Modem Init Strings

AT Command Guidelines

The basic AT commands used to control modem operation are defined in this section. All these commands may not be available in a specific product depending upon supported data rates and modes (data/fax/voice, error correction, data compression, and data throughput enhancement). The default values are typical of a fully configured modem supporting all data rates, modes, and options. The actual default value is dependent upon modem firmware as defined by the firmware release notes.

Under AT operation, the serial interfaced modem performs an auto baud/auto parity/auto length function on each AT header entered. The auto length/auto parity facility can detect 7- or 8-bit characters of even, odd, or no parity with one stop bit. This is not necessary for the parallel interfaced modem since it has direct access to the UART registers.
Under the AT command set (with the exception of the A/ command), each command line sent by the DTE must begin with the character sequence AT and must be terminated by a carriage return. Commands entered in upper case or lower case are accepted, but both the A and T must be of the same case. The command line interpretation begins upon receipt of the carriage return character.

The modem supports the editing of command lines by recognizing a backspace character. When modem echo is enabled, the modem responds to receipt of a backspace or delete by echoing a backspace character a space character, and another backspace. The hex value to be used for the backspace character is programmable through register S5. Values equal to 0 or greater than 127, or the value which corresponds to the carriage return character, cannot be used for the backspace character. This editing is not applicable to the AT header of a command. A command line may be aborted at any time by entering < Ctrl-x > (18h).

The AT sequence may be followed by any number of commands in sequence, except for commands such as Z, D, or A. Commands following commands Z, D, or A on the same command line will be ignored. The maximum number of characters on any command line is 256 (including "A" and "T"). If a syntax error is found anywhere in a command line command, the remainder of the line will be ignored and the ERROR result code will be returned.

Most commands entered with parameters out of range will not be accepted and the ERROR response will be returned to the DTE.

Commands will only be accepted by the modem once the previous command has been fully executed, which is normally indicated by the return of an appropriate result code. Execution of commands D and A, either as a result of a direct command or a re execute command, will be aborted if another character is entered before completion of the handshake.

Escape Code Sequence

When the modem has established a connection and has entered on-line data mode, it is possible to break into the data transmission in order to issue further commands to the modem in an on-line command mode. This is achieved by the DTE sending to the modem a sequence of three ASCII characters specified by register S2. The default character is '+'. The timing of the three characters must comply with specific time constraints. There is a guard time before the first character (the pre-sequence time), a guard time following the third character (the post-sequence time), and a guard time-out between the first and second characters and between the second and third characters (the inter-character time). These times are controlled by the value recorded in register S12.

AT Hayes Command Set

COMMAND FUNCTION
+++ Switch from data to Command Mode; pause one second before typing;

NOTE:
Do not follow this command with a carriage return (see registers S2 and S12). This command is entered without the AT command.

A Go off-hook and answer incoming call, then initiate handshake
A/ Repeat last command execution once.

NOTE: This command is entered without the AT command.
A> Repeat last command execution continuously.

NOTE: This command is entered without the AT command.
AT ATTENTION command. Must precede commands except A/, A> & +++.

B - Select Communication Standard
COMMAND FUNCTION
B0 CCITT V.22/v.22bis compatibility
B1 Bell 103/212A compatibility
B2 Autoscan V.32/V.22BIS/V.22
B3 CCITT V.23 mode only
B4 300 bps connection only
B5 1200 bps connection only
B6 2400 bps connection only
B7 4800 bps connection only
B8 9600 bps connection only
B9 14400 bps connection only
B10 16800 bps connection only
B11 19200 bps connection only
B12 21600 bps connection only
B13 24000 bps connection only
B14 26400 bps connection only
B15 28800 bps connection only

C - Carrier Control Selection
COMMAND FUNCTION
C0 Carrier transmitter off.
C1 Carrier transmitter on.

D - Dial Command and Modifiers

NOTE:
x may contain the digits 0-9, A, B, C, D, , , or the following codes:

COMMAND FUNCTION
J Perform MNP 10 link negotiation at 1200 BPS (this call only)
K Enable power level adjustment during MNP 10 link negotiation (this call only)
L Follow immediately after D to redial last number
P Pulse dialing
R Originate a call in answer mode, directs modem to act as if it were answering the modem sending the handshake tones.

NOTE:
This command must me placed at the end of the dialing string
S=n Dial one of four telephone numbers (n = 0-3) stored in modem's non-volatile memory
T Touch tone dialing
W Wait for dial tone per register S7's value before dialing digits
@ Wait for one or more rings, followed by five seconds of silence
, (The comma.)Pause before continuing dial. Length of pause is defined by S8.
! Flash. Modem will go on hook for time defined by S29.
; Return to command mode after dialing.
( ) Space. These symbols are ignored in the dial string and can be used for formatting.

E - Command State Character Echo Selection

COMMAND FUNCTION
E0 Commands are not echoed
E1 Commands are echoed

F - On-line State Character Echo Selection

COMMAND FUNCTION
F0 On-line character echo enabled (Error if not supported)
F1 On-line character echo disabled

H - Hook Command Options

COMMAND FUNCTION
H0 Executes hang-up sequence (modem is on-hook).
H1 Modem is off-hook.
H2 Modem line relay

I (letter I) - Internal Memory Tests

COMMAND FUNCTION
I0 Returns a 3 digit number, left 2 digits are modem product code, right is modem version number.
I1 Returns the ROM checksum.
I2 Perform ROM checksum test
I3 MNP/V.42/v.42bis Identification
I6 Returns the abbreviated name and speed, 4 digit model number, 2 character country code, product version number, copyright year.

L - Speaker Volume Level Selection

COMMAND FUNCTION
L0 Low speaker volume
L1 Low speaker volume
L2 Medium speaker volume (default)
L3 Loud speaker volume

M - Speaker on/off Selection

COMMAND FUNCTION
M0 Internal speaker off.
M1 Internal speaker on until carrier detected.
M2 Internal speaker always on.
M3 Speaker on after dialing until carrier detected.

+MS=- bps Line Modulation

COMMAND FUNCTION
+MS=w, x, y, z w = 2 (V.22 bis 2400 or 1200 bps line modulation); 9 (C.32 9600 or 4800 bps line modulation); 10 (V.32 bis 14400, 12000, 9600, 7200, or 4800 bps line modulation); 11 (V.34 28800, 26400, 24000, 21600, 19200, 16800, 14400, 12000, 9600, 7200, 4800, or 2400 bps line modulation)
x = 0,1 auto mode
y = minimum speed 300 - 28800
z = maximum speed 300 - 28800
N - Negotiation of Handshake Options

COMMAND FUNCTION

N0 Handshake at communication standard.
N1 Handshake attempted at detected modem type.
N2 Handshake attempted at detected modem type.
N3 Handshake at communication standard.
N4 Handshake at communication standard.
N5 Handshake attempted at detected modem type.

O - On Line Command

COMMAND FUNCTION
O0 Return to Data mode

O1 Return to Data mode and initiate an equalizer sequence.
O3 Initiate a rate re-negotiation procedure.

P - Set pulse dialing as default

COMMAND FUNCTION
P Set dialing
Q - Result Code Display Options
COMMAND FUNCTION
Q0 Modem sends responses
Q1 Modem does not send responses
Q2 RING, CONNECT, and NO CARRIER responses only

Sr- -Address and S Register

COMMAND FUNCTION
Sr= Set register r equal to value n. See S-Registers below.
Sr? Return value of register r

T - Set tone dialing as default

COMMAND FUNCTION
T Set tone dialing

V- -Result Code Format Options

COMMAND FUNCTION
V0 Return numeric responses. See Modem Responses below.
V1 Return word responses

W - Negotiation Progress Message Selection

COMMAND FUNCTION
W0 Return CONNECT DTE speed, disable extended result codes.
W1 Return CONNECT DTE speed, CARRIER, PROTOCOL extended result codes.
W2 Return CONNECT DCE, speed, disable extended result codes.

X - Call Progress Options

COMMAND FUNCTION
X0 CONNECT result code only. Busy and dial tone disabled.
X1 All CONNECT codes enabled. Busy and dial tone disabled.
X2 All CONNECT codes enabled. Busy tone disabled.
X3 All CONNECT codes enabled. Dial tone disabled.
X4 All CONNECT codes enabled. Busy and dial tones enabled

Y - Long Space Disconnect Options

COMMAND FUNCTION
Y0 Modem does not send or respond to break signals
Y1 Modem sends break signal for four seconds before disconnecting

Z - Soft Reset Command

COMMAND FUNCTION
Z0 Retrieves active configuration profile from stored configuration profile 0 and performs a two second modem self-test
Z1 Retrieves active configuration profile from stored configuration profile 1

+FCLASS=? - This Command will tell the Class of a Fax/Modem
COMMAND Possible Result
+FCLASS=? Response: 0,1 = class 1
Response: 0,2 = class 2
Response: Error = not a fax modem
Response:0 = not supported

CID- Caller ID (identification)
COMMAND FUNCTION
CID=? Responds with enabled/disabled state as given below.
CID=0 Disable caller ID
CID=1 Enable caller ID

&A - Auto Answer Options
COMMAND FUNCTION
&A0 Auto answer (originate a call) default.
&A1 Auto answer (answer a call).

&B - V.32 Auto Retrain Options
COMMAND FUNCTION
&B0 Disable V.32 Auto Retrain
&B1 Enable V.32 Auto Retrain

&C - Data Carrier Detect Options
COMMAND FUNCTION
&C0 Carrier Detect signal always ON
&C1 Turn on Carrier Detect signal after CONNECT result code is received.
&C2 Turn on Carrier Detect signal while remote carrier signal is present.

&D - Data Terminal Ready Options
COMMAND FUNCTION
&D0 Modem ignores the Data Terminal Ready signal
&D1 Modem returns to Command Mode and synchronous operation following an ON-to-OFF Data Terminal Ready transition.
&D2 Modem hangs up, returns to the Command Mode, and prepares for asynchronous operation following an ON to OFF DTR Transition
&D3 Modem resets following an ON to OFF DTR transition

&F - Recall Factory Profile
COMMAND FUNCTION
&F0 Returns the modem to Factory configuration.
&F1 Reset to MNP/Class 5/V.42bis configuration and Xon/Xoff flow control
&F2 Reset to MNP/Class 5/V.42bis configuration and RTS/CTS flow control

&G - Guard Tone Selection
COMMAND FUNCTION
&G0 Guard Tone Disabled
&G1 550 Hz guard tone
&G2 1800Hz guard tone, (U.K.)

&J - Jack Type Selection

COMMAND FUNCTION
&J0 Modem will use an RJ11, RJ14S, or RJ45s telephone jack

&J1 Modem will use an RJ12 or RJ13 telephone jack.
&K - Flow Control Selection

COMMAND FUNCTION
&K0 Flow Control Disabled
&K3 Hardware (RTS/CTS) flow control enabled.
&K4 XON/XOFF DTE/DCE flow control enabled.
&K5 Enables transparent XON/XOFF flow control.
&K6 Enables both RTS/CTS and XON/XOFF flow control.

&L - Line Type Selection

COMMAND FUNCTION
&L0 Modem is set up for dial up operation

&L1 Modem is set up for leased-line operation

&M - Asynchronous / Synchronous Mode Selection

COMMAND FUNCTION
&M0 Selects direct asynchronous operation
&M1 Modem enter synchronous mode after dialing asynchronously
&M2 Synchronous terminal support only
&M3 Manually originating a synchronous call

&O - PAD Channel Selection

COMMAND FUNCTION
&O0 Perform like a normal modem
&O1 Perform like an originate-only modem

&P - Phone line Setting Options

COMMAND FUNCTION
&P0 Selects 10 pulses per second pulse dial with 39%-61% off-hook (make)-to-on-hook (break) ratio
&P1 Selects 10 pulses per second pulse dial with 33%-67% off-hook (make)-to-on-hook (break) ratio
&P2 Selects 20 pulses per second pulse dial with 39%-61% off-hook (make)-to-on-hook (break) ratio
&P3 Selects 20 pulses per second pulse dial with 33%-67% off-hook (make)-to-on-hook (break) ratio

Communications Modem Options

COMMAND FUNCTION
&Q0 Selects direct asynchronous operation. See &M0
&Q1 Selects synchronous connect mode with async off-line command mode. See &M1
&Q2 Selects synchronous connect mode with async off-line command mode. See &M2
&Q3 See &M3
&Q5 Modem will try to negotiate a corrected error link.
&Q6 Selects asynchronous operation in normal mode (speed buffering).

&R - RTS / CTS Options

COMMAND FUNCTION
&R0 Modem turns on Clear to Send (CTS) when it detects Request to Send (RTS)
&R1 Modem ignores RTS signal and turns on CTS when its ready to receive data

Data Set Ready Options

COMMAND FUNCTION
&S0 DSR remains on at all times
&S1 DSR operates according to RS-232C specifications

&T - Test Options

COMMAND FUNCTION
&T0 Ends test in progress
&T1 Perform Local Analog Loopback Test
&T3 Perform Local Digital Loopback Test
&T4 Modem acknowledges Remote Digital Loopback test performed by a remote modem
&T5 Modem ignores a remote modem's request for a Remote digital Loopback Test
&T6 Perform a Remote Digital Loopback Test
&T7 Perform a Remote Digital Loopback Test and Self-Test
&T8 Perform Local Analog Loopback Test and Self-Test
&T19 Perform RTS/CTS Cable Test

&U - Trellis Coding Options

COMMAND FUNCTION
&U0 Enable Trellis Coding
&U1 Disable Trellis Coding

&V - View Configuration Profiles

COMMAND FUNCTION
V View configuration Profiles

&W - Write Active Profile to Memory

COMMAND FUNCTION
&W0 Stores the modem's active configuration profile in stored profile0
&W1 Stores the modem's active configuration profile in stored profile 1

&X - Synchronous Clock Transmit Source

COMMAND FUNCTION
&X0 Modem provides synchronous clock on EIA Pin15
&X1 Modem accepts an externally provided synchronous clock on EIA pin 24 and provides it on EIA pin 15
&X2 Modems accepts an externally provided clock from the carrier detect signal being received and provides the clock on EIA pin15

&Y - Select Stored Profile for Hard Reset

COMMAND FUNCTION
&Y0 Designates configuration profile 0 to be the default configuration profile. When the modem is turned on or reset, configuration profile 0 will be retrieved as the active configuration profile.
&Y1 Designates configuration profile 1 to be the default configuration profile when the modem is turned on or reset, configuration profile 1 will be retrieved as the active configuration profile.

&Z - Stored Telephone Numbers Options

COMMAND FUNCTION
&Zn=x Stores up to four telephone numbers in the modem's nonvolatile memory. Use DS=n to dial the number.
&Zn? Returns phone number stored in location n.
%An - Set auto-reliable fallback character to n

COMMAND FUNCTION
%An Set auto-reliable fallback character to n
%C - MNP Data CompressionOptions

COMMAND FUNCTION
%C0 Disable MNP 5 or V.42BIS data compress
%C1 Enable MNP 5 or V.42BIS data compress
%D - Clear Down Options

COMMAND FUNCTION
%D0 Disable Clear-Downsignal
%D1 Enable Clear-Down signal
%E - Auto-Retrain Options

COMMAND FUNCTION
%E0 Disable Auto-Retrain
%E1 Enable Auto Retrain
%P - Power-On Auto-Connect

COMMAND FUNCTION
%P0 Disable Power-OnAuto-Connect
%P1 Enable Power-On Auto-Connect
%S - Callback Security Options

COMMAND FUNCTION
%S0 Disable call back security
%S1 Enable Password Check only
%S2 Enable call back security, using the number stored in location 0 (%Z0=Ph)and using Password Check
\P - Password Commands

COMMAND FUNCTION
\P=x Stores password x(x = ASCII characters 1 - 127 excluding "?" max 7 characters)
\P=? Display stored Password

How do I make an initialization string?