Chapter 2. Basic Command Set

AT Command prefix

Function

Prefix to modem commands. "AT" may be in lowercase or uppercase, but not mixed case.

Command Syntax

AT <Argument>

Argument

None.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

In order for the modem to accept the "AT", there must be 1 ms of inactivity preceding the command on the DTE TD line. This timing constraint is a result of rack applications, where older versions of product, experienced a situation where DTR dropped or the remote DCE disconnected during an ASCII file transfer. The ASCII file that was still being sent to the modem at a high baud rate after it disconnected contained the characters "AT". The product then went into command mode and waited for the line terminator character (S3) to follow. The host was unaware that it had sent an "AT" to the modem, but reported that the modem was unresponsive.

"AT" must precede all other commands except the A/, +++, and A> commands. Any characters that preceded the "AT" are ignored. Any characters that follow the "AT" are treated as commands, until the line terminator character (S3) is received.

When a command prefix is entered, modem clears previous command buffer in preparation for accepting a new command line.

A Answer

Function

Command to execute answer sequence. Modem goes off hook, waits for billing delay time, then sends answer tone and goes into handshake sequence.

Command Syntax

ATA

Arguments

None.

DTE Interface

DSR is asserted after modem goes off hook, if &S0=1, and modem is not in test mode (following ITUT V.22bis recommendation, self test section)

LED

None.

Aborting Events

Any key pressed during the answer sequence will abort it and return modem to command mode.

DTR is not asserted and &D is not equal 1; or the time stored in S register 7 expires.

Other

The speaker is activated when the modem goes offhook, as set by the M command.

Any other commands that follow ANSWER (A) are ignored.

A/ Re-execute Command

Function

The A/ command causes the modem to re-execute the last command that was executed one time. This command does not take the AT prefix or a carriage return.

Command Syntax

A/

Arguments

None.

DTE Interface

None.

LEDS

None.

Aborting Events

None.

A> Re-execute Command Continuously

Function

The A> command causes the modem to re-execute the last command that was executed continuously. The S6 register value is used as a delay between re-executions. This command does not take the AT prefix or a carriage return.

Command Syntax

A>

Arguments

None.

DTE Interface

None.

LEDS

None.

Aborting Events

<Any Key> during the execution delay period, will terminate the operation.

B US/ITUT Answer Sequence

Function

Select between US answer sequence (2325 Hz) and ITUT answer sequence (2100 Hz and 2250 Hz).

Command Syntax

ATB <argument>

Arguments

0

ITUT V.25 answer sequence. Also used to answer calls originating outside the US or Canada [Default].

1

Bell answer tone.

If no argument is given an argument value of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

B0 is required to activate &G1 and &G2 commands.

C Transmitter

Command is ignored and does not generate "ERROR" message.

D Dial

Function

Modem goes off hook, enters originate mode (unless R command is used), waits the number of seconds stored in the S6 register, if X command is set to 0,1,3 or 5, and dials string that follows. Call progress result codes (if any) are sent to the DTE (See the Q, V and X commands). The result is that the modem establishes a data connection and goes into data mode (or command mode: see ";" argument), or fails to establish a data connection and reverts to command mode.

Command Syntax

ATD <argument>

Arguments

[0..9]

Numeric digits.

#,*

Extended touch tone pad tones.

,

Pause modem delays for the number of seconds stored in the S8 register before executing the following commands or arguments in dial string.

;

Return to command mode after dialing is completed.

!

Flash switch hook . The modem goes off hook for 0.5 second , then goes on hook for 0.5 seconds and goes offhook again. This command is used to transfer calls to another extension.

T

Touch tone dialing S11 resister sets duration and spacing of touch tones.

P

Pulse dialing modem pulse dials using &P command parameter.

@

Wait for answer modem will dial string, detect at least one ring signal, wait for five seconds of silence at the remote end for up to the number of seconds stored in the S7 register, and then execute the rest of the dial string that follows the @ command. This command is functional when the X command is set to 3,4,5 and 6.

R

Reverse frequencies modem reverses originate and answer frequencies, so that it originates in answer mode.

Sn

Modem dials string found in NVRAM location n (n = 03).

"

Quote mode when inserted at the beginning of a dial string, it can be followed by "dialable" letters in either touch tone or pulse dial modes. Also used to indicate termination of dial string. The second quote is not required unless other commands follow the dial string.

/

Short delay modem delays 125 ms before proceeding with dial string execution. Can also be a nondial command.

W

Wait for second dial tone before proceeding with dial tone execution. This feature is active when result code option X3 or greater has been issued . If the modem is set to X2 or lower, the modem interprets the W as a comma (two seconds pause default value or the value of S8).

L

Causes the modem the dial the number that is stored in last dialed buffer. This buffer is reset on ATZ or power on reset. ATDL? will display the number that is in the buffer.

If no argument is given, modem goes off hook waits for answer tone in preparation for making a data connection.

DTE Interface

DSR is asserted after dialing, when the modem detects the remote modem's

answer tone if &S1 (DSR is always on if &S0)

LED

None

Aborting Events

• Any key pressed When a dial string is aborted, any additional commands following the dial string are not executed.
• Failure to establish data connection.
• No carrier sensed after time in S7 register has elapsed.
• Failure to detect ring signal or silence during processing of an @ command.
• The modem detects a busy signal and the X parameter is set to 3, 4, 5 and 6.
• The modem detects no dial tone and the X parameter is set to 2, 4 or 6.

Other

• Modem will go off hook and dial as soon as it detects dial tone, if X command is set to 2 , 4 or 6 ("fast dial" mode).
• The speaker is activated when modem goes offhook, as set by the M command.
• Dial string may include up to 60 characters, excluding "AT" prefix, <CR> character and spaces.

E Echo

Function

Enables echo of commands to DTE in command mode. Echo is initialized by DIP switch # 4. Echo is also initialized by system reset commands (see Z command).

Command Syntax

ATE <argument>

Arguments

0

Modem does not echo commands to DTE in command mode.

1

Modem echoes commands to DTE in command mode [DEFAULT].

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

Echo is turned off when parsing a command line, and reverts to the state defined by the E command otherwise.

F Duplex

Function

Modem echoes transmitted data to DTE in online mode.

Command Syntax

ATF <argument>

Arguments:

0

Transmitted data is echoed to DTE in online mode.

1

Transmitted data is not echoed to DTE in online mode [Default].

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

H Off Hook

Function

Command the modem to connect with the phone line.

Command Syntax

ATH <argument>

Arguments

0

Modem goes on hook (opens phone line relay).

1

Modem goes off hook (closes phone line relay).

If no argument is given an argument of 0 is assumed.

DTE Interface

None

LED

None.

Aborting Events

None.

I Inquiry

Function

Command returns various information screens to DTE.

Command Syntax

ATI <argument>

Arguments

0

4 digit product code (yyyx, where x is a revision identifier and y is the maximum speed divided by 10) is sent to the DTE. (1440 for Sportster)

1

Modem performs checksum operation on supervisor code and sends results to DTE.

2

Modem tests RAM by writing and reading alternating Hex bytes 55h and AAh into the RAM, and returns the results by "ERROR" or "OK" result code to the DTE.

3

Modem returns Product ID string. The string contains the Company name, the Product line name and the speed of the product. Additionally, some special features like FAX and VOICE will also be listed.

4

Modem sends one screen of data to the DTE indicating the present configuration of the following settings:

B, E, F, M, Q, V and X commands

DTE baud rate, parity, word length, dial type (pulse or tone), and H setting (On or Off Hook) .

&A, &B, &C, &D, &G, &H, &I, &K, &M, &N, &P, &R, &S, &T, and &Y

S register values from (S0 S42)

LAST DIALED #:

5

Modem sends two screens of data to DTE indicating present configuration of the following commands stored in each NVRAM template:

Dial type, B, F, M, X commands.
For PC Internal version, E, Q, and V commands

Stored default baud rate, Stored parity, Stored Word length.

&A, &B, &G, &H, &I, &K, &M, &N, &P, &R, &S, &T, and &Y settings.
For PC Internal version &D and &C commands.

S register values from S0, S2S15, S19, S21S23, S25, S27, S28, S29 S36, S38 S42.

Phone numbers stored in locations 0 through 3.

6

Modem sends diagnostic screen to DTE with the following information from the previous data connection:

Numbers of characters sent, received, lost.

Numbers of octets (compressed characters) sent, received.

Numbers of blocks sent, received, resent.

Numbers of retrains requested, granted.

Number of line reversals.

Numbers of protocol blocks in error.

Numbers of link timeouts, link "naks".

Negotiated settings for: data compression (on/off), equalization (long/short contained in S15 bit 1).

Fallback enabled/disabled (indicates whether modem negotiated a fallback during connection).

Error Correcting Protocol (LAPM, MNP or NONE).

DCE speed.

Disconnect reason.

Duration of the last call.

7

Product configuration. One screen of data is sent to the DTE which contains the following information:

Product type (External or Internal).

Options: V.32

Clock Frequency

Eprom Size

RAM Size

Code date.

Code revision.

8

Black list screen (International Products Only).

9

"Plug and Play" feature

10

Reserved.

11

Extended Link Diagnostics Modem will provide extended information to aid customer support configuration of the product

DTE Interface

None.

LED

None.

Aborting Events

<ctrl> C or <ctrl> K Aborts display from that point on.

Display of screens can be halted by <ctrl>S and restarted by any key.

L Volume

Function

Command is used to control modem speaker volume on the PC Internal form factor.

Command Syntax

ATL<argument>

Arguments

0

Low Volume.

1

Low Volume.

2

Medium Volume [ Default ].

3

High Volume.

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

M Speaker

Function

Command is used to control modem speaker.

Command Syntax

ATM <argument>

Arguments

0

Turns speaker off.

1

Speaker is on during dial string execution until carrier is detected or modem goes on hook [Default].

2

Speaker is turned on.

3

Speaker is turned on after last digit in dial string is dialed, and then turned off when carrier is detected or until time stored in S7 has elapsed.

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

O On line

Function

Commands modem to return to previously established connection.

Command Syntax

ATO <argument>

Arguments

0

Issued when offhook and when S14.1 = 0 for detection of escape code (online command mode). The modem will remain on line and return to a connected data transfer mode.

1

Issued when modem is in online command mode. Causes modem to return into data mode and at the same time initiate a retrain. Retrain will only be initiated at speeds above 1200 baud.

Note: When issued in onhook state result code "OK" is returned.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

If modem is in online command mode, the command causes it to terminate online command mode and return to data mode.

P Pulse Dial

Function

Command causes the modem to dial in pulse mode when dialing a dial string. This is the default setting on power up.

Command Syntax

None.

DTE Interface

None.

LED

None.

Aborting Events

None.

Q Quiet

Function

Command enables or disables display of result codes. Quiet mode is set by DIP switch # 3 on the external modem.

Command Syntax

ATQ <argument>

Arguments

0

Result codes are sent to DTE [Default].

1

Result codes are not sent to DTE.

2

Result codes are not sent when in Answer mode.

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

Quiet mode is used in some applications such as printer modem installations, where publishing the result code to the DTE would be undesirable.

S S registers

Function

Commands the modem to alter an S register setting or send the contents to the DTE.

Command Syntax

ATS <argument>

Arguments

Sr = n

where r is the S register number and n is the value Sr is set equal to.

Sr.b = n

where r is the S register number and b is the bit position; n is the value (0 or 1) Sr.b is set to.

If no argument is given for b, n or r, arguments of 0 will be assumed.

Note: to have a value for b used, r must be explicitly used with a period immediately following it.

Note: 0<=n<=255. If the value of n is outside of this range, result code "ERROR" is issued.

T Tone Dialing

Function

Command places the modem in touch tone dialing mode for dialing strings.

Command Syntax

ATT <argument>

Arguments

None.

DTE Interface

None.

LEDS

None.

Aborting Events

None.

V Result Code Enable

Function

Command instructs modem to send result codes in either verbal or numeric modes to the DTE. Verbal response mode is controlled by DIP switch # 2 on the external modem. Verbal response mode is also set from software reset.

Command Syntax

ATV <argument>

Arguments

0

Enables numeric mode for result codes. Numeric codes are followed by a terminating character (S3 Default = <CR>, 0Dh) only.

1

Enables verbal mode for result codes. Verbal codes are preceded and followed by S3 and S4 settings ( <CR> and <LF> are defaults).

If no argument is given an argument of 0 is assumed.

DTE Interface

None.

LED

None.

Aborting Events

None.

X Result Code Options

Function

Command selects or deselects result codes and call progress options according to the Result Code table below:

Command Syntax

ATX <argument>

Arguments

0

Basic subset is selected, according to table below.

1

Extended subset, shown in table below [Default].

2 - 6

Advanced call progress codes, shown in the table below..

If no argument is given an argument of 0 is assumed.

RESULT CODE TABLE

* Requires @; replaces NO CARRIER

Functions

Below is a table of special dialing functions. These function are activated by the value of the X command. In the case of both Adaptive dialing and Fast dial, neither function will run if the X command is not set for it. In the case of Wait for 2nd dial tone and Wait for answer, only a fixed delay will be used if the X command is not set for them.

Adaptive dialing function modem dials first digit of dial string using touch tone, and senses whether phone line dial tone terminates. If so, it continues to execute the dial string using tone dialing. If not, it reverts to pulse dialing and dials the entire string, including the first digit.

Wait for second dial tone modem dials the digits in the dial string before the W, then senses second dial tone before continuing to dial the rest of the digits. If no dial tone is sensed after the time stored in the S7 register, modem sends "NO CARRIER" code to the DTE.

Fast dial modem dials string as soon as it detects dial tone.

Result Codes

The codes below are comprehensive.

Use &A0 or &A1 to disable or enable the following /ARQ result codes. A setting of X1 or higher is also required to enable the result codes. The default is &A1,/ARQ codes (messages 05 to 94) enabled.

Also if S27 is set to 128 the result codes displayed for connections above 7200 will be displayed as 9600 message.

Use &A2 and a setting of X1 or higher to substitute the following 2400 through 56000 bps result codes. These codes display the call's modulation, x2, V34, VFC or V.32, as well as ARQ and non ARQ status.

Use &A3 and a setting of X1 of higher to display the following protocol: LAPM, or MNP, and data compression V42BIS and MNP5.

DTE Interface

None.

LED

None.

Aborting Events

None.

Y Set Default Profile

Function

Select default system profile. This command allows one of three profiles to be chosen for use at power and upon software reset. The modem will use either of the stored NVRAM configurations or it will use the factory default settings. This parameter is stored separately within the NVRAM and is read in before any other values. The modem uses the parameter to determine its course of action during any kind of reset. If no parameter is provided, then 0 is assumed. This parameter is reset by th e &F command.

Command Syntax

ATY <argument>

Arguments

0

Use NVRAM configuration 0 [Default].

1

Use NVRAM configuration 1.

2

Use factory configuration 0

3

Use factory configuration 1.

4

Use factory configuration 2.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

Sends "OK" result code to DTE before executing the command.

Clears command line buffer. If "A/" command is entered subsequently, modem sends OK result code to DTE, but doesn't execute any command.

Arguments which follow in the command buffer are not executed.

Z Reset

Function

Software reset command. Modem resets to either factory defaults or NVRAM settings, dependent parameter issued with the command. The modem uses the parameter and changes settings accordingly. If no parameter is provided, then 0 is assumed. Sportster products also use DIP switch #7 to determine which configuration is loaded.

Command Syntax

ATZ <argument>

Arguments

0

Load configuration indicated by Yn command (also use DIP switch #7 in the external form factor)

1

Reset the Load NVRAM configuration 0.

2

Reset then Load NVRAM configuration 1.

3

Reset then Load factory configuration 0.

4

Reset then Load factory configuration 1.

5

Reset then Load factory configuration 2.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

Sends "OK" result code to DTE before executing the command.

Clears command line buffer.

Arguments which follow in the command buffer are not executed.

+++ Escape Code

Function

Command is a three character sequence using the character defined by S2 register [Default = "+", decimal 43]. Used when modem is in data mode to either terminate the connection or to proceed to online command mode, depending on the setting of S14.

Command Syntax

+++ <arguments>

Arguments

None.

DTE Interface

None.

LED

None.

Aborting Events

None.

Other

None.

Escape code sequence must be preceded and followed by "guard time" of number of 1/50 of a second found in S12 register, to be executed.

<Any Key>

Function

Terminate current dial/answer operation resulting from an issued Dial or Answer command.

Command Syntax

<any key>

Arguments

None.

DTE Interface

None.

LED

None.

Aborting Events

None.

<Ctrl> S

Function

Command will stop/restart any of the help screens that can be displayed.

Command Syntax

<ctrl> C

Arguments

None.

<Ctrl> C or K

Function

Command will cancel the display of the help screens.

Command Syntax

<ctrl>C or K

Arguments

None.