The following points are useful when entering AT commands:

Before terminating the AT command line you can edit mistakes using the backspace key. This will delete the last character entered, but it will not delete the AT at the beginning of the line.

Typing AT on its own will result in the OK message being returned by the modem.

The AT can be entered in either upper or lower case, but a combination of both is not valid.

You can enter more than one command on a line between the AT and the carriage return. Spaces are ignored.

AT command descriptions

ATA    Answer

This command instructs the modem to "pick up" the line (go off-hook) and go to line in answer mode immediately. An incoming ringing signal does not have to be detected by the modem. The modem will issue answer frequencies and attempt to train up to the calling modem. If a connection is not established within the time period defined by S register 7, then the NO CARRIER message will be displayed.

ATB   Mode of operation

This command is used to put the modem into Bell mode or ITU-T (CCITT) mode. Bell modes are American modes of operation at 300bps or 1200bps.

ATD  Dial command and dial modifiers

ATD causes the modem to dial a number according to the suffixed modifier. e.g. ATDT12345 causes the modem to Tone dial 12345.

Dial string modifiers:

ATE  Command echo

The ATE command controls the echoing of commands to the DTE device when in command mode.

ATH  Hang up

The ATH command puts the modem into an on-hook or off-hook state e.g. when in command mode ATH would disconnect the call by hanging up the line.

ATI  Interrogate modem

The ATI commands interrogate the modem and returns the relevant information

ATL  Speaker volume

The ATL commands are used to set speaker volume where appropriate.

ATM  Speaker control

The ATM command controls when a speaker is active.

ATN  Automode detection

The ATN command controls the automode detection.

ATO  Modem on-line

The ATO command is used to return a modem to data mode when it is on line and in command mode.

ATQ  Quiet message control

This command is used to switch result codes from the modem to the DTE device on or off.

ATS  Set S register

The ATS command is used to either read the value of an S register or set it to another value. See the Special Commands and Features section for more details.

ATV  Result code format

The ATV command determines the format of the result messages returned by the modem.

ATW  Connect message format

This command determines the format of the messages returned by the modem when it connects in error corrected mode.

ATX  Result code set and blind dialling

The ATX command determines which result code set is to be used by the modem and also determines the level of network tone recognition. See the

ATY  Break disconnect format

This command is used to switch the break disconnect off or on. When the modem is in a non-error corrected mode and the long space disconnect is switched on, the modem will transmit a 4 second break before going on hook. In error corrected mode the modem will go on hook if it receives a break of greater than 1.6 seconds.

ATZ  Modem reset

The ATZ command resets the modem to the profile selected. For example, ATZ1 will reset the modem to profile 1. If no profile number is specified, profile 0 will be used.

AT&C  Data carrier detect

AT&C controls how the modem presents the DCD signal.

AT&D  DTR options

The AT&D command in conjunction with the AT&Q command determines how the modem will react to a loss of DTR.

AT&F  Restore factory configuration

This command loads the factory default configuration.

AT&K  Flow control options

The AT&K command selects the type of flow control to be used by the modem. Flow control is essential when the DTE speed is greater than the actual line speed.

AT&Q  Asynchronous/synchronous operation

The AT&Q command selects the data and transmission mode.

AT&R  CTS control

AT&R controls the response of the CTS signal. CTS is also affected by the AT&K command.

AT&S  DSR control

This command determines how the DSR signal operates.

AT&T  Loopback test options

These commands are used to perform V.54 modem self tests. The tests operate for the length of time specified in S register 18. If this is set to 0, tests can be cancelled by AT&T0.

AT&V  Display modem configuration

AT&V displays the current configurations and the other stored profiles.

AT&W  Save to non-volatile memory

This command saves the current configuration into non-volatile memory.

AT&Y  Set power on default

AT&Y determines which profile is to be loaded when the modem is powered on e.g. AT&Y1 means that the profile stored in location 1 is loaded on power up.

AT&Z  Store telephone numbers

The AT&Z command stores a telephone number into the modems telephone directory. There are 4 telephone locations available, each containing up to 24 digits. e.g. AT&Z2=12345 stores the telephone number 12345 in location 2.

AT\A  Set MNP packet sizes

The AT\A command sets the maximum block size used during an MNP connection. This command is only used when the phone line is very noisy.

AT\B  Set transmit break

The AT\B command is used to transmit a break from the local modem to the remote modem

AT\K  Break control

The AT\K command determines how the modem will react when a break is received. A break can be received by the modem from the remote modem, or the DTE device, or from the local modem with the AT\B command. This command only affects the modem in non-error corrected links.

AT\N  Error correction protocol

AT\N selects the error correction protocol to be used by the modem. Both LAPM and MNP4 are supported. e.g. AT\N4 will cause the modem to establish a LAPM error corrected link only, if an error corrected link cannot be established the call is dropped. In reliable or auto-reliable V.42 mode, LAPM takes precedence over MNP.

AT+MS Select line modulation

This extended format command selects the modulation, enables or disables automode, specifies the lowest and highest connection rates, specifies mu-Law or A-Law codec types, enables or disables robbed bit signalling generation, and specifies the uplink rate.

The command format is:

AT+MS= <mode>, <automode>, <min_rate>, <max_rate>, <x_law>, < rb_signaling>, <uplink_rate>

To determine what options are currently selected, use the command:

AT+MS?

This command returns the current selected parameters e.g.56,1,300,56000,1,0,33600.

To determine what options the modem supports, use the command:

AT+MS=?

This command returns the available parameter values:

(0,1,2,3,9,10,11,56,64,69), (0,1),

(300-56000), (300-56000), (0,1), (0,1),

(300-33600)

The parameters for the AT+MS command are as follows:

<automode>

<x_law>

<rb_signaling>

<uplink_rate>

AT%C  Data compression options

The AT%C command is used to select the data compression mode. The modem supports both MNP5 and V.42bis.

AT%E Auto retrain options

This command selects the auto-retrain facility. When enabled, the modem monitors the line quality and performs a retrain when the line deteriorates. If retraining is unsuccessful, the modem disconnects the call.

AT%L Receive line signal level

The AT%L command reports the receive line signal level. This command is used when the modem is on line but in command mode. A value of 009 indicates a receive line of -9dBm.

AT%Q Receive line noise level

The AT%Q command reports signal quality. This command is used when the modem is on line but in command mode. The higher the returned value, the noisier the line.

Special commands and features

A/ and +++ commands

There are two modem configuration commands that must not be preceded by the AT attention code:

A/

Typing A/ in the terminal emulation window causes the modem to re-execute the command previously entered. Note that it is not necessary to follow A/ with a carriage return.

+++

When in data mode, if the string +++ is sent to the modem preceded and followed by a pause (which by default is one second), the modem will exit from data mode and enter command mode. Meanwhile, the call is not automatically disconnected; data mode can be resumed by issuing the ATO command or the call manually disconnected by issuing ATH command.

Fax mode

Your modem is capable of sending and receiving faxes. Fax operation is controlled automatically by the software that may have been supplied with your modem. Your modem can send and receive faxes at up to 14400bps. The fax feature is compatible with Group 3 fax machines and is fully compliant with the Class 1. Class 2 is supported on all cards in GSM mode (requires GSM Upgrade pack)

S Registers

Your Gold Card modem contains a set of internal registers (known as "S" registers) which are used to control the fine details of its operation.

Most S registers are not applicable to every day use of your Gold Card Global modem and can be ignored.

1. The number in brackets following the S register number shows the default factory setting.
2. When specifying bit-mapped registers with multiple options, the bit pattern is displayed in binary format starting with the most significant bit to the left.
3. Modifying the contents of bit-mapped S registers is not recommended
4. All S register values must be input as 8-bit decimal numbers

S0 (0) Auto answer ring number

Units: Rings
Range: 0 - 255
Defines the number of ring bursts before the modem automatically answers an incoming call. When set to zero, auto-answer is disabled.

S1 (0) Incoming ring count (read only register)

Units: Rings
Range: 0 - 255
Counts the number of ring bursts received. Reset to zero after 8 seconds of no ring.

S2 (43) Escape character

Units: ASCII
Range: 0 - 127
Defines the ASCII character used to exit into command mode from data mode. A value greater than 127 disables escape code detection.

S3 (13) Carriage return character

Units: ASCII
Range: 0 - 127
Specifies the ASCII code to be used as carriage return.

S4 (10) Line feed character

Units: ASCII
Range: 0 - 127
Specifies the ASCII code to be used as line feed.

S5 (8) Backspace character

Units: ASCII
Range: 0 - 127
Specifies the ASCII character to be used to erase the last command character entered.

S6 (4) Wait time for dial tone before blind dialling

Units: Seconds
Range: 4-7
Determines the period of time that the modem waits after connecting to line before commencing blind dialling of the telephone number specified. The W modifier in the dial string will override this and cause the modem to wait for a dial tone before commencing dialling.

S7 (40) Wait for carrier or silence after dialling

Units: Seconds
Range: 1-58
Determines the period of time that the modem waits for carrier from the remote modem before hanging up.

S8 (4) Pause time for the comma (,) dial modifier

Units: Seconds
Range: 4- 11
This register contains the pause time of the (,) dial modifier used in the dial string. Consecutive commas will invalidate the modem's approval if the total pause period exceeds 12 seconds.

S9 (6) Carrier detect response time

Units: tenths of a second
Range: 1-255
This register contains the time period that a received carrier signal must be present for the modem to recognise it and turn on the DCD signal.

S10 (14) Loss of carrier to hang up delay time

Units: tenths of a second
Range: 1-255
This register contains the time period that the modem takes to disconnect from the telephone line upon detection of loss of carrier. If S10 is set to a value less than S9 any loss of carrier will result in disconnection. The loss of carrier time period that can be tolerated is the difference between S9 and S10.

S11 (95) Duration and spacing of DTMF tones

Units: milliseconds
Range: 50-255
This register contains the time period of the duration and inter-digital pause of the DTMF dialling tones. This is a read only register.

S12 (50) Escape code guard time

Units: fiftieths of a second
Range: 0-255
This register contains the time period of the escape code guard time. The escape code guard time is the delay required prior to and immediately succeeding the escape code. If the guard time is defined as 0, there will be no guard time and 3 consecutive escape characters will cause the modem to enter the command mode.

S14 (138) Bit mapped register

S16 (0) Test options, bit mapped (read only register)

S18 (0) Test timer

Units: seconds
Range: 0-255
This register defines the time period (in seconds) of the modems diagnostic tests. When a test has been active for a period given by the register then the modem will automatically cancel the test. A value of 0 will disable the test timer and any test will remain active until cancelled by the user.

S21 (52) Bit mapped register

S22 (119) Bit mapped register

S23 (182) Bit mapped register

S25 (5) Delay to DTR

Units: seconds
Range: 0-255
Sets the length of time that the modem will ignore DTR before hanging up.

S26 (1) RTS to CTS delay

Units: hundredths of a second
Range: 0-255
Sets the time delay before the modem turns CTS on after detecting an off-to-on transition on RTS when &R0 is commanded.

S27 (9) Bit mapped

S29 (0) Flash dial modifier

Units: 10 milliseconds
Range: 0-255
Sets the length in time, in units of 10ms, that the modem will go on-hook when it encounters the flash (!) dial modifier in the dial string.

S30 (0) Disconnect inactivity timer

Units: tens of seconds
Range: 0-255
Sets the length of time that the modem will stay on line before disconnecting when no data is sent or received. In error correction mode, any data transmitted or received will reset the timer. In other modes, any data transmitted will reset the timer.

S31 (194) Modem modes

S32 (17) XON character

Units: ASCII
Range: 0-255
Sets the value of the XON character.

S33 (19) XOFF character

Units: ASCII
Range: 0-255
Sets the value of the XOFF character.

S36 (7) LAPM failure control

This value indicates what should happen upon a LAPM failure. These fallback options are initiated upon connection if S48=128.

S37(0) Desired line connection speed

S38 (20) Delay before hanging up

Units: seconds
Range: 0-255
This register determines the time period that the modem waits before dropping the line when in error correction mode.

S39 (3) Flow control

S40 (104) Bit mapped

S41 (195) Bit mapped

S46 (138) Data compression control

Range: 136 or 138

S48 (0) V.42 negotiation action

Range: 0, 7 or 128
The V.42 negotiation process determines the capabilities of the remote modem. However, when the capabilities of the remote modem are known and the negotiation is unnecessary, this process can be bypassed if so desired. If an invalid number is entered, it is accepted but S48 will act as if 128 has been entered.

S86 (0) Connection failure identification (read only register)

This register gives diagnostic information regarding why the modem failed to connect.

S95 (44) Extended result codes

Modem Connect Messages

Your modem responds to commands and events by returning result codes. Result codes can be verbal (the default setting), numeric or can be turned off entirely. You can easily understand the verbal form, but your computer may find it easier to handle the numeric form. The table below lists the Hayes digital codes and their verbal equivalents.