CUSTOMER
SUPPORT
INFORMATION
Order toll-free in the U.S.: Call 7877-877-BBOX (outside the U.S. call 724-746-5500)
FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746
Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • Email: info@blackbox.com
AUGUST 2000
MD1640A
MD1641A
Series II Modem 336
Series II Modem 336+
Series II Intelligent Data/Fax Modems
Model 336 (Product Code MD1641A)
Model 336+ (Product Code MD1640A)
User Guide
336 and 336+
Series II Modems
2
SERIES II INTELLIGENT DATA/FAX MODEMS
DISCLAIMER
This publication may not be reproduced, in whole or in part, without prior
expressed written permission from the manufacturer. The manufacturer
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. The manufacturer reserves the right to revise this
publication and to make changes from time to time in the content hereof
without obligation of the manufacturer to notify any person or organization
of such revisions or changes.
TRADEMARKS USED IN THIS MANUAL
MNP and Microcom Network Protocol are trademarks of Microcom Inc.
AS/400 and System3x are registered trademarks of IBM.
Appletalk, Mac, and Macintosh are registered trademarks of Apple
Computer Inc.
Unix is a registered trademark of X/Open Co. Ltd.
Microsoft and Windows are registered trademarks of Microsoft Corporation.
All other trademarks mentioned in this manual are the property of their
respective owners.
3
Table of Contents
Contents
Chapter 1 - Introduction and Description
1.1 Introduction............................................................................7
1.2 How To Use This Manual ......................................................7
1.3 What is in Your Modem Package? ......................................10
1.4 Modem Features ..................................................................10
1.5 Fax Features ..........................................................................11
1.6 Technical Specifications ......................................................12
1.7 Power ....................................................................................16
1.8 Modem LED Indicators ......................................................16
1.9 Controls on PC Board..........................................................18
Chapter 2 - Installation and Connection
2.1 Safety Warnings ....................................................................19
2.2 Installation ............................................................................20
2.3 Is Your Series II Modem Ready for Use? ............................23
2.4 Operating Your Series II Modem ......................................24
2.4.1 Simple Operations ......................................................25
2.5 The Answer/Originate - Voice/Data Toggle Switch..........25
Chapter 3 - Software Configuration
3.1 Introduction ........................................................................26
3.2 Serial Port Limitations ........................................................26
3.2.1 How Can You Identify Your UART Type? ....................27
3.2.2 The 16550 UART and Windows 3.1 ............................28
3.3 Configuring Your Software..................................................29
3.3.1 Configuring Software for Your Modem ......................29
3.4 PC Initialization Strings ......................................................30
3.4.1 Changing Default Parameters ......................................30
3.4.2 Other Parameters ........................................................31
3.5 Macintosh Initialization ......................................................31
3.6 Configuring Software for Your Computer..........................32
3.6.1 Configuring Software for the Remote System ............32
3.6.2 Terminal Emulation ......................................................33
3.6.3 File Transfer Protocols ..................................................33
4
SERIES II INTELLIGENT DATA/FAX MODEMS
3.7 When to Disable Data Compression ..................................33
3.7.1 Disabling Error Correction ..........................................34
Chapter 4 - Manual Dial and Automatic Answer
4.1 Introduction ........................................................................35
4.2 Dialing/On-Line/Answering ..............................................35
4.3 Auto. Leased Line Restoral Operation (336+ Only) ........37
4.4 Manual Dial Backup Call Termination (336+ Only) ........37
4.5 Dial Backup and Leased Line Restoral (336+ Only) ........37
4.6 Dial-Up Operation (336+ Only)..........................................39
4.7 Manual Call Origination......................................................39
4.8 Automatic Answering ..........................................................40
4.9 Manual Answering................................................................41
4.10 Handshaking Details ............................................................41
4.11 Call Termination ..................................................................42
Chapter 5 - Command Mode
5.1 Introduction..........................................................................44
5.1.1 AT Command Editing ..................................................44
5.1.2 Functional Modes..........................................................45
5.2 Summary of AT Commands ................................................46
5.3 Result Codes ........................................................................50
5.4 Dialing Commands ..............................................................52
5.4.1 Dialing Action Commands ..........................................52
5.4.2 Dial Modifier Commands ............................................54
5.4.3 Phone Number Memory Commands ..........................58
5.4.4 Configuration and Default Storage Commands ........60
5.4.5 Command Response (Result Code) Commands........63
5.4.6 Phone Line Conditioning Commands ........................66
5.4.7 RS232C Interface Control Commands........................68
5.4.8 Error Correction Commands ......................................70
5.4.9 Flow Control Commands..............................................75
5.4.10 Compression, Error Correction, Flow Control,
Pass-Through and Pacing Commands ........................81
5.4.11 Speed Conversion Commands ....................................82
5
Table of Contents
5.4.12 Immediate Action Commands ....................................85
5.4.13 Line Probe Commands ................................................90
Chapter 6 - S-Registers
6.1 Introduction..........................................................................92
6.2 Reading and Assigning S-Register Values ..........................102
6.2.1 Examples of Assigning Values ......................................102
6.2.2 Examples of Reading Values ........................................103
6.3 AT Command and S-Register Summary ............................103
Chapter 7 - Callback Security and Remote
Configuration
7.1 Introduction..........................................................................104
7.2 Callback Feature Description ..............................................104
7.3 Remote Configuration Description ....................................105
7.3.1 Initial Setup Procedures for Callback and Remote ..
Configuration. ..............................................................105
7.3.2 Remote Configuration Procedures..............................111
7.4 Remote Configuration and Callback Security AT ............
Commands ..........................................................................112
7.5 Remote Configuration/Callback Security S-Registers ......114
Chapter 8 - Modem Testing
8.1 Introduction ........................................................................116
8.2 Local Analog Loopback Test/V.54 Loop 3 ........................117
8.3 Digital Loopback Test/V.54 Loop 2 (Local/Manual) ......118
8.4 Digital Loopback Test/V.54 Loop 2 (Remote/Auto.) ......120
8.5 Back-to-Back Test ..................................................................121
8.6 Synchronous Mode Testing ................................................123
8.7 Local Analog Loopback Test (Synchronous Mode) ..........123
6
SERIES II INTELLIGENT DATA/FAX MODEMS
8.8 Digital Loopback Test (Local/Manual) (Sync Mode) ......124
8.9 Digital Loopback Test (Remote/Auto.) (Sync Mode) ......125
Chapter 9 - DIP-Switch Settings
9.1 Introduction..........................................................................127
9.2 DIP-Switch Option Settings ................................................128
9.3 Speaker Volume Control ....................................................136
9.4 Recording Option Configurations......................................137
Appendix A - Troubleshooting
A.1 Possible Causes and Solutions ............................................139
A.2 Contacting Black Box ..........................................................147
A.2.1 Recording Modem Information ..................................147
A.2.2 Making the Call ............................................................148
A.3 Shipping and Packaging ......................................................148
A.4 Upgrading the Series II Modem’s Firmware......................149
Other Appendixes
Appendix B - Dial Pulse and Tone-Dial Frequencies ......................150
Appendix C - Command Summary ..................................................151
Appendix D - DIP-Switch Summary ..................................................164
Appendix E - S-Register Summary ....................................................167
Appendix F - Result Code Summary ................................................171
Appendix G - V.25bis Operation........................................................174
Appendix H - Series II Modem Cables..............................................187
Appendix I - RS232C Interface Specifications ................................189
Appendix J - Regulatory Information ..............................................195
7
CHAPTER 1: Introduction and Description
1. Introduction and Description
1.1 Introduction
Welcome to the world of data communications. You have acquired one
of the finest intelligent desktop data/fax modems available today, a
Series II Modem from Black Box. Your Series II Modem provides data
communication at 33,600-14,400 bps (Enhanced V.34/V.32bis), as well
as other prevalent datacomm standards. The Modem supports adaptive
protocol enhancing used in typical Unix
®
batch file transfers and
support for IBM's AS/400
®
and System/3X®environment. If your
Series II Modem is a 336+ model, it also performs dial backup with
automatic lease line restoration. This Owner’s Manual will help you
install, configure, test and use your Modem.
1.2 How To Use This Manual
This manual is divided into nine chapters. There are also several
appendices at the end of this manual, most of which repeat information
contained in the chapters, but in a more condensed form. These appendices can be used as a quick reference. The information contained in
each chapter and appendix is as follows:
Chapter 1 - Introduction and Description
This chapter begins with a short introduction, followed by a guide (which
you are now reading) to the use of this manual. There is a discussion
about what components you can expect in your Series II Modem
package. We then provide a more detailed description of the modem,
including the modem’s technical specifications. Chapter 1 includes
sections covering power, LED indicators and a brief summary of PC
board controls. (Chapter 9 covers switch settings more thoroughly.)
8
SERIES II INTELLIGENT DATA/FAX MODEMS
Chapter 2 - Installation and Connection
Chapter 2 covers the procedure for connecting the Series II Modem to
your computer and to the phone line. Details are given, supported by
illustrations on the Modem's back panel connections as a guide to
install your Modem to the point of operation.
Chapter 3 - Software Configuration
Chapter 3 documents communication software configuration
recommended specifically for the Series II Modem. There is also some
discussion of how to identify the limitations and capabilities of your
computer before the software installation process is done. Other issues
covered include setting up initialization strings, changing default
parameters, configuring software for the remote system and file
transfer protocols.
Chapter 4 - Manual Dial and Automatic Answer
This chapter covers some modem operations, but delays discussion on
Command Mode operation until Chapter 5. Automatic Leased Line
Restoration, Dial backup, Manual Dial Mode, and Answer Mode operation are covered in detail, as well as the handshaking procedures
employed between two modems in an auto-answer application.
Chapter 5 - AT Command Mode Operation
This may be the most important chapter of this manual. It begins with
an introduction and discussion on Command Mode fundamentals. A
flow chart is provided to illustrate Command Mode and On-Line Mode
operation and the methods used in each mode. Next, there is a
summary of the modem’s commands and responses. We then go into
a detailed explanation of each Series II Modem command, providing
examples where applicable.
Chapter 6 - S-Registers
Chapter 6 covers the Series II Modem's S-Registers, which enable the
user to establish, read, and modify various modem options. All of the
S-Registers are charted and explained, followed by instructions on
accessing the S-Registers and reading or changing their values.
9
CHAPTER 1: Introduction and Description
Chapter 7 - Callback and Remote Configuration
Chapter 7 documents instructions on how to operate the Series II
Modem's Callback and Remote Configuration features; and the usage of
LOGIN Passwords, Set-Up Passwords and Remote Escape Characters as
network management tools.
Chapter 8 - Testing Your Modem
This Chapter covers the modem's built-in test features. These are:
Power-on Self Test, Back-To-Back Test, Local Analog Loopback, Digital
Loopback and Remote Digital Loopback Tests. We have included a
description of each test and how to use each test procedure.
Chapter 9 - DIP-Switches
The Series II Modem printed-circuit board options are covered in this
chapter. Sixteen DIP-Switch settings and the modem's speaker volume
control are explained in detail, including all default settings.
Appendix A - Troubleshooting
Appendix B - Pulse Dial and Tone-Dial Frequencies
Appendix C - AT Command Summary
Appendix D - DIP Switch Summary
Appendix E - S-Register Summary
Appendix F - Result Code Summary
Appendix G - V.25bis Operation
Appendix H - Series II Modem Cables
Appendix I - RS232 Interface Specifications
Appendix J - Regulatory Information
10
SERIES II INTELLIGENT DATA/FAX MODEMS
1.3 What is in Your Modem Package?
Your Series II Modem is made up of many components. Make sure you
have them all before trying to operate your modem. Your package
should include:
• The Series II Modem itself
• AC Power Transformer
• (2) RJ-11 to RJ-11 telephone cords
• This Owner’s Manual
• 336+ (MD1640A) only: (1) RJ-11 to spade lugs leased-line cable
If any of these items are missing, please contact Black Box.
1.4 Modem Features
Your Series II Modem meets the proposed Enhanced V.34 ITU standard
for data signalling rates as high as 33.6/31.2K bps in full duplex mode.
Connections can be made on Public Switched Telephone Networks
(PSTNs) and/or point-to-point 2-wire and 4-wire leased telephone type
circuits. Enhanced V.34 is an extension of V.32/V.32bis/V34 standards,
and supports and is compatible with those features, including EIA
extended Automode; adaptive line probing; automatic symbol rate and
carrier frequency during start-up; and retrain and rate renegotiation
(in 2400 bps increments).
Your modem is compatible with the AT command set and the ITU
V.25 bis standard for sunchronous dialing. It also features ITU V.42
error correction and V.42bis data compression, providing 100% errorfree data transmission. V.42 error correction incorporates MNP (Classes
3 and 4) and LAP-M. You may select V.42bis data compression for 4-1
throughput, or MNP Class 5 for 2-1 throughput.)
11
CHAPTER 1: Introduction and Description
Your Series II Modem offers interactive automatic dialing, as well
as Command Mode option configuration. You may store up to ten
command line/telephone numbers, of up to 60 characters each, in
the modem’s nonvolatile memory. The modem pulse or tone dials,
and recognizes dial tones and busy signals for reliable call-progress
detection. The modem can detect AT&T calling card tones. It is
FCC-Registered for connection to telephone networks without any Data
Access Arrangements (DAA’s).
Your modem also features Callback Security to protect networks from
unauthorized use, and to manage phone line costs. By using the
modem’s phone number and password directory, a host site can, upon
receipt of a call, callback to a remote site at a predetermined number.
Remote Configuration permits you to assist users at remote sites, saving
you the time and trouble of site visits and preventing misinterpretation
of configuration instructions.
In addition, the major application for the 336+ (MD1640A) model of
the Series II Modem is in 4-wire leased line networks with the addition
of dial backup capability. With this capability, the dialup feature
prevents downtime if the leased line fails. Since the Modem operates
according to ITU V.34 modulation, it can operate full-duplex over two
wires, so that the dial backup mode performs the same throughput as
the leased line.
1.5 Fax Features
Your Series II Modem meets the ITU V.17 standard for sending and
receiving faxes. When linked to a compatible fax machine or modem,
it can transmit faxes at 14,4 K bps. It also meets the ITU’s Group 3
Designation for sending and receiving faxes at 9600 bps; and Group 2
Designation for sending and receiving faxes at 4800 bps. The Modem is
also downward-compatible with modems to speeds as low as 300 bps, so
it can send and receive faxes with any fax machine in the world.
12
SERIES II INTELLIGENT DATA/FAX MODEMS
1.6 Tec hnical Specifications
Your Series II Modem data/fax modem meets the specifications listed
below:
Data Rates (modem) 33,600, 31,200, 28,800, 26,400, 24,000,
21,600, 19,200, 16,800, 14,400, 12,000, 9600,
7200, 4800, 2400, 1200, 0-300 bps
Data Rates (fax) 14,400, 9600, 7200, 4800 bps
Data Format Serial, binary, asynchronous at 0-300, 1200,
2400, 4800, 7200, 9600, 12,000, 14,400,
16,800, 19,200, 21,600, 24,000, 26,400,
28,800, 31,200, 33,600 bps; synchronous at
1200, 2400, 4800, 7200, 9600, 12,000,
14,400, 16,800, 19,200, 21,600, 24,000,
26,400, 28,800, 31,200, 33,600 bps
Compatibility ITU V.42bis, V.42, Pending ITU Enhanced
V.34 approval, ITU V.34, ITU V.32bis, V.32,
V.22bis, V.22, V.25bis, Bell 212A and
103/113, ITU V.17, Group 3 T.4, T.30 and
EIA TR-29 Class 2
Error Correction V.42 (LAP-M or MNP 3 & 4) error
correction
Data Compression V.42bis, (4:1 throughput) or MNP 5
(2:1 throughput) data compression
Speed Conversion Serial port data rates adjustable to 300,
1200, 2400, 4800, 9600, 19,200, 38,400,
57,600 and 115,200 bps
Flow Control Xon/Xoff, Hardware RTS/CTS, ENQ/ACK
Options Unix-to-Unix Copy Protocol (UUCP)
"Spoofing"
13
CHAPTER 1: Introduction and Description
Mode of Operation Full duplex over both dial-up lines and
2-wire or (336+ [MD1640A] only) 4-wire
leased lines; automatic or manual dialing,
automatic or manual answer; and (336+
[MD1640A] only) automatic dial backup on
separate lines in leased line operation
Intelligent Features Fully “AT command” compatible, micropro-
cessor controlled remote configuration, EIA
extended Automode, adaptive line probing,
automatic symbol rate and carrier
frequency during start-up, retrain and rate
renegotiation, autodial, redial, repeat dial,
dial linking, pulse or tone dial, dial tone
detection, dial pauses, call status display,
auto-parity and data rate selection,
keyboard-controlled modem options,
nonvolatile memory and on-screen displays
for modem option parameters and up to
ten telephone numbers/command lines of
up to 60 digits each, help menus
Command Buffer 60 characters
Modulation Trellis Coded Modulation (TCM) at 33,600,
31,200, 28,800, 26,400, 24,000, 21,600,
19,200, 16,800, 14,400, 12,000 and 9600
bps, Quadrature Amplitude Modulation
(QAM) at 9600 (non-trellis), 4800 and 2400
bps, PSK at 1200 bps, FSK at 300 bps
Fax Modulations V.21CH2 FSK at 300 bps
V.27ter DPSK at 4800 and 2400 bps
V.29 QAM at 9600 and 7200 bps
V.17 TCM at 14400, 12000, 9600,
and 7200 bps
14
SERIES II INTELLIGENT DATA/FAX MODEMS
Fax Carrier V.21CH2 (Half Duplex)
Frequencies 1650Hz Mark, 1850Hz Space for Transmit
Originate
1650Hz Mark, 1850Hz Space for Transmit
Answer
V.27ter 1800Hz Originate/Answer
V.29 QAM 1700Hz Originate/Answer
V.17 TCM 1800Hz Originate/Answer
Lease Line Restoral 336+ (MD1640A) only: When in dial backup
mode, modem attempts leased line restoral
periodically (controlled by S-Register S18
setting)
Carrier Frequencies 1800 Hz V.32/V.32bis/V.34/Enhanced V. 34 :
33.6K/31.2K/28.8K/26.4K/24K/21.6K/
19.2K/16.8K/14.4K/12K/9.6K/7.2K/4.8K
Carrier Frequencies Transmit Originate: 1200 Hz
2400 & 1200 bps Transmit Answer: 2400 Hz
(V.22bis/V.22 or Receive Originate: 2400 Hz
Bell 212A Standard) Receive Answer: 1200 Hz
Carrier Frequencies, 1270 Hz Mark, 1070 Hz Space for
300 bps (Bell Standard) Transmit Originate
2225 Hz Mark, 2025 Hz Space for Receive
Originate
2225 Hz Mark, 2025 Hz Space for Transmit
Answer
1270 Hz Mark, 1070 Hz Space for Receive
Answer
T ransmit Level -11dBm (dial-up), -9 or -15 dBm (leased-
line); dBm level selectable with DIPSwitch #3 in leased line setting
Frequency Stability ±0.01%
15
CHAPTER 1: Introduction and Description
Receiver Sensitivity -43 dBm under worst case conditions
AGC Dynamic Range 43 dB
Interface EIA RS-232C/ITU V.24
Connectors Both models: (1) DB25 female for RS232C,
(1) RJ-11 female for phone hadset, (1)
Power inlet;
336+ (MD1640A) model only: (1) RJ-11
female for dialup line, (1) RJ-11 female
for 2- or 4-wire leased line;
336 (MD1641A) model only: (1) RJ-11 female
for dialup line or 2-wire leased line
Diagnostics Power-on Self Test, Local Analog Loop,
Local Digital Loop, Remote Digital Loop,
Back-to-Back Test.
Indicators All front-mounted LEDs:
Both models: Transmit Data, Receive Data,
Carrier Detect, Speed Indicators, Off Hook,
Terminal Ready, Error Correction, and Fax;
336+ (MD1640A) model only: Error
Controls Toggle switches for Power and for
Voice/Data with Originate or Answer, DIP
Switches for various modem options, and
volume knob
Speaker Speaker for call progress monitoring
Operating Temperature 0˚ to 50˚C (32˚ to 120˚F)
Power Requirements 115-VAC, 60Hz, 0.3amp (2-prong outlet-
mounted transformer)
Dimensions
1.38"H x 6.2"W x 9"D (3.5 x 15.6 x 22.9 cm)
Weight 1.6 pounds (0.7 kg) without transformer,
2.6 pounds (1.2 kg) with transformer
16
SERIES II INTELLIGENT DATA/FAX MODEMS
1.7 Power
Power is supplied through an AC power transformer terminated with a
standard two-prong plug. The transformer supplies low voltage AC to
the modem, and plugs into any conventional 115 volt AC, 60 Hz, twoprong power outlet. The power transformer supplied with the modem
is the only one that should be used. Use of any other transformer could
cause damage to the modem. A Power On/Off switch is located on the
back of the modem.
1.8 Modem LED Indicators
The Series II Modem has fourteen diagnostic LED indicators. They are:
Figure 1-1. LED Displays of the 336 (MD1641A, top)
and 336+ (MD1640A, bottom)
1) Transmit (Send) Data (SD). This LED blinks when data is being
transmitted, on for a space, off for a mark. The state of this LED
matches the TD circuit on Pin 2 of the RS-232C/V.24 interface.
2) Receive Data (RD). This LED blinks when data is being received,
on for a space, off for a mark. The state of this LED matches that of
the RD circuit on Pin 3 of the RS-232C/V.24 interface.
3) Carrier Detect (CD). This LED is lit when a valid carrier tone
has been detected.
SD
SendRDRcvCDCarr
33.6
33.6K
24.0
24.0K
19.2
19.2K
14.4
14.4K969600242400OHOff HkTRRdyECV.42FXFax
ERR
Error
Answ
Orig
Voice/
Data
SD
SendRDRcvCDCarr
33.6
33.6K
24.0
24.0K
19.2
19.2K
14.4
14.4K969600242400OHOff HkTRRdyECV.42FXFax
Answ
Orig
Voice/
Data
17
CHAPTER 1: Introduction and Description
4) 28,800 bps (28.8). This LED behaves differently depending on your
connection:
• When the modem is connected at 33,600 bps, it blinks 5 times/sec.;
• When the modem is connected at 31,200 bps, it blinks once/sec.;
• When the modem is connected at 28,800 bps, it is solidly lit.
Note: if the modem falls back to 26.4K bps while in V.34 mode,
both the 28.8 and 24.0 LEDs light.
5) 24,000 bps (24.0). This LED is lit when the modem is connected at
24,000 bps. Note: if the modem falls back to 21.6K bps while in V.34
mode, both the 24.0 and 19.2 LEDs light.
6) 19,200 bps (19.2). This LED is lit when the modem is connected
at 19,200 bps.
7) 14,400 bps (14.4). This LED is lit when the modem is connected at
14,400 bps. Note: if the modem falls back to 12,000 bps while in V.32bis
mode, both the 14.4 and 96 LEDs light.
8) 9600 bps (96). This LED is lit when the modem is connected at
9600 bps.
9) 2400 bps (24). This LED is lit when the modem is connected at
2400 bps.
10) Off Hook (OH). This LED is lit when the phone line is "off hook".
This occurs when the modem is dialing, on-line, or answering a call.
This LED also flashes when the modem is pulse dialing in Command
mode.
11) Terminal Ready (TR). When the TR LED is lit, the modem is
permitted to answer an incoming call. When it goes off, a connected
modem will disconnect. The state of the TR LED matches that of the
DTR circuit on Pin 20 of the RS-232C/V.24 interface.
12) Error Correction (EC). This LED is lit when the modem is set for
V.42 error correction, and flashes on and off when data compression
is activated.
18
SERIES II INTELLIGENT DATA/FAX MODEMS
13) F AX (FX).This LED is lit when the modem is connected in FAX
mode.
14) 336+ (MD1640A) only: ERROR (ERR). When this LED is lit, either
the leased line is down and the modem is in dial backup mode, or else
the self-test has failed.
1.9 Controls on PC Board
The Series II Modem is designed on a single printed circuit (PC) board.
This board contains one 16-position DIP-Switch (numbered 1-16). The
DIP-Switches are accessible through a cut-out on the side of the
modem. There is also a knob which is used to adjust the speaker
volume. This knob is accessible through the modem's rear panel.
The sixteen DIP-Switches control various modem options or set default
values for Command Mode operation. There is a difference in how
several of the switches operate depending on whether you are in synchronous or asynchronous mode. Refer to the switch label on the
bottom of the Modem for an exact list of the switch functions in
asynchronous and synchronous operation.
Chapter 9 of this manual also provides detailed instructions on
configuring all of the Modem's PC board options.
19
CHAPTER 2: Installation and Connection
2. Installation and Connection
2.1 Safety Warnings
1. Never install telephone wiring during a lightning storm.
2. Never install telephone jacks in wet locations unless the jack
is specifically designed for wet locations.
3. Never touch uninsulated telephone wires or terminals unless the
telephone line has been disconnected at the network interface.
4. Use caution when installing or modifying telephone lines.
5. Avoid using a telephone (other than a cordless type) during an
electrical storm. There may be a remote risk of electrical shock
from lightning.
6. Do not use the telephone to report a gas leak in the vicinity
of the leak.
20
SERIES II INTELLIGENT DATA/FAX MODEMS
2.2 Installation
The installation of the Series II Modem consists of making the physical
connections necessary to render the modem functional with your
computer. This includes making the proper serial, phone line, and
power connections. Refer to Figure 2-1 below for the Series II Modem
336 (MD1641A) or to Figure 2-2 on the next page for the Series II
Modem 336+ (MD1640A). Following the installation instructions are
some preliminary aspects of issuing AT commands and the Modem's
"Originating/Answering" capabilities.The installation process involves:
1. Verify the settings of DIP switches #5 (Originate vs. Answer mode)
and #10 (Lease Line vs. Dial-Up operation). See Chapter 9.
2. Attach the Series II Modem to a dialup phone line and/or a 2-wire
leased line using the included RJ11 telephone cords. For the 336
(MD1641A) model, run a cord from the LINE jack to the dialup
21
CHAPTER 2: Installation and Connection
wall jack or the leased-line wall jack or terminal (refer to Figure 2-1
below). For the 336+ (MD1640A) model, run a cord from the
PSTN jack to the dialup wall jack if you’re connecting to a dialup
line; run a cord from the LEASE jack to the 2- or 4-wire leased-line
wall jack or terminal if you’re connecting to a leased line (refer to
Figure 2-2 on the next page). 336+ (MD1640A) models only: For fourwire lines, the modem uses pins 1 and 6 to transmit and pins 2 and
5 to receive.
Figure 2-1. Series II Modem 336 (MD1641A) Connections
Figure 2-2. Series II Modem 336+ (MD1640A) Connections
VOLUME
INTERFACELINE
POWER
ON
OFF
PHONE
PSTNPHONE
VOLUME
INTERFACELEASE
POWER
ON
OFF
22
SERIES II INTELLIGENT DATA/FAX MODEMS
2. Attach your Modem to your PC or terminal with an RS-232
(or V.24) cable.
3. Connect telephone set to phone jack (if desired).
4. Attach your Modem to the AC Power transformer and plug t
he AC connector into a live AC outlet.
5. Turn on power by flipping the "ON/OFF" switch at the left rear
of the Modem to the "ON" position.
6. Assuming you have already chosen Dial-Up mode (DIP Switch #10
in the UP/OPEN position) or Leased Line mode (DIP-Switch #10
in the DOWN/CLOSED position, assign your modem to either
“originate” or “answer” mode. It doesn’t matter which mode you
select — just give the modem you’re connecting to the opposite
setting. For example, if you place DIP-Switch #5 UP, that modem
will be the answering modem. Then you should place DIP-Switch
#5 DOWN on the other modem so that it will be the originating
modem. Again, it doesn’t matter which is which, as long as the local
and remote modems have opposite settings.
7. Verify transmit dBm levels. The transmit level for dial-up lines is -
11dBm. The transmit level for leased lines is -9 dBm and may be
set alternately to -15 dBm with DIP-Switch #3.
8. Verify remote modem's current configuration settings with your
Series II Modem in terms of data compression, error correction,
transmission rate, etc. (per Chapter 5, Section 5.7.12, ATL5and
ATL7 Commands).
9. Make sure modem and computer/terminal serial port baud rates
are adjusted. (Note that several programs can check this for you.
If you have MS-DOS 5.0 or higher, a program called MSD.EXE
(Microsoft Diagnostics) is in your DOS directory. Typing MSD at
the DOS prompt brings up a screen that provides a variety of
information about your computer. Select COM ports and it lists
information about your com port, e.g., UART Type, Address, and
IRQ to name a few. Once you know your serial port's UART type,
you can set your communications's software appropriately.)
10. Verify self-test results (Section 2.2).
11. Proceed to Chapter 3 of this manual, or to your data communica-
tions software manual.
23
CHAPTER 2: Installation and Connection
Note: Appendix A lists some basic and specific troubleshooting
actions to take if your Modem is not operational.
2.3 Is Your Series II Modem Ready for Use?
As soon as you connected power to the modem, it performed a
diagnostic self-test. The speed indicators flashed in sequence for
approximately four seconds, then the 28.8 indicator is lit. The TR
indicator should be lit as well. The SD, RD, CD, and OH indicators
should remain off at this time. If not, check that the transformer is
solidly connected and that your AC outlet is live.
If you’re an experienced modem user, you may simply want to check
your modem’s settings for data compression, error correction, and so
on. You may find that you can get moving quite quickly if you just issue
an ATL5, ATL6and an A TL7 command. These commands lists how
your modem is currently configured. If you come across a setting you’re
unsure of, refer to Chapters 5 and 6 of this manual for AT command
and S-Register explanations and defaults.
If you’re a novice, please continue to the next sections of this chapter.
24
SERIES II INTELLIGENT DATA/FAX MODEMS
2.4 Operating Your Series II Modem
You control your Series II Modem by issuing AT commands, setting
S-Registers, and setting DIP-Switches. You can easily change the settings
of your DIP-Switches, as they are located on the right side of your
Modem’s chassis. Right now your Modem is set up for the most typical
user application, that is, as a traditional modem set to make a dial-up
call to a remote installation where the call is answered automatically;
therefore, you shouldn’t need to change the DIP-Switches. (If however,
you know that your application does not follow this profile, please refer
to Chapter 9 of this manual for full details on DIP-Switch settings.)
While you may operate your Series II Modem manually, it is more
likely that you will use your data communications software to either:
• enter “terminal” mode, where you can “speak most directly” to
the modem by issuing AT commands, or to
• launch a datacomm session through a set of modem configurations
which you select and then associate with a target telephone
number. Once you have created, saved, and named this set of
information according to your connection needs and your
datacomm software’s conventions, the software then simplifies
your dialing because you needn’t re-configure your modem, nor
run the risk of mistakenly keying-in incorrect information.
Either way, you need to understand that an AT command is the method
by which your modem is controlled, and must therefore prefix nearly all
commands. AT stands for attention, and alerts the modem that a command follows. You may enter these commands with either upper- or
lowercase characters. Entering AT automatically sets the modem’s serial
baud rate to match your computer’s and also sets the modem’s parity. It
also clears the modem’s command buffer.
Once you’re in terminal mode, enter AT followed by <CR> to check
whether your modem is operational. If everything’s fine, your modem
will respond OK. (If your Modem is a 336+ [MD1640A] model, refer to
Chapter 4 for additional details on Dialing, Automatic Answering, Dial
Back-Up and Automatic Leased Line Restoral.)
25
CHAPTER 2: Installation and Connection
2.4.1 Simple Operations
You can dial a number by using the ATD command and the phone
number of the modem with which you wish to connect, e.g.,
ATD6127853500. Your modem will dial the number, and hear a
“scrambling” noise as the modem negotiates the kind of connection it
can make, and once the modems have settled on a common
connection, you will receive a connect message on your computer’s
video display. As the modem dials and connects, you may notice
changes across its front LED panel: the OH (Off Hook) LED lights to let
you know the modem is operating as if you had picked up the handset
to a phone. The CD (Carrier Detect) LED lights to let you know the
modem has detected a device it can connect to. A speed LED lights to
let you know at which speed the connection has been made.
To hang up a call, enter +++ATH<CR>. Your modem will return on
hook, just as if you had returned a phone’s handset to its cradle. Notice
also that the OH, CD and speed LED’s are no longer lit. Your video now
displays OK, signifying that your modem is ready for your next
command.
2.5 The Answer/Originate - Voice/Data Toggle Switch
Located on the front of the modem is a Voice/Data "toggle" switch with
Originate/Answer capabilities. This switch enables the modem to automatically dial a phone number stored in the N1 location of memory
whenever this switch is toggled. (Note that you must first enter
AT$VD1&W0<CR>. This command string enables Voice/Data dialing
when the Voice/Data toggle switch is activated.)
If you are "manually" dialing with an attached telephone device (and
not with your keyboard), your Modem originates when this switch is
toggled to the corresponding position (DOWN); and if you are
"manually" answering (modem is not configured to automatically
answer via S-Register S0 setup), the Modem answers when this switch
is toggled to the corresponding position (UP).
26
SERIES II INTELLIGENT DATA/FAX MODEMS
3. Software Configuration
3.1 Introduction
Since your communications software configuration is affected by the
capabilities of your computer, this chapter begins with a discussion of
the limitations of some serial ports and how to identify them. It then
discusses communications configuration in general and recommends
settings specifically for the Series II Modem.
3.2 Serial Port Limitations
When you configure your software, you need to consider how the
hardware on both ends of the connection will affect the connection.
Some serial ports, particularly those in older PC-compatible computers,
may limit the performance of the Series II Modem. You should know if
yours is one of them.
The limiting factor is an integrated circuit called a Universal Asynchronous Receiver/Transmitter, or UART. All data from your modem
flows through it. The UARTs typically used in PC-compatible computers
are types 8250, 8250A, 16450, and 16550AFN. The 8250 is unreliable
above 9,600 bps, and the 8250A and 16450 are unreliable above 19,200
bps. If the modem sends data to the UARTs above those speeds, the
UARTs may not be able to process the data fast enough to keep from
losing some of it. The 16550AFN, however, can safely handle data to
115,200 bps.
When a modem communicates with V.42bis 4-to-1 compression enabled, it sends up to four times as much uncompressed data to the serial
port as it receives compressed over the telephone line. Therefore, a
modem communicating at 14,400 bps may require a serial port that can
reliably transfer data at four times 14,400 bps, or 57,600 bps; at 19,200
bps it may require one that works reliably up to four times 19,200 bps,
or 76,800 bps; and at 28,800 and 33,600 bps it may require one that
works reliably up to a maximum of 115,200 bps. If your serial port
cannot handle these speeds, we recommend that you replace your
present serial card with one that has a 16550AFN UART or equivalent.
27
CHAPTER 3: Software Configuration
Macintosh®computers do not use UARTs. The Macintosh SE through
IIfx models use a Zilog
®
Z8530 chip called a Serial Communications
Controller, or SCC, that has a maximum speed of 57,600 bps. This
speed can be compromised by other serial communications, including
printer transmissions and Appletalk
®
, the networking software that
allows Macintoshes to share files. When Appletalk is active it controls all
serial communications on the Macintosh. Because it gives priority to
network communications, it may lose modem data at higher
transmission speeds. Therefore, when Appletalk is active you risk losing
data on serial port communications over 2400 bps, though most users
can work up to 9600 bps without problems. Other activities that could
cause the serial driver to drop bits at high speeds include the floppy disk
driver formatting a disk, the CPU paging in or out in virtual memory
mode, and the Mac
®
IIci or IIsi running the on-board video in 8-bit
mode. Therefore, for maximum communications speed on the
Macintosh, we recommend as few concurrent activities as possible. To
use V.42bis compression at 19,200 bps or faster, we recommend that you
install a high speed serial port card. Newer Macintosh computers, such
as the Quadra and Centris models, support serial port speeds up to
115,200 bps.
3.2.1 How Can You Identify Your U ART Type?
If you have MS-DOS 6.0 or later, you can find your UART type from
a diagnostic program called MSD. To use it, type MSD at the DOS
prompt. After the opening screen, select COM Ports.... The last line of
the report tells you what type UART you have for each COM port. MSD
does not distinguish between the 8250 and the 8250A. However, if you
have an IBM AT or newer computer, you likely have an 8250A or 16450
UART installed, both of which are reliable to 19,200 bps. If you would
like more detailed information about your UART than MSD can
provide, you can download shareware UART identification programs
from the World Wide Web, from the IBM Communications Forum on
CompuServe
®
, or from a local BBS.
28
SERIES II INTELLIGENT DATA/FAX MODEMS
3.2.2 The 16550 UAR T and Windows 3.1
Windows 3.1 may cause a loss of data when communicating at high
speed, even with a 16550 UART installed. Because Windows is multitasking—it switches between several programs running at the same time—
it can make the serial port wait briefly while Windows performs other
tasks. Meanwhile, incoming data can be lost. The older 8250A and
16450 UARTs can store data in a one-byte first in-first out (FIFO) buffer
(a memory area in the UART in which the first bit in is the first out),
but once the buffer is full, the data is lost. The 16550 has a 16-byte FIFO
buffer, which accounts for much of its high speed. However, in Windows
3.1, the 16550’s FIFO buffer is disabled by default. To enable the buffer,
use Notepad to open the SYSTEM.INI file in your Windows directory,
and add the following line to the [386Enh] section:
COMnFIFO=1
where n is the number of the COM port the 16550 is installed on.
For example, if the 16550 is installed on COM2, the line should be:
COM2FIFO=1
After you save SYSTEM.INI you must restart Windows for the change
to take effect.
However, there is another problem when the FIFO buffer is enabled:
Windows cannot recognize the COM port because of a bug in the
Windows 3.1 serial port driver, COMM.DRV. The only way around this
problem is to replace the COMM.DRV file in the WINDOWS\SYSTEM
directory with another driver. Several drivers are available commercially,
on the World Wide Web, or on BBSes that will solve this problem.
A freeware driver called CyberCom is available as CYBERC.ZIP on
CompuServe in the IBM Communications Forum, Library 0. CyberCom
will enable Windows communications at speeds up to 115,200 bps if you
have a 16550 UART installed.
29
CHAPTER 3: Software Configuration
3.3 Configuring Your Software
Communications software must be configured to work with your modem, your computer, and the remote system it is calling. Fortunately,
most communications programs make the process easy by providing a
default initialization string for your modem as well as defaults for most
of the other required parameters.
3.3.1 Configuring Software for Your Modem
Because remote computers may have different connection requirements such as speed, number of bits, parity, log-on sequences, etc.,
communications software is typically configured by sessions, each session
having a unique configuration for a given connection (e.g., to the
Internet, to a BBS, or to a commercial on-line service). Most communications programs, however, have a separate modem configuration menu
because modem configurations rarely change from session to session.
The most important configuration is the modem initialization string.
This is a sequence of commands the software uses to configure the
modem when the communications software is loaded or when a session
begins. Always begin the initialization string with the ATtention
command AT, then follow it with the modem reset command, &F.
Issuing a reset command before other commands ensures that you are
starting with a known state.
The rest of the commands in the initialization string depend on the
capabilities of the modem and what you want it to do. Some older
communications programs require you to create the initialization string
by yourself. Most modern communications programs, however, provide
you with a ready-made initialization string that is automatically selected
when you choose your modem model from a list. It is a poor idea to use
an initialization string intended for another modem, especially one
from another manufacturer, because modem capabilities and command
implementations vary from modem to modem. However, if your Series
II Modem does not appear on a modem list, you may use any initialization string labeled “MultiModemII” that might appear in the list.
30
SERIES II INTELLIGENT DATA/FAX MODEMS
3.4 PC Initialization Strings
We recommend the following initialization string for a Series II Modem
connected to a PC-compatible computer when sharing a line with a
telephone:
AT &F X4 S0=0 ^M
This string resets the Modem to the factory default settings, selects extended result codes with NO DIAL TONE and BUSY, and turns off auto-
answer. ^M must end every string sent to the modem from software.
It is the ASCII code for the RETURN key on most keyboards, and the
default code for the carriage return character in the Modem and most
communications programs. The carriage return character is defined in
the Modem in S-register S3; if you change it, you must also change the
carriage return character code used in your communications software.
If you send a command directly to the modem in terminal mode rather
than indirectly through communications software, you must end the
command string by pressing the RETURN key (<CR>) instead of adding
^M to the string.
The following initialization string is for a Modem on a telephone line
that functions solely as a DATA LINE:
AT &F X4 S0= 2 ^M
3.4.1 Changing Default Parameters
By default, the Series II Modem will answer after the first ring and try to
communicate with a modem on the other end of the line. If you have
one telephone line for voice, fax, and modem communications, the
Modem may attempt to answer all incoming calls, voice as well as data.
To change auto-answer to default off, open your communications
program and type the following string in the terminal window:
AT &F S0=0 &F9 &W0 <CR>
31
CHAPTER 3: Software Configuration
This string selects the factory default parameters, then turns autoanswer off and stores that setting, along with all other current parameters, in nonvolatile memory. The &F9 command causes the modem
to load the values from nonvolatile memory the next time it receives
the &F command. You will use the same initialization string as before:
AT &F X4 ^M
But now the Modem will load the values stored in nonvolatile memory
when you turn on the modem and when you issue the ATZ or AT&F
reset commands.
Note: Because it clears the command buffer, you should not use ATZ
in an initialization string.
3.4.2 Other Parameters
The default values for the other parameters in modem configuration
menus rarely need changing. They typically include the dialing prefix
(ATDT for touch-tone service and ATDP for rotary service), the dialing
suffix (^M), the hang-up string (+++ATH0^M), and response messages
(RING, NO CARRIER, BUSY, etc.). Communications software with a host
mode might also include an auto-answer string (ATS0=1^M).
3.5 Macintosh Initialization
Macintosh computers cannot use RTS/CTS hardware flow control
without a serial cable wired for hardware control. The Macintosh 128
and 512 models cannot use RTS/CTS flow control at all. For those
Macintoshes turn off the default RTS/CTS hardware flow control, turn
on XON/XOFF flow control and pacing, and ignore DTR:
AT &F X4 &E5 &E13 &D0 ^M
For hardware flow control, use the following initialization string:
AT &F X4 &E13 &D0 ^M
Add S0=0 to both strings to disable auto-answer if the Series II Modem
is on a voice line.
32
SERIES II INTELLIGENT DATA/FAX MODEMS
Chapter 3: Software Configuration
You can store the initialization string in nonvolatile memory. With your
communications software open and connected to the modem’s COM
port, type the initialization string in the terminal window, substituting a
carriage return for ^M. To store the string, enter
AT &F9 &W0 <CR>
Now you can initialize your modem with the following simple string:
AT Z ^M
3.6 Configuring Software for Your Computer
You must configure your communications software to match your computer’s configuration. If the Series II Modem is connected to the COM2
serial port, you must tell the software you are using COM2. Another
important parameter is the serial port baud rate. This is the speed at
which your modem communicates with your computer, not the speed at
which your modem communicates with another modem. When V.42bis
data compression is enabled, you must have a serial port baud rate four
times the transmission speed of the modem to fully optimize
compression. So if your UART is fast enough, you should set the serial
port baud rate to a minimum of four times the top speed of your
modem.
If you have an 8250 UART, your most reliable serial port speed will be
9600 bps; if you have an 8250A or a 16450 UART, try 19,200 bps; if you
have a 16550 UART or equivalent, a serial port setting of 115,200 bps
can be set reliably.
3.6.1 Configuring Software for the Remote System
You must meet the requirements of the remote system for successful
communications. Though the Series II Modem can automatically match
the speed of the other modem, you must specify parameters such as
type of flow control, break length, number of data bits, number of stop
bits, and parity. If you set these parameters incorrectly with the remote
system, gibberish will appear on your screen.
33
CHAPTER1: Specifications
User Guide for Series II Modems
3.6.2 Terminal Emulation
If you are accessing the remote computer as if from an on-site terminal,
the keyboard codes used by your computer may not match the ones
used by the remote computer. To be compatible with the remote computer, your software must be able to substitute the appropriate codes in
what is known as terminal emulation. Most communications programs can
emulate the most common mainframe terminals, including the DEC
VT100, VT102, and VT52 terminals, and the basic TTY mode. If in
doubt about which to choose for a Telnet session, a BBS connection,
etc., try ANSI or VT100 first.
3.6.3 File Transfer Protocols
When you upload or download files with your Series II Modem through
a browser, it will transparently use the appropriate protocol (usually
http or ftp). When you are uploading or downloading through a
terminal emulator, however, the host computer will ask which file
transfer protocol you want to use. Most communications programs allow
you to choose a default protocol. Your software’s documentation should
list the ones it can use (not all communications programs support all
protocols). Zmodem is the recommended protocol for most transfers.
3.7 When to Disable Data Compression
If your serial port cannot keep up because it has an older UART, you
may lose data when using data compression. Also, the speed advantage
hardware compression gives you is entirely dependent on how much
the data being transmitted can be compressed. If the data is already in
compressed form—a .ZIP or a .SIT file, for example—trying to compress it more will actually slow the transmission slightly compared to
transmitting the same file with compression disabled. This effect will be
most noticeable if your modem negotiates MNP 5 compression with the
other modem. V.42bis will not try to further compress a compressed file,
but MNP 5 will.
34
SERIES II INTELLIGENT DATA/FAX MODEMS
The command to disable compression is AT &E14 <CR>. If you have
an older UART or if you use your modem mostly for downloading long,
compressed files from BBSs, you may want to include the &E14
command in your initialization string as follows:
AT &F S0=0 X4 &E14 ^M
As a general rule, you should try to transmit files in already-compressed
form rather than relying on V.42bis hardware compression. Because
software compression is more efficient than hardware compression, you
will have a higher throughput with the former. Of course, this efficiency
does not include the time spent compressing and decompressing .ZIP
or .SIT files, but it will save on phone bills. And hardware compression
will still be there for those occasions when it is inconvenient to
compress a file with software. Note also that when you download files
with compression disabled, you can use a slower serial port if you have
an older UART.
3.7.1 Disabling Error Correction
By default, the Series II Modem is set to auto-reliable mode. In this
mode the Modem determines during the handshake whether the other
modem is using V.42 error correction. If it is, the Modem then switches
itself to reliable mode and enables error correction. If it is not, the
Modem remains in non-error correction mode.
Normally, we recommend that you leave the Modem set to auto-reliable
mode (&E1). However, you may encounter some circumstances in
which the Modem will work better with error correction turned off. For
example, it has been reported that on CompuServe error correction will
slow file transfers at modem speeds of 9600 bps and under. If this is a
problem for you, you can turn off error correction with the command
AT &E0, or you can include the command in your initialization string as
follows:
AT &F S0=0 X4 &E0 ^M
35
CHAPTER 4: Manual Dial and Automatic Answer
4. Manual Dial and Automatic Answer
4.1 Introduction
We’ll assume that yours is the very common application, where you are
using a Series II Modem to dial up a remote computer. The Series II
Modem has been factory preset for originating a call to a compatible
33,600 bps modem (also set up for hardware flow control, V.42 error
correction, V.42bis data compression and CTS/RTS operation). If the
answering modem is not set up similarly, the Modem automatically
adjusts to the appropriate protocol.
4.2 Dialing/On-Line/Answering
There are several basic steps for “originating” and “answering” in data
communication mode:
1. Load communication software
2. Dial
3. Establish On-Line connection
4. Terminate Call
A simple way to dial is from the keyboard of your computer or terminal.
You enter a command on the keyboard to tell the Series II Modem to
dial.
If you use a sophisticated communications software package, the
software tells you to enter phone numbers and other information. If
this is the case, the software, and not you, gives the dialing commands
to the modem. All of the commands, option registers and intelligent
features of the Series II Modem are taken care of by the software.
If you are giving commands directly to your modem (and not through
your software), each command must begin with AT (A
Ttention
Characters). AT characters may be entered in upper or lower case.
36
SERIES II INTELLIGENT DATA/FAX MODEMS
Entering AT automatically sets the modem’s speed to match the speed
of the computer or terminal, and also sets the modem’s parity.
The AT characters alert the modem that a command follows. The AT
Command can also be used to clear the command buffer, by simply
typing AT and hitting RETURN.
The letter D in a command causes the modem to dial the numbers
immediately following it (e.g., ATD7247465500). You have a choice
of either pulse (ATDP) or tone (ATDT) dialing methods.
The Modem responds with “CONNECT” on your video display after the
number is dialed and a connection signal is detected (since the Modem
defaults to Enhanced V.34/V.42/V.42bis, the actual response is
"CONNECT LAPM COMPRESSED”), if the Series II Modem “connects”
with a similar modem (see section 5.3 Result Code Summary). The
modem is now in “On-Line” mode, and is ready to communicate with a
host site.
If no connection signal is detected within 45 seconds (this time period
can be adjusted by S-Register S7), the Modem goes On Hook/hangs up
and returns to Command mode. At this point, your video displays “NO
CARRIER”.
Enter +++ATH to Hang Up On-Line (bring modem on-hook), and
terminate the modem's On-Line mode. At this point, your video
displays “OK”.
In addition to the call originating capabilities, the Modem can also
automatically answer incoming calls. You need not be present. You can,
however, control the situation by configuring the modem to either
answer or not to answer, or to answer after a specified number of rings.
This is done by setting the value of S-Register S0 (modem defaults to
automatically answer an incoming call after one ring). Refer to
Chapter 6 for S-Register details.
37
CHAPTER 4: Manual Dial and Automatic Answer
4.3 Automatic Leased Line Restoral Operation
(336+ Only)
When the Series II Modem 336+ (MD1640A) is in Dial Backup mode, it
periodically checks the leased line to see if it's operational and tries to
restore the leased line if possible. S-Register S18 determines how often
restoral attempts occur. The default for S18 is 30 minutes, and can be
set in one minute increments from 10 to 255 minutes. Setting the
restoral attempts under 10 minutes causes excessive breaks in the
dial-up operation.
Note: Both local and remote modems must have S-Register S18 set
identically. Refer to Chapter 6 for more information on S-Register S18.
4.4 Manual Dial Backup Call Termination (336+ Only)
With your Series II Modem 336+ (MD1640A) in leased line mode (DIPSwitch #10 in the DOWN position) and with dial backup operation in
process, there are two ways to manually terminate the dial backup call
(other than automatic leased line restoral). In each case, you will try to
establish the leased line connection because it is back in operating
condition. The methods of dial backup call termination are:
1) Manual Control. The "Voice/Data" switch can be used to change
from a dial back line to leased line by toggling down once. When
that is done, the Modem tries the leased line connection, and, if it
is good, the modem disconnects the dial back call and establishes
a leased line connection.
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50
milliseconds or more, a disconnect occurs. This is probably the
most common method used by computer systems at the automatic
answer end of the line to cause the answering modem to
disconnect after toggling off procedures.
4.5 Dial Backup and Leased Line Restoral (336+ Only)
The dialing associated with the Series II Modem 336+ (MD1640A) when
it's in "leased line with dial-back" mode, involves placing a call from the
originating modem due to a leased line failure.
38
SERIES II INTELLIGENT DATA/FAX MODEMS
After a preset period of time (determined by S-Register S18), the
modem automatically tries to restore the leased line.
The parameters used to determine if a leased line is down (so automatic
dial back can occur), is based on the Series II Modem doing a “retrain”
on the leased line due to an error condition in the transmission. An
error condition is defined as a "hit" on the line (the Carrier gets
interrupted).
The retrain is a "handshake" procedure between the modems to
establish the Carrier again. If the retrain fails, both modems (originate
and answer modems) start their Dial-back timers. The time is
determined by S-Register S19 settings. The S19 default setting is one
minute. During that minute, the originate modem tries to establish the
leased line link. If the leased line is established during that time, the
timer is cleared and everything is back to normal. If the timer expires,
the modems goes to dial-back mode.
The purpose of the timer for the Answer modem is to determine when
it accepts a dial-up call. When both timers have expired and the leased
line has not been established, the dial-back procedure starts. The
number dialed is the one stored in location N9 of the originate
modem's phone number memory. In the preparation for proper
dial-back operation, enter the proper number in the N9 location using
the commands detailed in Chapter 5. Keep in mind that the number
also can be dialed in V.25bis Command mode.
39
CHAPTER 4: Manual Dial and Automatic Answer
4.6 Dial-Up Operation (336+ Only)
When your Series II Modem 336+ (MD1640A) is used as a dial-up
modem (DIP-Switch #10 in the UP position), it can both originate and
answer calls. To originate calls, you use the automatic dialing capability
of the Modem's Command mode.
To do this, use the computer or terminal keyboard to enter a few
command letters, followed by the phone number you wish to dial. If you
have a computer with sophisticated communications software, you may
end up talking back and forth with the software, and the software will
take care of talking to the modem.
It is still possible, however, to dial your data calls using a telephone set.
There are few reasons why you would want to do this, but if you have a
need to use the telephone set to dial, we explain how in the next
section. We will delay our coverage of Command Mode autodialing,
and all other Command Mode features, until Chapter 5.
4.7 Manual Call Origination
You can use the Series II Modem to both originate and answer calls.
To originate calls in Asynchronous mode, you will most likely use the
Modem's Command mode, and give the modem automatic dialing
commands (we will delay our discussion of the Command mode until
Chapter 5). When using your modem in Synchronous mode, the
Command mode is disabled, so you must automatically dial your calls
with a telephone set. To use manual dialing, you first connect an
ordinary telephone set (either touch tone or rotary dial) to the
modem's PHONE Jack, if you have not already done so. Next, set the
speed selection, (DIP-Switches #13 and #14), to the speed at which you
wish to communicate. These DIP-Switches are located on the side of the
modem. (Refer to Chapter 9 for DIP-Switch settings.) Your computer or
terminal may be set for up to 115,200 bps.
When your telephone set is connected, you can use it to dial the
modem you wish to call. Simply dial the number, and then listen to the
dialed modem's answer tone. When you hear it, press the Voice/Data
switch on the front of the modem down (to the Originate position). You
don't have to hold it down. Just "toggle it" (press it once and let it go).
40
SERIES II INTELLIGENT DATA/FAX MODEMS
Once you press the switch, the tone you hear should change to another
pitch, or change into a rough-sounding scrambled noise. You then
replace the telephone handset in its cradle, and your data
communications begins.
Note that the Series II Modem may call manually via the keyboard
command ATD, or by pressing the Voice/Data switch on the modem's
front panel downward. To force the Modem to automatically answer
calls, either type ATA, or press the Voice/Data switch on the modem's
front panel upward.
4.8 Automatic Answering
The Series II Modem can be used as an automatic answering modem.
No special modifications or settings are required other than making
sure that the Auto-Answer select switch is set to Auto-answer enabled
(DIP-Switch #5 UP).
The Modem, when in its idle state, is set for Originate mode frequencies.
An incoming ring signal automatically switches the modem into Answer
mode.
You can program the modem to answer a call after a certain number of
rings using S-Register S0 (see Chapter 6). Refer to Section 4.10 for the
handshaking procedures used by the Modem when in automatic answer
mode.
In many originate-only applications, you may wish to disable the
automatic answer capability of the modem. If a telephone set is
connected to the modem, you may wish to receive incoming calls in
a voice mode for normal voice conversation. If auto-answer is not
disabled, all incoming calls are answered by the modem, preventing
voice communications. To disable automatic answer, place DIP-Switch
#5 to the DOWN (Disable Auto Answer) position (refer to Chapter 9).
Another way to disable automatic answer is to use S-Register S0 to
configure the modem to answer on the nth ring, where n equals zero
(0). Another alternative is to have the modem answer after five or six
rings, which gives you time to answer it manually if you wish. (See
Chapter 6 for S-Register information.)
41
CHAPTER 4: Manual Dial and Automatic Answer
4.9 Manual Answering
We have shown that the Series II Modem can automatically answer
incoming calls. The Modem can also answer manually, under your
control. The most typical application involves you and another person,
who, after carrying on a voice conversation, want to convert to data
communications between your modems without having to hang up
and dial again.
The problem here is that both modems are in originate mode. For two
modems to communicate, one of them must be in originate mode and
the other must be in answer mode. The solution here is to force either
one of the two modems to Answer mode, and the other to Originate
mode.
The Modem can be forced into either Answer mode or Originate mode
by using the Voice/Data switch on the front of the modem.
In our example, let's say that you and your friend Bill have just had a
voice conversation. Both of you have your telephones connected to your
Series II Modems, and your modems are connected to computers or
terminals. Set the speed switches to the proper speed on both modems.
To switch to Data mode from Voice mode, you would switch the
Voice/Data switch Down (to the Originate position), and Bill would
switch his up to Answer. This switches your modem to the originate online mode, and Bill's to the Answer on-line mode. You would both then
hang up your telephone handsets, and continue the conversation via
your keyboards.
4.10 Handshaking Details
This section briefly explains what happens between two modems in a
normal call. We are assuming that there are Series II Modems at both
the originating and at the answering end of the telephone line. (If
other brands of modems are used with our modems, they will still
communicate, but each manufacturer tends to use slightly different
delay timings and sequences, and many of the brands vary in their
LED designations.)
42
SERIES II INTELLIGENT DATA/FAX MODEMS
When a call is dialed from the originating modem, the called modem
responds to the ringing by switching into Answer mode and by turning
on its RI (Ring Indicator, RS-232C/V.24 Pin 22) signal as the rings are
detected. (The Modem-MAC does not use DTR.)
Note that in order for the called modem to be able to answer the call, it
must have a high DTR (Data Terminal Ready) signal. This signal comes
from the computer or terminal to which it is attached, on RS232C Pin 20.
When the called modem answers the call, its OH (Off Hook) circuit
comes on and the ringing stops. Two seconds after the call is answered,
the called modem begins transmitting its answerback tone.
The originating modem, which has been off hook and waiting for the
answerback tone, turns on its transmitter when it hears the tone. Then
after a one second delay, the orignating modem's CD (Carrier Detect)
comes on.
The called modem then responds to the originating modem by turning
on its CD (Carrier Detect) signal, and the handshaking is completed.
Note: With the modem in Reliable or Auto-Reliable mode, some
additional handshaking takes place. This is explained in Section 5.4.8.
4.11 Call Termination
There are a number of ways to terminate a call, or simply stated, hang
up. They are:
1) Command Mode Control. To terminate a call by Command
Mode, enter +++ATHthen RETURN; or, send a BREAK signal
followed by ATH and a RETURN.
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50
milliseconds or more, a disconnect occurs. This is probably the
most common method used by computer systems at the automatic
answer end of the line to cause the answering modem to
disconnect after logging off procedures.
3) Loss of Carrier. After a data connection is established, the
modem disconnects if a loss of carrier occurs for 700 milliseconds
(0.7 seconds) or more. Note that one cause of carrier loss would be
if one of the modems disconnect normally.
43
CHAPTER 4: Manual Dial and Automatic Answer
4) Abort Timer.
Answer Mode: When OH (Off Hook) comes on, the called modem
starts a forty-five-second timer and waits for a carrier signal from
the originating modem. If carrier is not detected within this period,
the modem disconnects (hangs up) and is ready for another call.
Originate Mode: The abort timer functions the same as in answer
mode, except that the timer begins after the modem has
completed dialing, instead of when it first goes off hook. It is
possible to change this forty-five second wait period to any other
value (from 0 seconds up to 255 seconds), or to disable the timer
completely by re-configuring S-Register S7 (see Chapter 6.)
5) Inactivity Timer. Causes the modem to disconnect if no data is
transmitted or received for a specified time. The timer is restored
any time a character is passed through the serial port in either a
send or receive state. This timer runs in both normal or reliable
connections and is controlled by S-Register S30. The Inactivity
Timer can be disabled by setting S30 to 0, which is the factory
default setting.
44
SERIES II INTELLIGENT DATA/FAX MODEMS
5. Command Mode
5.1 Introduction
AT commands are the means by which you, and your communications
software, are able to communicate with and configure your modem.
They enable you to establish, read, and modify parameters in addition
to dialing. The following provides both a summary and a detailed
explanation of the AT commands recognized by the Series II Modem.
5.1.1 AT Command Editing
The BACKSPACE key on your keyboard can be used to edit characters
in the AT command line. An AT command is not executed until the
RETURN key is pressed. The BACKSPACE key erases the previous
character for reentering.
The BACKSPACE key does noterase the AT characters once they are
entered. If your keyboard has no BACKSPACE key, CTRL-H does the
same thing. The character recognized by the modem as BACKSPACE
may be changed to any other ASCII character with S-Register S5.
If you wish to cancel an entire command that has been entered but not
yet executed, enter CTRL-X. This also clears the command buffer. The
effect is the same as backspacing to cancel the entire command, only
quicker.
Characters entered in a command are stored in the modem's Command Buffer (memory) until executed by hitting RETURN. The
Command Buffer's capacity is sixty characters. The Attention Characters
AT do not count in the sixty allowed Command characters. Spaces,
which may be used for increased display readability, may be used when
entering a command, but are not stored in the Command Buffer and
are not counted in the sixty allowed characters. Hyphens, parentheses,
etc. are not allowed.
If the sixty character limit is exceeded or if invalid characters are
entered, the Command Buffer automatically erases, and an ERROR
message appears. You would then re-enter your command within the
sixty-character maximum, using only the allowed characters.
45
CHAPTER 5: Command Mode
5.1.2 Functional Modes
The Series II Modem can be in one of two functional states (see Figure
5-1). These are "Command mode" and "On-line mode". (There is also an in-
between state, "Wait-for-Carrier", where the modem is out of Command
mode but not yet really On-Line.
When the modem is initially powered up, it is in Command mode and
is ready to accept commands from your keyboard or software. The
Modem enters On-line mode after dialing, making a connection with
another modem, and then detecting a valid carrier signal. If no carrier
is detected within a certain time frame, the modem abandons the call
and re-enters Command mode.
Once on line, the modem exits On-line mode if one of two conditions is
met. If the carrier is lost or intentionally dropped, the modem hangs up
and re-enters Command mode. Also, if the Modem recognizes the
Escape sequence for which it is configured (i.e., either the Escape
characters in the serial data stream, the Remote Escape characters in
the modulated data stream, or the Break signal), the Modem will exit
On-line mode, retain the datacomm link, and enter Command mode.
You can force the Series II Modem into On-line mode without dialing
by sending the ATD or ATA command to the modem.
46
SERIES II INTELLIGENT DATA/FAX MODEMS
Figure 5-1. Functional Modes
5.2 Summary of AT Commands
A wide variety of autodial operations and modem options can be controlled when the Series II Modem is in Command Mode. Remember,
nearly all commands begin with AT.
These commands are organized into several functional groups. An alphabetical summary of commands is provided in Appendix D.
HO
W
TO COMMANDS
DIAL D Dial
A: or : Continuous Redial
$D DTR Dialing
$VD Voice/Data Dialing
N Dial a Stored Number
MODIFY DIALING P/T Pulse/Tone Dialing
PROCEDURES &P Set Pulse Dial Ratios
, Automatic Pauses in dialing
Y Long Space Disconnect
W Wait for New Dial Tone
COMMAND
MODE
WAIT FOR
CARRIER
HANG
UP
+++AT
AT0
command
carrier lost
carrier detected
no carrier
detected
Dial (D or A)
command, or
incoming
phone call
ON-LINE
MODE
47
CHAPTER 5: Command Mode
; Return to Command Mode After Dial
Command
R Reverse Mode of Operation
! Flash On Hook
$ AT&T "Calling Card" Tones
@ Quiet Answer
MEMORIZE PHONE
NUMBERS D...N Store Phone Numbers
NN Number Linking
L List Numbers Stored in Memory
STORE MODEM &F Load Factory Defaults
CONFIGURATIONS &W Store Configuration & S-Register
AND DEF AULTS Parameters
Z Reset Modem
$SP UNIX/"Spoofing”
#V 336 (MD1641A) only: Enable/Disable
V.32terbo
&M Synchronous/Asynchronous Mode
Select
&X Synchronous Transmit Clock Select
CONFIGURE Q Result Codes Enable/Disable
COMMAND Response
RESPONSES &Q Result Code Selection
E Echo Command Characters
V Result Code Terse/Verbose
X Result Code...Basic/Extended/Call
Progress
CONDITION &G Guard Tones
PHONE LINE M Enable/Disable Monitor Speaker
AND MODEM &T Remote Digital Loop Signal
HARDWARE #T Enable/Disable Trellis Coded
Modulation
#F Fallback When On-Line
$FC 336+ (MD1640A) only: Enable/Disable
Lowspeed Fast Connect
&CD Cleardown at Disconnect
#A Auto-Speed Detect
48
SERIES II INTELLIGENT DATA/FAX MODEMS
CONTROL RS232C &C Carrier Detect Control
INTERFACE &D Data Terminal Ready Control
&R Clear To Send Control
&S Data Set Ready Control
&RF CTS/RTS Control
&SF DSR/CD Control
CONFIGURE &E0 Normal Mode
ERROR &E1 Auto-Reliable Mode
CORRECTION &E2 Reliable Mode
#L0 Negotiate V.42 Mode During
Handshake
#L1 MNP On/LAPM Off
#L2 LAPM On/MNP Off
#L3 Direct LAPM/Phase Out Handshake
$A Auto-Reliable Buffering
$F Enable/Disable Auto-Reliable
Fallback Character
$R Retransmit Count
$E Error Correction at 300 bps
CONFIGURE &E3 Flow Control Disabled
FLOW CONTROL &E4 Hardware Flow Control
&E5 Xon/Xoff Modem-Initiated
&E6 Xon/Xoff Modem Responds/No Pass-
Through
&E7 Xon/Xoff Modem Responds/Pass-
Through Allowed
#X Send Single/Multiple Xoff Characters
&E8 Enq/Ack Off
&E9 Enq/Ack On
&E10 Normal Mode Modem Flow Control
Off
&E11 Normal Mode Modem Flow Control
On
&E12 Computer-Initiated/Off
&E13 Computer-Initiated/On
&BS Maximum Block Size
49
CHAPTER 5: Command Mode
$EB 336 (MD1641A) only: 10/11-Bit
Asynchronous Format
#P Parity Selection
CONFIGURE DATA &E14 Data Compression Disabled
COMPRESSION &E15 Data Compression Enabled
CONFIGURE SPEED $BA0 Speed Conversion On
CONVERSION $BA1 Speed Conversion Off
$MB Set modem speed (e.g., $MB33600)
$SB Set serial port speed
(e.g., $SB115200)
EXECUTE $H Help
IMMEDIATE I Product Code Inquiry
ACTION I 9 Windows 95 Autodetect Inquiry
COMMANDS L5 List Current Operating Parameters
L6 List S-Register Values
L7 List additional Configuration
Parameters
L8 List On-Line Diagnostics
H Off Hook
+++AT<CR>
Escape Sequence: Entering
Command Mode while On-Line
%E Escape Sequence Options...Entering
Command Mode while On-Line
A Force Answer Mode
O Exit Command Mode/Go Back On-
Line
EXECUTE %DF Format Line Probe Display (Graph or
LINE Table Format)
PROBE %DP Enable/Disable Reading Line Probe
COMMANDS L9 Display of Signal Strength
Information
L10 Display Signal to Noise Ratio (SNR)
L11 Display of Noise Information
&RP Initiates Retrain to Read Line Probe
Parameters
50
SERIES II INTELLIGENT DATA/FAX MODEMS
READ AND Sr? Read Current S-Register Value
ASSIGN Sr= Assign S-Register Value
S-REGISTER
V ALUES
REMOTE #CBN Passwords for Callback Phone #s
CONFIGURATION #DB Callback Security Enable/Disable
& CALLBACK #I Change LOGIN Password
SECURITY #RCBNxx
Erase Password Linked with
Memory Location xx
#S Change SETUP Password
TEST MODEM U Self-Test Modem (Chapter 8)
&T Enable/Disable Digital Loopback
Signal
5.3 Result Codes
The Series II Modem Command mode provides you with several responses, or “Result Codes”, that can aid you in Command mode
operation. These Result Codes are displayed on your video monitor.
You can choose result codes that closely match those of the standard AT
command set, or choose enhanced function result codes that have been
used in Series II Modems (“Series II" responses). The &Q command
selects which result codes will be used.
You can choose to have these Result Codes displayed in either “verbose”
(full words) or “terse” (digits) format. This is controlled by the ATV0
(terse) or ATV1 (verbose) commands. The Series II Modem defaults to
verbose format.
AT&Q0 selects Series II responses with Reliable/LAPM/Compression
modifiers. The terse response code for CONNECT 2400 is 9. AT&Q1
selects Standard AT command set responses. The terse result code for
CONNECT 2400 is 10.
51
CHAPTER 5: Command Mode
The following tables define the result codes generated by the &Q
command (refer to Appendix G for Result Code Summary).
Table 5-1 &Q0 "Series II" Result Codes
TERSE VERBOSE TERSE VERBOSE
0 OK 11* CONNECT 4800
1 CONNECT 12* CONNECT 9600
2 RING 13* CONNECT 14400
3 NO CARRIER 19* CONNECT 19200
4 ERROR 21* CONNECT 21600
5* CONNECT 1200 24* CONNECT 24000
6 NO DIALTONE 26* CONNECT 26400
7 BUSY 28* CONNECT 28800
8 NO ANSWER 31* CONNECT 31200
9* CONNECT 2400 33* CONNECT 33600
* With MNP error correction on, RELIABLE (or R) is added to these result
codes. With LAP-M error correction on, LAP-M (or L) is added to these result
codes. With data compression on, COMPRESSED (or C) is added. (Note these
"Extended" Result Codes are displayed when your modem is set up to do so with
an X1, X2, X3, or X4 command.)
Table 5-2 &Q1 “Standard AT” Result Codes
TERSE VERBOSE TERSE VERBOSE
0 OK 11 CONNECT 4800
1 CONNECT 12 CONNECT 9600
2 RING 13 CONNECT 14400
3 NO CARRIER 19 CONNECT 19200
4 ERROR 21 CONNECT 21600
5 CONNECT 1200 24 CONNECT 24000
6 NO DIAL TONE 26 CONNECT 26400
7 BUSY 28 CONNECT 28800
8 NO ANSWER 31 CONNECT 31200
10 CONNECT 2400 33 CONNECT 33600
*Reliable/Compression modifiers are not displayed with Standard AT Result
Codes.
52
SERIES II INTELLIGENT DATA/FAX MODEMS
5.4 Dialing Commands
5.4.1 Dialing Action Commands
Dial Command D
The letter D in a command causes the Series II Modem to dial the
telephone number immediately following it. For example, if you enter
ATD5551212 and hit RETURN, the Modem dials the number 555-1212.
The D command is also used in conjunction with a telephone set for
manual dialing. You dial the number on your telephone set, and after
hearing the answer tone on your handset, you type ATD on your
keyboard and hit RETURN. Then hang up the headset. Unless you have
a specific need to dial in this manner, we recommend you use the first
method, where the telephone number is entered on your keyboard.
The Series II Modem gives you several choices of dialing methods. You
can use tone or pulse dialing, by inserting a letter T or a P in the
command string. (See the section on Dial Modifiers.)
You can also configure the modem to either wait for and detect dial
tones and busy signals (which we call “Wait-for-Dial-Tone” dialing or
“Smart” dialing), or work with timed pauses without dial tone and
busy signal detection (which we call “Blind” dialing; see Section on “
X” Command.)
Note: There is another method of dialing, called “DTR Dialing”, where
by manipulating the DTR signal on pin 20 of the RS-232C/V.24
interface, a number stored in the modem's memory is automatically
dialed. See the section on the DTR Dialing ($D) command for details.
Continuous Redial A: or :
If you select the Wait-For-Dial-Tone method of dialing (see X3 or X4
command), you can command the Series II Modem to continuously
redial a busy number until your call is answered. This is done with the
A: command.
53
CHAPTER 5: Command Mode
This command would be used only if you had already reached a busy
number after executing a normal dial command. You simply enter A:
(you need not enter AT, nor do you need to hit RETURN), and the
modem will redial the number for you. If you again reach a busy signal,
it re-dials again and again until it no longer detects a busy signal. You
can stop the Series II Modem from re-dialing by pressing any key.
Another method used to cause the modem to redial a phone number
continuously is to enter a colon : at the end of the phone number. The
result is the same as if you had entered A: after personally observing
that the number was busy on the first dialing attempt. Using the colon
in the dialing string is a step saver.
Dialing a Stored Number N
A telephone number that you have stored in the Series II Modem’s
number memory may be automatically dialed by entering ATNnwhere
n = 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. For example, a number stored at N3
would be dialed by entering ATN3 and RETURN. Do not include the
letter D in this command, or the stored number will be erased (also see
Section 5.4.3., on Phone Number Memory Commands).
DTR Dialing $D
An alternate method of causing the Series II Modem to automatically
dial is DTR Dialing. Data Terminal Ready (DTR) is a signal that comes
into the modem from the terminal or computer to which it is
connected, on pin 20 of the RS232C interface. In DTR dialing, the
modem automatically dials a stored number as soon as it receives a high
DTR Signal. The DTR dialing method is popular in synchronous applications.
To activate DTR Dialing, enter AT$D1 and hit RETURN. The modem
dials the phone number stored in the N0 location of memory when it
receives a high DTR signal. DTR must remain high for the duration of
the call, until disconnect. To deactivate DTR dialing, enter AT$D0 and
hit RETURN.
Note that when you use DTR Dialing in a synchronous application, you
need to make sure DIP-Switch #8 is in the UP position to disable V.25bis
Command mode.
54
SERIES II INTELLIGENT DATA/FAX MODEMS
Voice/Data Dialing $VD
Another alternate method of causing the Series II Modem to
automatically dial is Voice/Data Dialing. With Voice/Data Dialing, the
modem automatically dials the phone number stored in the N1 position
of memory whenever the Voice/Data switch is toggled. You must first
enter AT$VD1&W0<CR>. This command string enables Voice/Data
dialing when the Voice/Data toggle switch is activated. To disable
Voice/Data Dialing (default), enter the command AT$VD0 W0<CR>.
5.4.2 Dial Modifier Commands
There are several command characters that can be included within a
dialing command (following the letter D), called “Dial Modifiers”. They
have various functions, including the selection of Pulse or Tone Dialing,
pauses in the dial sequence, automatic re-dials if a number is busy, and
reverting to the Command mode or switching to the Answer mode after
dialing.
Pulse or Tone Dial P or T
The Series II Modem dials numbers using either pulse or tone dialing,
or a combination of both methods. Pulse dialing is a method used by
rotary-dial telephones, which involves the timed opening and closing of
line relay.
Tone dialing is the method used by push-button (touch tone) telephones,
and is sometimes referred to as DTMF, or Dual-Tone Multi-Frequency
dialing.
The method used is selected by including a P for Pulse or a T for Tone
in the dialing command, right before the digits you wish to have dialed
in that manner.
For example, you would pulse-dial the number 555-1212 by entering
ATDP5551212 and hitting RETURN. You could tone-dial the same
number by entering ATDT5551212 and hitting RETURN. If neither
Pulse nor Tone dialing is specified in the dial command, the Series II
Modem uses whatever method used last. If the modem has been reset or
just powered up, it uses Pulse dialing, even if the letter P is not included
in your dial command.
55
CHAPTER 5: Command Mode
Nearly all telephone systems in the U.S. are now compatible with tone
dialing. Since that is the faster method, you will probably choose the
tone method for your dialing.
An example of combining pulse and tone dialing could involve a PBX
system where 9 had to be pulse-dialed first, then the rest of the number
tone-dialed after pausing for a second dial tone. The number would be
dialed by entering ATDP9, T5551212 and RETURN. (The comma
causes a pause, which we’ll explain soon.)
Set Pulse Dial Ratios &P
This command sets the time ratios between the open and closed
portions of the dialing pulse frequencies. To select a dialing pulse ratio
of 60 mSec/40 mSec, enter AT&P0. To select a ratio of 67 mSec/
33 mSec, enter AT&P1. The factory default is &P0.
Automatic Pauses in Dialing ,
You can cause the Series II Modem to pause during the dialing
sequence by entering a comma character where the pause is desired.
This pause lasts two seconds. If a longer pause is desired, more than one
comma may be entered consecutively, with each comma causing a two
second pause. You also have the option of changing the length of the
pause caused by the comma, from two seconds to any other value from
0 up to 255 seconds. This is done by setting S-Register S8 (refer to
Chapter 6). Each comma in a dialing command counts as one of the
sixty allowed characters.
Long Space Disconnect Y
When two modems are connected in Normal mode (that is, without
error correction) there is no "polite" means of requesting a disconnect.
A link disconnect request packet is sent under reliable connections. As a
result some "garbage" may be received when a hang-up command is
issued. The Y1 command enables the modem to use the break signal
which accomplishes the hang-up as an instruction to shut off its receiver
and disconnect (both modems must have Y1 enabled for this feature to
be effective). Y0 (factory default) disables this function.
56
SERIES II INTELLIGENT DATA/FAX MODEMS
Wait for New Dial-Tone W
A W inserted in the dialing command causes the Series II Modem to
wait for another dial tone, and not resume dialing until another dial
tone is detected.
It is not necessary to enter a W at the beginning of the dialing
command to wait for a modem dial tone, because the modem
will do that first (pause automatically).
In order for this command to work, you must select Wait-For-Dial-Tone
dialing with the X2 or X4 command, so that your modem will be able to
detect the dial tone.
Return to Command Mode after Dial Command Execution ;
A semicolon (;), entered as the last character of a dialing command
causes the Series II Modem to return to the Command mode
immediately after executing the command, instead of waiting for a
carrier signal and going on line.
For example, entering ATDT5551212; would tone-dial the number, and
do nothing afterwards except go back into Command mode. This can
be useful in dialing applications where modem data transfer is not
desired, such as voice communications, or in applications involving
the use of touch tones as a data entry method, such as bank-by-phone.
Reverse the Mode of Operation R
In certain operations you may need to reverse the mode of operation
for your modem from originate to answer or answer to originate so that
it would answer the phone and go into answer mode. This command
turns off the reversing function with the R0 command and turns it on
with the R1 command with the modem in either command mode. If
you want to reverse from the originate mode, use R (with no number)
in the dialing string.
57
CHAPTER 5: Command Mode
Flash On Hook !
Some switchboard systems react to a momentary On Hook. An
exclamation mark inserted in the command causes the modem to
“flash” on hook for a half of a second, as if you had held the switch hook
button on a telephone down for a half second.
For example, to flash On Hook after dialing the number 555-1234
in order to transfer to Extension #5678, you might enter
ATDT5551234,,!5678. The commas cause a 4 second pause (just to
be safe).
"Calling Card" Detect T ones $
The Series II Modem has the capability to detect AT&T "calling card"
tones for the purpose of utilizing the user's calling card number to
originate an on-line connection. An $ symbol placed in the dialing
string causes the modem to pause and wait for an AT&T "calling card" or
a 1600 Hz tone (prevalent in the United Kingdom). When the tone is
detected, the rest of the dialing string is processed. If no tones are
detected within the time period set by S-Register S7 (default 45
seconds), the modem will abort by indicating a NO CARRIER message.
Hitting any key also aborts the $ command.
The following is an example of this command:
ATDT101099907247465500$0123 4567 8910 1112
Quiet Answer @
The @ command causes the Series II Modem to wait before processing
the next symbol in the dialing string. The wait is for one or more
ringbacks followed by 5 seconds of silence. If the time specified by
S-Register S7 passes before the rings and silence, a NO ANSWER (R)
result code is processed. The @ command is used for accessing a system
that does not provide a dial tone.
For example, ATDT5551212@7465500 causes the Series II Modem to
dial the first number (555-1212) and wait for the time specified in S7
58
SERIES II INTELLIGENT DATA/FAX MODEMS
for at least one ringback and 5 seconds of silence. If a busy signal is
detected, the Series II Modem hangs up and generates a BUSY result
code. If it does not detect 5 seconds of silence, a NO ANSWER result
code is generated after hanging up. If 5 seconds of silence is detected,
the second number (746-5500) is then dialed.
5.4.3 Phone Number Memory Commands
Storing Phone Numbers D...N
A telephone number and command line of up to sixty characters may
be stored in the Series II Modem’s number memory. As many as ten of
these numbers may be stored. Each number will be given a name, using
the codes N0, N1, N2 up to N9.
A phone number is stored by entering ATD, then the number as it
would be dialed, along with any P, T, R, ; or comma characters, and
then entering N followed by the number’s “name,” which would be
any number from 0 through 9, and then hitting RETURN.
For example, the tone-dialed number 1-612-631-3550 would be stored
as number N3 by entering ATDT17247465500N3 and RETURN. The
number is not dialed with this store command. After storing a number,
check to see that it has been stored correctly by typing ATL and hitting
RETURN.
When phone numbers are stored, the entire command line is also
stored so that you can effectively create a macro for each number. For
example, if you know a particular number needs to have extended
result codes, detect busy or dial tone, error correction, Xon/Xoff flow
control, pacing, and data compression enabled, the command line
would be:
ATX4&E1&E5&E13&E15DT17247465500N3
This would store the entire command at location N3.
Number Linking NN
You may command the Series II Modem to dial another number
automatically if the first number dialed is busy. This would be useful in
a situation where a computer can be accessed through more than one
phone number. This is called “linking”.
59
CHAPTER 5: Command Mode
To link the number in N1 to the number N2, simply enter ATN1N2 and
hit RETURN. Several numbers can be linked in the same command.
For example, you could link N1 to N2 to N3 to N4 by entering
ATN1N2N3N4 and RETURN or you could link N1 to N2 and back to
N1 and then back to N2 by entering ATN1N2N1N2 and RETURN.
The only limit on the number of numbers that can be linked is the 60
characters allowed in a command line. Number linking can not be used
with blind dialing, since busy signals would not be detected. You would
have to select the Wait-for-Dial tone dialing method using the
X Command in order to use the Number Linking feature.
Listing Numbers Stored in Memory L
Telephone numbers that you have stored in the Series II Modem’s
memory may be listed and displayed with the L command. It will display
all ten stored N numbers in a format like that shown below. All digits
and command letters will be shown. The phone number’s single-digit
designation (0 through 9) is shown first, followed by the complete
dialing command and telephone number as originally entered.
Simply enter ATL and hit RETURN to display these numbers on your
video screen or printer. An example of an L command listing is shown
below:
0 DT14922345678
1 DT17245551212;
2 DP9,T14929876543
3 DT3738315,12101,17247465500
4 DT7465500R
5
6 DP9,4258513
7
8 DTX4&E1&E5&E13&E15DT17247465500
9 DT12138880123
60
SERIES II INTELLIGENT DATA/FAX MODEMS
5.4.4 Configuration and Default Storage
Commands
Store Configuration & S-Register Parameters
in Non-Volatile Memory &W
The Series II Modem can store configuration parameters and S-Register
values in its nonvolatile read/write Random Access Memory (RAM)
memory. The &W command does this, which prevents any reconfiguration from being lost on a power-down or Reset (ATZ)
condition.
&W0 (or AT&W) causes the Modem to store your customized AT
command settings and S-Register values in its nonvolatile RAM. &W0
also sets the modem so that it reads your customized settings stored in
nonvolatile RAM when powered down or reset. (The &W0 command
only changes the settings stored in nonvolatile RAM that you specifically
intend to alter. All other default parameters are applicable.)
&W1 causes the Modem not to store your customized settings to
nonvolatile RAM so that, after powering down or resetting the modem,
it reads the factory default settings stored in ROM.
Loading Factory Defaults &F
The &F command provides a choice between customized configuration
settings in RAM and the factory default configuration settings in ROM.
The &F8 and &F9 commands define the function of the &F command.
The Series II Modem is shipped from the factory with a pre-configured
set of command and S-Register default settings. This set of factory defaults can be recalled by issuing the &F command.
In addition to being able to recall the factory-installed defaults, the &F
command can also recall those defaults stored under &W0.
This is done using the &F9 command. If you have stored parameters
with the &W0 command and wish these settings to always be used as
your defaults, you would enter &F9&W0.
To return the &F command to read factory installed defaults, enter
&F8&W0. &F8 is the factory default.
(access/phone number) (credit-card number)
61
CHAPTER 5: Command Mode
Many datacomm program issue the &F command automatically—the
&F9 command allows the user to select their own factory defaults. Note
that the &F8/&F9 commands should be used with &W0.
Following is a summary of how the &F and Z reset commands interact
with the &W command; note how the &F reset command operates
differently from the Z reset command:
Pre
vious Command AT&F Power-On and ATZ
AT&W1 (default) ROM ROM
AT&W0 ROM NVRAM
AT&F8&W0 ROM NVRAM
AT&F9&W0 NVRAM NVRAM
Modem Reset Z
The Z command can be used to reset the entire Command Mode
buffer and the result is the same as if you had disconnected, and
then reconnected power to the modem. When an ATZ command is
executed, the state of the &W command determines where the default
values originate. &W0 defaults come from RAM and &W1 defaults
come from ROM.
Unix UUCP Spoofing $SP
The Series II Modem can be configured in a Unix environment that
employs ACK flow control as a means of monitoring data integrity. The
Modem can do “UUCP spoofing”, where the modem is able to generate
ACKs at the DTE interface. Data is transmitted more time efficiently
because the delay of waiting for data to be received, then for an ACK
to be returned at the remote end, is eliminated. The $SP1 command
enables UUCP spoofing and the default command $SP0 disables
UUCP spoofing.
V.32terbo Enable/Disable #V (336 Only)
Other types of V.32/V.32bis modems have problems handshaking when
the Series II Modem 336 (MD1641A) includes V.32terbo mode (19,200 bps)
in its handshaking process. The bits that are used in the rate sequence for
V.32terbo can cause handshaking failure.
62
SERIES II INTELLIGENT DATA/FAX MODEMS
User Guide for Series II Modems
The #V command gives the user the option of including V.32terbo as
part of the handshaking process in both Orignate and Answer modes.
Entering AT#V0&W0<CR> includes the V.32terbo mode in
handshaking. Entering AT#V1&W0<CR> disables the Series II Modem
336 from using V.32terbo mode in the handshaking process (default).
Async/Sync Mode Switching &M
This command can be used to set the on-line mode to either
synchronous or asynchronous. AT&M0 will set the Series II Modem to
Asynchronous mode, and all communications will be asynchronous in
both On-line and Command modes. AT&M1 causes the Modem to com-
municate asynchronously when in Command mode and switch to synchronous mode while on-line. The modem defaults to &M0
(asynchronous communications) on reset or power-up.
Synchronous Transmit Clock Select &X
The &X command selects the Synchronous Transmit Clock Source in
conjunction with DIP-Switch #11. DIP-Switch #11 in the UP position
enables External clocking. DIP-Switch #11 in the DOWN position
enables Internal clocking (default position). External clocking is when
the DTE provides transmit clocking to the modem on pin 24 of the
RS232C interface.
&X0 is the default setting, which allows DIP-Switch #11 to control
Internal/External Clocking (default Internal). Internal clocking is
when the modem provides transmit clock to the DTE on pin 15 of the
RS-232C/V.24 interface. The &X1 command overrides DIP-Switch #11
and selects External clocking. If DIP-Switch #11 is UP (External
clocking), you can not override Internal clocking. &X2 enables Slave
Clocking. The &X2 Command causes the Series II Modem to generate
the transmit clock timing (pin 15) from the receive clock (pin 17) from
the DTE (therefore 15 and 17 are the same). In this mode (Slave
Clocking), all timing is controlled by the receive clock.
63
CHAPTER1: Specifications
Chap 5: Command Modeter
5.4.5 Command Response (Result Code)
Commands
Echo Command Mode Characters E
If the Series II Modem is connected to a full-duplex computer, it may
be necessary for the modem to be configured to echo back characters
entered while in the Command Mode in order for them to be displayed.
The E command is used to configure the Command Mode echo, with
ATE0 disabling the echo and ATE1 enabling the echo (default).
Result Codes Enable/Disable and No Response Answer Q
The Q command enables or disables Result Codes and the No Response
Answer mode of operation. Result Codes may be disabled altogether in
certain applications, such as computer-controlled auto dialing, using
the Q command. ATQ1 disables Result Code transmissions. ATQ0 (or
ATQ) enables Result Code transmission.
Regarding No Response Answer, you may want the answer mode
handled without responses and echo turned off, but want the originate
mode still intelligent. This is called the No Response Answer mode.
ATQ2 selects the No Response Answer mode. If you do not select any
mode, the factory default setting (enable Result Codes) is automatically
selected.
Result Codes ("Series II" or "Standard AT") &Q
The Series II Modem gives you a choice between the Series II Result
Codes, and Result Codes that more closely match the standard AT
command set responses (see section 5.3).
AT&Q1 selects AT responses with no Reliable/Compression
modifiers. With this command, the terse result code for CONNECT 2400
is 10.
AT&Q0 selects Series II responses with Reliable/Compression
modifiers. With this command, the terse result code for CONNECT 2400
is 9.
64
SERIES II INTELLIGENT DATA/FAX MODEMS
Result Codes (Verbose/Terse) V
The V command controls whether the Series II Modem’s result codes
are displayed as word (“verbose”) or single digit (“terse”) messages.
For example, if after dialing, no carrier signal is detected, the resulting
message can be displayed either as NO CARRIER, or as the digit 3.
Entering ATV0 (or ATV) causes the Modem to display the Result Codes
as digits, while ATV1 displays them as words. If you do not select a
method, the factory default setting causes the modem to display Result
Codes as words.
Result Codes (Basic and Extended) and Call Progress
Selection X
The X Command is used to select one of two possible dialing methods
(“dumb” or “smart”), and to select various response combinations related
to these methods. You can choose to have certain responses suppressed,
or whether or not you want speed indications along with the CONNECT
responses. You can also pick and choose certain responses in order to
match up with “Standard AT” responses. (Refer to Appendix G for a
summary of Result Codes.)
The Series II Modem provides “Basic” and “Extended” Result Code sets.
The difference between the two is the Basic set provides one response
(CONNECT) to indicate a connection, while the Extended set provides
several responses for different speeds (CONNECT, CONNECT 2400,
CONNECT 4800, CONNECT 9600, CONNECT 14400, CONNECT 19200,
CONNECT 21600, Etc.).
When the Extended set is chosen, you also have the option of matching
them up with Standard AT 2400 response code sets, by including or not
including the BUSY and/or NO DIAL TONE responses while excluding
the DIAL TONE response. The X command is used to select which
responses are provided.
65
CHAPTER 5: Command Mode
Regarding the Series II Modem’s method of dialing, the Modem can
detect standard dial tones and busy signals. This capability (“smart
dialing”) allows the modem to wait for a dial tone, and when one is
detected, to begin dialing immediately.
The Modem also can detect a distant busy signal if, after dialing, it
reaches a busy number. This is useful because it allows the modem to
immediately abandon a call, rather than wait 45 seconds for a carrier
signal that will never come. S-Register S7 defines the wait for carrier
time (refer to Chapter 6).
The Series II Modem gives you a choice between the wait-for-dial-tone
(“smart”) method we just described, and blind (“dumb”) dialing, where
instead of detecting actual dial tones, the modem relies on timed
pauses. When the wait-for-dial-tone method is chosen, the busy signal
detection capability is also activated. The X command is also used to
select which dialing method is used.
Five different X commands are available (X0 through X4), with five
different effects on the Modem’s Result Codes.
X0 Provides the basic (short) result codes and provides
“dumb” dial capabilities.
X1 Provides the extended result codes and provides “dumb”
dial capabilities.
The remaining X commands affect Call Progress, and turn on Extended
Result Codes.
X2 Looks for dial tone only and will not provide a busy
response.
X3 Looks for busy only and not look for dial tone.
X4 Looks for dial tone and for busy.
The factory default setting is X0, which selects Basic Result Codes
and the blind (“dumb”) method of dialing.
66
SERIES II INTELLIGENT DATA/FAX MODEMS
5.4.6 Phone Line Conditioning Commands
Guard T ones &G
The &G command is used to control the presence or absence of guard
tones from the transmitter when in Answer mode, at either 1200 or
2400 bps. Guard tones are used in Europe and other areas for the
modem to function in the telephone systems. Guard tones are not used
in the United States. &G0 (default), turns off CCITT guard tones. &G1
turns on 550 Hz guard tones. &G2 turns on 1800 Hz guard tones.
Phone Line Monitoring Speaker M
The Series II Modem has an internal on-board speaker, which functions
like the speaker in a telephone handset, to enable you to monitor
phone line activity. The M command can be used to determine when
the speaker is operational.
Entering ATM0 disables the speaker completely, while ATM1 causes the
speaker to be on only until a carrier signal is detected. ATM2 causes the
speaker to remain on at all times. ATM3 causes the speaker to be on
during dialing and off during handshake. ATM1 is the default setting,
and the one that should be used in most applications.
Enable or Disable Recognition of Remote Digital Loop
Signal &T
The Series II Modem has several self-test features (covered in Chapter
8). The tests are activated with different U commands, such as ATU1,
and so forth. The &T command is a phone line conditioning command
that enables or disables the modem’s ability to recognize the Remote
Digital Loop (RDL) test signal.
The AT&T4 command lets the Modem respond to a RDL signal, and
places itself in digital loop. The AT&T5 command causes the modem
to ignore the RDL signal. The factory default is &T5.
Enable/Disable T relis Coded Modulation #T
This command enables or disables the Trellis Coded Modulation of the
Series II Modem. There is usually no need to disable (turn off) Trellis
67
CHAPTER 5: Command Mode
codings except under an unusual line condition called impulse noise.
AT#T0 turns Trellis coding off and AT#T1 turns Trellis coding on
(factory default).
Fallback Modes When On-Line #F
If line conditions deteriorate, the Series II Modem automatically drops
its transmission speed (“fallback”). The #F command controls the
different ways the Modem falls back. During operation, if the error rate
becomes too great, the modem performs a retrain. If after the retrain,
the error rate is still too high for 33600 bps operation, the modem
initiates a retrain at 4800 bps. If after the first retrain the modem
returns on line at 33600 bps, the modem then starts a counter and a
timer. If three retrains occur within a two minute period, the modem
falls back to 4800 bps.
Entering AT#F0 (or AT#F) allows no fallback when on-line. AT#F1
allows the Modem to fallback (based on the error rate or if three
retrains have occurred within a two minute period) from 33.6K to 31.2K
to 28.8K to 26.4K to 24K to 21.6K to 19.2K to 16.8K to 14.4K to 12K to
9.6K to 4.8K bps. The AT#F2 command enables incremental fall back
from 33.6K to 4.8K, but also enables incremental fall forward (from
4.8K to 33.6K) if the phone line improves. AT#F2 is the factory default
setting.
Enable/Disable Lowspeed Fast Connect $FC (336+ Onl y)
With the Series II Modem 336+ (MD1640A), entering
AT$FC0&W0<CR> sets up the data pump so that it will not transmit a 5
second 2100 Hz signal. Entering AT$FC0&W0<CR> allows the modem
to transmit a 5 second 2100 Hz signal and is the factory default.
Cleardown at Disconnect &CD
The &CD command is used for control of cleardown at disconnect in
V.32, V.32bis, V.34 and V.34 enhanced modes.
A cleardown usually adds 1-2 seconds to the time it takes for the modem
to go on-hook after a disconnect. A cleardown makes a disconnect by
the remote modem easier to detect and a subsequent re-connection
more likely. Enter AT&CD0&W0<CR> to execute a cleardown at
disconnect (default); and enter AT&CD1&W0<CR> to disable the
cleardown function.
68
SERIES II INTELLIGENT DATA/FAX MODEMS
Auto Speed Detect #A
The function of the #A command is to detect and select the operational
data rates (the “starting” speeds) with which the Series II Modem uses
for initial handshake and speed selection.
Remember, this command does not control the originating data rate of
the modem (that is done by the Modem Baud Rate command $MBn),
but only the Answer mode “starting” speeds. Entering
AT#A0 (or AT#A) causes the Modem to operate starting at 33,600 bps,
with fallback to 28,800 to 19,200 to 14,400 to 9600 to 4800 to 2400 to
1200 and to 300 bps. Entering AT#A1 causes 33,600 bps operation only.
Entering AT#A2 causes the modem to operate at starting speeds of
33,600 bps, with incremental fallback to 28,800, 19,200, 14,400, 9600
and 4800 bps. The AT#A3 command causes the modem to begin
operation as a V.22bis modem at 2400 bps, with fallback to 1200
to 300 bps. AT#A0 is the factory default value.
5.4.7 RS232C Interface Control Commands
Carrier Detect Control &C
The &C command allows you to control the status of the Carrier Detect
signal (CD, Pin 8) on the RS232C line. You have four choices.
You can force the signal high, or allow it to act normally, or force the
modem to reset when CD drops, or set it to stay high until the modem
disconnects, go low momentarily, and then go high again. The last
option is useful with some CBX phone systems and mainframe front
ends, which require CD to act in this manner.
To allow CD to act normally, enter the command AT&C1 (the factory
default setting). To force CD on, enter AT&C0. To reset the modem to
its current parameters when CD drops, enter AT&C4. To set up CD so
that it drops for one second on disconnect and then comes up again,
enter AT&C2. (If you want the drop time to be something other than
one second, use S-Register S24 to change this value. Refer to the
Chapter 6 instructions for S24.)
69
CHAPTER 5: Command Mode
Data Terminal Ready Control &D
Data Terminal Ready (DTR) on Pin 20 of the RS232C interface is
required in order for the Series II Modem to operate. A high DTR
signal tells the modem that the device to which it is connected is active,
or "ready" to communicate through the modem. If the signal is not
being provided on the RS232C interface, you can force DTR high with
DIP-Switch #1 (Chapter 9).
DTR has some other Modem functions. DTR can be used to trigger a
dialing sequence, called DTR Dialing. The condition of DTR can also
be used to cause the modem to reset to its default parameters, just as if
you had given the modem an ATZ command. To do this, enter the
command AT&D3 and hit RETURN.
The modem will now reset itself whenever DTR is dropped from On to
Off, and will also go on-hook (hang up) if it is on-line.
Entering AT&D0 or AT&D causes the Modem to ignore DTR. Entering
AT&D1 causes the modem to go on-hook (hang up) with loss of DTR.
The modem enters Command mode when DTR goes high again. Autoanswer is disabled while DTR is low. Entering AT&D2 causes the modem
to go on hook with loss of DTR. The modem enters command mode
when DTR goes high again.
Clear to Send Control &R
The &R command allows you to control the Clear to Send signal (CTS,
Pin 5) on the RS232C interface. You have three choices. You can force
the CTS signal high, allow it to act normally, or set it to stay high until
the modem disconnects, go low momentarily, and then go high again.
The last option is useful with some CBX phone systems and mainframe
front ends, which require CTS to act in this manner.
To allow CTS to act normally, enter the command AT&R0. To force
CTS on, enter the command AT&R1 (this is the factory default setting).
When the modem goes on-line, CTS still provides flow control. To set
up CTS so that it drops for one second on disconnect and then comes
up again, enter the command AT&R2. (If you want the drop time to be
something other than one second, use S-Register S24 to change this
value. Refer to Chapter 6).
70
SERIES II INTELLIGENT DATA/FAX MODEMS
Data Set Ready Control &S
The &S command allows you to control the status of the Data Set Ready
signal (DSR, Pin 6) on the RS232C interface. You have three choices.
You can force the signal high, allow it to act normally, or set it to stay
high until the modem disconnects, go low momentarily, and then go
high again. The last option is useful with some CBX phone systems
and mainframe front ends, which require DSR to act in this manner.
To allow DSR to act normally, enter the command AT&S1 (the default
setting). To force DSR on, enter the command AT&S0. To set up DSR
so that it drops for one second on disconnect and then comes up again,
enter A T&S2. (If you want the drop time to be something other than one
second, use S-Register S24 to change this value. Refer to Chapter 6.)
CTS/RTS Interaction Control &RF
In typical operation, Clear to Send follows Request to Send when the
modem is on-line. In other words, if RTS goes off, CTS goes off in
response. The &RF0 command enables CTS to follow RTS. In some
applications, however, it may be necessary for CTS to operate independently of RTS. &RF1 allows CTS to operate independently regardless
of the state of RTS, and is the factory default. If this is the case, refer
to the &R command for control of the Clear to Send signal.
DSR/CD Interaction Control &SF
In typical applications, Data Set Ready (DSR) follows Carrier Detect
(CD). &SF0 enables DSR to follow CD, and is the factory default. &SF1
enables DSR to operate independent of CD. If this is your application,
refer to the &S command for control of the Data Set Ready signal.
5.4.8 Error Correction Commands
You can use AT commands to place your Series II Modem one of three
V.42 (error correction) modes of operation. These are the Normal,
Auto-Reliable, and Reliable modes.
71
CHAPTER 5: Command Mode
Normal Mode &E0
In Normal mode of operation, the Series II Modem’s V.42 error correction capabilities are disabled, and the modem functions as a non-errorcorrecting modem.
Auto-Reliable Mode &E1
In Auto-Reliable mode during the handshaking procedures at the start
of the on-line connection, the Series II Modem automatically
determines whether or not the modem with which it is communicating
is using V.42 error correction. If the Modem determines that the other
modem is using V.42, it switches itself into MNP or LAPM Reliable
(V.42) mode and its error-correction capability is enabled. If it is determined that the other modem is not using V.42, the Modem remains in
Normal mode, without error correction. The default setting is AutoReliable mode (&E1).
The method the Modem uses to determine if the modem it calls is a
V.42 modem involves the use of a “Link Request”.
When the Series II Modem is in Auto-Reliable mode and originates a
call, it goes through normal handshaking procedures just like any dialup modem. After establishing the on-line connection, the Modem
transmits a Link Request message to the answering modem. (The Link
Request message is generally about 33 coded characters.) If the
answering modem replies with an appropriate V.42 acknowledgment
response, the Modem switches into Reliable mode. Otherwise it stays
in Normal mode. This V.42 Link Request handshaking procedure
generally takes about five seconds.
When operating in V.42 Reliable mode, the Series II Modem uses its
memory, or buffer, to store data as it is received. During periods of
error-caused retransmissions or compression slowdowns, this buffer
may fill up. To prevent buffer overflow and subsequent loss of data, the
modem uses "flow control" to signal the computer attached to its RS232C
port that the modem buffer is close to being full. This causes the computer to pause in its data transmission until the modem is able to empty
its buffer sufficiently to accept more data, at which time the modem
signals the computer that it may resume transmission. (Flow Control is
discussed in section 5.4.9.)
72
SERIES II INTELLIGENT DATA/FAX MODEMS
Reliable Mode &E2
In Reliable mode, the Series II Modem uses its V.42 error correction
capabilities during all transmissions, and must be connected to another
modem with a similar protocol activated (MNP or LAP-M).
V.42 Mode Select #L
The V.42 standard implements both MNP Class 3 & 4 and LAP-M error
correction methods. The V.42 Mode Select command (#L) selects which
type of error correction (MNP or LAP-M) your Series II Modem uses for
transmissions.
The various #L command options are as follows.
#L0 Command The #L0 Command allows a pair of
modems to negotiate which V.42 mode
(MNP or LAP-M) will be used in their
transmissions.
Originate Mode
a. If both modems have LAP-M capability,
the modems use LAP-M mode.
b. If one or both modems do not have LAPM capability and both have MNP, the
modems use the MNP mode.
#L0 Command (cont'd) Answer Mode
a. The answering modem responds to either
an MNP Link Request or LAP-M Originator
Detection Pattern (ODP) signal depending
on which the originating modem issues.
#L1 Command The #L1 Command sets your modem to
MNP error correction and disables LAP-M.
This command is for Originate mode only.
In Answer mode, the modem still accepts
MNP or LAP-M.
#L2 Command The #L2 Command sets your modem to
LAP-M error correction, and disables MNP.
73
CHAPTER 5: Command Mode
This command is for Originate mode only.
Answer mode still accepts MNP or LAP-M.
#L3 Command In the prior commands, the modems use a
two phase process to establish a V.42
connection (detection to establish whether
the remote modem is also error correcting,
and then protocol establishment to determine parameters and to establish the error
correction connection). If you know that
the other modem is a V.42 error correcting
modem, and you wish to use LAP-M, the
#L3 command disables the detection phase
and goes directly to protocol establishment.
Both modems must have #L3 in effect.
Auto-Reliable Buffering $A
In Auto-Reliable mode, the modem is given four seconds to establish a
Reliable connection. After this four-second period, the modem drops to
Normal mode. Any data which is received during this period is typically
discarded. The $A command can be used to cause the modem to buffer
(save) data that is received during this Auto-Reliable time-out period.
This data will then be output by the modem after the
CONNECT message.
AT$A0 = Discard data received during auto-reliable time period.
AT$A1 = Buffer data received during auto-reliable time period.
The factory default is $A0.
Enable/Disable Auto Reliable Fallback Character $F
In Auto-Reliable mode, the modem is given four seconds to establish a
Reliable connection. If a single CARRIAGE RETURN is received from
the remote modem during this four second period, the Auto-Reliable
modem assumes that the remote modem is not in Reliable mode and
drops to Normal ( non-error correcting) mode. The CARRIAGE
RETURN is the only character which causes the modem to drop to
Normal mode. Any other character will either be buffered or discarded.
74
SERIES II INTELLIGENT DATA/FAX MODEMS
The $F command can be used to disable this fallback-to-Normal-due-toCARRIAGE-RETURN feature.
The Auto-Reliable fallback character ($F) and Auto Reliable buffering
($A) commands can be used together to cause the modem to buffer all
data received up until the CARRIAGE RETURN, and then drop to
Normal mode. All data received will then be output following the
CONNECT message.
AT$F0 = Do not fall back to Normal if CARRIAGE RETURN
received.
AT$F1 = Fall back to Normal mode if CARRIAGE RETURN
received.
The factory default is $F0.
Retransmit Count $R
If errors are received during a Reliable connection, the modem
re-sends the block of data which contained an error. With the $R0
command, if another error occurs, the block will be re-sent again. The
modem counts the number of times that a data block is re-sent. If the
same block of data is resent 12 times and still has not been received
properly, the modem assumes that the transmission line is unsuitable
for transmission, and abort the connection.
This retransmit counter is disabled by the $R1 command. When the
retransmit counter is disabled, the modem keeps trying to send data
and will not abort, no matter how many times the same block is resent.
AT$R0 = Disconnect if retransmit count is exceeded.
AT$R1 = Do not disconnect due to retransmits.
The factory default setting is $R0.
75
CHAPTER 5: Command Mode
V.42 Error Correction/300bps $E
At 300 bps, error correction is not typically used. $E1 lets the Series II
Modem function at 300 bps in either Normal (&E0), Auto-Reliable
(&E1) or Reliable (&E2) mode. $E0, which is the Modem’s default,
disables 300 bps/V.42 error correction altogether.
AT$E0 = No V.42 Error correction at 300 bps.
AT$E1 = V.42 Error Correction at 300 bps.
The factory default setting is $E0.
5.4.9 Flow Control Commands
Flow control refers to the techniques used by computer devices to stop
and restart the flow of data to and from each other. Flow control is
necessary so that a device does not receive more data than it can
handle. In the case of the Series II Modem, there is a need for flow
control in both directions. As illustrated on the next page, flow control
for data passing from your computer to the modem is called ModemInitiated Flow Control and flow control for data passing from the
modem to your computer is called Computer/Terminal-Initiated
Pacing.
The Series II Modem supports both hardware and software Modem
Initiated Flow Control. On the Computer/Terminal-Initiated Pacing
side, it supports hardware and software flow control, and a special
version used by Hewlett-Packard
®
compatible systems called ENQ/ACK
Pacing. The Modem allows hardware and software pacing to be passed
through the modem to the other end of the link so that your computer
or terminal can control data start/stop activity through your modem.
This is called Xon/Xoff Pass-Through. To state it simply, “Flow Control”
is something the modem does to the computer, while “Pacing” is
something the computer does to the modem.
76
SERIES II INTELLIGENT DATA/FAX MODEMS
Figure 5-2. Flow Control and Pacing
Hardware Flow Contr ol &E4
With Hardware Flow Control, the modem uses its RS232C interface to
control the flow of data from the computer or terminal to which it is
attached. The CTS (Clear to Send) signal on Pin 5 of the RS232C
interface is brought low to stop the flow of data, and is brought high
to restart it. When you select Hardware Flow Control as your Modem
Initiated Flow Control method, you will also be selecting it for Pacing.
The difference between the two, however, is that Modem-Initiated Flow
Control uses the Pin 5 CTS output signal, while Pacing uses the Pin 4
RTS input signal.
Modem commands are used to select the method of flow control used
by the Series II Modem when its error correction capabilities are used.
These commands are covered in Section 5.4.9. If neither method is
selected, the modem defaults to no flow control (&E3).
Modem
Modem
Computer or
Terminal
Computer,
Terminal, or
Printer
Modem-Initiated Flow Control
Computer-Initiated Flow Control
RS/232/V.24
data flow
data flow
RS/232/V.24
77
CHAPTER 5: Command Mode
Xon/Xoff Flow Control &E5
Xon/Xoff is the most commonly used method of flow control. Under
this method, control characters known as “Xon” and “Xoff” are inserted
by the modem into the data to start and stop the flow of data from the
computer or terminal to which the modem is attached. Xoff, which is a
Control-S, stops the flow of data, and Xon, which is a Control-Q, restarts
it. With regard to Binary Data, Xon/Xoff flow control is not recommended because an Xoff character may be part of the data and would
trigger an Xoff of the modem or software package, which would halt
data flow.
Xon/Xoff Pass-Through &E7
So far, you have had three choices to make regarding pacing:
1. You can set the modem to respond to Xon/Xoff pacing.
2. You can set the modem to respond to RTS pacing.
3. You can set the modem to ignore pacing completely.
Well, we’re not done with pacing yet. There’s another choice you can
make (which actually can apply to both pacing and modem-initiated
flow control, although it applies mainly to pacing) and that is
something called “Xon/Xoff Pass-Through.”
This means that if your modem is set to respond to Xon/Xoff commands, you can have the modem do one of the following:
1. The modem responds to the Xon and Xoff pacing commands
while at the same time allowing these commands to pass through
the modem and on to the remote location. We call this “Respond,
Pass-Through”.
2. The modem responds to Xon/Xoff pacing, but does not allow the
pacing signals to pass through the modem and on to the remote
location. We call this “Respond, No Pass-Through”.
When Xon and Xoff commands are allowed to pass through the
modem, the computer or terminal at the remote site will receive these
commands, and depending on how it is configured, the computer or
terminal may respond to them also.
78
SERIES II INTELLIGENT DATA/FAX MODEMS
When two Series II Modems are connected in Normal mode (not using
error correction), Xon/Xoff can be used to control the flow of data
between the modems. Flow Control can be turned on or off with the
Normal Mode Modem Flow Control commands. When the modems
are connected in Reliable mode, a different method of modem Flow
Control is used, and the commands for Normal Mode Modem Flow
Control are ignored.
When you are using Speed Conversion in Normal Mode, you must
activate the modem’s Normal Mode Modem Flow Control. (Speed
Conversion is explained in Section 5.4.11.)
Send Xon/Xoff Characters #X
The #X phone interface command allows the Series II Modem to send
either a single or multiple Xoff characters at the modem's buffer full
level. When the Modem's buffer reaches it's "buffer full" level, the next
character received causes another Xoff to be sent for every character
subsequently received by the Modem.
The AT#X0 command (factory default setting) causes one Xoff to be
sent until the buffer reaches the Xon level. The AT#X1command
causes an Xoff to be sent for every character received after the modem
reaches its buffer full level.
Hewlett-Packard ENQ/ACK Pacing &E9
If the Series II Modem is being used with Hewlett Packard (or similar)
equipment that employs ENQ/ACK pacing, the modem can be
configured to respond to ENQ/ACK commands, making it compatible
with HP systems. Doing so does not affect any other flow control or
pacing already configured in the modem.
When configured for ENQ/ACK, the ENQ (Control-E) and ACK
(Control-F) signals from the HP equipment will be accepted and responded to according to Hewlett-Packard protocol.
Normal Mode Modem Flow Control On &E11
When two Series II Modems are connected in Normal mode (not using
error correction), Xon/Xoff can be used to control the flow of data
between the modems. Flow Control can be turned on or off with the
Normal Mode Modem Flow Control commands. When the modems are
79
CHAPTER 5: Command Mode
connected in Reliable mode, a different method of modem flow control
is used, and the commands for Normal Mode Modem Flow Control are
ignored.
When you are using Speed Conversion in Normal Mode, you must
activate the modem’s Normal Mode Modem Flow Control. (Speed
Conversion is explained in Section 5.4.11.)
Terminal/Computer Initiated Pacing &E13
As mentioned earlier, the Series II Modem can initiate flow control by
issuing Xon/Xoff commands or toggling the CTS signal on the RS232C
interface. The modem can also be configured to react to similar commands and signals from the computer or terminal to which it is
attached via the RS232C interface. We refer to the computer or
terminal initiated flow control as Pacing. When the modem is set for
Pacing On, the modem will respond to the terminal or computer
pacing. When the modem is set for Pacing Off, it will ignore pacing.
In order for the Series II Modem to be set for Pacing On, a modeminitiated method of flow control must be previously selected. Once this
is done, the Modem will respond to either Xon/Xoff commands, or to
the toggling of the RTS (Request to Send) signal on Pin 4 of the
RS232C interface, depending on what you selected earlier as your
Modem-Initiated Flow Control method.
Maximum Block Size &BS
The maximum size of Reliable mode data blocks can be controlled with
the &BS command. MNP 3 sends blocks of 1 to 64 characters. MNP 4
and 5 typically send blocks of 1 to 256 characters and LAP-M typically
send 128 characters. For MNP Classes 4 and 5 and for LAP-M, reducing
the block size to 64 characters may give a smoother flow of data, and
better throughput on noisy phone lines. Using smaller block sizes over
good phone lines may cause a slight loss in throughput (speed).
AT&BS0 = Maximum transmit block size of 64 characters
AT&BS1 = Maximum transmit block size of 128 characters
(LAP-M) or 256 characters (MNP)
The factory default setting is &BS1.
80
SERIES II INTELLIGENT DATA/FAX MODEMS
Asynchronous Word Length Selection $EB (336 Onl y)
The Series II Modem 336 (MD1641A) has an 11-bit capacity when
operating asynchronously. The $EBcommand selects between 11-bit
and 10-bit operation. AT$EB1 enables 11-bit format (1 start bit, 8 data
bits, 1 parity bit, and 1 stop bit). AT$EB0 (default) enables 10-bit
format (1 start bit, 7 data bits, 1 parity bit, and 1 stop bit). $EB is
functional in both command and on-line mode. $EB0 automatically
detects parity when any AT command is issued.
AT$EB0 = Use 10-bit words
AT$EB1 = Use 11-bit words
The factory default setting is AT$EB0.
Parity Selection #P
The #P command enables the setting of parity. AT#P0 selects no parity.
AT#P1 selects odd parity. AT#P2 selects even parity and is the default
value. Note when setting up your data comm software, it is critical that
both your remote and local system's parity selection be set identically.
AT#P0 = no parity
AT#P1 = odd parity
AT#P2 = even parity
The factory default setting is AT#P2.
81
CHAPTER 5: Command Mode
5.4.10 Compression, Error Correction, Flow
Control, Pass-Through and P acing
Commands
The Series II Modem has a variety of commands to control its error
correction and data compression options. These additional commands
are listed below. (Remember to precede each command with the AT
characters.) Factory-default settings are marked with asterisks.
Normal/Auto-Reliable/Reliable Mode Commands:
&E0 = Normal Mode
&E1 = Auto-Reliable Mode*
&E2 = Reliable Mode
Modem-Initiated Flow Control Commands:
&E3 = Disables flow control (no flow control)
&E4 = Hardware flow control (CTS on/off and RTS on/off)*
&E5 = Xon/Xoff flow control
Xon/Xoff Pass-Through Commands:
&E6 = Modem responds to Xon/Xoff characters, but does not
allow Xon/Xoff characters to pass through to remote
site.*
&E7 = Modem responds to Xon/Xoff characters, and allows
them to pass through to remote site.
#X0 = Selects single Xoff character until Xon level returns*
#X1 = Selects multiple Xoff characters after buffer levels is
full.
*Factory-default setting.
82
SERIES II INTELLIGENT DATA/FAX MODEMS
Enq/Ack Pacing Commands:
&E8 = Enq/Ack method of pacing off*
&E9 = Enq/Ack method of pacing on
Normal Mode Modem Flow Control Commands:
&E10 = Normal Mode Modem Flow Control off*
&E11 = Normal Mode Modem Flow Control (Xon/Xoff) on
Computer-or Terminal-Initiated Flow Control (Pacing) Commands:
&E12 = Pacing off*
&E13 = Pacing on (either RTS on/off or Xon/Xoff depending on
the setting of &E4 or &E5).*
Data Compression Commands:
&E14 = Data Compression disabled
&E15 = Data Compression enabled*
*Factory-default setting.
5.4.11 Speed Conversion Commands
Speed conversion is a necessary part of data compression since data
must be presented to the modem faster than it can handle data, if data
compression is to be effective.
Speed conversion allows the Series II Modem to communicate at one
speed over the phone line, and at another speed at the RS232C
interface. The speed (also referred to as “data rate” or “baud rate”) can
be fixed at the RS232 interface independently of the baud rate of the
on-line transmissions.
In addition to data compression, another popular application for speed
conversion involves an auto-answer Series II Modem connected to a
computer that does not have autobaud capability. This means that the
83
CHAPTER 5: Command Mode
computer must be set at a fixed baud rate, regardless of whether the
modem is communicating over the phone line at 300, 1200, 2400, 9600,
14,400,19,200, 24,000, 28,800 or 33,600 bps. In this application, speed
conversion allows the modem to match its speed to that of the calling
modem, while at the same time communicating with the attached
computer through its RS232C port at a fixed baud rate, which can be
pre-selected at 300, 1200, 2400, 4800, 9600, 19,200, 38,400, 57,600 or
115,200 bps.
Speed Conversion $BA
When using speed conversion, you must set the modem so that it does
not adjust its speed at the RS232C serial port, even if the modem does
adjust its data rate. To turn Speed Conversion ON, enter the command
AT$BA0&W0 and hit RETURN.
To turn Speed Conversion OFF, enter AT$BA1&W0 and hit RETURN.
The modem will now match its RS232C speed to that of the computer,
and will adjust its speed to any changes in the computer’s speed in
Originate mode, or to the speed of the originating modem in Answer
mode. The speed at which the modem communicates over the phone
line will always be the same as the speed at which it communicates via its
RS232C serial port.
Modem Baud Rate $MB
The $MB command presets the Series II Modem’s transmission baud
rate for originate operations, (i.e., the speed of the modem’s transmissions over the telephone lines when originating a call). With speed conversion, this transmission speed can be a different baud rate than the
serial port speed.
When the Series II Modem receives (answers) a call from another
modem, it automatically switches its phone line transmission speed to
match the calling modem. However, if the Modem originates a call to
another modem that is unable to connect at the baud rate of the
Modem, it automatically drops to a lower baud rate in an attempt to
match the speed of that modem. For example, if the Modem is set for
19,200 baud and calls another modem that has a top speed of
2400 baud, it drops to 2400 baud.
84
SERIES II INTELLIGENT DATA/FAX MODEMS
The command to set the Modem Baud Rate is AT$MBn, where n can
be 300, 1200, 2400, 4800, 9600, 14,400,19,200, 28,800 or 33,600 bps as
listed below:
AT$MB300 = 300 bps
AT$MB1200 = 1200 bps
AT$MB2400 = 2400 bps
AT$MB4800 = 4800 bps
AT$MB9600 = 9600 bps
AT$MB14400 = 14400 bps
AT$MB19200 = 19200 bps
AT$MB28800 = 28800 bps
AT$MB33600 = 33600 bps
The factory default is 33600 bps.
Serial Port Baud Rate $SB
The $SB command presets the speed of the Series II Modem’s serial
(RS-232C) port, in both Originate and Answer modes. Speed
conversion allows you to set this serial port baud rate at a fixed speed
of up to 115,200 bps, regardless of the modem’s transmission speed
setting.
In order for this command to be effective, the modem’s Speed
Conversion feature must first be turned off with the $BA command.
When Baud Adjust is on, the Modem automatically adjusts its serial port
baud rate to match the speed of the computer or terminal it is connected to, as soon as it receives its first AT command. However, in many applications, such as automatic answer, the modem may not receive AT
commands, in which case it is very useful to be able to preset the serial
port baud rate with this $SB command.
In addition to setting the Modem’s serial port speed, this command also
sets the speed at which the modem issues Command mode responses.
The Modem will accept AT commands at any speed, regardless of the
speed preset by the $SB command. If the modem receives such a command at a speed that is different than the preset speed, the modem
switches its serial port baud rate to match the new AT command speed,
although the baud rate value stored by the $SB command remains the
85
CHAPTER 5: Command Mode
same. This provides you with a convenient way to switch the serial port
speed, and still make it easy to go back to the original speed automatically the next time the modem is powered up or reset with an ATZ
command.
The command to set the Serial Port Baud Rate is AT$SBn, where n can
be 300, 1200, 2400, 4800, 9600, 19,200, 38,400, 57,600 or 115200 bps as
listed below:
AT$SB300 = 300 bps
AT$SB1200 = 1200 bps
AT$SB2400 = 2400 bps
AT$SB4800 = 4800 bps
AT$SB9600 = 9600 bps
AT$SB19200 = 19,200 bps
AT$SB38400 = 38,400 bps
AT$SB57600 = 57,600 bps
AT$SB115200 = 115,200 bps
The factory default is 115,200 bps.
Note: Some serial ports, particularly those in older PC-compatible
computers, may limit the performance of a higher speed modem like
the Series II Modem (see Chapter 3). The limiting factor is a circuit
called a Universal Asynchronous Receiver/Transmitter, or UART. All
data from your modem flows through it. 8250, 16450, and 16550 are
UARTs typically used in PC-compatible computers. The 8250 is
unreliable above 9,600 bps and the 16450 is unreliable above 19,200
bps. The 16550 UART, however, is reliable to at least 115,200 bps. With
V.42bis data compression enabled, the Modem can achieve throughputs
approaching 115.2K (depending on line quality and file content).
5.4.12 Immediate Action Commands
Help Screens $H
The Help command is designed to give you short explanations on how
to use each Series II Modem command. The Help command can be
quite useful if your manual is not handy and you are in the middle of a
communications session. Although the explanations are quite abbreviated compared to those in this manual, they should prove to be helpful
reminders when needed.
86
SERIES II INTELLIGENT DATA/FAX MODEMS
At the time of this writing, we have three screens of Help information
(Screen #1, #2 and #3), and more screens may be added in the future.
The Help commands are structured so that you can call up one of three
Help screens, as follows:
AT$H1 = Help Screen #1
AT$H2 = Help Screen #2
AT$H3 = Help Screen #3
Inquiry for Product Code I
Some systems or software packages automatically check the
“identification” of the modem with which they are communicating, by
using the I command. This “read” command lets the software to determine the type of modem with which it is communicating.
When ATI or ATI0 is entered, the Series II Modem responds with 247.
When ATI1 is entered, the modem responds with a three-digit code
indicating the firmware version number. When ATI2 is entered, the
modem responds with MD1641A if it’s a 336 model or MD1640A if
it’s a 336+ model.
Windows 95 Autodetect Inquiry I9
This read command permits a Windows 95 operating system to query
the Series II Modem's characteristics. When ATI9<CR> is entered, the
symbols BA 28800 FAX CT (336 model) or BL 28800 FAX CT (336+
model) are displayed; which indicates to the Windows 95 system that
your particular modem is a Series II Modem 336 or 336+, 28,800 bps, fax
Class 2 capable modem. With autodetect support in your Modem, your
PC can automatically allocate resources and configure it and other
devices. The Modem implements autodetect capability in the form of
a single .INF (Information) file that specifies AT Command mode and
Result Code "Registry Keys" that are specific to your Modem.
87
CHAPTER 5: Command Mode
Listing Current Operating Parameters L5 L7
The L5 and L7 commands list the current operating parameters of your
modem. This information can be very useful when you are changing
communications software or when you are changing modem default
settings.
The command to list the Series II Modem’s current operating parameters is ATL5 for the basic parameters. Entering ATL7 lists additional
parameters on the Modem.
Listing S-Register Values L6
Entering ATL6 lists the current values stored in the modem’s S-Register.
This information can be very useful if you wish to change S-Register
values. (Refer to Chapter 6 for more information on S-Registers).
Listing On-Line Diagnostics L8
The L8 command displays the current on-line CONNECT status of the
Series II Modem. This display can be printed and used as a modem
status report or as diagnostic information (such as when calling Tech
Support). To activate this command first type +++AT<CR>(on-line escape
command while maintaining command mode), then type ATL8. What then
displays on your monitor is your modem's current on-line condition
(e.g., Link Type, Line Speed, Serial Speed, Type of Error
Correction/Data Compression, Number of past Retrains, etc.).
See Figure 5-2 on the next page for a sample screen as displayed
through a Windows based terminal program.
88
SERIES II INTELLIGENT DATA/FAX MODEMS
Figure 5-2. On-line diagnostics information.
On or Off Hook H
You can make the Series II Modem hang up (go On Hook). Entering
ATH1<CR> brings the line Off Hook, just as if you picked up the
telephone set. You can hang up by entering ATH0 or ATH (the default
is 0 when no number is entered).
Escape Sequences- Entering Command Mode While Still
On-Line +++AT<CR>
It is possible to cause the Series II Modem to enter Command mode
after the modem has gone on-line with a remote modem without
disconnecting the call. This is done by entering an Escape Code. The
default Escape Code used by the Modem is three plus signs (+++)
followed by the letters A and T, up to sixty command characters (most
typically “H”, to hang up), and a RETURN. The number of command
characters allowed after +++ AT<CR> , is defined by S-Register S34.
S-Register S34 defaults to ten command characters.
File Edit Setup Perform Transfer Windows Help
MEWDEFFeb29, 96 4:50pm
024 2A71 0213
*********** ***********
LINK TYPE V.34
LINE SPEED 28800/26400
SERIAL SPEED 19200
ERROR CNTRL/COMPRESS LAPM
FALL BACK/FORWARD LOCALLY ENABLED
DATA FORMAT ASYCHRONOUS
SYMBOL RATE(SYMETRIC) 3429/3429
CARRIER FREQUENCY 1959/1959
TRELLIS ENCODER 4D 16-STATE/4D 16-STATE
PRECODING OFF/OFF
LINE TYPE DIAL UP
RECV. SIGNAL LEVEL -024.5 dBm
TRANS SIGNAL LEVEL -011 dBm
NUMBER OF RETRAINS 000
ROUND TRIP DELAY 0005 ms (MEANINGFUL IN V34 AND V32 MODE)
NEAR/FAR ECHO LEVEL -028.0/072.0 dBm
F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
ONLINE DIAGNOSTICS
Connected to device
DCD
CTS
DSR
00:04:55
89
CHAPTER 5: Command Mode
When this is done, the modem escapes to Command Mode, executes
the command (if any), and then remain in Command mode. For
example, to hang up the modem at the end of a call, enter +++ATH and
hit RETURN. There is no need to incorporate pauses before and after
the plus signs, as done in earlier modems.
BREAK AT<CR>
The Series II Modem provides an alternative Escape method, using a
Break signal as the Escape Code. The Break signal allows the start-stop
DTE (data terminal equipment) to signal the modem without loss of
character transparency. With this method, a BREAK signal is used
instead of the three plus signs. The BREAK is followed by the letters A
and T, up to 60 command characters, and RETURN. When this is done,
the modem executes that command, but remains in On-Line mode
unless the command was to hang up and/or reset the modem (an H or
Z), in which case the modem would be in the Command Mode after executing that command.
Escape Sequence Options - Entering Command Mode
While On-Line %E
As mentioned, the default escape sequence setting is for the modem to
respond to the +++ escape method. Optional settings are for the
modem to respond to the Break method, for the modem to respond to
either the +++ or the Break Methods, for the modem to ignore both
methods and not escape, for the modem to respond with no "OK" to
+++, and for the modem to respond with "OK" to +++. The %E com-
mand is used to select these options, as follows:
%E0 = Modem Won’t Escape
%E1 = +++ AT<CR> Method (default)
%E2 = Break Method
%E3 = Either +++ or Break Methods
%E4* = No "OK" Response to +++
%E5* = "OK" Response to +++
* The %E4 and %E5 commands enable or disable an "OK" response,
which is required by some software packages during an escape
sequence.
90
SERIES II INTELLIGENT DATA/FAX MODEMS
Force Answer Mode A
You can force the Series II Modem into Answer mode with the modem’s
A command.
Entering ATA when in Command mode immediately brings your modem off-hook, out of Command mode and into On-Line Answer mode,
and causes it to transmit its carrier signal over the phone line. If no
responding carrier tone is received by your modem within forty-five
seconds (or some other time as determined by S-Register S7), your
modem stops transmitting its tone, hangs up, and goes back into
Command mode.
Exiting Command Mode, Going Back On-Line O
You can bring the Series II Modem out of Command mode and back
into On-Line mode by entering ATO (where O is the letter O, not the
number 0). In this case, the O command reverses what was done by
entering the Escape Code. The O command will bring the modem into
the same On-Line mode (Originate or Answer) that it was in prior to
going into Command mode.
5.4.13 Line Probe Commands
Before V.34 negotiation takes place, remote and local modems transfer
their functional capabilities using modulated calling and answering
tones; indicating the common capabilities of the modem at each end.
Once this is done, a probing signal is passed between the modems to
identify impairments in the telephone channel (e.g., Receive Signal
Strength vs. Frequency, Noise vs. Frequency and Signal to Noise Ratio
vs. Frequency). After receiving the results of the probing signal, the
modem receivers and transmitters begin with the lowest speed and
move up until reaching the highest speed at which they can exchange
data. All this occurs in about five seconds.
There are a number of Line Probe Commands. These commands are
configurable and can be stored to RAM (via AT&W0).
91
CHAPTER1: Specifications
These commands are listed below.
Enable/Disable Reading of Line Probe Information Commands:
%DP0
Do not read Line Probe information from DSP during handshake
(Default).
%DP1
Read Line Probe information from DSP during handshake.
Format of Line Probe (Graph or Table) Commands:
%DF0
Data is displayed in Graph format. Y axis is shown in dBms (Default).
%DF1
Data is displayed in Table format. Numeric values are displayed
150 Hz to 3750 Hz in 75-Hz increments.
Immediate Action Line Probe Commands:
To activate these commands first type +++AT<CR> (on-line escape
command while maintaining command mode), then type the Command
prefixed by an AT.
&RP
This command initiates a retrain that makes the processor read Line
Probe information. Valid only when on-line in V.34 mode.
L9 = Displays Signal Strength information.
L10 = Displays Signal to Noise Ratio information (SNR).
L11 = Displays noise information.
92
SERIES II INTELLIGENT DATA/FAX MODEMS
6. S-Registers
6.1 Introduction
Certain Command Mode configurations are stored in memory registers
called, S-Registers. The S command is used to assign a value to, and to
read the current value of an S-Register. To assign a value to an SRegister, enter the letter S, followed by the S-Register number and an
equals sign (=), and then a decimal response to the message “ENTER
THE NEW VALUE IN DECIMAL FORMAT”. To read an S-Register value,
enter the letter S followed by the S-Register number and a question
mark (?), then hit RETURN. To verify that the S-Register value was
entered correctly, enter for example, ATS8? and hit RETURN. You
should receive a response of the assigned value given to that S-Register.
Refer to Section 6.2, Reading and Assigning S-Register Values.
S0
Number of Rings Until Modem Answers
Unit: Rings
Range: 0-255
Default: 1
Description: S0 defines the number of rings the modem waits
before answering an incoming call. The default
value is one ring (Decimal 1), which means that
the modem answers the call immediately after
the first ring. The maximum number of rings
that can be configured is 255. Setting the value
to zero (0) disables auto-answer completely.
S1
Rings Which Have Occurred
Unit: Rings
Range: 0-255
Default: 0
Description: S1 counts the number of rings that have
occurred. It is a “read” type of register and is
seldom, if ever, used in typical operation. Each
93
CHAPTER 6: S-Registers
time an incoming ring signal is detected, S1
increases its value by one, up to a maximum of
255. If you set S1 to a value other than its default
value of zero, or if the value is increasing with
rings, this new value remains stored in S1 for
eight seconds after the last ring is counted, after
which time the value reverts to zero.
S2
Escape Code Character
Unit: Decimal equivalents of ASCII characters
Range: 0-127
Default: 43 (+)
Description: S2 defines the escape code character. The
default character is the plus (+) sign
(43 decimal), but may be set for any ASCII
character. Setting an S2 value greater than 127
results in no escape character, and therefore no
means of entering Command mode from Online mode without breaking the on-line
connection.
S3
Return Character
Unit: Decimal equivalents of ASCII characters
Range: 0-127
Default: 13 (^M)
Description: S3 defines the character recognized as Carriage
Return (RETURN) or “Enter”. S3 may be set for
any ASCII character.
S4
Line Feed Character
Unit: Decimal equivalents of ASCII characters
Range: 0-127
Default: 10 (^J)
Description: S4 defines the character recognized as Line
Feed. S4 may be set for any ASCII character.
94
SERIES II INTELLIGENT DATA/FAX MODEMS
S5
Backspace Character
Unit: Decimal equivalents of ASCII characters
Range: 0-127
Default: 8 (^H)
Description: S5 defines the character recognized as
BACKSPACE. S5 may be set for any ASCII
character.
S6
Wait Time for Dial Tone
Unit: Seconds
Range: 2-255
Default: 2
Description: S6 sets the time the modem waits after the
RETURN key is pressed before executing a dial
command. The default setting is two seconds.
S7
Time for Carrier (Abort Timer)
Unit: Seconds
Range: 1-255
Default: 45
Description: S7 defines the Abort Timer (lack of carrier)
delay time. The default value is 45 seconds. This
means that, after dialing, the modem waits for a
carrier signal for up to 45 seconds and, if none is
detected, aborts the call. The maximum S7 value
is 255.
S8
Pause Time for Comma
Unit: Seconds
Range: 0-255
Default: 2
Description: S8 sets the length of the pause caused by a
comma inserted in a dialing command. The
95
CHAPTER 6: S-Registers
default setting is two seconds. S8 may be set for
up to 255 seconds.
S8 also sets the time the modem waits before
retrying a call after detecting a busy signal. Some
computer systems need more than two seconds
to reset (in which case you should increase the
value of S8).
S9
Carrier Detect Response Time
Unit: 100-mSec intervals
Range: 1-255
Default: 6
Description: S9 sets the time delay between when the modem
first detects a valid incoming carrier signal and
when the modem turns on its Carrier Detect
circuit. The default setting is 600 milliseconds
(six units of 100 mSec each). S9 may be set to a
maximum of 255 (25.5 seconds).
S10
Carrier Loss Disconnect Delay Time
Unit: 100-mSec intervals
Range: 0-255
Default: 7
Description: S10 sets the time a carrier signal must be lost
before the modem disconnects. The default
setting is 700 mSec (seven units of 100 mSec
each). Maximum delay is 25.4 seconds (S10 set
to 254). Setting the S10 value to 255 causes the
modem to not disconnect with loss of carrier.
(This S-Register applies at speeds of 2400 bps
and less.)
96
SERIES II INTELLIGENT DATA/FAX MODEMS
S11
Tone Dialing:Tone Spacing and Duration
Unit: Milliseconds (mSec)
Range: 1-255
Default: 70
Description: S11 sets the speed of tone dialing (spacing and
tone duration times). The default value is
70 mSec, meaning that each tone is on for
70 mSec with a 70 mSec pause between each.
The minimum S11 value allowed by most
telephone systems is 50 mSec. Very few
telephone systems can handle anything faster
than that. The maximum S11 value is 255 mSec.
S13
Remote Configuration Escape Character
Unit: Decimal equivalents of ASCII characters
Range: 0-127
Default: 37 (%)
Description: S13 defines the remote configuration escape
character (which becomes your modem’s
remote configuration character). The default is
three percent symbols (%%%). When the S13
character is entered three consecutive times
from a remotely connected site, your modem
responds with its Remote Configuration
procedure.
S15
Callback Time Delay
Unit: Seconds
Range: 10-255
Default: 20
Description: S15 defines the time delay between Callback
attempts after initial passwords have been
exchanged between modems. Refer to Chapter 7
for Callback Security information.
97
CHAPTER 6: S-Registers
S16
Callback Attempts
Unit: Attempts
Range: 1-255
Default: 4
Description: S16 defines the number of attempts allowed
after initial passwords have been exchanged
between modems.
S17
Changing Break Time
Unit: 10-mSec intervals
Range: 0-250
Default: 250
Description: S17 defines the break time (space) sent to the
local PC. The default is set for a 250-mSec
(2.5-second) break. The break time can be
changed in 10-mSec increments by increasing
or decreasing the value of S17.
S18
Automatic Leased Line Restoral (336+ Only)
Unit: Minutes
Range: 10-255
Default: 30
Description: When the Series II Modem 336+ (MD1640A) is
in dial backup mode, it periodically checks the
lease line to see if it is operational and tries to
restore the lease line if possible. S18 defines
how often attempts occur. The default of S18
is 30 minutes and can be set in one-minute
increments from 10 to 255 minutes. Setting the
S18 restoral under 10 minutes causes excessive
breaks in dial-up operation.
S19
Dial-Back Timer (336+ Only)
Unit: Minutes
Range: 0-255
Default: 1
Description: In the Series II Modem 336+ (MD1640A), S19
is a timer that begins when the lease line goes
down. S19 specifies the duration of time the
modem attempts to reestablish the lease line
connection.
S24
PBX/CBX Disconnect Drop Time for DSR/CTS/CD
Unit: 50-mSec intervals
Range: 0-255
Default: 20
Description: Some PBX and CBX phone systems require the
modem’s DSR, CTS, and/or CD signal(s) to
behave in a certain manner when calls are
disconnected. The Series II Modem’s &R, &S,
and &C commands cause the modem to drop
these signal(s) for a specified time period upon
disconnect, and then bring the signal(s) up
again. S24 defines the length of time that the
signals drop. The default setting of 20 results in
a one-second drop time, which is what most
PBX/CBX systems with this requirement need.
S25
DTR Dropout Time
Unit: 100-mSec intervals
Range: 0 (50 mSec), 1-255
Default: 0
Description: S25 defines the amount of time that DTR must
be dropped before the modem disconnects.
Typically, a disconnect occurs when DTR is
dropped for 50 milliseconds or more. This
98
SERIES II INTELLIGENT DATA/FAX MODEMS
99
CHAPTER 6: S-Registers
dropout time can be increased in 100-mSec
intervals, up to a maximum of 25.5 seconds
(S25 set to 255). The default S25 setting of zero
corresponds to a dropout time of 50 mSec.
All other possible settings (1 through 255)
correspond to their multiples of 100 mSec.
S26
Failed Password Attempts
Unit: Failed attempts
Range: 0-255
Default: 0
Description: S26 counts the number of times there has been
a failed password attempt. For example, if you
entered ATS26? and the message 003 were
displayed, it would mean that someone has
failed three times to gain access to your modem
using its password security system.
S29
Local Inactivity Timer
Unit: Minutes
Range: 1-255
Default: 20
Description: S29 defines the amount of idle time that can
elapse between AT commands after the SETUP
password has been entered. If this timer expires,
the LOGIN and SETUP passwords will have to
be re-entered. S29 only takes effect when the
modem has been sent a #DB1 command, which
secures the modem from local and remote configuration or dialing (i.e., no AT commands can
be sent until the LOGIN and SETUP passwords
have been entered).
Loading...