Multi-Tech Systems MT2456SMI22 User Manual

SocketModemÔ

Embedded Modem

MT2456SMI–22

Serial Interface

Developer’s Guide

Copyright

SocketModemÔ

MT2456SMI–22
Developer’s Guide

PN S000281A, Version A

Copyright

This publication may not be reproduced, in whole or in part, without prior expressed written permission from Multi­Tech Systems, Inc. All rights reserved.
Copyright © 2003, by Multi-Tech Systems, Inc.

Multi-Tech Systems, Inc. makes no representations or warranties with respect to the contents hereof and specifically
disclaims any implied warranties of merchantability or fitness for any particular purpose. Furthermore, Multi-Tech
Systems, Inc. reserves the right to revise this publication and to make changes from time to time in the content hereof
without obligation of Multi-Tech Systems, Inc. to notify any person or organization of such revisions or changes.

Revisions

Revision Level Date Description

A 03/20/03 Initial release.

Trademarks

Multi-Tech Systems, Inc. trademarks include the SocketModem and the Multi-Tech logo.
Microsoft, Windows, Windows 95, Windows NT, and Windows 2000 are registered trademarks or trademarks of
Microsoft Corporation in the United States and/or other countries.

Patents

This device covered by one or more of the following patents: 6,031,867; 6,012,113; 6,009,082; 5,905,794; 5,864,560;
5,815,567; 5,815,503; 5,812,534; 5,809,068; 5,790,532; 5,764,628; 5,764,627; 5,754,589; 5,724,356; 5,673,268;
5,673,257; 5,644,594; 5,628,030; 5,619,508; 5,617,423; 5,600,649; 5,592,586; 5,577,041; 5,574,725; 5,559,793;
5,546,448; 5,546,395; 5,535,204; 5,500,859; 5,471,470; 5,463,616; 5,453,986; 5,452,289; 5,450,425; 5,355,365;
5,309,562; 5,301,274
Other Patents Pending

World Headquarters

Multi-Tech Systems, Inc.
2205 Woodale Drive
Mounds View, Minnesota 55112
Phone: [phone] or 800-328-9717
Fax: [phone]

Technical Support

Country By Email By Phone

France: [e-mail] (33) 1-64 61 09 81
India: [e-mail] 91 (124) 6340778
U.K.: [e-mail] (44) 118 959 7774
U.S. and Canada: [e-mail] [phone]
Rest of the World: [e-mail] [phone]

Internet Address: http://www.multitech.com

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 2

Contents

Chapter 1 – Product Description and Specifications .................................................................................................4

Product Description....................................................................................................................................................4

Technical Specifications.............................................................................................................................................5

Chapter 2 – Mechanical Specifications........................................................................................................................6

Physical Dimensions..................................................................................................................................................6

Pin Configurations......................................................................................................................................................7

Chapter 3 – Electrical Characteristics .........................................................................................................................9

Chapter 4 - V.22bis Commands, S-Registers, and Result Codes ............................................................................10

V.22bis Generic Modem Control Commands...........................................................................................................12

V.22bis DTE/DCE-Modem Interface commands......................................................................................................15

V.22bis Call Control Commands ..............................................................................................................................21

V.22bis Modulation Control Commands...................................................................................................................27

V.22bis Error Control and Data Compression Commands.......................................................................................29

V.22bis Synchronous Access Mode Commands .....................................................................................................31

V.22bis FastConnect Command ..............................................................................................................................33

V.22bis Line Side Device Commands......................................................................................................................34

V.22bis S-Parameters..............................................................................................................................................35

V.22bis Result Codes...............................................................................................................................................45

Appendix A – Test/Demo Card Information...............................................................................................................47

Block Diagram..........................................................................................................................................................47

Appendix B - Product Approvals, Compliance, and Layout Considerations .........................................................48

Product Safety and EMC Approvals.........................................................................................................................48

Regulatory Design Considerations...........................................................................................................................49

SocketModem Placement ........................................................................................................................................51

Compliance ..............................................................................................................................................................52

Index .............................................................................................................................................................................57

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 3

Chapter 1 – Product Description and Specifications

Chapter 1 – Product Description and

Specifications

The Multi-Tech SocketModem supports analog data modem operation with V.22bis Fast Connect, V.42bis data
compression, and V.80 synchronous access mode. The SocketModem is a space-efficient (1" × 2.5"), embedded
modem that is ready-to-integrate into your applications; therefore, dramatically reducing development time and
costs for system designers. The SocketModem also complies with telecom requirements globally and can be
shipped worldwide.

This guide provides the information needed to effectively integrate the SocketModem into your equipment. It also
includes the AT commands for the configuration and control of a data modem and the result codes that the
modem issues in response to the commands.

Product Description

The MT2456SMI SocketModem is a standard 64-pin modem used for integrating data communications. It is a
single-port 5V or 3.3V modem that integrates a modem controller, DSP, and DAA in a 1" x 2.5" form factor and
communicates to a host controller via an asynchronous serial interface.

A SocketModem kit is available. It includes one development board with an RS-232 DB-25 connector, wall power
adapter, RJ-11 jack, and RS-232 cable.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 4

Chapter 1 – Product Description and Specifications

Technical Specifications

The SocketModem meets the following specifications:

Client-to-Server Data Rates

Client-to-Client Data Rates

Data Format

Modem Compatibility

Error Correction

Data Compression

Speed Conversion

Modes of Operation

Flow Control

Command Buffer

Transmit Level

Frequency Stability

Receiver Sensitivity

Interface

Diagnostics

Weight

V.22 bis

2400, 1200, 0-300 bps

Serial, asynchronous

V.22bis, V.22; Bell 212A and 103/113; ITU-T V.21 & V.23

ITU-T V.42 (LAP-M or MNP 2–4)

ITU-T V.42bis

Serial port data rates adjustable to 300, 1200, 2400, 4800, 9600, 19,200, 38,400,
57,600, and 115,200

Full duplex over dial-up lines; data mode, command mode, and online command
mode

XON/XOFF (software), RTS/CTS (hardware)

50 characters

–12 dBm (varies by country setting)

±0.01%

–43 dBm under worst-case conditions

Serial ITU-T V.24 logical interface

Local analog loop

0.02 Kg. (0.04 lb.)

Dimensions

Power Consumption

Operating Voltage

Operational Temperature

Storage Temperature

Intelligent Features

1.045" × 2.541" × 0.680" (2.7 x 6.5 x 1.8 cm)

Typical: 70 mA (.235 W @ 3.3V DC); Maximum: 80 mA (.264 W @ 3.6V DC)

Typical: 3.3V DC +/- 5%; Absolute Maximum Supply Voltage: 3.7 V DC

0 to +70° C ambient under closed conditions; humidity range 20% to 90% (non­condensing)

-10° to +85° C

TIA-602 command compatible
V.22bis fast connect
Supports V.80
Supports Fast POS 9600
Line polarity reversal detection
Line current loss detection
Line-in-use detection during on-hook operation
Extension pickup detection
Call waiting detection
Caller ID (US configuration only)
DTMF detection
autodial, redial
pulse or tone dial
auto answer
call status display

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 5

Chapter 2 - Mechanical Specifications

Chapter 2 – Mechanical Specifications

Physical Dimensions

Figure 2–1. Maximum Component Height

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 6

Chapter 2 - Mechanical Specifications

Pin Configurations

The MT2456SMI SocketModem with a serial interface use a 16-pin interface to provide an on-board DAA with tip
and ring connections, audio circuit for call-progress monitoring and serial interface via logic level signals.

Pin Descriptions

Pin#Signal

Name

1 Tip I/O

2 Ring I/O

24 –RESET I

26 DGND

29 DCDIND

30 RXIND

31 DTRIND

32 TXIND

33 –RTS I

34 –RXD O

35 –TXD I

I/O

Type

Figure 2–2. Serial SocketModem Pins

Description

Tip Signal from Telco. Tip connection to the phone line (RJ11 Pin 3).

SocketModem is Tip/Ring is polarity insensitive.
Ring Signal from Telco. Ring connection to the phone line (RJ11 Pin 4).
SocketModem is Tip/Ring is polarity insensitive.
Modem Reset (with weak pull-up). The active low –RESET input resets the
SocketModem logic and returns the AT command set to the original factory
default values or to "stored values" in NVRAM. –RESET is tied to VCC
through a 250 ms time constant circuit for "Power-on-Reset" functionality. The
modem is ready to accept commands within 6.5 seconds of power-on or reset.
Reset must be asserted for a minimum of 300 ns.

Ground.

DCD LED Indicator.

RXD LED Indicator.

DTR LED Indicator.

TXD LED Indicator.

Request to Send. RTS signal is used for hardware flow control.

Received Data. Used to send data received from the telephone line and also

modem responses to the DTE. Modem response take priority over incoming
data. When no data is transmitted, the signal is held in mark condition.
Transmit Data. The DTE uses this line to send data to the modem for
transmission over the telephone line or to transmit commands to the modem.
The DTE should hold this circuit in the mark state when no data is being
transmitted or during intervals between characters.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 7

Chapter 2 - Mechanical Specifications

36 –RI O

37 –DSR O

38 –CTS O

39 –DCD O

40 –DTR I

41 DGND

61 VCC

63 AGND

64 SPKR

Ring Indicate. –RI output ON (low) indicates the presence of an ON segment
of a ring signal on the telephone line. The modem will not go off-hook when –
RI is active; the modem waits for –RI to go inactive before going off-hook.
Data Set Ready. -DSR indicates modem status to the DTE. –DSR OFF
(high) indicates that the DTE is to disregard all signals appearing on the
interchange circuits except Ring Indicator (–RI). It reflects the status of the
local data set, and does not indicate an actual link with any remote data
equipment.
Clear To Send. –CTS is controlled by the modem to indicate whether or not
the modem is ready to transmit data. –CTS ON, indicates to the DTE that
signals presented on TXD will be transmitted to the telephone line. –CTS OFF
indicates to the DTE that it should not transfer data across the interface on
TXD.
Data Carrier Detect. –DCD output is ON (low) when a carrier is detected on
the telephone line or OFF (high) when carrier is not detected.
Data Terminal Ready (Active Low). The –DTR input is turned ON (low) by
the DTE when the DTE is ready to transmit or receive data. –DTR ON
prepares the modem to be connected to the telephone line, and, once
connected, maintains the connection. –DTR OFF places the modem in the
disconnect state.

Ground.

3.3V DC Power.

Analog Ground. Analog ground is tied common with DGND on the

SocketModem. To minimize potential ground noise issues, connect audio
circuit return to AGND.
Speaker Output. SPKR is a single ended-output. SPKR is tied directly to the
CODEC. One side of a differential AC output coupled through a 6.8K ohm
resistor and capacitor.
The call progress speaker interface signal is:
Digital speaker output (DSPKOUT); output
DSPKOUT is a square wave output in data mode used for call progress or
carrier monitoring. This output can be optionally connected to a low-cost on­board speaker, e.g., a sounducer, or to an analog speaker circuit.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 8

Chapter 3 - Electrical Characteristics

Chapter 3 – Electrical Characteristics

3.3V and 5V Serial SocketModem

3.3V DC Characteristics (TA = 0°C to 70°C; VDD = 3.3 V ± 0.3 V) VDDMAX = 3.6 V

5V DC Characteristics (TA = 0°C to 50°C; VDD = 5 V ± 0.25 V)

VDDMAX = 5.25 V

Inputs

–DTR (40), –TXD (35), –RTS (33), –RESET (24) Min 2.0 V Max 0.8 V

Outputs Output High Output Low

–DCD (39), –CTS (38), –DSR (37), –RI (36), –RXD (34)
2mA, Z

= 120 Ω

INT

Digital Input Capacitance

Input High Input Low

Min 2.4 V Max 0.4 V

50pF

Handling Precautions

All electronic devices should be handled with certain precautions to avoid damage due to the accumulation of
static charge. Although input protection circuitry has been incorporated into the devices to minimize the effect of
this static buildup, proper precautions should be taken to avoid exposure to electrostatic discharge during
handling and mounting.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 9

Chapter 4 - V.22bis Commands

Chapter 4 - V.22bis Commands, S-

Registers, and Result Codes

The V.22bis Commands are covered in the following order in this chapter:

Generic Modem Control Commands

Z Soft Reset and Restore Profile

+VCID Caller ID
+VRID Report Retrieved Called ID
\N Operating Mode - Error Correction
I Identification
+GCI Country of Installation
&F Restore Factory Configuration (Profile)
&T Local Analog Loopback Test
** Load to Internal RAM

DTE/DCE Commands

E Echo
Q Quiet Result Codes
V Result Code Form
W Connect Message Control
X Extended Result Codes (& Call Progress Information)
&C RLSD Option
&D DTR Option
&K Flow Control
&R RTS/CTS Option
\G Modem-to-Modem Flow Control (XON/XOFF)
+IFC DTE-Modem Local Flow Control
+IBC In Band Commands

Call Control Commands

DDial
T Set Tone Dial (Default)
P Set Pulse Dial
A Answer
H Disconnect (Hang Up)
O Return to On-line Data Mode
L Monitor Speaker Volume
M Monitor Speaker Mode Control
&G Select Guard Tone
&P Select Pulse Dial Make/Break Ratio
&V Display Current Configuration and Stored Profiles
%L Report Line Signal Level
%Q Report Line Signal Quality
*B Display Blacklisted Numbers
*D Display Delayed Numbers

-STE Set Telephony Extension
+PCW Call Waiting Enable
+VDR Distinctive Ring

Modulation Control Commands

+MS Modulation Selection
%E Enable/Disable Line Quality Monitor
BITU-T or Bell

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 10

Chapter 4 - V.22bis Commands

Error Control and Data Compression Commands

+ESR Select Repeat
\B Transmit Break to Remote
\K Break Control

Synchronous Access Mode Commands

+ESA Configure Synchronous Access Submode
+ITF Transmit Flow Control Thresholds

Fast Connect Command

$F Fast Connect Control

Line Side Device Commands

-TTE Threshold Adjustments for Telephony Extension

-TRV Tip and Ring Voltage Measurement

A Note About Compatibility Commands

You may notice that some commands are available but do not support any function. These commands exist for
compatibility purposes only. If you enter these commands, you may receive an OK result; however, no changes
are made to the configuration or control of the modem. Examples of these commands are:
Y, &S, &V1, +VDT, and \A,

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 11

Chapter 4 - V.22bis Commands

V.22bis Generic Modem Control Commands

Z Soft Reset and Restore Profile

This command causes the modem to perform a soft reset and restore (recall) the factory default configuration
(profile). If no <value> is specified, zero is assumed.

Syntax Z<value>
Defined Values

<value> Decimal number corresponding to the selected profile.
0 Soft reset and restore stored profile.
1 Same as 0; allowed for compatibility.
Result Codes OK <value> = 0 or 1

ERROR Otherwise

+VCID Caller ID (CID)

This command controls the reporting and presentation of data associated with the Caller ID services in the Incoming
Call Line ID (ICLID) data format for the next call.

Syntax +VCID=<pmode>
Defined Values

<pmode> Decimal number corresponding to the selected option.
0 Disable Caller ID reporting. (Default).
1 Enables Caller ID with formatted presentation to the DTE. The modem presents the data items in a

<Tag><Value> pair format. The expected pairs are date, time, name, and caller code (telephone number).

2 Enables Caller ID with unformatted presentation to the DTE.

Reporting Current or Selected Values

Command: +VCID?
Response: +VCID: <pmode>
Example: +VCID: 0 For the default setting.

Reporting Supported Range of Parameter Values

Command: +VCID=?
Response: +VCID: (<pmode> range)
Example: +VCID: (0-2)

+VRID Report Retrieved Caller ID (CID)

This command reports the data associated with the Caller ID services in the Incoming Call Line ID (ICLID) data
format for the last received call.

Syntax +VRID=<pmode>
Defined Values

<pmode> Decimal number corresponding to the selected option.
0 Reports Caller ID with formatted presentation to the DTE. The modem presents the data items in a <Tag><Value>

pair format. The expected pairs are date, time, name, and caller code (telephone number).

1 Reports Caller ID with unformatted presentation to the DTE.

Reporting Supported Range of Parameter Values

Command: +VRID=?
Response: +VRID: (<pmode> range)
Example: +VRID: (0,1)

\N Operating Mode

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

Syntax \N<mode>
Defined Values

<mode> Decimal number which corresponds to the selected mode.
0 Selects normal speed buffered mode (disables error-correction mode). (Forces &Q6.)
1 Serial interface selected - Selects direct mode and is equivalent to &M0, &Q0 mode of operation. (Forces &Q0.)

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 12

Chapter 4 - V.22bis Commands

2 Selects reliable (error-correction) mode. The modem will first attempt a LAPM connection and then an MNP

connection. Failure to make a reliable connection results in the modem hanging up. (Forces &Q5, S36=4, and
S48=7.)

3 Selects auto-reliable mode. This operates the same as \N2 except failure to make a reliable connection results in

the modem falling back to the speed buffered normal mode. (Forces &Q5, S36=7, and S48=7.)

4 Selects LAPM error-correction mode. Failure to make an LAPM error-correction connection results in the modem

hanging up. (Forces &Q5 and S48=0.)

5 Selects MNP error-correction mode. Failure to make an MNP error-correction connection results in the modem

hanging up. (Forces &Q5, S36=4, and S48=128.)

Result Codes OK <mode> = 0 to 5

ERROR Otherwise

I Identification

This command causes the modem to reports the requested result according to the command parameter.

Syntax I<value>
Defined Values

<value> Decimal number corresponding to the selected information.
0 Reports product code, e.g., “2400”.
1 Reports the least significant byte of the stored checksum in decimal. Reports 255 if the prestored checksum value

is FFh.
2 Reports "OK".
3 Reports identification codes.

RevisionName = masked firmware code version. Example: Patton Modulation = V.22bis

Example:

Patton-V22B
4 Reports OEM defined identifier string in either Hayes-compatible binary format (default), e.g.: a007040284C6002F

bC60000000r10051111510120003000111170000000
5 Reports Country Code parameter (see +GCI).
6 Reports “OK”.
7 Reports “OK”.
Result Codes OK <value> = 0 - 7

ERROR Otherwise

+GCI Country of Installation

This extended syntax command selects and indicates the country of installation for the modem. This parameter
selects the settings for any operational parameters that need to be adjusted for national regulations or telephone
networks. Additional country profiles can be uploaded and existing ones can be modified by minor firmware upgrade
via SRAM patch.

Syntax +GCI=<country_code>
Country Code

Japan 00
Argentina 01
Taiwan 02
New Zealand 03
Singapore 04
Australia 09
Euro/NAM B5
International 99
Malaysia 6C
South Africa 9F
Default If the modem is specified for use in only one country, that country code is the default. Otherwise, the default

is defined by the OEM. Factory default is B5 (United States).

Reporting Current or Selected Values

Command: +GCI?
Response: +GCI: <current country_code>
Example: +GCI: B5 The modem is set for U.S.

Reporting Supported Range of Parameter Values

Command: +GCI=?

Response: +GCI: (<country_code>[,<country_code>[,<country_code].......]]

Example: +GCI: (00,B4,B5) The modem can be set for Japan, United Kingdom, or the United States.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 13

Chapter 4 - V.22bis Commands

&F Restore Factory Configuration (Profile)

The modem loads the factory default configuration (profile). The factory defaults are identified for each command and
in the S-Parameter descriptions. A configuration (profile) consists of a subset of S-Parameters.

Syntax &F[<value>]
Defined Values

<value> Decimal number corresponding to the selected configuration.
0 Restore factory configuration 0.
1 Same as 0; allowed for compatibility.
Result Codes OK

ERROR If the modem is connected

&T Local Analog Loopback Test

The modem will perform the local analog loopback test if &T1 is selected. The test can be run only when in an
asynchronous operation in non-error-correction mode (normal), e.g., AT&Q6. To terminate the test in progress, the
escape sequence must be entered first.

Syntax &T[<value>]
Defined Values

<value> Decimal number corresponding to the selected option.
0 Terminates test in progress. Clears S16.
1 Initiates local analog loopback, V.54 Loop 3. Sets S16 bit 0. If a connection exists when this command is issued,

the modem hangs up. The CONNECT XXXX message is displayed upon the start of the test.

** Load to Internal RAM

This command allows the internal SRAM to be loaded with patch code for minor firmware upgrade including country
profile customization. This process transfers the S37 file from the host computer to the modem. The data transfer is
done via an ASCII transfer. A successful upload can be verified by invoking ATI3 and/or ATI4 command depending
on which of the two were modified. The patch is erased when the power is turned off.

Procedure

1. Configure the communications application program for a DTE rate of 115200 bps.

Check the modem for response by typing AT.

2. Issue AT** command to initiate the download process. The following message appears:

Download initiated.

3. Send the patch code (e.g., patv00028.s37). The following message appears on successful upload:

Modem Firmware Successfully Loaded

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 14

Chapter 4 - V.22bis Commands

V.22bis DTE/DCE-Modem Interface commands

The parameters defined in this section control the operation of the interface between the DTE/DCE and modem.

E Command Echo

The modem enables or disables the echo of characters to the DTE. The valid parameter value is written to S14 bit 1.

Syntax E<value>
Defined Values

<value> Decimal number corresponding to the option.
0 Disables command echo.
1 Enables command echo. (Default)
Result Codes OK <value> = 0 or 1

ERROR Otherwise

Q Quiet Result Codes Control

The command enables or disables the sending of result codes to the DTE. The parameter value, if valid, is written to
S14 bit 2.

Syntax Q<value>
Defined Values

<value> Decimal number corresponding to the option.
0 Enables result codes to the DTE. (Default)
1 Disables result codes to the DTE.
Result Codes OK <value>= 0 or 1

ERROR Otherwise

V Result Code Form

This command selects the sending of short-form or long-form result codes to the DTE. The parameter, if valid, is
written to S14 bit 3.

Syntax V<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 Enables short-form (terse) result codes. Line feed is not issued before a short-form result code.
1 Enables long-form (verbose) result codes. (Default)
Result Codes OK <value>= 0 or 1

ERROR Otherwise

W Connect Message Control

This command, in conjunction with S95 bits 0, 2, and 3, (bits 2 and 3 can be written directly by the host), control the
format of CONNECT messages. The actual result code messages reported reflect the W command setting and the
S95 bit settings.
The W parameter value, if valid, is written to S31 bits 2 and 3.

Syntax W<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 Upon connection, the modem reports only the DTE speed (e.g., CONNECT 19200). Subsequent responses are

disabled. (Default)
1 Upon connection, the modem reports the modulation, line speed, the error correction protocol, and the DTE

speed, respectively. Subsequent responses are disabled.
2 Upon connection, the modem reports the DCE speed (e.g., CONNECT 2400). Subsequent responses are

disabled.
Result Codes OK <value> = 0, 1, or 2

ERROR Otherwise

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 15

Chapter 4 - V.22bis Commands

X Extended Result Codes

This command selects the subset of the result code messages used by the modem to inform the DTE of the results of
commands. Blind dialing is enabled or disabled by country parameters. If the user wishes to enforce dial tone
detection, a "W" can be placed in the dial string (see D command). The information below is based upon the default
implementation of the X results table.

Syntax X<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 Disables reporting of busy tones unless forced otherwise by country requirements; send only OK, CONNECT,

RING, NO CARRIER, ERROR, and NO ANSWER result codes. Blind dialing is enabled/disabled by country

parameters. If busy tone detection is enforced and busy tone is detected, NO CARRIER will be reported. If dial

tone detection is enforced or selected and dial tone is not detected, NO CARRIER will be reported instead of NO

DIAL TONE. The value 000b is written to S22 bits 6, 5, and 4, respectively.
1 Disables reporting of busy tones unless forced otherwise by country requirements; send only OK, CONNECT,

RING, NO CARRIER, ERROR, NO ANSWER, and CONNECT XXXX (XXXX = rate). Blind dialing

enabled/disabled by country parameters. If busy tone detection is enforced and busy tone is detected, NO

CARRIER will be reported instead of BUSY. If dial tone detection is enforced or selected and dial tone is not

detected, NO CARRIER will be reported instead of NO DIAL TONE. The value 100b is written to S22 bits 6, 5,

and 4, respectively.
2 Disables reporting of busy tones unless forced otherwise by country requirements; send only OK, CONNECT,

RING, NO CARRIER, ERROR, NO DIAL TONE, NO ANSWER, and CONNECT XXXX. If busy tone detection is

enforced and busy tone is detected, NO CARRIER will be reported instead of BUSY. If dial tone detection is

enforced or selected and dial tone is not detected, NO DIAL TONE will be reported instead of NO CARRIER. The

value 101b is written to S22 bits 6, 5, and 4, respectively.
3 Enables reporting of busy tones; send only OK, CONNECT, RING, NO CARRIER, ERROR, NO ANSWER, and

CONNECT XXXX. Blind dialing is enabled/disabled by country parameters. If dial tone detection is enforced and

dial tone is not detected, NO CARRIER will be reported. The value 110b is written to S22 bits 6, 5, and 4,

respectively.
4 Enables reporting of busy tones; send all messages. The value 111b is written to S22 bits 6, 5, and 4,

respectively. (Default)
Result Codes OK <value> = 0 to 4

ERROR Otherwise

Table of Result Codes

Short Form Long Form

0OK XXXXX
1 CONNECT XXXXX
2RING XXXXX
3 NO CARRIER X X X X X
4 ERROR X X X X X
5 CONNECT 1200 1 X X X X
6 NO DIAL TONE 3 3 X X X
7BUSY 333XX
8 NO ANSWER X X X X X
9 CONNECT 600 1 X X X X
10 CONNECT 2400 1 X X X X
11 CONNECT 4800 1 X X X X
12 CONNECT 9600 1 X X X X
13 CONNECT 7200 1 X X X X
14 CONNECT 12000 1 X X X X
15 CONNECT 14400 1 X X X X
16 CONNECT 19200 1 X X X X
17 CONNECT 38400 1 X X X X
18 CONNECT 57600 1 X X X X
19 CONNECT 115200 1 X X X X
22 CONNECT 75TX/1200RX 1 X X X X
23 CONNECT 1200TX/75RX 1 X X X X
24 DELAYED 4 4 4 4 X
32 BLACKLISTED 4 4 4 4 X
40 CARRIER 300 X X X X X
41 CARRIER 1200/75 X X X X X

0 1 2 3 4

n Value in ATXn Command

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 16

Chapter 4 - V.22bis Commands

Short Form Long Form

42 CARRIER 75/1200 X X X X X
46 CARRIER 1200 X X X X X
47 CARRIER 2400 X X X X X
67 PROTOCOL: V42 X X X X X
70 PROTOCOL: NONE X X X X X
83 LINE IN USE X X X X X
85 OFF-HOOK INTRUSION X X X X X
86 LINE REVERSAL DETECTED X X X X X
87 NO LINE X X X X X

Note:

An 'x' in a column indicates that the message (either the long form if verbose, or the value only for short form) will
be generated when that particular value of 'n' (shown at the top of the column) has been selected by the use of
ATXn. If the column is blank, then no message will be generated for that x option. A numeral indicates which less
explicit message (verbose or short form) will be output for that X option.

&C RLSD Option

The modem controls the RLSD output in accordance with the parameter supplied. The parameter value, if valid, is
written to S21 bit 5.

Syntax &C<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 RLSD remains ON at all times.
1 RLSD follows the state of the carrier. (Default)
Result Codes OK 0 or 1

ERROR Otherwise

0 1 2 3 4

n Value in ATXn Command

&D DTR Option

This command interprets the ON to OFF transition of the DTR signal from the DTE in accordance with the parameter
supplied. The parameter value, if valid, is written to S21 bits 3 and 4. Also, see S25.

Syntax &D<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 DTR drop is interpreted according to the current &Qn setting as follows:

&Q0, &Q5, &Q6: DTR is ignored (assumed ON). Allows operation with DTEs, which do not provide DTR.

&Q1: DTR drop causes the modem to hang up. Auto-answer is not affected.

&Q2, &Q3: DTR drop causes the modem to hang up. Auto-answer is inhibited.
1 DTR drop is interpreted according to the current &Qn setting as follows:

&Q0, &Q1, &Q5, &Q6: DTR drop is interpreted by the modem as if the asynchronous escape sequence had been

entered. The modem returns to asynchronous command state without disconnecting.

&Q2, &Q3: DTR drop causes the modem to hang up. Auto-answer is inhibited.
2 DTR drop is interpreted according to the current &Qn setting as follows:

&Q0 through &Q6: DTR drop causes the modem to hang up. Auto-answer is inhibited. (Default)
3 DTR drop is interpreted according to the current &Qn setting as follows:

&Q0, &Q1, &Q5, &Q6: DTR drop causes the modem to perform a soft reset as if the Z command were received.

&Q2, &Q3: DTR drop causes the modem to hang up. Auto-answer is inhibited.

&K Flow Control

This command defines the DTE/DCE (terminal/modem) flow control mechanism. The parameter value, if valid, is
written to S39 bits 0, 1, and 2.

Syntax &K<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 Disables flow control.
3 Enables RTS/CTS flow control. (Default for data modem modes.)
4 Enables XON/XOFF flow control.
5 Enables transparent XON/XOFF flow control.
Result Codes OK <value> = 0, 3, 4, or 5

ERROR Otherwise

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Chapter 4 - V.22bis Commands

&R RTS/CTS Option

This selects how the modem controls CTS. CTS operation is modified if hardware flow control is selected (see &K
command). The parameter value, if valid, is written to S21 bit 2.

Syntax &R<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 In sync mode, CTS tracks the state of RTS; the RTS-to-CTS delay is defined by S26. In async mode, CTS is

normally ON and will turn OFF only if required by flow control.
1 In sync mode, CTS is always ON and RTS transitions are ignored. In async mode, CTS is normally ON and will

turn OFF only if required by flow control.
Result Codes OK <value> = 0 or 1

ERROR Otherwise

\G Modem-to-Modem Flow Control (XON/XOFF)

The modem enables or disables the generation or recognition of modem-to-modem XON/XOFF flow control
according to the parameter supplied. The parameter value, if valid, is written to S41 bit 3.
Due to the buffering system used in the modem, modem-to-modem flow control is normally disabled.

Syntax \G<value>
Defined Values

<value> Decimal number corresponding to the selected option.
0 Disables modem-to-modem XON/XOFF flow control. (Default.)
1 Enables modem-to-modem XON/XOFF flow control.
Result Codes OK <value> = 0 or 1

ERROR Otherwise

+IFC DTE-Modem Local Flow Control

This extended-format compound parameter controls the operation of local flow control between the DTE and the
modem during the data state when V.42 error control is used, or when fallback to non-error control mode is specified
to include buffering and flow control. It accepts two numeric subparameters.

Syntax +IFC=[<modem_by_DTE>[,<DTE_by_modem>]]
Defined Values

<modem_by_DTE> Specifies the method to be used by the DTE to control the flow of received data from the modem.

0 None.
1 XON/XOFF on transmitted data (XON/XOFF on transmit data); do not pass XON/XOFF characters to the

remote modem.
2 Circuit 133 (Ready for Receiving). (Default)
3 DC1/DC3 on circuit 103 (Transmitted Data) with DC1/DC3 characters being passed through to the remote

DCE in addition to being acted upon for local flow control

<DTE_by_modem> Specifies method to be used by the modem to control the flow of transmitted data from the DTE.

0 None.
1 XON/XOFF on received data.
2 CTS/RTS. (Default)

Reporting Current or Selected Values

Command: +IFC?
Response: +IFC: <modem_by_DTE>,<DTE_by_modem>
Example: +IFC: 2,2 For the defaults.

Reporting Supported Range of Parameter Values

Command: +IFC=?
Response: +IFC: (<modem_by_DTE> range),(<DTE_by_modem> range)
Example: +IFC: (0-3),(0-2)

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 18