The Hayes AT command set is the industry standard method of communicating with and setting up a modem. These represent commands for the Rockwell chipsets.




Syntax Rules

 


Hayes AT Commands

AT or at always precedes a command. The modem needs these two letters to adjust itself to the settings of the PC’s comport. The modem then switches automatically to the defined baud rate and parity, until the next command is issued or the modem is turned off. The modem will not respond to any commands not preceded by an AT.

The modem recognises following formats :

1 or 0 start bits, 7 or 8 data bits, no, odd or even parity and 1 or 2 stop bits.

The commands can be issued at a rate between 300 and 115,000bps. In V.23 mode, the commands are sent at 1,200bps. The modem’s replies are then sent at 75bps to the PC.

The command interpreter recognizes AT and at, but not At or aT. Both characters have to be sent in upper- or lowercase and must be sent directly after one another.

 

  • +++ Switch from data mode to command mode without dropping the line. A second before and after this command, no other character may be sent to the modem, including a <CR>.
  • A/ Repeat last command, no <CR>

     

    ATA Answer incoming call

     

    When you want to answer a call manually, you type this command after a ring has appeared on the screen of your Terminal emulator.

     

     

     

    D Dial a telephone number

     

    ATDTn After issuing this command, the modem will attempt to establish a connection and dial the number n.

     

    Options to the command D:

  • W Wait for dialtone. When using a PABX this is used to wait for the second dialtone. Note: not all PABXs give a second dialing tone. Consider using "@" instead.

    @ Wait for silence for 5 seconds.

    , Pause for 2 seconds (S8)

    ! Flash ( on-hook for value in S29 )

    ; Return to command mode after dialing.

    P Pulse dial

    T Tone dial

    n The telephone number to be dialed

    Sn Dial number stored in directory entry &Zn where n=0..19. The selected number is shown on the screen for verification.

    J Perform MNP10 link negotiation at highest supported speed (for this call only).

    L Redial last number.

    ^ Disable calling tone, this call only.

  • The call can be aborted at any stage before the connect message appears, by entering any character except Linefeed.

     

    ATE Command echo to host

     

    E0 Commands are not echoed

    E1 Commands are echoed

     

    With this command you can select if the modem should return all the commands to the screen or not. This is useful to check if all characters are received by the modem. If characters appear double on the screen, disable echoing by the modem or by your terminal. The value of ATE can be written in the RAM of the modem using AT&W.

     

    ATFn Select transmission mode/speed

     

    F0 Auto mode

    F1 V.21 300bps

    F3 V.23 75Tx/1200Rx with AT%F1

    V.23 1200Tx/75Rx with AT%F2

    F4 V.22 1,200bps

    F5 V.22bis 2,400bps

    F6 V.32bis 4,800bps

    F7 V.32bis 7,200bps

    F8 V.32bis 9,600bps

    F9 V.32bis 12,000bps

    F10 V.32bis 14,400bps

     

    These commands are not valid for V.34 modems. The equivalent command for the V.34 modems is +MS, please refer to this command.

     

     

    ATH Go on-hook, hang up.

     

    H0 Go on-hook ( Hang up )

    H1 Go off-hook

     

    ATI Identifiers

     

    I0 Product code

    I1 Pre-computed Checksum

    I2 Returns OK

    I3 Returns OK

    I4 OEM String

    I5 - I11 Returns OK

    I12 ROM Checksum

    I13 RC Version number

    I14 Shows Firmware version

    I15 Shows selected country

    I17 GSM option

    I18 Shows Supported GSM Kit (GSM-ready™ only)

     

    ATL Speaker volume settings

     

    L0 Lowest speaker volume

    L1 Low speaker volume

    L2 Medium speaker volume

    L3 Highest speaker volume

     

    With this command the speaker volume can be set.

     

    ATM Speaker control

     

    M0 Speaker always off

    M1 Speaker on until carrier detected

    M2 Speaker always on

    M3 Speaker on only while answering

     

    ATNn Select Auto mode

     

    N0 Auto mode disabled

    N1 Auto mode enabled

     

    This command is not longer valid for the V.34 modems.

     

    ATOn Return to data mode

     

    O0 Return to data mode from command mode, only if on-line.

    O1 Return on-line and initiate retrain (2400bps or higher)

     

    ATQn Result codes

     

    Q0 Modem returns result codes

    Q1 Quiet mode enabled. Modem gives no result codes.

     

    If the quiet mode is enabled, the responses from the modem are not sent to the PC.

     

     

     

    ATSn Sets and reads the selected register

     

    Sn=x Sets register n to the value x

    Sn? Reads the value of register n

     

    n is a numeric value, varying between 0 and 255 (depending on the register).

     

    ATVn Result codes in numerical or verbose form

     

    V0 Returns the code in numerical form

    V1 Full-word result codes

     

    ATWn Connect messages formatting

     

    W0 DTE rate ( connect rate )

    W1 Hayes 4 line format : Carrier, Protocol, Compression, DTE rate

    W2 Result code is DCE rate ( carrier rate )

     

    ATXn Extended Result codes

     

    X1 Ignore dialtone and busy tone

    X2 Ignore busy tone

    X3 Inner dialtone

    X4 Modem recognises dialtone and busy tone

     

    X3 and X1 set the modem for Blind Dialing. This option is country specific, because some countries do not allow blind dialing.

     

    ATYn Long Space disconnect

     

    Y0 Disable long space disconnect

    Y1 Enable long space disconnect

     

    If the modems receives after activating this function, a BREAK-signal of at least 1.6 seconds coming from the remote PC, it will send a BREAK-signal of 4 seconds back to the remote PC before hanging up the telephone line.

     

    ATZn Resetting the modem

     

    Z0 Restore stored profile 0

    Z1 Restore stored profile 1

     

    If this command is issued to the modem during a connection, the modem will drop the line. According to the parameter n, the modem will restore the values stored in the non-volatile RAM (See also &W ).

     

    AT&Cn Carrier-detect

     

    &C0 DCD is always active

    &C1 DCD is active if modem is on-line

     

    Data Carrier Detect (DCD) is a hardware signal that notifies the software that the modem is in communication with another modem. Most software’s will not start-up properly if the DCD is active. Default is &C1.

     

     

    AT&Dn Data Terminal Ready settings

     

    &D0 Modem ignores DTR

    &D1 Go to command mode on ON-to-OFF DTR transition.

    &D2 Hang up on DTR-drop and go to command mode

    &D3 Reset (ATZ) on DTR-drop. Modem hangs up.

    AT&F Restore Factory Settings

     

    &F0 Use profile 0

    &F1 Use profile 1

     

    The modem is reset to the default firmware settings. If the modem is on-line, the command will not be executed.

     

    AT&Gn Select guard tone

     

    &G0 Disables guard tone

    &G1 Disables guard tone

    &G2 Selects 1800Hz guard tone

     

    This command may not be permitted in some countries.

     

    AT&Kn Flow Control

     

    &K0 Flow control disabled

    &K3 RTS/CTS flow control (Hardware)

    &K4 XON/XOFF flow control (Software)

    &K5 Transparent XON/XOFF flow control

    &K6 RTS/CTS and XON/XOFF flow control

     

    Flow control is the use of characters or RS232 signals to start and stop the flow of data to avoid data loss during buffering. This is extremely important when the DTE/DCE rate is different from the line speed, e.g. when data compression is used. The DTE/DCE rate must be higher then the line speed.

     

    RTS/CTS flow control (Hardware flow control)

     

    The PC will send data to the modem. The modem will store this data in a buffer. When this buffer is full, the modem will drop the CTS-line, telling the PC that it has to stop transmitting data until the signal raises again. If the RTS-signal is OFF, transmitting data to the PC is stopped until the signal switches to ON.

     

    XON/XOFF flow control (Software flow control)

     

    If the modem receives a XON-character (S32) from the PC, it stops transmitting data to the PC until it receives a XOFF-character (S33). The process is similar if the PC is sending data to the modem.

     

    NOTE : The preferable setting is RTS/CTS flow control

     

    AT&Pn Pulse dial make-break

     

    &P0 : 61/39 ratio at 10pps

    &P1 : 67/33 ratio at 10pps

    &P2 : 39/61 ratio at 20pps

    &P3 : 33/67 ratio at 20pps

     

    Settings may be locked depending on country selection. Default is also country dependent.

    AT&Qn Sync/Async Mode

     

    &Q0 : Selects direct async operation.

    &Q1 : Selects synchronous connect mode with async off-line command mode.

    &Q2 : Selects synchronous connect mode with async off-line command mode and enables DTR dialing.

    &Q4 : Selects Autosync™ mode

    &Q5 : The modem will try to negotiate an error corrected link.

    &Q6 : Selects async operation in normal mode.

     

    This command is used to control the connection modes permitted.

     

    AT&Rn CTS/RTS option

    &R0 : In sync mode, CTS tracks the state of RTS. In async mode, CTS acts according V.25bis handshake.

    &R1 : In sync mode CTS is always on. In async mode, CTS will drop only if required by flow control.

     

    This selects how the modem controls CTS. CTS operation is modified if hardware FC is selected ( AT&Kn ).

     

    AT&Sn DSR Override

     

    &S0 : DSR will remain on at all times.

    &S1 : DSR will become active after answer tone has been detected and inactive after the carrier has been lost.

     

    This command selects how the modem will control DSR.

     

    AT&Tn Test and diagnostics

     

    &T0 : Terminates test

    &T1 : Initiates local analogue loop back

    &T2 : Returns ERROR

    &T3 : Initiates local digital loop back

    &T4 : Enables digital loop back acknowledgment for remote request.

    &T5 : Disables digital loop back acknowledgment for remote request.

    &T6 : Requests a remote digital loop back without self test.

    &T7 : Requests a remote digital loop back with self test

    &T8 : Initiates local analogue loop back with self test.

     

    The modem will perform selected test and diagnostic functions according to the parameter supplied. A test can be run only when in an asynchronous operation in non-error-correction mode. To terminate a test in progress, the escape sequence must be entered first, except for parameters 7 and 8.

     

    AT&Vn Display current configuration and stored profiles

     

    Reports the current (active) configuration, the stored (user) profiles, and the first four stored telephone numbers.

     

    AT&Wn Store current configuration

     

    &W0 : Store current configuration in profile 0

    &W1 : Store current configuration in profile 1

     

    AT&Xn Select Synchronous Clock Source

     

    &X0 : Selects internal timing

    &X1 : Selects external timing

    &X2 : Selects slave receive timing

     

    Selects the source of the transmit clock for the synchronous mode of operation.

     

    AT&Yn Designate a default reset profile

     

    &Y0 : The modem will use profile 0

    &Y1 : The modem will use profile 1

     

    Selects which user profile will be used after a hard reset.

     

    AT&Zn Store telephone number

     

    &Zn=x n=0 to 3 and x=dial string

     

    AT%En LQM and Auto-retrain or FB/FF

     

    %E0 : Disable Line Quality Monitor and auto-retrain

    %E1 : Enable Line Quality Monitor and auto-retrain

    %E2 : Enable Line Quality Monitor and fall back/fall forward. (V.34 only)

     

    Controls whether or not the modem will automatically monitor the line quality and request a retrain or fall back / fall forward depending on the line quality.

     

    AT%Cn Enable/Disable data compression

     

    %C0 : Disables data compression

    %C1 : Enables MNP5

    %C2 : Enables V.42bis

    %C3 : Enables both V.42bis and MNP5 data compression.

     

    Enables or disables data compression negotiation. The modem can only perform data compression on an error corrected link.

     

    AT\Gn Modem to modem flow control

     

    \G0 : Disables modem-to-modem flow control

    \G1 : Enables modem-to-modem flow control

     

    In non-error correction mode, the modem enables or disables the generation or recognition of modem to modem XON/XOFF flow control according to the parameter supplied. In error correction mode, the setting of \G is ignored.

     

    AT\Nn Operating mode

     

    \N0 : Normal speed buffered mode. (&Q6)

    \N1 : Serial interface selected. (&Q0)

    \N2 : Reliable connection ( First V.42 the MNP4). Failure to make a reliable connection results in modem hanging up.

    \N3 : Auto reliable mode ( First V.42, then MNP4 then speed buffered )

    \N4 : V.42 (LAPM) . If connection fails, modem hangs up.

    \N5 : MNP4 EC mode. Failure results in hanging up.

     

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

     

    \An Select maximum MNP block size

     

    \A0 64 characters

    \A1 128 characters

    \A2 192 characters

    \A3 256 characters

     

    )Mn Enable cellular power level adjustment

     

    )M0 : Disables transmit power level adjustment during MNP10 link negotiation.

    )M1 : Enables transmit power level adjustment during MNP10 link negotiation. V.34 : Uses the @Mn value to establish initial cellular connection. After connection power level is determined by modem.

    )M2 : Enables transmit power level adjustment during MNP10 link negotiation. Uses the @Mn value to establish initial cellular connection. After connection power level is fixed. (V.34 only)

     

    Enables or disables automatic adjustment of the transmit power level to accommodate the signaling requirements of cellular telephone equipment.

     

    -Kn MNP Extended Services

     

    -K0 Disables V.42 LAPM to MNP10 conversion

    -K1 Enables V.42 LAPM to MNP10 conversion

    -K2 Enables V.42 LAPM to MNP10 conversion, inhibits MNP ES initiation during V.42 LAPM answering mode detection Phase (V.34 only)

     

    Enables or disables conversion of a V.42 connection to a MNP10 connection.

     

    V.34 Commands

    Following commands are valid only for the V.34 modems.

     

    @Mn Initial Cellular Power Level setting

     

    @M0 -26dBm (Default)

    @M1 -30dBm

    @M2 -10dBm

    @M3-@M10 -10dBm

    @M11 -11dBm

    ...

    @M31 -31dBm

     

    Sets the initial power level for up shift at connect until line conditions can be determined.

     

    :En Compromise Equalizer Enable command

     

    :E0 Disables the equalizer

    :E1 Enables the equalizer

     

    Enables or disables the V.32 compromise equalizer. This command can be used when the modem is attached to either a flat line or a cellular connection.

     

    +MS Select Modulation

     

    Note : The use of the Nn command is not recommended for speeds higher than 14.400.

    Syntax:

     

    +MS=<mod>[,[<auto mode>][,[<min-rate>][,[max_rate>]]]]

     

    +MS? Reports selected options

     

    response : +MS:11,1,300,33600 (example)

     

    +MS=? Reports supported options

    response : +MS:(0,1,2,3,8,9,10,13,64,69,74),(0,1),(300-33600),(300-33600)

    Sub parameter definitions:

    1. Mod

     

    <mod>

    Modulation

    Bps

    0

    V.21 300

    1

    V.22 1200

    2

    V.22bis 2400 or 1200

    3

    V.23 1200/75

    9

    V.32 9600,4800

    10

    V.32bis 14400,9600,7200, 4800,1200

    11

    V.34 33600,32100,28800, 26400,24000, 21600, 19200, 16800, 14400,9600,7200, 4800, 2400

    64

    Bell 103 300

    69

    Bell 212 1200

    74

    V.FC 28800,26400,24000,21600, 19200, 16800, 14400,9600,7200,4800,2400

     

    2. <Auto mode> is an optional numeric value which enables or disables automatic modulation negotiation using V.8 or V.32bis Annex A. The options are :

     

    0 Auto mode disabled

    1 Auto mode enabled using V.8 or V.32bis Annex A

     

    The default value is 1, which enables auto mode. Note, however, there are modulations for which there is no automatic negotiation, e.g., Bell 212.

     

    <Auto mode>=1

     

    The modem connects at the highest possible rate in accordance with V.8 or V.32bis Annex A if V.8 is not supported by the remote modem.

     

    A. If <max_rate> is greater than the highest speed supported by then modulation specified by <mod>, the modem auto modes down from the highest rate to the selected modulation. For example : +MS=10,1,1200,24000 selects auto moding down from V.32bis 14400bps.

     

    B. To emulate issuance of the N1 command, specify the modulation and the rate to start auto moding down from using <mod> and <max_rate>, respectively. Examples :

     

    +MS=11,1,300,16800 auto mode at V.34 16800bps

    +MS=9,1,300,12000 auto mode at V.32bis 12000bps

    3. <Min_rate> is an optional number which specifies the lowest rate at which the modem may establish a connection. The value is decimal coded, in units of BPS, e.g. 2400 specifies the lowest rate to be 2400. The default is 300 for 300bps.

     

    3. <Max_rate> is an optional number which specifies the highest rate at which the modem may establish a connection. The value is decimal coded, in units of BPS, e.g. 14400 specifies the lowest rate to be 14400. The default is 33,600 for 33,600bps.

     

     


    AT Command Result Codes

    The modem responds to commands from the DTE ( PC ) and to activity on the line by signaling to the DTE in the form of result codes. The result codes that the modem can send are described below.

    Value Verbose

     

    0 OK

    1 RING

    3 NO CARRIER

    4 ERROR

    5 CONNECT 1200

    6 NO DIALTONE

    7 BUSY

    8 NO ANSWER

    9 CONNECT 0600

    10 CONNECT 2400

    11 CONNECT 4800

    12 CONNECT 9600

    13 CONNECT 7200

    14 CONNECT 12000

    15 CONNECT 14400

    16 CONNECT 19200

    17 CONNECT 38400

    18 CONNECT 57600

    19 CONNECT 115200

    22 CONNECT 75TX/1200RX

    23 CONNECT 1200TX/75RX

    24 DELAYED

    32 BLACKLISTED

    33 FAX

    35 DATA

    40 CARRIER 300

    44 CARRIER 1200/75

    45 CARRIER 75/1200

    46 CARRIER 1200

    47 CARRIER 2400

    48 CARRIER 4800

    49 CARRIER 7200

    50 CARRIER 9600

    51 CARRIER 12000

    52 CARRIER 14400

    53 CARRIER 16800

    54 CARRIER 19200

    55 CARRIER 21600

    56 CARRIER 24000

    57 CARRIER 26400

    58 CARRIER 28800

    59 CARRIER 31200

    60 CARRIER 33600

    61 CONNECT 16800

    62 CONNECT 21600

    63 CONNECT 24000

    64 CONNECT 26400

    65 CONNECT 28800

    66 CONNECT 33600

    67 COMPRESSION: CLASS 5

    68 COMPRESSION: V.42 bis

    69 COMPRESSION: NONE

    70 PROTOCOL: NONE

    77 PROTOCOL: LAPM

    80 PROTOCOL: ALT

    81 PROTOCOL: ALT-CELLULAR

    +F4 +FCERROR

     

     


    Supported countries

     

    To change the country settings, use followingfollow next procedure :

     

    AT*NCnn

    Modem responds with OK

    ATZ

    Modem responds with OK

     

    Note : Some counties do not allow their country settings to be altered.

     

    *NCnn Country select

     

    40 Australia

    1 Austria

    2 Belgium

    3 Denmark

    4 Finland

    5 France

    6 Germany

    17 Greece

    10 Netherlands

    7 Ireland

    8 Italy

    43 Japan

    26 Namibia

    11 Norway

    12 Portugal

    27 South Africa

    13 Spain

    14 Sweden

    15 Switzerland

    16 UK

    19 Czech Republic

    24 Poland

    25 Russia

    22 United States

     

    Note : Use the Interactive Manual™ to setup the country.

     


    S-Registers

    S0 Auto-answer

  • Sets the number of the rings required before the modem automatically answers a call. Setting this register to zero disables auto-answer mode

    Range : 0 to 255

    S1 Ring counter

    S1 is incremented each time the modem detects a ring signal on the telephone line.

    Range : 0 to 255

    S2 Escape character

    S2 holds the decimal value of the ASCII character used as the escape sequence. A value over 127 disables the escape process.

    Range : 0 to 127 (Default = 43)

    S3 Carriage Return Character

    Sets the command line and result code terminator character. Pertains to asynchronous operation only.

    Range : 0 to 127 ASCII decimal (Default=13)

    S4 Line feed Character

    Sets the character recognised as a line feed. Pertains to asynchronous operation only.

    Range : 0 to 127 ASCII decimal (Default=10)

    S5 Backspace Character

    Sets the character recognised as a backspace.

    Range : 0 to 32 ASCII decimal (Default=8)

    S6 Wait for dialtone

    Sets the time in seconds that the modem will try to detect a dialtone (if set) and wait before starting to dial.

    Range : 2 to 255 seconds

    S7 Wait for Carrier after dial

    Sets the time in seconds that the modem will wait for a carrier before hanging up.

    Range : 1 to 255 seconds

    S8 Pause time for delay

    Sets the time the modem must pause when the ‘,’ dial modifier is used.

    Range : 0 to 255 seconds

    S9 Carrier detect response time

    Sets the time in 10th of a second, that the carrier must be present before the modem considers it valid and turns on RLSD.

    Range : 1 to 255 tenths of a second.

    S10 Lost carrier to Hang-up delay

    Sets the time in 10th of a second, that the modem waits before hanging up after a loss of carrier.

    Range : 1 to 255

    S11 DTMF Tone duration

    Range : 50 to 255 milliseconds (Default=95)

    S12 Escape Prompt Delay

    Defines the maximum period, in fifties of a second, allowed between receipt of the last character of the three escape character sequence and the sending of the OK message.

    Range : 0 to 255 1/50 of a second

    S18 Test timer

    Sets the length in seconds that the modem conducts a test.

    Range : 0 to 255 seconds

    S25 Delay to DTR

    Sets the time that the modem will ignore DTR before taking action specified by &Dn.

    Range : 0 to 255 seconds

    S26 RTS to CTS delay

    Sets the time delay, before the modem turns on CTS after detecting an OFF-ON transition on RTS when &R0 is commanded.

    Range : 0 to 255 hundredths of a second

    S32 XON Character

    Range : 0 to 255 ASCII decimal (Default=17)

    S33 XOFF Character

    Range : 0 to 255 ASCII decimal (Default=19)

    S38 Delay Before Forced Hang-up

    This register sets the delay between the modem’s receipt of the H command to disconnect and the disconnect operation.

    Range : 0 to 255 seconds

    S86 Call Failure Reason Code

    When the modem issues a NO CARRIER result code, a value is written to this S-register.

    Range : 0,4,5,9,12,13 or 14

    0 Normal disconnect, no error occurred

    4 Loss of carrier

    5 V.42 negotiation failed

    9 The modems could not find a common protocol

    12 Normal disconnect initiated by the remote modem

    13 Remote modem does not respond after 10 re-transmissions of the same message.

    14 Protocol violation

    S91 PSTN Transmit level Attenuation

    Sets the transmit level attenuation level from 0 to 15dBm for the PSTN mode. Some countries may not permit changing the transmit level.

    Range : 0 to 15dBm (Corresponding to 0 to -15dBm transmit level)

    Default : 10dBm

  • S95 Extended Result Codes

  • The bits in this register can be set to override some of the Wn command options. A bit set to a 1 in this register will enable the corresponding result code regardless of the Wn setting.

    Bit 0 Connect message indicates DCE speed

    Bit 1 Append /ARQ to CONNECT XXXX

    Bit 2 Enable CARRIER XXXX message

    Bit 3 Enable PROTOCOL message

    Bit 4 Reserved

    Bit 5 Enable COMPRESSION XXXX

    Bit 6 Reserved

    Bit 7 Reserved



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