBn command option selected.
....... During handshaking, fall back to a lower speed,
....... if required (default setting).
On Online Command
If the modem has been switched to command mode, typing the ATO0 (AT "oh" "zero") command will return it to the online mode with the existing connection.
O0 .... Instructs modem to leave online command mode and return
...... to data mode (see +++ Escape Sequence under "Special
...... Commands")
O1 .... This setting issues a retrain command before returning
...... to online data mode.
O2 .... This setting issues a rate negotiation command before
...... returning to online data mode.
P Select Pulse Dialing
The ATP command instructs the modem to use pulse (rotary) dialing. This mode will remain in force for all dialing procedures unless an ATT command is issued or the dial string contains a T dial modifier.
Qn Result Code Display Options
The setting of the ATQn command, where n represents 0 or 1, determines whether or not result codes (such as OK, CONNECT, RING, NO CARRIER, and ERROR) are displayed on your PC screen.
Q0 .... Display of result codes enabled.
Q1 .... Display of result codes disabled.
Repeat command
See "Special Commands" at the beginning of this topic.
T Select Tone Dialing
The ATT command instructs the modem to use tone dialing. This mode will remain in force for all dialing procedures unless an ATP command is issued or the dial string contains a P dial modifier. Tone dialing is the factory-default setting.
Vn Result Code Format Options
The ATVn command, where n represents 0 or 1, determines if result codes are displayed as numeric (short form) codes or words (long form). Numeric result codes contain only one or two digits and this form could be used, for example, when the modem is controlled by a software terminal emulation program that uses script files. See the list at the beginning of this topic showing result codes in both long and short formats. Type the command ATV or ATV0 to select numeric result codes. The factory default is to display the result codes as words (ATV1). You should issue an ATV1 command either to reset the factory default after a change has been made or to select the verbos (word) result codes. Negotiation progress messages (extended result codes) are those with a numerical value of 40 or more.
Four other AT commands, two dial modifiers, and an S-Register are also directly involved in the generation and display of result codes. These are the ATQn, ATVn, ATWn, and ATXn commands, the ATDW and ATD@ dial modifiers, and S95-Register.
Wn Negotiation Progress Message Selection
The ATWn command, where n represents 0, 1, or 2, works in conjunction with the S95-Register to determine how that subset of the result codes - called negotiation progress messages or extended result codes - will be used to report the type of connection, protocol, and other communication techniques that resulted from handshaking and subsequent negotiation.
The options available to represent n in the ATWn command are:
W0 .... CONNECT result code reports DTE speed. If S-Register
...... S95=0, disable the display of all extended result codes.
W1 .... CONNECT result code reports DTE speed. If S95=0, enable
...... the display of CARRIER and PROTOCOL extended result
...... codes only.
W2 .... CONNECT result code reports DCE (modem-to-modem) speed.
...... If S95=0, disable the display of all extended result
...... codes.
Xn Result Code Set/Call Progress Option
The ATXn command, where n represents 0-4, controls how the modem responds to dial tone and busy signals and how it displays CONNECT result codes. The options available to specify with the ATXn command are:
X0 .... Result codes 0-4 enabled. Busy detect and dial tone
...... detect disabled.
X1 .... Result codes 0-5, and 10 enabled. Busy detect and dial
...... tone detect disabled.
X2 .... Result codes 0-6, and 10 enabled. Busy detect disabled
...... and dial tone detect enabled.
X3 .... Result codes 0-5, 7, and 10 enabled. Busy detect
...... enabled and dial tone detect disabled.
X4 .... Result codes 0-7, and 10 enabled. Busy detect and dial
...... tone detect enabled.
Some countries do not allow busy detect or dial tone detect to be disabled.
Yn Long Space Disconnect Option
The ATYn command, where n represents 0 or 1, determines whether or not the modem will disconnect a call when it receives a long space (1.6 seconds Break) signal during a V.22bis connection.
Y0 .... Disables the long space disconnect facility (supported
...... for backward compatibility reference only).
Y1 .... Enables the long space disconnect facility (not
...... supported).
Zn Recall Stored Profile
The ATZn command, where n represents 0, disconnects any call that is currently in progress and reloads the user configuration profile stored in nonvolatile memory as the active configuration profile.
Z0 .... Disconnect and reload the profile contained in storage
....... location 0 as the active configuration profile.
&Bn V.32 Automatic Retrain Options
The Xircom modem always retrains. The automatic retrain feature cannot be disabled.
&B0 .... Disables the V.32 automatic retrain capability (not
....... supported).
&B1 .... Enables the V.32 automatic retrain capability
....... (supported for backward compatibility only).
&Cn Data Carrier Detect (DCD)
The AT&Cn command, where n represents 0 or 1, selects the method by which the modem handles the carrier detect signal.
&C0 .... The carrier detect signal is forced on regardless of
....... the condition of the distant modem's carrier.
&C1 .... The state of the carrier from the remote modem is
....... monitored. The local modem's DCD signal is on when the
....... remote modem's carrier signal is detected, and off when
....... it is not (default).
&Dn Data Terminal Ready (DTR) Options
The AT&Dn command, where n represents 0-3, controls how the Data Terminal Ready (DTR) signal is used by the modem.
&D0 .... Ignore the DTR signal from the computer and treat it as
....... always on.
&D1 .... Monitor DTR and, when an ON-to-OFF transition of the
....... DTR signal occurs, switch to command mode, issue an OK
....... result code, and remain connected.
&D2 .... Monitor DTR and, when an ON-to-OFF transition of the
....... DTR signal occurs, hang up the line and switch to
....... command mode.
&D3 .... Monitor DTR and, when an ON-to-OFF transition of the
....... DTR signal occurs, hang up, reset the modem and switch
....... to the initialization state.
&Fn Load Factory Settings
The AT&F command loads factory default parameters from ROM into the active configuration profile, replacing the parameters stored there.
This command must be issued by itself. If it is used with another AT command, its function will be ignored.
&F0 ... Recall factory settings as active configuration
&F5 ... Recall factory settings appropriate for ETC mode as
...... active configuration. This command enables ETC
...... operation. It is automatically set upon detection of
...... a cellular phone.
The following options are set with &F5:
Local Factory Settings MTC
Function Implementation
LAPM-only error correction ................ \N4
Transmit level fixed per cellular phone ... S92
Wait for carrier = 90 .................... S7=90
CD loss delay = 10 sec .................... S10=100
Auto FF/FB enabled ........................ N/A
Start up at 9600bps ....................... S40=2
&Gn V.22bis Guard Tone Selection
This option is for international use only. It is not used in North America. The AT&Gn determines which guard tone, if any, to transmit while in answer mode (transmitting in the high band). The value of n can be 0, 1, or 2. This parameter is set automatically for most countries that require it.
&G0 ... No guard tone set
&G1 ... 550-Hz guard tone set
&G2 ... 1800-Hz guard tone set
&Jn Auxiliary Relay Option
&J0 ... Auxiliary relay is never closed
&J1 ... Not supported (returns ERROR)
&Kn Local Flow Control Options
The AT&Kn command, where n represents 0-4, determines how the flow control between the computer and the local modem is handled.
&K0 ... Disable local flow control.
&K1 ... Reserved.
&K2 ... Reserved.
&K3 ... Enable RTS/CTS flow control (default).
&K4 ... Enable XON/XOFF flow control.
&Mn Asynchronous Communications Mode
The AT&Mn command, where n represents 0-4, determines how the flow control between the computer and the local modem is handled.
&M0 ... Asynchronous mode (default; supplied for backward
....... compatibility only).
&M1 ... Reserved.
&M2 ... Reserved.
&M3 ... Reserved.
&M4 ... Reserved.<
Pn Pulse Dial Make-to-Break Ratio Selection (Japan only)
The AT&Pn command, where n represents 0 or 1, controls the ratio of the off-hook (make) to on-hook (break) interval used by the modem when it pulse dials.
&P0 ... Selects 39:61 make/break ratio at 10 PPS (default)
&P1 ... Selects 33:67 make/break ratio at 10 PPS
&P2 ... Selects 33:67 make/break ratio at 20 PPS
&Qn Asynchronous Communications Mode
&Q0 ... Asynchronous mode, buffered (same as \N0)
&Q1 ... Reserved
&Q2 ... Reserved
&Q3 ... Reserved
&Q4 ... Reserved
&Q5 ... Error control mode, buffered (default; same as \N3)
&Q6 ... Asynchronous mode, buffered (same as \N0)
&Q7 ... Reserved
&Sn Data Set Ready (DSR) Options
The AT&Sn command controls the functions of the modem's DSR circuits.
&S0 ... The DSR signal remains on all the time the modem is
....... powered on (default)
&S1 ... The DSR signal is on during handshaking and is off when
....... carrier is lost.
&Tn Self-Test Commands
The AT&Tn command allows the user to perform diagnostic tests on the modem.
&T0 ... Abort. Stops any test in progress.
&T1 ... Local analog loop. this test verifies modem operation,
....... as well as the connection between the modem and computer.
....... The modem must be off-line when this test is run.
&T3 ... Local digital loopback test.
&T6 ... Remote digital loopback test. This test can verify the
....... integrity of the local modem, the communications link,
....... and the remote modem. The modems must be online with
....... error control disabled when this test is run.
&V View Configuration Profile
The AT&V command displays the contents of the active configuration profile.
&Wn Write Active Profile to Memory
The AT&Wn command, where n is 0, allows you to save a copy of the current active configuration profile to nonvolatile memory. This profile can be restored at any time by using the ATZ command or a power-up reset of the modem.
&Yn Select Stored Profile for Hard Reset
This command is included for compatibility with applications that use the &Y0 command. It does not affect the behavior of the modem.
&Y0 ... Select stored profile 0 on power up
&Y1 ... ERROR
&Zn=x Store Telephone Number
The AT&Zn=x command is used to store a telephone number for later dialing using the ATDS=n (dial stored number) command. In this command, n is 0 or 1 representing 2 storage locations and x is the stored number. The dial string may contain up to 40 characters.
\Gn Modem Port Flow Control
The AT\Gn command determines whether XON/XOFF flow control will be used.
\G0 ... Returns OK for compatibility (default)
\G1 ... Not supported; returns ERROR
\Jn Adjust BPS Rate Control
\J0 ... Turn off feature (default)
\J1 ... Turn on feature
\Kn Break Control
The AT\Kn command determines how the modem processes a Break signal received from the local DTE during a connection (online).
\K5 ... Modem sends Break to remote modem in sequence with
....... transmitted data, non-destructive/non-expedited (default)
\Nn Error Mode Control Selection
The AT\Nn command sets the type of error correction supported by the modem when sending or receiving data.
\N0 ... Buffered mode. No error control (same as &Q6).
\N1 ... Buffered mode (same as \N0)
\N2 ... LAPM, MNP or disconnect mode. This is also known as
....... reliable mode.
\N3 ... LAPM, MNP, or buffered (default). The modem attempts to
....... connect in LAPM error control mode. If this fails, the
....... modem attempts to connect in MNP mode. If this fails,
....... the modem connects in buffered mode and continues
....... operation. This is also known as V.42 auto-reliable
....... mode (same as &Q5)
\N4 ... LAPM or disconnect. The modem attempts to connect in
....... LAPM error control mode. If this fails, the call will
....... be disconnected.
\N5 ... MNP or disconnect mode. The modem attempts to connect
....... using MNP 2-4 error control procedures. If this fails,
....... the modem disconnects. This is also known as MNP
....... reliable mode.
\Qn Local Flow Control Selection
The AT\Qn command sets the type of flow control used on the serial port to adjust for differences in modem port speed.
\Q0 ... Disables flow control (same as &K0)
\Q1 ... Sets flow control to XON/XOFF (same as &K4)
\Q3 ... RTS/CTS to DTE (default; same as &K3)
\Tn Inactivity Timer Limit
The AT\Tn command specifies length of time (in minutes) that the modem waits before disconnecting when no data is sent or received. The time period can be set at n = 0 - 255. A setting of zero disables the timer. As an alternative, the timer may be specified in the S30-Register. This function is only applicable in buffered mode.
\Xn XON/XOFF Pass Through
\X0 ... Modem process XON/XOFF flow control characters locally
....... (default)
\X1 ... Not supported; returns ERROR
%B View Numbers in Blacklist
If blacklisting is in effect, the AT%B command displays the numbers for which the last call attempted in the past two hours failed. In countries that do not require blacklisting, this command returns ERROR.
%Cn Data Compression Control
The AT%Cn command determines the operation of V.42bis and MNP class 5 data compression. Online changes do not take effect until a disconnect occurs.
%C0 ... V.42bis/MNP Class 5 compression disabled (no data
....... compression)
%C1 ... MNP Class 5 compression enabled (no V.42bis)
%C2 ... V.42bis compression enabled (no MNP Class 5)
%C3 ... V.42bis/MNP Class 5 data compression enabled (default)
-Cn Data Calling Tone
Data calling tone is a tone of a certain frequency and cadence specified in V.25 that allows remotes data/fax/voice discrimination. The frequency is 1300 Hz with a cadence of 0.5 seconds on and 2 seconds off.
-C0 ... Disables calling tone (default)
-C1 ... Enables calling tone
Some countries do not permit calling tone to be disabled.
+GCAP Request Complete Capabilities List Syntax:
AT+GCAP
AT+GCAP=?
This command displays one or more lines of information text, in a standard format, describing the basic capabilities of the modem. This allows a software package to determine which groups of extended-syntax commands the modem supports. The response may contain one or more of the following responses:
+CGSM GSM ............... (+C) commands.
+DS Data Compression .... (+D) commands.
+ES Error Control ....... (+E) commands.
+FCLASS Fax ............. (+F) commands.
+MS Modulation Control .. (+M) commands.
+W Wireless ............. (+W) commands.
+GCAP=? may be used to determine whether the modem supports the +GCAP command: an OK response indicates support, ERROR indicates non-implementation.
+GCI Country of Installation Syntax:
AT+GCI=
AT+GCI?
AT+GCI=?
This command configures the modem for the country of use, selecting operational parameters and ensuring conformity to the requirements of the selected country's telephone network. The +GCI parameter may only be changed when the modem is in an idle state.
<T.35 code> refers to the 8-bit hexadecimal number next to the country in the list below.
To determine which countries are currently supported, use AT+CGI=? The command will respond with the T.35 codes for the countries supported. To determine the current country setting, use AT+GCI? The command will respond with the T.35 code for the country selected.
To change the current country selection, use AT+GCI=<T.35 code>
Country <T.35 code>
Australia 09
Austria 0A
Belgium 0F
Canada 20
China 26
Denmark 31
Finland 3C
France 3D
Germany 04
Hong Kong 50
Indonesia 54
Ireland 57
Italy 59
Japan 00
Korea 61
Malaysia 6C
Netherlands 7B
New Zealand 7E
Norway 82
Portugal 8B
Singapore 9C
Spain A0
Sweden A5
Switzerland A6
Taiwan FE
Thailand A9
United Kingdom B4
United States B5
+GMI Request Manufacturer Identification Syntax:
AT+GMI
AT+GMI=?
This command displays one or more lines of information text, identifying the manufacturer of the modem. +GMI=? may be used to determine whether the adapter supports the +GMI command: an OK response indicates support, ERROR indicates non-implementation.
+GMM Request Model Identification Syntax:
AT+GMM
AT+GMM=?
This command displays one or more lines of information text, identifying the modem model. +GMM=? may be used to determine whether the modem supports the +GMM command: an OK response indicates support, ERROR indicates non-implementation.
+GMR Request Revision Identification Syntax:
AT+GMR
AT+GMR=?
This command displays one or more lines of information text, identifying the revision level of the firmware of the modem. +GMR=? may be used to determine whether the adapter supports the +GMR command: an OK response indicates support, ERROR indicates non-implementation.
+MS Modulation Selection Syntax:
AT+MS=<carrier>,<automode>,<min_rate>,<max_rate> AT+MS? AT+MS=?
The AT+MS parameter controls data modulations and bit rates that may be negotiated between a local and remote modem. It accepts four subparameters.
+MS? .. Reports the current settings of subparameters
+MS=? . Displays range of acceptable values for each subparameter
<carrier> Specifies the preferred modulation to be used in originating or answering a connection. The <carrier> subparameter is an unquoted string of characters. If the <carrier> parameter is specified, the other subparameters will revert to factory defaults. If <carrier> is omitted, any unspecified parameters will keep their current values (for example, AT+MS=,0 or AT+MS=,,,2400).
Values accepted for <carrier> are the following:
B103 .. Bell 103 (300bps)
B212 .. Bell 212A (1200bps)
V21 ... ITU-T V.21 (300bps)
V22 ... ITU-T V.22 (1200bps)
V22B .. ITU-T V.22bis (2400bps)
V23C .. ITU-T V.23 with constant carrier(1200/75 or 75/1200bps)
V32 ... ITU-T V.32 (4800 or 9600bps)
V32B .. ITU-T V.32bis (4800 - 19200bps)
V34 ... ITU-T V.34 (2400 - 33600bps)
K56 ... (default) Lucent/Rockwell K56Flex (32000 - 56000bps)
<automode> Enables or disables negotiation of an alternative <carrier> if the preferred modulation is not available. Values accepted for <automode> are the following:
0 .... Disabled. Modem will disconnect if it is unable to
...... negotiate a connection with the specified <carrier>.
1 .... Enabled (default). If the specified <carrier> is
...... unavailable, modem will attempt to negotiate an
...... alternative carrier as appropriate.
<min_rate> Specifies the lowest bit rate at which the modem may
establish a connection. (This value is fixed at zero for the Xircom modem.)
<max_rate> Specifies the highest bit rate at which the modem may
establish a connection. For modulations that support only a fixed bit rate (such as V.22bis), <max_rate> has a fixed value to which it defaults. If the default rate or a rate other than zero is specified, the modem will return ERROR.
This subparameter accepts the following values: 0, 300, 1200, 2400, 4800, 7200, 9600, 12000, 14400, 16800, 19200, 21600, 24000, 31200, 33600bps. If unspecified (set to 0), <max_rate> is determined by the value of <carrier>. If the <carrier> setting is K56, the <max_rate> subparameter should be left at the default value (zero).
Modem S-Registers
This topic provides a reference to all the S-Registers supported by the Xircom modem.
Introduction to S-Registers
The Xircom CreditCard Modem 56T uses memory storage locations, or S-Registers, to hold information controlling its operating environment. Few of these S-Registers require attention from modem users. Some of the S-Registers are reserved. These either contain parameter bit maps for the internal use of the modem or are not in current use. Generally, modem users should not alter or write to any of these reserved S-Registers because doing so could result in the modem behaving unpredictably.
To display the value of an S-Register, type ATSn?, where n is the number of the S-Register, then press Enter.
To modify the value of an S-Register, type ATSn=r where n is the S-Register number and r is the new value or setting, then press Enter.
S-Register Reference
S0 Ring to Answer After
The contents of register S0 sets the number of rings required before the modem goes off-hook to answer an incoming call (auto answer). The value can range from 0 to 255. ATS0=0 disables the auto-answer function. The default is 0.
S1 Ring Counter
This register is read only. The value of S1 increments with each ring. If no rings occur over a six-second interval, the register is cleared. The value of S1 can range from 0 to 255. The default is 0. Limits are country specific.
S2 AT Escape Character
Register S2 defines the ASCII character used in the Escape sequence. This command is used to return to command mode without losing the connection with a remote modem. Default is S2=43, which is the "+" character. Thus, the default Escape sequence is +++. ASCII values 127 and below can be used. To disable this Escape sequence, set S2 equal to a value greater than 127.
S3 Command Line Termination Character
This register contains the ASCII value of the command line terminating character (carriage return). The factory default value is ASCII 13 - the carriage return character. You can set register S3 to any value between 0 and 127.
S4 Response Formatting Character
This register contains the ASCII value of the line feed character. The factory default value is 10. You can set register S4 to any value between 0 and 127. The modem uses a line feed character in command mode when it responds to the computer.
S5 Command Line Editing Character
This register contains the ASCII value of the backspace character and is applicable to asynchronous transmissions only. The factory default value is 8. You can set register S5 to any value between 0 and 32, or to 127. The modem will not recognize the backspace character if it is set to a value greater than ASCII 32.
S6 Wait Before Blind Dialing
This register determines how long the modem waits after going off-hook before dialing the first digit. The wait must be at least 2 seconds. Register S6 can be set to any value between 2 and 65 seconds. The default is 2 seconds. The value of the W dial modifier will override the value in register S6. This operation, however, may be affected by some ATX options according to country restrictions. Defaults and limits are country-specific.
S7 Connection Completion Time-Out
This register determines the number of seconds the originating modem waits for a carrier signal from the answering modem before hanging up. The timer is started when the modem finishes dialing (originate), or goes off-hook (answer). In originate mode, the timer is reset upon detection of an answer tone if allowed by country restriction. The timer also specifies the wait for silence time with the @ dial modifier (in seconds). S7 is not associated with the W dial modifier. Register S7 can be set at from 1 to 255 seconds with a default of 50 seconds. Defaults and limits are country-specific.
S8 Duration of Pause for Comma Dial Modifier
This register determines the number of seconds to pause for each comma (,) in a dial string or command line. The default is 2 seconds, but any value from zero to 65 is acceptable. Defaults and limits are country-specific.
S10 Delay Between Lost Carrier/Hang Up
This register specifies the time (in tenths of a second) that the modem waits after carrier loss before hanging up. The default is 20 (2.0 seconds). This allows for temporary carrier loss without causing the local modem to disconnect. Register S10 will accept a value ranging from 1 to 254 in tenths of a second (0.1 to 25.4 seconds). Defaults and limits are country-specific.
S11 DTMF Tone Duration
This register determines the "touch tone" dialing speed which is prefixed for each country. The value can range from 50 to 150 milliseconds. The default is 95 milliseconds. The value of register S11 has no effect on pulse dialing. Defaults and limits are country-specific.
S12 Escape Guard Time
This register sets the value (in 20 ms increments) of the required pause after the escape sequence. Range is 0 = 255, default is 50 units of 0.02 seconds each, or one second.
S28 V.34 Modulation Enable/Disable
This register enables or disables V.34 modulation. Default setting is 1, valid values are 0 or 1. A value of zero disables V.34 modulation. Any other value in the range enables it.
S30 Inactivity Timer
The value specified by this register sets how long the modem will wait (in minutes) before disconnecting when no data is sent or received. This function is only applicable in buffer mode. It is set by AT\Tn. Values are 0-255. Default is 0 (disabled).
S34 DTE Throughput Limit
This register specifies whether the modem should limit throughput when the DTE is operating at higher speeds (57,600 or 115,200bps).
S34=0 Do not limit throughput (default).
S34=1 Limit throughput to DTE speed.
S35 Data Calling Tone
This register enables or disables a tone of a certain frequency and cadence as specified in V.25 that allows remote data/fax/voice discrimination. It is set by AT-Cn. The frequency is 1300 Hz with a cadence of 0.5 seconds on and 2 seconds off. The default is country-specific. Some countries do not allow data calling tone to be overridden.
S35=0 Data calling tone disabled (default)
S35=1 Data calling tone enabled
S36 Negotiation Fallback
This register specifies the action to be taken in the event of a negotiation failure when error control is selected.
S36=0,2 Hang up
S36=1,3 Fall back to an asynchronous connection
S36=4,6 Attempt MNP. If MNP fails, hang up.
S36=5,7 Attempt MNP. If MNP fails, fall back to asynchronous connection. Default is 7.
S37 Dial Line Rate
S37=0 Maximum modem speed (default)
S37=1 Reserved
S37=2 1200/75bps
S37=3 300bps
S37=4 Reserved
S37=5 Attempt to connect at 1200bps
S37=6 Attempt to connect at 2400bps
S37=7 Attempt to connect at 4800bps
S37=8 Attempt to connect at 7200bps
S37=9 Attempt to connect at 9600bps
S37=10 Attempt to connect at 12000bps
S37=11 Attempt to connect at 14400bps
S37=12 Attempt to connect at 16800bps
S37=13 Attempt to connect at 19200bps
S37=14 Attempt to connect at 21600bps
S37=15 Attempt to connect at 24000bps
S37=16 Attempt to connect at 26400bps
S37=17 Attempt to connect at 28800bps
S37=18 Attempt to connect at 31200bps
S37=19 Attempt to connect at 33600bps
S40 ETC Startup Autorating
S40=0 Start up with normal autorating (default)
S40=1 Start up at initial rate of 4800 or below
S40=2 Start up at initial rate of 9600 or below
S42 Auto Rate
V.32bis and V.22bis auto rate is disabled. Retrain operation is disabled or enabled in date mode, and fallback is disabled in data mode.
S42=0 Auto rate disabled
S42=1 Auto rate enabled (default)
S43 Auto Mode
V.32bis startup auto mode operation disabled.
S43=0 Auto mode disabled
S43=1 Auto mode enabled (default)
S46 Data Compression Selection
The setting of this register is used to turn data compression on or off. It is set by AT%Cn.
Data compression can only be enabled when the modem is operating in an error-control (EC) mode using either V.42 LAP-M or MNP protocols.
S46=0 Modem will not attempt negotiation for data compression
S46=2 Modem will negotiate with a remote modem for data compression (default).
S46=136 Same as S46=0
S46=138 Same as S46=2
S48 LAPM Error Control and Feature Negotiation
S48=7 Negotiation enabled
S48=128 Negotiation disabled; forces immediate fallback options specified in S36.
The following table shows the S36 and S48 configuration settings needed to negotiate certain types of connections.
S48=7
S48=128
S36=0,2 LAPM or hangup do not use
S36=1,3 LAPM or buffered buffered
S36=4,6 LAPM, MNP, or hangup MNP or hangup
S36=5,7 LAPM, MNP, or buffered MNP or buffered
S89 Timer to Control Sleep Mode
This register displays the number of seconds of inactivity (no characters sent from DTE, no RING) in the off-line command state before the modem places itself into standby mode. A value of zero prevents standby mode. Default is 30. Range is 0 and 5 - 65.
S91 Line Transmit Level
This register is effective only for Japan. It specifies the line transmit level, in dB, with an implied minus sign. Default is 15 dB, range is 6 - 15.
S92 Direct Connect Transmit Level
This register sets the transmit level, in dBm, for direct connect cellular. This value may have different settings for different phones. Default is 0 dBm.
S95 Negotiation Message Options
This register enables various result codes indicating the sequence of events in an error-controlled connection. This S-Register does not affect the way the connection is negotiated, it just enables extended messages.
S95=0 Disables extended result code messages.
S95=1 Use DCE (modem-to-modem) speed when reporting CONNECT result codes.
S95=2 Append "/ARQ" to CONNECT result code when an error-controlled (EC) connection is established.
S95=4 Enable CARRIER result codes.
S95=8 Enable PROTOCOL result codes.
S95=32 Enable COMPRESSION result codes.
S98 C Cable Detection Options
This register controls the automatic detection and reporting of changes in the cable or alternative connector attached to the modem.
S98=0 Disables cable detection and reporting.
S98=1 Enable cable detection; disable reporting.
S98=2 Enable cable detection and reporting.
This applies to:
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