The following reference manual specifies the command set for the 56K
Softmodem.
The 56K Softmodem supports a broad base of commands for data and FAX. The
command set includes support for the basic data commands standardized by ITU-
T recommendation V.250
ITU-T recommendation T.31 (08/95).
This document contains an overview of the supported commands, responses, and
registers used by the 56K Softmodem. However, a particular modem may not
support the entire AT command set. Some features are dependent on product
application, licensing, and other contractual agreements.
56K Softmodem
Command Reference
1
(05/99), and class 1 FAX commands standardized by
How to Use This Manual
The 56K Softmodem AT command set consists of commands based on data and
FAX communication. The commands presented in this manual follow the
conventions set by ITU-T recommendation V.250 (05/99), which standardized
many of the common AT extensions.
This section identifies the relevant standards from V.250 and any modifications to
presentation that have been made for clarity and ease of use.
The 56K Softmodem AT command set also includes commands that have not
been standardized by a specific ITU recommendation. Some of these commands
support legacy systems, other commands support test and debug efforts, and
others support features which are specific to USRobotics’s products.
1.* This document contains additional commands that support V.92.
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56K Softmodem
Command Reference
- 2
AT Command Conventions
This document describes the AT commands and S registers supported in the
USRobotics 56K Softmodem. Presentation format for each command has a
standard layout consisting of the following:
•A command title.
•A general command description.
•Result codes including the conditions for obtaining the result.
•A detailed command description.
The command title is formatted in large bold letters and contains the command, its
parameters, and a descriptive command name. The general command
description identifies in broad terms the function of the command and when to use
it. The detailed command description breaks down the effect of each of the
parameters’ values. This section may also contain supplementary information
needed for proper usage of the command.
56K Softmodem
Command Reference
The modem or data circuit terminating equipment (DCE) returns at least one
result code for each command submitted to it by the host system or data terminal
equipment (DTE). Conditions for receiving the result code follow the listed result
code.
Sample Command
E<value>—Command Echo
Use this command to instruct the modem to echo characters sent to it. When the
echo feature is selected, characters sent to the modem are sent back to the host
and displayed on the monitor.
Result codes:
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
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Table 2-1: E<value> Commands
Command Function
E0 Disables echo command.
E1 Enables echo command (default).
Basic Syntax Commands
Basic syntax commands use the following format:
<command>[<parameter>]
••
Where <command> is a single character or a group of characters that represent
the command and <parameter> is an optional decimal number. There are some
exceptions to these rules and they are noted for each command as needed. The
echo command in the previous example follows the basic commands syntax
structure.
56K Softmodem
Command Reference
Extended Syntax Commands
Extended syntax commands2 have three different command formats:
Where <name> is the name of the command and begins with an alphanumeric
character and <parameterX> is an optional decimal number. There are some
exceptions to these rules, and they are noted for each command as needed.
In addition to the standard command format, extended commands have a read
and test syntax. The host system uses the read syntax to pole the modem and
determine the current setting for the command parameters. Read syntax has the
following format:
Read syntax: +<name>?
The host system uses the test syntax to pole the modem and determine the
supported parameter values for the command. Test syntax has the following
format:
2.* The description of extended syntax commands presented here is a simplified version of the information presented in ITU-T recom-
mendation V.250 (05/99). For further details, refer to Section 5.4 of recommendation V.250.
- 4
Test syntax: +<name>=?
The modem responds to this command with a list of the supported parameter
ranges.
S Register Conventions
S registers contain parameters used by the modem. The presentation format for
an S register is similar to the format used for an AT command. Each S register has
a standard layout consisting of the following:
S register title.
S register description.
Parameter description.
The S register title is formatted in large bold letters and begins with a capital S
followed by the register number. The title also includes a descriptive name for the
register. The S register description defines the parameter the S register
represents.
56K Softmodem
Command Reference
S register parameters can have a variety of effects on the functionality of the
modem. As a result, the parameter description can have several forms. The most
common form includes the parameter range, the parameter default, and the units
used by the parameter.
Sample S2—Escape Character (User-Defined)
S2 contains the decimal value of the ASCII character used as the escape
character. The default value corresponds to an ASCII +. The escape sequence
allows the modem to exit data mode and enter command mode when on-line. A
value over 127 disables the escape process, i.e., no escape character will be
recognized.
Range: 0—255.
Default: 43 (+).
Units: ASCII.
Other Document Conventions
For the sake of clarity, the following conventions have been adopted and used
throughout this document.
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56K Softmodem
Command Reference
Table 2-2: Other Document Conventions
Item Example Conventions Description
AT Command &C<value> AT commands are all capitals followed by their parameter values in bold print.
This document does not explicitly use the AT prefix when presenting commands. However, the AT prefix is used for all examples.
S Registers S<value> S registers have a capital S followed by the register number.
Parameters <value> Parameters or variables always use lowercase lettering enclosed in brackets,
<>.
Results Codes OK Result codes are all capitals and italics.
Examples
—
Examples use the courier font and are shown exactly as they appear when the
commands are entered into a terminal program such as Windows
nal.
** Windows is a register trademark of Microsoft Corporation.
*
Hypertermi-
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56K Softmodem
Command Reference
AT Command Set
AT commands are issued to the modem to control the modem’s operation and
software configuration. The basic command syntax is as follows:
•<command><parameter>.
The <command> is a combination of the attention prefix (AT) followed by the AT
command. The <parameter> is a string that represents a numeric decimal value.
Note:If a parameter value is not entered, then the 56K Softmodem assumes a parameter value of zero.
Any command issued is acknowledged with a response in either text or numeric
values. These responses are known as result codes. The result codes are listed in
Table 5-1: Result Code Summary.
AT commands can only be entered while the modem is in command mode.
Command mode is entered under one of the following conditions:
After powerup, at the termination of a connection, or after the execution of a
command other than dial or answer.
Upon the receipt of the escape sequence (three consecutive characters matching
the contents of register S2) while in on-line mode.
Upon the on-to-off transition of DTR if &D1, &D2, or &D3 has been set.
Data and General Commands
+++Escape Sequence
An escape sequence allows the modem to exit data mode and enter on-line
command mode. While in on-line command mode, AT commands are sent directly
to the modem. Use the return to on-line data mode command (see “O<value>—
Return to On-Line Data Mode” on page 15) to return to data mode.
Place a pause before and after the escape sequence to prevent the modem from
interpreting the escape sequence as data. The length of the pause is set by
register S12 (see “S12—Escape Guard Time” on page 88), the escape guard
time. Register S2 (see “S2—AT Escape Character (User-Defined)” on page 86)
identifies the escape sequence character.
A/—Repeat Last Command
Use this command to repeat the last AT command. The modem repeats the
command currently in the command buffer. Do not use the AT prefix with this
command. Do not conclude the command with a terminating character such as
enter.
- 7
A—Answer
This command instructs the 56K Softmodem to go off-hook and answer an
incoming call.
B<value>—Communication Standard Setting
Use this command to select the communication standard used by the 56K
Softmodem.
Result codes:
OK if <value> = 0—3, 15, 16.
ERROR if <value> does not equal 0—3, 15, 16.
Table 3-1: B<value> Commands
Command Function
56K Softmodem
Command Reference
B0 Selects CCITT V.22 mode when the modem is at 1200 bits/s.
B1 Selects Bell 212A when the modem is at 1200 bits/s (default).
B2 Deselects V.23 reverse channel (same as B3).
B3 Deselects V.23 reverse channel (same as B2).
B15 Selects V.21 when the modem is at 300 bits/s.
B16 Selects Bell 103J when the modem is at 300 bits/s (default).
C<value>—Carrier Control
This command is supported to ensure compatibility with communications software
that issues the C1 command. However, this modem does not support the C0
command. The C0 command instructs some modems not to send carrier (i.e., it
puts them in receive-only mode).
Result codes:
OK if <value> = 1.
ERROR if <value> does not equal 1.
Table 3-2: C<value> Commands
CommandFunction
C1Normal transmit carriet switching (default).
D<dial string>—Dial
This command instructs the 56K Softmodem to go off-hook and begin the dialing
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56K Softmodem
Command Reference
sequence. The dial string (<dial string>, including modifiers and the telephone
number) is entered after the D command.
A dial string can be up to sixty characters long. Any digit or symbol may be dialed
as touchtone digits. Characters such as spaces, hyphens, and parentheses are
ignored by the modem and may be included in the dial string to enhance
readability.
Table 3-3:
Dial Modifiers
Modifier Function Name Description
L Dial the last number Instructs the modem to dial the last number dialed. This modi-
fier is valid only if it is the first symbol of the dial string. All consecutive characters are discarded.
P Select pulse dialing
T Select tone dialing (default)
W Wait for dial tone Instructs the modem to wait for a second dial tone before
, Dial pause Instructs the modem to pause before processing the next char-
! Hook flash Instructs the modem to go on-hook for 0.5 s and then return to
@ Wait for quiet answer Instructs the modem to wait for 5 s of silence after dialing the
; Return to command mode Instructs the modem to return to command mode after it has
—
—
processing the dial string.
acter in the dial string. Register S8 (see “S8—Pause Time for
Dial Delay Modifier” on page 88) determines the length of the
pause.
off-hook.
number. If silence is not detected, the modem sends a NO ANSWER result code back to the user.
finished dialing without disconnecting the call. This modifier
must be the last character in the dial string.
$ Bong tone detection
S=<location> Dial from register Instructs the modem to dial a telephone number previously
E<value>—Echo Command
Use this command to enable or disable the 56K Softmodem echo feature. When
the echo feature is selected and the modem is in command mode, characters sent
to the modem are sent back to the host and displayed on the monitor.
Result codes:
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
—
stored using the &Z<location>=<dial string> command. Valid
storage locations are 0—3.
- 9
Table 3-4: E<value> Commands
Command Function
E0 Disables echo command.
E1 Enables echo command (default).
F<value>—On-Line Data Character Echo Command
This command is supported to ensure compatibility with communications software
that issues the F1 command. The F0 version of this command is not supported.
This command was originally used to set echo features for the DTE.
Result codes:
OK if <value> = 1.
ERROR if <value> does not equal 1.
Table 3-5: F<value> Commands
56K Softmodem
Command Reference
Command Function
F0 On-line data character echo enabled (not supported).
F1 On-line data character echo disabled.
H<value>—Hook Control
This command instructs the modem to go either on-hook to disconnect a call
or off-hook to make the telephone line busy.
Result codes:
OK if <value> = 0—1*.
ERROR if <value> does not equal 0—1.
Command Function
H0
H1
Table 3-6: H<value> Commands
56K Softmodem goes on-hook (default).
56K Softmodem goes off-hook.
I<value>—Request ID Information
This command displays specific product information about the modem. Result
codes:
As described in Table 3-7: if <value> = 0—11.
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56K Softmodem
Command Reference
ERROR if <value> does not equal 0—11.
Note:ITU-T Recommendation V.250 (05/99) standardized this command. However, the standard does not
include the additional functionality added with the H1 command.
Table 3-7:
TI<value> Commands
Command Function
I0, I3 Returns modem identity string and driver version number.
I1 Returns OK.
I2 Returns OK.
I4 Returns the driver build date.
I5 Returns the driver version, bus type (PCI, AC97), codec type, and country.
I6 Returns OK.
I7 Hardware version.
I8 Codec type.
I9 Returns country ID in English.
I10, I11 Displays connection information as described below. If the modem has not connected with a
remote DCE the ATI 11 commands returns No Previous Call.
The ATI11 results are listed on two screens. To get to the second screen, the user
must hit any key. The following is an example of the AT I11 results.
Description Status
Last Connection V.90
Initial Transmit Carrier Rate 26400
Initial Receive Carrier Rate 52000
Final Transmit Carrier Rate 26400
Final Receive Carrier Rate 52000
Protocol Negotiation Result LAPM
Data Compression Result V.42bis
Estimated Signal/Noise Ratio (dB) 46
Receive Signal Power Level (-dBm) 33
Transmit Signal Power Level (-dBm) 18
Round Trip Delay (msec) 13
Near Echo Level (-dBm) 24
Far Echo Level (-dBm) 80
- 11
Transmit Frame Count 0
Transmit Frame Error Count 0
Receive Frame Count 0
Receive Frame Error Count 0
Retrain by Local Modem 0
Retrain by Remote Modem 0
Rate Renegotiation by Local Modem 0
Rate Renegotiation by Remote Modem 0
Call Termination Cause 1
Robbed-Bit Signaling 0
Digital Loss (dB) 06
Remote Server ID NA
OK
56K Softmodem
Command Reference
The ATI11 command may be issued from on-line command mode or after
the end of a call. After a call, some of the values are no longer valid.
The following table describes each of the results listed for the ATI11
command.
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56K Softmodem
Command Reference
Table 3-8: ATI11 Command Results
Result Description
Last Connection V.92, V.90, V.34, or V.32, depending on the type of connection negoti-
Final Transmit Carrier Rate Current or final upstream rate.
Final Receive Carrier Rate Current or final downstream rate.
Protocol Negotiation Result LAPM, MNP *, or none, depending on V.42 negotiation.
Data Compression Result LAPM, MNP, or none, depending on V.42 negotiation.
Estimated Signal/Noise Ratio Signal to noise ratio with implied negative. Higher values indicated better
conditions.
Receive Signal Power Level (–dBm) The received signal power, although labeled with units of –dBm, is only a
relative measure for comparing calls to/from different locations. This
value is valid only during a call.
Transmit Signal Power Level (– dBm) Upstream transmit signal power.
Round Trip Delay (ms) Round trip delay in milliseconds.
Near Echo Level (–dBm) Near echo levels only.
Far Echo Level (–dBm) Far echo levels only.
Transmit Frame Count Number of LAPM frames sent upstream during this call. Count wraps
around at 65535.
Transmit Frame Error Count Number of REJ frames received at the analog client modem.
Receive Frame Count Number of LAPM frames received by the client during this call. Count
wraps around at 65535.
Receive Frame Error Count Number of frames received in error by the client.
Retrain by Local Modem Number of retrains or rate renegotiations requested by the modem.
Retrain by Remote Modem Number of retrains or rate renegotiations requested by the remote
modem.
Call Termination Cause Reason for call ending. Only valid after call ends. Result codes are as fol-
lows: • 0 = local modem command: ATH, DTR drop. • 1 = remote modem:
cleardown, loss of signal. • 2 = no answer, busy, etc. • 3 = training failure
V.90 or V.34. • 4 = protocol failure if required by \N4, for example.
Robbed-Bit Signaling For PCM connection only, a hexadecimal 6-bit pattern of T1 frames with
robbed-bit signaling.
Digital Loss (dB) For PCM connection only, the downstream digital loss.
Remote Server ID
Note:* MNP is a trademark of Microcom Sysems, Inc.
—
- 13
L<value>—Speaker Volume
Use this command to set the monitor speaker volume setting when the speaker is
on. Result codes:
OK if <value> = 0—3.
ERROR if <value> does not equal 0—3.
Command Function
L0 Low volume.
L1 Low volume.
L2 Medium volume (default).
L3 High volume.
56K Softmodem
Command Reference
Table 3-9: L<value> Commands
M<value>—Speaker Control
Use this command to turn the monitor speaker on or off. Result codes:
OK if <value> = 0—3.
ERROR if <value> does not equal 0—3.
Table 3-10: M<value> Commands
Command Function
M0 Speaker is off.
M1 Speaker is on until the modem detects the carrier signal (default).
M2 Speaker is always on when the modem is off-hook.
M3 Speaker is on until the carrier is detected, except when dialing.
N<value>—Modulation Handshake
Use this command to set the modem protocol for handling handshake negotiation
at connection time if the communication speed of the remote modem is different
from the speed of the local modem.
Result codes:
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
- 14
56K Softmodem
Command Reference
Table 3-11: N<value> Commands
Command Function
N0 When originating or answering, this is for handshake only at the communication standard
specified by register S37 (see “S37—Dial Line Rate*” on page 90) and the B<value>
(“B<value>—Communication Standard Setting” on page 8) command.
N1 When originating or answering, begin the handshake only at the communication standard
specified by S37 and the B<value> command. During handshake, fallback to a lower speed
may occur (default).
O<value>—Return to On-Line Data Mode
Use this command to exit on-line command mode and reenter on-line data mode.
If the modem is not in on-line command mode when this command is received, it
generates an ERROR result code.
Result codes:
CONNECT if <value> = 0, 1, 3 and the result code and call progress monitor is set
to 0 (X0).
CONNECT <text> if <value> = 0, 1, 3 and the result code and call progress
monitor is not set to 0 (X<value> where <value> = 1—7).
NO CARRIER if the connection is not successfully resumed.
ERROR if <value> does not equal 0—1, 3.
Table 3-12: O<value> Commands
Command Function
O0
O1 Issues a retrain before returning to on-line data mode.
O3 Issues a rate renegotiation before returning to on-line data mode.
Instructs the 56K Softmodem to exit on-line command mode and return to data mode
(“+++Escape Sequence” on page 7).
P—Select Pulse Dialing
Use this command to configure the modem for pulse dialing. All subsequent
D<dial string> commands use pulse dialing until either the T command or a tone
dial modifier is received by the modem. Tone dialing is the default setting. Do not
supply parameters with this command unless it is used as part of a dial modifier.
Q<value>—Result Code Control
Result codes are informational messages sent from the modem and displayed on
the monitor. Basic result codes include OK, CONNECT, RING, NO CARRIER, and ERROR. The Q<value> command allows the user to turn result codes on or off.
- 15
Result codes:
56K Softmodem
Command Reference
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
Table 3-13:
Q<value> Commands
Command Function
Q0 Enables result codes (default).
Q1 Disables result codes.
S<register_number>=<value>—S Register Control
Use this command to view or change an S-register. S-registers contain
parameters used by the modem. This command has two forms: one to show the
contents of the register and one to change the contents of the register. Some
registers are read only and are not affected by the S<register number>=<value>
command. Each register has a specific function. See “S-Registers” on page 84.
Result codes:
OK if <register number> is a valid register (see Table 5-3: S-Register Summary).
ERROR if <register number> is not a valid register.
S<register_number>=<value> Sets the contents of the register to <value> if the register is not read
only.
T—Select Tone Dialing
Use this command to configure the modem for DTMF tone dialing. All subsequent
D<dial string> commands use tone dialing until either the P command or a pulse
dial modifier is received by the modem. Tone dialing is the default setting. Do not
supply parameters with this command unless it is used as part of a dial modifier.
V<value>—DCE Response Format
The 56K Softmodem generate result codes using one of two formats. Verbose
mode generates result codes in a text format using words. Numerical mode
generates result codes as a number. Each result code has a number assigned to
it (see “Result Codes” on page 81). Use this command to switch between
numerical and verbose modes. Call progress and negotiation progress messages
are affected by this command.
- 16
Result codes:
Command Function
V0 Displays result codes as digits. Numerical mode.
V1 Displays result codes as text (default). Verbose mode.
56K Softmodem
Command Reference
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
Table 3-15: V<value> Commands
Table 3-16:
V<value> Result Code Formats
Command Result Code Format
V0 <numeric code><CR>
V1 <CR><LF><verbose code><CR><LF>
W<value>—Result Code Option
Use this command to select the modems CONNECT message options. Result
codes:
OK if <value> = 0—2.
ERROR if <value> does not equal 0—2.
Table 3-17: W<value> Commands
Command Function
W0 CONNECT result code reports DTE receive speed. Disables protocol result codes.
W1 CONNECT result code reports DTE receive speed. Enables protocol result codes.
W2 CONNECT result code reports DCE receive speed. Enables protocol result codes (default).
X<value>—Extended Result Codes Control
Use this command to select which result codes are used by the modem. The
parameter of this command is stored in bits 4—6 of register S22.
- 17
56K Softmodem
Command Reference
Table 3-18: X<value> Commands
Command Description
X0 Busy detection is disabled; blind dialing (no dial tone detection) is enabled. The following result
codes are supported: • OK •CONNECT •RING •NO CARRIER •ERROR
X1 Busy detection is disabled; blind dialing (no dial tone detection) is enabled. The following result
codes are supported: • OK •RING •NO CARRIER •ERROR •CONNECT <RATE>
X2 Busy detection is disabled; blind dialing is disabled. The dialing cannot be conducted unless a dial
tone is detected. If dial tone is not detected within the time specified by register S6, the NO DIAL-
TONE result code will be reported. The following result codes are supported: • OK • RING • NO
CARRIER • ERROR • NO DIALTONE • CONNECT <RATE>
X3 Busy detection is enabled; blind dialing is enabled. The following result codes are supported: • OK
• RING • NO CARRIER • ERROR • BUSY • CONNECT <RATE> • BLACKLISTED
X4 Busy detection is enabled; blind dialing is disabled. The dialing cannot be conducted unless a dial
tone is detected. If dial tone is not detected within the time specified by register S6, the NO DIAL-
TONE result code will be reported. The following result codes are supported: • OK • RING • NO
CARRIER • ERROR • NO DIALTONE • BUSY • CONNECT <RATE> • DELAYED • BLACKLISTED
• WARBLE • CALL WAITING DETECTED
X5 Busy detection is enabled; blind dialing is disabled. The dialing cannot be conducted unless a dial
tone is detected. If dial tone is not detected within the time specified by register S6, the NO DIAL-
TONE result code will be reported. The following result codes are supported: •
CARRIER • ERROR • NO DIALTONE • BUSY • CONNECT <RATE> • RRING • NO BONGTONE •
DELAYED • BLACKLISTED • WARBLE • CALL WAITING DETECTED
OK • RING • NO
Y<value>—Long-Space Disconnect
This command is supported to ensure compatibility with communication software
that issues the Y0 command.
Long-space disconnect is always disabled.
Result codes:
OK if <value> = 0.
ERROR if <value> does not equal 0.
Table 3-19: Y<value> Commands
CommandFunction
Y0Disabld long-space disconnect (default).
Z<value>—Reset and Recall Stored Profile
Use this command to force the 56K Softmodem to go on-hook and restore a
profile saved by the &W command. The 56K Softmodem has two stored profiles
and the active profile. The <value> parameter selects the stored profile to copy
into the active profile.
- 18
Result codes:
OK if <value> = 0, 1.
ERROR if <value> does not equal 0, 1.
Table 3-20: Z<value> Commands
Command Function
Z0 Reset and restore stored profile 0.
Z1 Reset and restore stored profile 1.
&B<value>—V.32 Auto Retrain
This command is supported to ensure compatibility with communications software
that issues the B1 command.
The B0 version of this command is not supported.
Result codes:
56K Softmodem
Command Reference
OK if <value> = 1.
ERROR if <value> does not equal 1.
Table 3-21: &B<value> Commands
Command Function
&B0 Disable V.32 auto-retrain (not supported).
&B1 Enable V.32 auto-retrain (default).
&C<value>—Data Carrier Detect (DCD) Control
Use this command to control the modem’s response to receiving a remote
modems carrier signal. Data carrier detect (DCD) is a signal from the modem to
the DTE indicating that the carrier signal is being received from a remote modem.
The modem typically turns off DCD when it no longer detects the remote modems
carrier signal.
Result codes:
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
- 19
56K Softmodem
Command Reference
Table 3-22: &C<value> Commands
Command Function
&C0 Modem ignores the state of the carrier from the remote modem. DCD remains on at all times.
&C1 Modem turns on DCD when the remote modem’s carrier signal is detected and turns off DCD
when the carrier signal is not detected (default).
&D<value>—Data Terminal Ready (DTR) Control
Use this command to set how the 56K Softmodem responds to the DTR signal.
Result codes:
OK if <value> = 0—3.
ERROR if <value> does not equal 0—3.
Table 3-23: &D<value> Commands
Command Function
&D0
&D1 If the DTR signal is not detected while in on-line data mode, the modem enters command
&D2 If the DTR signal is not detected while in on-line data mode, the modem disconnects
&D3* Reset modem on the on-to-off DTR transition.
The 56K Softmodem ignores the true status of DTR and treats it as always on. Use this
selection only if the computer does not provide DTR to the modem.
mode, issues the OK result code, and remains connected.
(default).
Note:ITU-T Recommendation V.250 (05/99) standardized this command. However, the standard does not
include the additional functionality added with the D3 command.
&F<value>—Restore Factory Default Configuration
Use this command to reset the modem to the configuration programmed at the
factory. This operation replaces all of the command options* and S-register
settings in the active configuration with factory default values.
Result codes:
OK if <value> = 0.
ERROR if <value> does not equal 0.
- 20
56K Softmodem
Command Reference
Table 3-24: &F<value> Commands
CommandFunction
&F0Restores factory default configuration.
&G<guard tone>—V.22 bis Guard Tone Control
Use this command to select which guard tone, if any, the modem will send while
transmitting in the high band (answer mode). This command is only used in V.22
and V.22 bis mode. This option is not used in North America; it is for international
use only.
Result codes:
OK if <guard tone> = 0—2.
ERROR if <guard tone> does not equal 0—2.
Note:* There are several noted exceptions to this command, and caution should be used when determin-
ing the state of the command options once this command has been executed.
Table 3-25:
&G<guard tone> Commands
Command Function
&G0 Disables guard tone (default).
&G1 Selects 550 Hz guard tone.
&G2 Selects 1800 Hz guard tone.
&J<value>—Auxiliary Relay Option
This command is supported to ensure compatibility with communications software
that issues the J0 command. Result codes:
OK if <value> = 0.
ERROR if <value> does not equal 0.
&J<value> Commands
CommandFunction
&J0The Auxiliary relay is never closed (default).
&K<value>—Local Flow Control Selection
Use this command to set the 56K Softmodem flow control method. Result codes:
OK if <value> = 0, 3, or 4.
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56K Softmodem
Command Reference
ERROR if <value> does not equal 0, 3, or 4.
Table 3-26: &K<value> Commands
Command Function
&K0 Disables flow control.
&K3 Enables RTS/CTS (hardware) flow control (default).
&K4 Enables XON/XOFF flow control.
&M<value>—Asynchronous Communications Mode
This command is supported to ensure compatibility with communication software
that issues the &M0 command. The preferred method for changing the
asynchronous communication mode is to use the \N<error control mode>
command.
Result codes:
OK if <value> = 0.
ERROR if <value> does not equal 0.
Table 3-27:
&M<value> Commands
CommandFunction
&M0Asynchronous mode (default).
&P<value>—Pulse Dial Make-to-Break Ratio Selection
This command is effective only for Japan. Result codes:
OK if <value> = 0—2.
ERROR if <value> does not equal 0—2.
Table 3-28: &P<value> Commands for Domestic Versions
Command Function
&P0 Selects 39%—61% make/break ratio at 10 pulses per second.
&P1 Selects 33%—67% make/break ratio at 10 pulses per second (default).
&P2 Selects 33%—67% make/break ratio at 20 pulses per second.
&Q<value>—Asynchronous Communications Mode
This command is supported to ensure compatibility with communication software
that issues the &Q<value> command. The preferred method for changing the
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56K Softmodem
Command Reference
asynchronous communication mode is to use the \N<error control mode>
command.
Result codes:
OK if <value> = 0, 5, 6, 8, or 9.
ERROR if <value> does not equal 0, 5, 6, 8, or 9.
Table 3-29: &Q<value> Commands
Command Function
&Q0 Asynchronous mode, buffered. Same as \N0.
&Q5 Error control mode, buffered (default). Same as \N3.
&Q6 Asynchronous mode, buffered. Same as \N0.
&Q8 MNP error control mode. If an MNP error control protocol is not established, the modem will
fall back according to the current user setting in register S36.
&Q9 V.42 or MNP error control mode. If neither error control protocol is established, the modem
will fall back according to the current user setting in register S36.
&S<value>—Data Set Ready (DSR) Option
Use this command to controls DSR action. Result codes:
OK if <value> = 0—1.
ERROR if <value> does not equal 0—1.
Table 3-30: &S<value> Commands
Command Function
&S0 DSR is always on (default).
&S1 DSR comes on after establishing a connection and goes off when the connection ends.
&T<value>—Self-Test Commands
Use this command to perform diagnostic tests on the modem. Each test is
designed to isolate a problem location when experiencing periodic data loss or
random errors.
Result codes:
OK if <value> = 0.
CONNECT if <value> = 1, 3, or 6.
ERROR if <value> does not equal 0, 1, 3, or 6.
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56K Softmodem
Command Reference
Table 3-31: &T<value> Commands
Command Function
&T0 Abort. Terminates the test in progress.
&T1 Initializes local analog loopback, V.56 Loop 3. If a connection exists when this command is
issued, the modem hangs up. The modem displays the CONNECT <rate> message at the
start of the test.
&T3
&T6 Requests a remote digital loopback, V.54 Loop 2 without self-test. If no connection exists,
&V<value>—Display Current Configuration
Result codes:
Local digital loopback test, V.54 Loop2. If no connection exists, the 56K Softmodem returns
ERROR.
the 56K Softmodem returns ERROR and generates the CONNECT<rate> result code.
Use this command to display the current 56K Softmodem configuration. The
modem maintains two stored profiles and the active profile. This command
displays all three configurations and any stored telephone numbers.
OK if <value> = 0.
ERROR if <value> does not equal 0.
The following is an example of the AT& V0 results.