AT Commands N-Z

		AT Commands N-Z

N Automode detection :

Options : N0, N1 Default : N1

The N command is linked with register S37 to determine how the modem reacts when automode detection is disabled.

N0	disables automode detection.
N1	enables automode detection.

\N Error correction mode select :

Options : \N0, \N1, \N2, \N3, \N4, \N5 Default : \N3

The \N command sets the preferred error correction mode. See the chapter Error correction and data compression for more information.

\N0	disables error correction. Speed buffering is enabled.
\N1	enables direct mode. Both error correction and speed buffering are disabled. ~#
\N2	enables reliable mode. This command should be used when an error corrected connection must be established.
\N3	enables auto reliable mode. If an error corrected connection cannot be established the modem falls back to a non-error corrected correction.
\N4	enables a V.42 LAPM error corrected connection only.
\N5	enables an MNP error corrected connection only.

~# External modems only

*NC Country select :

Options : *NC?, *NC=?, *NC=x, *NCx Default : as supplied

This command allows the modem to be configured for operation in any one of the supported countries. The values of 'x' available varies according to model and can be entered as a decimal number or as a 2 or 3 letter code. Use the *NC=? command to determine the countries supported by your modem. Care should be exercised in the use of this command as an inappropriate selection may invalidate the telecom approval of your modem.

After a valid country has been selected by entering the appropriate code, a power on reset or a Z command must be performed for the changes to take effect.

Writes the value x to the currently selected S register. An S register can be selected by using the Sn command (where n equals the number of the register).

O Return to on-line mode :

Options : O0, O1

Issuing the O0 command after the escape sequence has been issued or an ON-to-OFF DTR transition takes place (only with &D1 in operation) forces the modem to go back on-line and issue the appropriate connect message. With no connection established the O0 command returns the ERROR result message.

The O1 command forces the modem to go back on-line and initiate an equaliser retrain sequence in V.22bis, V.32, V.32bis, V.FC and V.34 modes. When unacceptable bit error rates are experienced due to loss of equalisation, the O1 can be issued to reduce those errors.

P Pulse dial :

By default the modem uses tone dialling when executing a dial string. However, entering the P command will return the modem to the pulse dialling option. Alternatively, the P can be entered in the dial string (e.g. ATD P 01234 567890). Pulse dialling will remain the default until tone dialling is specifically selected.

&P Pulse make/break ratio :

This command is included for completeness and performs no function within the modem.

*P Store a password/telephone number pair :

Options : *P0 to *P19

The *P command is used to create a table of secure access passwords and associated dial back telephone numbers. The following command line is used where n equals a number from 0 to 19 inclusive. See the chapter Secure Access for further details.

AT*Pn :: <Return>

The OK message indicates that the operation was successful. The password must be between 6 and 12 characters long. The telephone number must not exceed 40 characters in length. To overwrite an existing entry, re-type the command line using the appropriate entry number. Where final colon and telephone number are omitted, direct access to the host system is permitted after password verification.

Q Quiet control :

Options : Q0, Q1 Default : Q0

The Q command enables or disables result codes and messages. By default the messages, such as ERROR or BUSY, are displayed at the DTE. This is a useful indication as to the status of the modem for users and software developers alike. It is sometimes desirable to disable these messages; for example, when printing hard copy of incoming data so that they do not appear in the listing.

Q0	enables result codes/messages.
Q1	disables result codes/messages.

%Q Line signal quality :

A measure of the line quality can be performed when in on-line command mode. Issuing the %Q command returns a three digit number. The lower the value, the better the receive quality. The values returned by this command for different line speeds are not directly comparable. This value is monitored by the modem and a retrain or rate change performed when necessary (if enabled by the %E command).

&Q Asynchronous/synchronous mode selection :

Options : &Q0 to &Q6 Default : &Q5

For asynchronous operation the &Q setting is controlled by the \N command (error correction select). It is therefore not necessary to directly set this command nor is it recommended. However, the &Q command should be used to gain access to the synchronous operating modes of external modems.

&Q0	selects direct (non-speed buffered) asynchronous operation.
&Q1	selects synchronous connect mode with asynchronous off-line command mode.
&Q2	is the same as &Q1 except that DTR dialling of directory entry 0 is enabled. The modem will disconnect if DTR is off for more than the period specified in S25. In order for DTR dialling to operate, the value of S24 MUST be set to zero.
&Q3	selects synchronous select mode with DTR acting as a voice/data switch. The call is manually initiated while DTR is off. The handshaking proceeds when DTR becomes active.
&Q4	is the same as &Q1.
&Q5	selects the default configuration in which the modem attempts to establish an asynchronous error corrected link. S36 may be used to determine the modem's behaviour if the V.42 LAPM connection attempt fails.
&Q6	selects normal (speed buffered) asynchronous operation.

The &Q command setting has a direct influence on the &D command.

&R Select RTS/CTS state :

Options : &R0, &R1 Default : &R1

This command determines how the modem controls the CTS line.

&R0	In synchronous mode, CTS tracks the state of RTS; the RTS to CTS delay being defined by register S26. In asynchronous mode, CTS acts as required by flow control except that it turns off whilst a connection is being established (V.25bis handshake).
&R1	In synchronous mode, CTS is always on. In asynchronous mode, CTS only drops if required by flow control.

*R Request remote configuration mode (Selected models only) :

The *R command sends a request to a remote modem asking it to be placed in remote configuration mode. The request may only be sent if the local modem is on-line, in command mode and with MNP error correction in operation. If remote configuration is available, the REMOTE PASSWORD prompt is returned.

If the password entered is successful the !AT message is returned, indicating that the remote modem is ready to be re-configured. Commands sent following this do not require the AT prefix. The commands are performed by the remote modem. To exit remote configuration mode, issue the *E command.

S Display/set S register :

Options : All S registers

The S command can be used either to set or to view the value in the S register nominated or to set the register specified as the currently selected register.

ATS10=255 <Return> sets register S10 with the value 255.

ATS3? <Return> displays the value in register S3.

ATS4 <Return> sets register S4 as the currently selected S register.

If an attempt to enter a value outside the range of the S register is made, the maximum or minimum value is assumed and stored in the register.

Note: Some S registers are read only.

\S Display current configuration :

This command requests a display of the currently active modem configuration.

&S DSR (Data Set Ready) control :

Options : &S0, &S1 Default : &S1

DSR is the signal sent to the DTE indicating that the modem is ready to communicate. The &S0 command forces DSR high (ON) at all times. This may be required by certain communications software.

&S1 makes DSR high (ON) when the modem is ready to communicate, i.e. after answer tone is detected until the loss of carrier.

-SDR Select Distinctive Ring :

Options : 0 to 7 Default : 0

This command enables or disables detection and reporting of distinctive ring. The syntax is AT-SDR=n, where n is a number from 0 to 7. One, two or three distinctive ring types can be simultaneously enabled, depending upon the value of n (bit mapped). The detected ring type is reported in the long form (verbose) of the result code by appending the ring type number to the end of the RING message.

-SDR=0	Disables Distinctive Ring. Any valid ring detected is reported as RING (default).
-SDR=1	Enables Distinctive Ring Type 1.
-SDR=2	Enables Distinctive Ring Type 2.
-SDR=3	Enables Distinctive Ring Type 1 and 2.
-SDR=4	Enables Distinctive Ring Type 3.
-SDR=5	Enables Distinctive Ring Type 1 and 3.
-SDR=6	Enables Distinctive Ring Type 2 and 3.
-SDR=7	Enables Distinctive Ring Type 1, 2 and 3.

The ring types supported and the corresponding ring cadence detect criteria are:

Ring Type	Ring Cadence Detect Criteria
1	2.0 sec ON, 4.0 sec OFF.
2	0.8 sec ON, 0.4 sec OFF, 0.8 sec ON, 0.4 sec OFF.
3	0.4 sec ON, 0.2 sec OFF, 0.4 sec ON, 0.2 sec OFF, 0.8 sec ON, 4.0 sec OFF.

T Tone dial :

Entering the T command selects tone dialling as the current dialling method until pulse dialling is explicitly selected. Tone dialling is the modem default and adaptive tone dialling is enabled on the first dialled call after a reset. See the chapter automatic dialling for full details.

Both pulse and tone dialling can be used in the same command line. For example, ATD T 9 W P01234 567890 uses tone dialling to dial the 9, waits for the secondary dial tone from the exchange and pulse dials the remainder of the dial string.

&T Modem self tests :

Options : &T0, &T1, &T3 to &T8 Default : &T4

The &T command selects one of five self tests used by the modem to pinpoint a failure in a communications link. Test duration is determined by the contents of register S18. See chapter Diagnostic and test facilities for more information.

&T0	terminates the current test in progress.
&T1	initiates a local analogue loopback test in accordance with ITU-T V.54 (loop 3).
&T3	initiates a remote digital loopback test of the local modem in accordance with ITU-T V.54 (loop 2).
&T4	grants a remote digital loopback request from the remote modem.
&T5	denies a remote digital loopback request from the remote modem.
&T6	initiates a remote digital loopback test in accordance with ITU-T V.54 (loop 2).
&T7	initiates a remote digital loopback test in accordance with ITU-T V.54 (loop 2) with self test.
&T8	initiates a local analogue loopback test in accordance with ITU-T V.54 (loop 3) with self test.

V Verbose/numeric result code selection :

Options : V0, V1 Default : V1

Result codes or messages returned to the DTE from the modem can be either numeric or verbose. In the numeric form a number is used to indicate the result code. This is useful when the modem is under software control as the codes can be more easily interpreted by a software program.

In the verbose or English form the messages appear as ERROR, NO CARRIER etc. and are more user-friendly when the modem is under manual control.

V0	selects the numeric form.
V1	selects the verbose form.

&V View current configuration :

The &V command displays the modem's current configuration, user profiles 0 and 1 and the first four stored telephone numbers.

W Connect message control :

Options : W0, W1, W2 Default : W2

Connect message control is used to select the type of speed information attached to CONNECT messages. In addition, information on the type of error correction in use can be enabled with this command.

W0	selects DTE speed.
W1	selects line speed, error correction protocol and DTE speed in that order.
W2	selects line speed.

Register S95 can also be used to influence CONNECT messages. For example, details regarding the type of data compression in use may be obtained by setting S95 = 32.

&W Write User defaults :

Options : &W0, &W1

The &W command writes the current S register and AT command settings to the non-volatile memory of the modem as User profile defaults. In effect, you customise your modem with the current configuration information.

&W0	writes the current configuration to User profile 0.
&W1	writes the current configuration to User profile 1.

Either profile can be selected by issuing the appropriate Z command. This remains the active profile until such a time as it is changed.

Also, either profile can be selected as the power up profile by issuing the appropriate &Y command. Again, this remains the active profile until changed.

Both profiles can be overwritten at any time by re-issuing the &W command. To return the factory default values as a User profile the &F&Wn command should be used (when n is 0 or 1 as appropriate).

\W Split speed mode (External modems only) :

Options : \W0, \W1 Default : \W0

Some DTE's require different baud rates when transmitting and receiving data from the modem. The V.23 mode of operation covers these split speed requirements. In originate mode V.23 will transmit at 75 bps and receive at 1200 bps. Conversely, in answer mode, V.23 will transmit at 1200 bps. conversely, in answer mode, V.23 will transmit at 1200 bps and receive at 75 bps. The %F command controls which direction has the 75 bps channel.

\W0	disables split speed mode.
\W1	enables split speed mode and forces V.23 operation.

X Extended result code selection :

Options : X0, X1, X2, X3, X4 Default : X4

The X command is used to determine the precise way that the modem behaves during dialling and connection to a remote service and which set of result codes are used. Further control over the actual message output during connection may be obtained by use of register S95.

X0	The modem attempts to dial regardless of the presence or absence of a dial tone after the period specified by register S6. After dialling, the modem: i) returns a CONNECT message having established a connection; or ii) returns the NO CARRIER message if the connection could not be made (line busy or no dial tone). This mode of operation is known as blind dialling.
X1	provides the same facility as X0 above but, additionally, the CONNECT message is enhanced with the connection speed.
X2	behaves as for X1 but only dials when a dial tone is detected. If dial tone is not detected within five seconds the NO DIALTONE message is returned. Engaged signals are not recognised.
X3	behaves as for X1 but detects engaged or number unobtainable signals and returns the BUSY message. Dial tone detection is disabled. This option is designed mainly for use in countries which have dial tones not recognised by the modem and would consequently prohibit its use if no X3 option was available.
X4	enables all messages and provides both dial tone and engaged signal detection.

&X Select synchronous clock source :

Options : &X0, &X1, &X2 Default : &X0

In asynchronous mode, the transmit and receive clocks are turned off. In synchronous mode, both clocks are turned on at a frequency of 1200 Hz or higher, corresponding to the line speed in use. Synchronous mode may only be used with external modems.

&X0	selects internal timing. The modem generates the transmit clock signal and applies it to the TXCLK output (pin 15) of the RS232 serial interface.
&X1	selects external timing. The local DTE generates the transmit clock signal and applies it to the TXCLK input (pin 24) of the RS232 serial interface. The modem applies this signal to the TXCLK output (pin 15) of the RS232 serial interface.
&X2	selects slave receive timing. The modem derives the transmit clock signal from the incoming receive carrier and applies it to the TXCLK output (pin 15) of the RS232 serial interface.

*X Exit remote configuration mode (Selected models only) :

Issued by the local modem to exit remote configuration mode. See Remote configuration and remote access for more information.

Y Long space disconnect :

Options : Y0, Y1 Default : Y0

The Y1 command enables the long space disconnect facility in the modem. This means that if a continuous break of equal to or greater than 1.6 seconds from the remote modem is experienced, the modem terminates the connection. In addition, the modem sends a 4 second long space prior to going on hook in response to the H0 command (or DTR ON-to-OFF transition). Y0 disables the facility and is the default setting.

&Y Select power up User profile :

Options : &Y0, &Y1 Default : &Y0

If User profiles are programmed to memory using the &W command, the &Y command can be used to select either profile as the next power up (not Z command) default.

&Y0	selects User profile 0.
&Y1	selects User profile 1.

Z Reset modem to User profile :

Options : Z0, Z1

The Z command conducts a modem software reset that restores the User profile selected.

Z0	performs a software reset to User profile 0.
Z1	performs a software reset to User profile 1.

If no User profiles exist the Z command restores the factory default settings.

&Z Store telephone number :

Options : &Z0 to &Z19

Used to add a telephone number in one of the twenty number stores available. Each entry may be up to 40 characters in length. Example: AT&Zn=x (where n is 0-19 and x is the telephone number).

Important note: Be very careful when entering numbers to ensure the correct number is stored. Repeated dialling of an incorrect number could be very inconvenient to the owner of the number!

? Read selected S register :

This command reads and displays the currently selected S register. The currently selected S register is chosen by using the Sn command (where n equals the number of the register).

=x Write to selected S register :

Options : All S registers Default : None

Writes the value x to the currently selected S register. An S register can be selected by using the Sn command (where n equals the number of the register).