28.8 DIGITAL SVD MODEM TECHNICAL REFERENCE GUIDE 1995 by U.S. Robotics, Inc. 8100 North McCormick Blvd. Skokie, Illinois 60076-2999 All Rights Reserved TABLE OF CONTENTS PLACING CALLS DIAL (D) Dial Type - Pulse or Tone Adaptive Dialing (X2 through X4) Wait for Another Dial Tone (W) Pause (,) Slash (/) Dial and Return to Command Mode (;) Dialing Letters (") Transferring Calls (!) Wait for an Answer (@) Reversing Originate/Answer Frequencies (R) REDIALING ANSWERING Suppressing Auto Answer Manual Answer Points to Remember DISCONNECTING AND HANGING UP Modem Response to +++ INTERNATIONAL CALLS MODEM CONFIGURATION FACTORY CONFIGURATION (&Fn and Yn) CUSTOMIZING YOUR DEFAULTS (&Wn) USING AT COMMANDS RESETTING THE MODEM (Z) DSVD OPERATIONS CONFIGURING MODEM SOFTWARE FOR DIGITAL SVD ENABLING SIMULTANEOUS VOICE AND DATA CAPABILITIES WITH MODEM SOFTWARE USING YOUR MODEM FOR SIMULTANEOUS VOICE AND DATA SETTING UP DATA MODEM SOFTWARE FOR DIGITAL SVD USE WHAT YOU HEAR DURING VOICE AND DATA TRANSITIONS MAKING A CALL USING DIGITAL SVD WITH OTHER APPLICATIONS TEMPORARILY CHANGING A SETTING TONE DIALING SPEAKER LOCAL ECHO S-REGISTERS RESULT CODES ERROR CONTROL (&Mn) DATA COMPRESSION (&Kn) DATA RATE COMMANDS Software Requirements FLOW CONTROL Software Flow Control Precautions When it is Required Hardware Control (&Rn) Software Control (&In) GETTING HELP INQUIRIES (In) S-REGISTER QUERY (SR?) STORED PHONE NUMBER QUERY (&Zn?) LAST-DIALED NUMBER QUERY (DL?) HELP SCREENS Stop/Restart Display Cancel Display TESTING THE MODEM TESTING WITH &Tn &T1 Command &T8 Command &T6 Command &T7 Command DIAL TEST—S16=2 OTHER OPERATIONS FAX OPERATIONS VOICE/DATA COMMUNICATIONS TECHNICAL SPECIFICATIONS COMPATIBILITY DEFAULT SETTINGS MODEM CONCEPTS HOW MODEMS WORK MODEM CONNECTIONS LINE TRAVEL DIGITAL DATA FLOW CONTROL ERROR CONTROL THROUGHPUT GUIDELINES Placing Calls Using AT at commands NOTE: Settings listed as "default" are those set for your Digital SVD modem when it is shipped from the factory. To send commands directly to your modem, first put your computer in Terminal mode. Some communications programs do this automatically upon loading. Others require you to display a communications terminal screen, press a Function key, or perform some other operation. Refer to your communications software documentation for instructions. 1. Type all commands in either upper case (AT) or lower case (at), but not a combination (At). 2. All commands except A/ (re-execute last command) and +++ (escape code) must be preceded by the AT prefix and are executed with the Enter/Carriage Return key (). 3. Command string length = 58 characters, maximum. The modem doesn't count the AT prefix, Carriage Return character, or spaces. In a dial string, it counts but doesn't act on punctuation such as hyphens and parentheses. 4. A missing numeric parameter is assumed to be zero, as in the command to hang up; ATH is the same as ATH0 . NOTE: Unless otherwise indicated, settings listed as default are based on the hardware flow control template stored in NVRAM when the modem is shipped. DIAL (D) To dial a phone number and place a call without using your software's dialing directory, first put the computer in Terminal mode. Then type the AT and D commands, the number you wish to connect with, and press Enter. Spaces in our command examples are ignored by the modem and are only included for readability. ATD 1234567 After you have entered the command (unless you lowered your modem's speaker volume) you will hear the modem go off hook and dial the telephone number, followed by a series of handshaking signals. The Dial command string may include up to 58 characters. The modem counts but ignores punctuation characters such as parentheses and hyphens. It does not count spaces, the AT prefix, or the Carriage Return key () required to execute the command. The modem also executes any other commands or options included in the command line. The following example Dial command instructs the modem to turn off the speaker (M0), and dial (D) the phone number (1234567) using tone dialing (T). AT M0 DT 1234567 You may want to review the many options on the next several pages that are available for tailoring Dial strings. The most typically used are the Dial Type (Pulse or Tone) and the Pause options (comma, slash, and W). Cancel Dialing To cancel the Dial command execution, press . If you inadvertently hit a key on the keyboard while the modem is dialing, the call is canceled. If this occurs, type the A/ command, which re-executes the last command you entered. Dial Command Options You can modify the dial string according to the needs of the connection. Listed below are options available to you when entering the Dial string. Dial Type-Pulse or Tone The modem defaults to pulse (rotary) dialing. To have the modem use tone dialing, which includes the asterisk (*) and pound sign (#), use the T option. Dial type commands may be included in the Dial string (ATDT number) or, issued separately (ATT or ATP). However, if you'll always use tone dialing, write tone dialing to NVRAM as the modem's default and/or use adaptive dialing, described below. NOTE: You can switch from one dial type to another within a dialing sequence. The modem remains set to the last dialing type instruction until it is reset by the ATZ command, or it receives a different dial-type command. Adaptive Dialing (X2 through X4) When any of the X2 through X4 (default) result code options is in effect and you do not issue a dial type in the Dial string, the modem defaults to pulse dialing. If you issue a tone dial command, the modem will default to Hunt dialing, beginning with tone and adapting to pulse when necessary. For instance, if the phone company's central office does not have tone-detection equipment, the modem automatically reverts to pulse dialing. Wait for Another Dial Tone (W) This command is useful in situations where you must wait for a second dial tone before continuing to dial. For example, if you need to dial for an outside line, as in the following example, the modem resumes dialing as soon as it detects the next dial tone. ATD9W1234567 NOTE: This command executes only if result code option X2 or X4 (default) has been issued. If the modem is set to X0, X1,or X3, the modem interprets the W as a comma (two-second pause). Pause (,) A comma causes a two-second delay in the dial sequence. The following example contains four-second delays at several points. ATDP 9,,7654321,,55555,,1 312 1234567 The first four-second pause permits time to access an outside line after dialing 9, but you may wish to use the W option, just described. The second pause is to make sure the remote system is ready for the user's account number, and the third, to delay before dialing the long-distance number. Such pauses, however, may not be necessary. Experiment and use delays only as required. The duration of the delay can be changed by using the S8 register. The default duration of the delay is 2 seconds. Slash (/) A slash (/) can be used in any command string to make the modem pause for only 125 milliseconds. Some users find it helpful to have the shorter delay resulting from a series of slashes, rather than the 2-second comma pause. Dial and Return to Command Mode (;) If your phone is plugged into the modem, you can use this option to have the modem Auto Dial a telephone rather than a modem. The modem dials, remains off hook, and returns the OK message, indicating it is in Command mode. For example, to have the modem place a voice call, enter the Dial command with a semicolon. ATDT5551234; When the modem returns the OK result, pick up your phone receiver so you can talk to the other party, and send the command that hangs up the modem. ATH Similarly, to call a recorded weather or other service, have the modem dial, listen to the recording over the modem's speaker and, when you are finished, instruct the modem to hang up. Dialing Letters (") Quotation marks are used to make the modem dial abbreviations and acronyms used as phone numbers. Quotation marks are inserted at the beginning of the alphabetic string. ATDT "DIAL MOM" NOTE: If you are including another command after the dial string, use another pair of quotation marks before the additional command. ATDT "DIAL MOM",,,1234 Transferring Calls (!) This command is used for modems installed where other modems share the phone line. The modem flashes the switch-hook. That is, it goes off hook 0.5 seconds, on hook for 0.5 seconds, and off hook again to dial the specified extension. The following example includes instructions to transfer the call to extension 1234, return to Command mode (;) and to hang up (H). ATDT !1234;H Wait for an Answer (@) Some online services answer the phone and return a tape-recorded request for information before processing transactions. In such instances, the @ command can be used in the Dial string to tell the modem to detect at least one ring, wait for five seconds of silence at the other end of the call, and then continue to execute the Dial string. To use the @ command, set the modem result code option to X3 or X4 (default). If the modem is set to X2 or lower, the modem returns an ERROR message when it encounters the @ character in a command string. In the next example, the modem is set to the X3 result code option and dials a banking service. Each occurrence of @ in the example indicates a five-second wait for silence. In this example, the pauses are for taped requests from the bank for: a password (12345), an account number (6789), and a transaction code (2). The transaction code might indicate, for example, a request for an account balance. ATX3 DT5551234 @ 12345 @ 6789 @ 2 If the necessary conditions do not occur - no rings, or no following five seconds of silence - the modem times out as it normally would (after 60 seconds). It then sends the message NO ANSWER to the screen and aborts the call. Reversing Originate/Answer Frequencies (R) This command allows calls to an originate-only modem (a modem set up to send only). It reverses the modem's originate/answer frequencies, forcing the modem to dial out at the answer frequency. The command follows the Dial command, before or after the phone number. AT D1234567R AT DR1234567 Dialing Stored Numbers (DSn) You can store up to four frequently used telephone numbers in nonvolatile random-access memory (NVRAM). Use the &Zn=s command to store telephone numbers, where n is the position of the number in NVRAM (03) and s is the stored number. The following command string stores the telephone number (4441212) at position 1 in NVRAM. AT&Z1=4441212 To dial a stored number, use the DSn command, where n is the position of the number in NVRAM (03). In the first example, the modem dials the phone number stored at position 0. In the second, the modem dials the phone number stored at position 3. ATDS0 ATDS3 You can also store a partial dial sequence. If you often call a set of phone numbers and only their last three or four digits differ, it might be useful to store the initial digits that are similar. The following example stores a partial phone number at position 1. AT&Z1 = 9W1 616 123 Once you have stored the partial phone number in NVRAM, use the DSn command to dial the partial number, placing a slash (/), and then the remainder of the number after the DSn command. The slash separates the DSn number from the remainder of the string, yet maintains the Dial command. You can also use a comma (,) to insert a 2-second delay that separates the number. AT DS1/4567 NOTE: Do not include modem settings in the &Zn=s string. If the call requires special settings, insert them in the command string before the DSn command. For example, &K3 (selective data compression) is inserted before the Dial command to call the number stored at position 0. AT&K3 DS0 This establishes &K3 as the current setting. To return to default data compression mode after the call, issue the following command. AT&K1 REDIALING The most frequent reason for redialing is receipt of a busy signal. Your Digital SVD modem provides two redialing options, as follows. Dial the Last-Dialed Number (DL) When you want to redial a number, enter the DL command. The modem dials the last-dialed number, which it has stored in a special buffer. ATDL To display the number stored in the last-dialed buffer, use the following query. ATDL? To write the last number dialed to NVRAM, use &Zn=L where n is the position in NVRAM. The following example stores the last-dialed number at position 3. &Z3=L If a number is already stored at position 3, that number is overwritten with the last-dialed number. Re-execute the Last Command (A/) Another option for redialing is to enter the A/ command. This command does not require the AT prefix or a carriage return. A/ When the modem receives a command, it stores it in its command buffer until it receives the next AT command. The A/ command reexecutes whatever AT command is currently stored in the buffer. Note that if you've sent the modem an additional AT command since the lastDial command, A/ repeats that command instead of redialing. ANSWER MODE Your modem is shipped with Auto Answer suppressed. To set the modem to automatically answer incoming calls, issue the following command to have the modem answer on the fourth ring: ATS0=4 NOTE: You can select how many rings must occur before the modem answers by setting n in ATS0=n to the number of rings you want. If you use your phone line for both voice and modem calls, you may not want the modem to answer immediately (so that you can answer voice calls). When the modem senses a call, it sends the RING result code to your screen, goes off hook, and sends the remote modem a high-pitched answer tone. If the sending modem does not receive back a Carrier Detect signal within 60 seconds, the sending modem hangs up. If the connection is made, the modem returns a CONNECT result code. When a call is disconnected by you or the remote user, the modem hangs up and returns the NO CARRIER code to the computer screen. Suppressing Auto Answer To disable Auto Answer, set the modem to answer on zero (or no) rings during the current session. ATS0=0 NOTE: The S-register setting S0=0 cannot be saved to NVRAM. Manual Answer If you've disabled Auto Answer but are expecting an incoming data call, use the Manual Answer (A) command. Send the modem the following command after the RING result code appears on your screen. ATA When the call is disconnected, the modem returns to its original state, Auto Answer disabled. Points to Remember 1. You can set the modem to receive calls when you're not at your computer. Load your communications software as you normally do, and set the modem to Auto Answer. Also set your software's file-save function to save incoming messages and/or files. 2. If you've attached your phone so it can be used for voice calls, disable Auto Answer when you are not expecting incoming data calls or set S0 to a high number. Otherwise, your modem may answer the phone before you do, greeting a voice caller with a high-pitched, irritating answer tone. Escape Code Operations (+++) Once the modem is online to another system, the only command it recognizes is an escape code of three plus symbols that forces the modem into Online-Command mode. Issue the escape command in the following sequence. -Wait one second after sending the last item of data. -Type three plus symbols (+++). -Wait one second before typing any data. Do not type the AT prefix or a carriage return. The guard time of one second before and after prevents the modem from misinterpreting the presence of the +++ symbols in the transmitted data stream. If necessary, the character used in the escape code or the duration of the guard time can be changed by resetting register S2 or S12. See the Modem Installation and User's Guide for more information. Modem Response to +++ When the modem receives +++, by default it enters Online-Command mode and returns the OK result code. It maintains the connection and is ready to act on commands. You may then choose one of the following options. -Issue commands to the modem and then return it online. -Hang up the modem. Alternatively, if you want the modem automatically to hang up on receiving the +++ escape code, set Register S14 to 1 and write the command to your NVRAM templates: ATS14=1 &W &W1 The modem disconnects and sends the NO CARRIER result code to the screen. Returning Online (On) After forcing the modem into Online-Command mode with the escape code sequence, you can issue commands and then switch (toggle) the modem back online with the O command, as in the following example. AT Q1 O O0 Return online (normal). O1 Return online and retrain. If errors occur during a non-ARQ (non-error control) connection, try this option. The modem returns online and requests that both modems resynchronize. DISCONNECTING AND HANGING UP Use the commands described below to instruct the modem to disconnect the call and hang up the line. Hanging Up (Hn) At its default setting, the escape code forces the modem into Online-Command mode but leaves the line open. To hang up the modem, issue the following command once the modem sends the OK result code. ATH H0 Hang up (go on hook). H1 Go off hook. NOTE: If a voice and data call is in progress, H0 hangs up the modem, but the voice call continues. Break Handling (&Yn) This command lets you send a Break signal to abort data transfer without disconnecting from the phone line interface. &Y0 Destructive, no Break signal transmitted: the modem clears the data from its transmit buffer (all data is lost) but does not transmit the Break signal to the remote modem. &Y1 Destructive, expedited: the modem clears the buffer and immediately sends a Break signal to the remote modem. Default. &Y2 Nondestructive, expedited: the modem retains data in the transmit buffer, but immediately sends a Break signal to the remote modem. &Y3 Nondestructive, unexpedited (send Break signal in sequence): the modem transmits any buffer data received before the Break signal, sends the Break signal, and then sends any subsequent input from the computer. NOTE: If the call is under MNP5 data compression, destructive Break signals cause both modems to reset their data compression tables. When transmission resumes, the modems build new tables, and the result is lower than normal throughput. INTERNATIONAL CALLS The following commands apply to international calls. ITU-T/Bell Answer Sequence (Bn) To answer international calls, use the default B0 setting. B0 Default. This setting is required for V.32 or higher modems to answer V.32 or higher calls. It also selects the ITU-T V.25 answer sequence, used outside of North America. B1 This setting selects the Bell 2225 Hz answer tone used in the U.S. and Canada and may be used when the remote modem operates at only 2400 bps or lower. However, if the modem is set to B1, it won't be recognized by V.32 bis modems and can't answer calls at 9600 bps and above. Guard Tone (&Gn) The United Kingdom and some Commonwealth countries use phone switching systems that require answering modems to send an 1800 Hz guard tone after they send an answer tone. Some other European phone networks require a 550 Hz guard tone. Guard tones are not used in the United States or Canada. &G0 No guard tone, U.S./Canada. Default. &G1 550 Hz guard tone follows answer tone. Requires B0 setting. &G2 1800 Hz guard tone follows answer tone, United Kingdom and some Commonwealth countries. Requires B0 setting. Pulse Dial Make/Break Ratio (&Pn) This command sets the ratio of the off-hook/on-hook (make/break) interval for pulse dialing. The default sets the modem for use in North America. The ratio must be changed if the modem is used to dial out in the United Kingdom and some Commonwealth countries. &P0 Make/break ratio, U.S./Canada: 39%/61%. Default. &P1 Make/break ratio, United Kingdom, some Commonwealth countries: 33%/67%. ITU-T V.21-300 bps Select this option to call or answer overseas modems at 300 bps. In V.21 mode, the modem answers Bell 103/V.21 calls, but only originates V.21 calls. This option is enabled in Register S27 with the following command. ATS27=1 ITU-T V.23-1200/75 bps Some United Kingdom and European systems require a V.23 connection (that is, 1200-bps speed with a 75-bps back channel). Enable the V.23 option with Register S34=8. In addition, force a 1200 bps connection with &N2, and disable error correction with &M0. Thus you can establish a V.23 connection with the following command. AT &M0 &N2 S34=8 MODEM CONFIGURATION Your Digital SVD modem is preconfigured at the factory so you should be able to connect the modem, set up your communications software, and be ready to send and receive data. It is not preconfigured for Digital SVD mode. See the section on Digital SVD Operations for more information on Digital SVD mode. Many users won't need to change the default configurations, but if you want to, this guide will tell you how. Many of the functions described below can be handled by your communications software, but you also have the power to place your computer in Terminal mode (via your communications software) and control the modem directly. FACTORY CONFIGURATION (&Fn and Yn) The modem is preconfigured at the factory with three permanent and two programmable templates. Permanent Configuration Templates (&Fn) The following permanent templates come with your modem. The default template (activated with &F1) consists of the most reliable settings, but these settings may not work for all users. See the Technical Specifications Section for the command settings stored in these templates. &F0 Low performance template. This template does not include performance features, such as a fixed serial port rate or hardware flow control. What it does offer is compatibility with nontypical computers or software that cannot handle flow control and other features. If you need a low performance template because of data-transfer difficulties, load this template by entering the following command: AT&F This template allows you to communicate with nontypical systems that cannot handle flow control and other features. &F1 Hardware flow control template. Default. This template sets the modem to hardware flow control, a fixed serial port rate, the highest level result codes, and the most complete result-code set. This template is recommended for all IBM-compatible computers, as long as your communications software supports hardware flow control, a fixed serial port rate, and the advanced result-code subset. &F2 Software flow control template. We recommend you do not use this template, unless your communications software supports software flow control ONLY. To load this template and save it as your power-on/reset default, enter the following command: AT&F2&W NOTE: Refer to the Programmable Templates section for more information on selecting and modifying templates to save as your start-up configuration. Programmable Templates (Yn) In addition to the &Fn permanent configuration templates, you can use two programmable templates. Your programmable templates are located in nonvolatile random access memory (NVRAM), which will retain values when the modem is powered off. By default, the modem loads NVRAM template 0 (or Y0) for its power-on/reset default settings. Possible NVRAM commands: Y0 Loads NVRAM template 0 used with the hardware flow control template (&F1). Default. Y1 Loads NVRAM template 1 used with the software flow control template (&F2). For example, if you want to switch the power-on/reset default NVRAM template from Y0 to Y1, enter the Y command, then reset the modem with the Z command: AT Y1 Z To customize other defaults you want to store in NVRAM as part of your customized power-on/reset template, use the &Wn command (see the next section). WARNING: The Yn command, which selects template settings to use as the power-on/reset default, may select different power-on/reset default settings than those currently loaded (if you altered the settings during the current session). Before changing a template, use option 4 of the Inquiry (I) command to display the current settings. AT I4 The Y setting on the ATI4 screen indicates whether Y0 or Y1 is the power-on/reset Default. To display all the NVRAM settings in both Y0 and Y1 templates, use option 5 of the Inquiry command (I). AT I5 CUSTOMIZING YOUR DEFAULTS (&Wn) When your Digital SVD modem is shipped, it uses template 0 in NVRAM as the power-on/reset Default. Template 0 (Y0) is initially loaded with the &F1 permanent configuration settings. Although you cannot alter the &F1 template, you can add, delete, or modify the settings stored in your NVRAM templates. It is more likely, however, that you will want to keep your power-on/reset default settings and simply change a setting for a current session. Refer to Temporarily Changing a Setting in this guide for more information. If you want to modify your default configuration settings, use the &Wn command. Possible command options are: &W0 Modifies the NVRAM 0 template (Y0). &W1 Modifies the NVRAM 1 template (Y1). Typically, users prefer the default settings stored in NVRAM when the modem is shipped, but you may set up different power-on/reset defaults. For instance, if your system supports hardware flow control, you can set your Y1 template to the settings for hardware flow control so both templates set the modem for hardware flow control. (The Y0 template is shipped with hardware flow control settings.) AT &F1 &W1 NOTE: Yn is unique because it writes itself to NVRAM - you do not need to use the &Wn command to load a programmable template. Similarly, if your system only supports software flow control, you can set your Y0 template to the settings for software flow control so both templates set the modem for software flow control. (The Y1 template is shipped with software flow control settings.) AT &F2 &W You may also specify the entire configuration in a single command string that ends with the &Wn command. The following example sets the modem for the current session and stores the configuration in NVRAM 1 (or Y1). AT &K3 &W1 After sending a configuration to NVRAM, you can change any setting just for the current session, as in the following example. The NVRAM configuration remains intact. AT &K3 But if you want the new setting to be a default, write it to NVRAM at the same time, as in the following example, which saves the setting to NVRAM template 0. AT &K3 &W If you've sent the modem commands to change settings throughout your session and want to save your current configuration, send just the &Wn command. The current settings are then written to NVRAM 0 (or Y0) in the example below. AT&W If you cannot use hardware flow control and need to use Xmodem-type file transfer protocols, use either Y0 or Y1 for a no flow control configuration with no error control. AT &F &M &W or AT &F &M &W1 RESETTING THE MODEM (Z) If you've changed several current settings and want to reset to your modem, use the following command. ATZn Z0 Resets modem to NVRAM profile selected by Y command Z1 Resets modem to NVRAM profile 0 Z2 Resets modem to NVRAM profile 1 Z3 Resets modem to factory default profile 0 (&F0) Z4 Resets modem to factory default profile 1 (&F1) Z5 Resets modem to factory default profile 2 (&F2) NOTE: You cannot issue additional commands on the same line with the Z command, because the modem will ignore everything following the Z command. For example, if you enter ATZE1Q0 the modem ignores the E1Q0 portion of the command string. DIGITAL SVD OPERATIONS Your Digital SVD modem comes with ProShare conferencing software, which is preconfigured for simultaneous voice and data use with your Digital SVD modem. If you want to use other modem software (such as the data communications portion of the QuickLink II software) with your Digital SVD modem, you need to configure that software for the modem. CONFIGURING MODEM SOFTWARE FOR DIGITAL SVD Selecting a COM Port, IRQ, and Modem Type Follow the steps below to configure other modem data modem software with your Digital SVD modem: 1. Install the data modem software. 2. Start the data modem software. 3. Locate a modem configuration or setup option in the data modem software. (Look for a menu in the software's main program or in a separate setup program. For further instructions, see the manual supplied with the data modem software.) 4. Specify the COM port and the IRQ used by your modem. (When you installed your modem, you wrote down these settings in the modem Quick Install Guide or Chapter 2 of the Modem Installation and User's Guide.) 5. If your data modem software provides a list of modems to choose from, select one of the following modem types from the software's modem menu. (If your data modem software does not provide a list of modems, go on to the next section.) 28.8 Digital SVD Modem Intel 28.8 Digital SVD Modem U.S. Robotics 28.8 Digital SVD Modem If these modem types are not listed on the software's modem menu, select a compatible U.S. Robotics modem from the list below: -Courier V.34 -Sportster V.34 -Courier 28.8 -Sportster 28.8 If none of these is listed, select a US Robotics V.32bis modem. Enabling Simultaneous Voice and Data Capabilities with Modem Software When your data modem software tells your modem to connect to another modem, the software first sends a series of commands to your modem to initialize it. This set of commands is called an initialization string (or setup string). See your data modem software's manual for information on how to change its initialization string. Append the following commands to the existing initialization string: &F1-SSE=1 You can also temporarily activate the modem's Digital SVD mode by sending it this AT command: AT-SSE=1 MAKING A CALL WITH A DIGITAL SVD MODEM Your modem supports simultaneous voice and data calls, as well as voice-only calls and data-only calls. Here's how to make each type of call. Voice-only calls: Even though your phone is connected to the modem and is getting its voice signals through the modem chassis, for voice-only calls the modem is bypassed by an internal switch. Thus, to make a voice call, dial the number as you normally do with your phone handset. No AT command is needed. Data-only calls: A data-only call (to a computer bulletin board, for instance) requires only normal AT commands. Simultaneous voice and data calls: If you want to talk with someone as you interact on your computers, both of you must set your Digital SVD modems to Digital SVD mode, as explained in the previous section. To connect, you can start with a voice call or a data call: Starting with a voice call: Use your phone handset and dial the voice call. Then, to make a data connection after the other person answers, each of you must enter an AT command. The person who will initiate the data connection types: ATX3D The person who will receive the data connection types the following to enable the receiving modem's auto-answer mode: ATA Because the phones are already connected, your modem does not have to dial a phone number. However, the modems must carry out their standard modem connection negotiations, and they must switch from ordinary voice to digitized voice signals. During this process, the phone's speaker will be muted for a short period. Once the voice-data connection is established, either person can hang up the phone to establish a data-only connection. And if you want to return to a voice-data connection, you need only pick up the phone. Picking it up will produce a ring at the other end, and digital voice will begin when the other phone is picked up. Starting with a data call: Use normal data modem AT dialing commands to dial the other modem. Once the data modem connection is made, you or the other person can speak to each other by simply picking up the phone handset. This will signal both modems to switch to digitized voice, resulting in a short period when the phone's speaker is muted. Once you hear the other person, you have a voice-data connection. DIGITAL SVD AT COMMANDS Use these commands to control Digital SVD mode. Digital SVD Mode (-SSE=n) Use this command to disable and enable Digital SVD operations. Add -SSE=1 to a data software modem initialization string to make the software and modem function as a simultaneous voice and data application -SSE=0 Disables Digital SVD mode. -SSE=1 Enables Digital SVD mode. Phone Status (-SPH=?) -SPH=? Provides status of phone connected to modem's PHONE jack. Returns 0 if phone is on-hook (hung up) and 1 if phone is off-hook. TEMPORARILY CHANGING A SETTING When you change a setting, the modem retains it until you do one of the following. - Change the setting again. - Issue the ATZ command to reset the modem to the profile selected by the Y command. - Turn the system off and power it on again. The commands described in this section are organized in the order of their likely use. That is, those you are most likely to use appear at the beginning of the section, and those you are least likely to use appear toward the end. TONE DIALING The modem defaults to pulse (rotary) dialing. To have the modem use tone dialing, which lets you use the asterisk (*) and pound sign (#) in the dialing string, use the T command. ATDT 4445555 To have the modem always use tone dialing, use the T and &W commands to place the tone option in both NVRAM templates: AT T &W &W1 SPEAKER The modem's speaker enables you to monitor the dial-connect process. There are several ways to make use of this feature. After the modem dials a number, it waits up to 60 seconds for a high-pitched answer tone from the other modem, immediately followed by data signals, called a carrier. These signals must occur before a data link is established. At the default X4 setting, the modem sends your screen the NO CARRIER message after 60 seconds. If you listen to the speaker and realize you have received a voice answer, you can respond immediately, instead of waiting for the modem to time out and send the NO CARRIER message, by pressing any key on the keyboard. This cancels the call. You can also hear if dialing is proceeding too quickly for the system. If so, terminate the call (press any key) and retype the Dial command, but insert a comma (,) or a couple of slashes (/), to have the modem pause during the dialing process. Volume Control (Ln) The following options allow you to adjust the speaker. L0 Low. L1 Low. L2 Medium. Default. L3 High. Speaker Control (Mn) This command disables the speaker entirely or sets the speaker to monitor different segments of the dial-connect sequence. M0 Disables the speaker entirely so that you don't hear the modem go off hook, dial, etc. M1 The speaker is on until your modem detects the remote modem's carrier signal. Default. You can monitor call progress until your modem detects the remote modem's carrier signal, or until the 60-second timeout and NO CARRIER result code display. When your modem detects a carrier signal, the modem disconnects the speaker and data-transmission sounds are suppressed. M2 The speaker is on continuously, including during data transmission. M3 The speaker doesn't turn on until after the last digit is dialed, then goes off when your modem detects the remote modem's carrier signal. LOCAL ECHO Local echo is the display of what you type at the keyboard and online echo is the display of data the modem transmits to another modem. The En command controls the display of your typed commands, when the modem is in Command mode. The Fn command controls the display of data when your modem is online to another system. Command Mode Local Echo (En) Use the En command to control the local echo for a current session, independent of the switch setting. This command may not be stored in NVRAM. E0 Command mode echo OFF. The modem does not display keyboard commands. E1 Command mode echo ON. Default NOTE: If double characters appear on the screen when you type, you have activated both the modem's and software's local echo commands. Online Local Echo (Fn) This command causes the modem to display a copy of the data it is transmitting to another system. Many receiving modems, however, also return a copy of received data, which is called a remote echo. If the modem's online echo is ON and there is also remote echoing, double characters appear on the screen. In some microcomputer documentation, the term duplex is applied to online local echoing, although the term is not technically accurate. F0 Online echo ON. Sometimes called half duplex. As the modem transmits data to a remote system, it also sends a copy of the data to the local screen. F1 Online echo OFF. Sometimes called full duplex. Default. S-REGISTERS The S-registers are used to set various timing parameters and to redefine selected ASCII characters and other configuration options. Users typically require the default values. To change a setting, use the ATSr=n command, where r is the register and n is a decimal value from 0–255 (unless otherwise indicated). The example below sets the modem's test timer (S-register 18) to 10 seconds. ATS18=10 The modem does not perform a value-range check. Thus, some values you select may not work with some equipment, and you'll have to readjust the settings. Use ATSr? to display the contents of a register, as follows. ATS18? S-Register Summary Register Default Function S0 0 Sets the number of rings on which to answer in Auto Answer Mode. When set to 0, Auto Answer is disabled. (This 0 setting cannot be saved in modems with DIP switches. See DIP switch 5). S1 0 Counts and stores the number of rings from an incoming call. (S0 must be greater than 0). S2 43 Stores the ASCII decimal code for the escape code character. Default character is +. A value of 128-255 disables the escape code. S3 13 Stores the ASCII code for the Carriage Return character. Valid range is 0-127. S4 10 Stores the ASCII decimal code for the Line Feed character. Valid range is 0-127. S5 8 Stores the ASCII decimal code for the Backspace character. A value of 128255 disables the Backspace key's delete function. S6 2 Sets the number of seconds the modem waits before dialing. If Xn is set to X2 or X4, the modem ignores this register and dials as soon as it detects a dial tone (fast dials). Register Default Function S7 60 Sets the number of seconds the modem waits for a carrier. May be set for much longer duration if, for example, the modem is originating an international connection. S8 2 Sets the duration, in seconds, for the pause (,) option in the Dial command. S9 6 Sets the required duration, in tenths of a second, of the remote modem's carrier signal before recognition by the Sportster. S10 7 Sets the duration, in tenths of a second, that the modem waits after loss of carrier before hanging up. This guard time allows the modem to distinguish between a line hit, or other disturbances that momentarily break the connection, from a true disconnect (hang up) by the remote modem. While we don't recommend connecting the modem to a line with call waiting, if you have it, you may wish to adjust this setting upward to prevent the modem from misinterpreting the second call signal as a disconnect by the remote modem. A better alternative is to ask your phone company how to temporarily disable call waiting (usually *70W). For example: ATDT *70W phonenumber. NOTE: If you set S10 = 255, the modem will not hang up when carrier is lost. Dropping DTR hangs up the modem. S11 70 Sets the duration and spacing, in milliseconds, for tone dialing. Register Default Function S12 50 Sets the duration, in fiftieths of a second, of the guard time for the escape code sequence (+++). S13 0 Bit-mapped register. Select the bit(s) you want on and set S13 to the total of the values in the Value column. For example, ATS13 = 17 enables bit 0 (value is 1) and bit 4 (value is 16). 0 1 Reset when DTR drops. 1 2 Reserved. 2 4 Reserved. 3 8 On DTR signal, auto dial the number stored in NVRAM at position 0. 4 16 At power on/reset, Auto Dial the number stored in NVRAM at position 0. 5 32 Reserved. 6 64 Disable MNP Level 3 (used for testing Level 2). 7 128 Reserved. S14 0 Bit-mapped register. Allowable non-default value is 1. Bit Value Result 0 1 The modem hangs up on receipt of +++, returns to command mode, and sends the NO CARRIER result code. 1-7 - Reserved. Register Default Function S15 0 Bit-mapped register. To set the register see the instructions for S13. Bit Value Result 0-2 - Reserved. 3 8 Reset non-ARQ mode transmit buffer from 1.5K bytes to 128. 4 16 Disable MNP Level 4; retransmitting the larger Level 4 data blocks may be a problem if you expect a great number of errors during a call. 5 32 Set Backspace key to delete. 6-7 - Reserved. S16 0 Bit-mapped test register. Allowable value is 2. Bit Value Result 0 - Reserved. 1 2 Touch tone dialing test. 2–7 Reserved. S17 0 Reserved.* The 1.5K-byte non-ARQ buffer allows data transfer with Xmodem- and Ymodem-type file transfer protocols without using flow control.The 128-byte option lets remote users with slower modems stop data you're sending from scrolling off their screens. When remote users send your computer an XOFF (Ctrl-S) and you stop transmitting, the data in transit from your modem's buffer doesn't exceed the size of their screen. This is also very helpful in situations when a remote modem/printer application is losing characters. Register Default Function S18 0 Test timer for &Tn loopback testing. Sets the time in seconds of testing before the modem automatically times out and terminates the test. When set to 0, the timer is disabled. S19 0 Sets the duration, in minutes, for the Inactivity Timer. The timer activates when there is no data activity on the phone line; at timeout the modem hangs up. S19 = 0 disables the timer. S20 0 Reserved. S21 10 Sets the length, in 10-millisecond units, of Breaks sent from the modem to the computer; applies to ARQ mode only. S22 17 Stores the ASCII decimal code for the XON character. Valid range is 0-127. S23 19 Stores the ASCII decimal code for the XOFF character. Valid range is 0-127. S24 0 Reserved. S25 5 Sets the duration, in hundredths of a second, that DTR must be dropped so that the modem doesn't interpret a random glitch as a DTR loss. (Most users will want to use the default; this register is useful for setting compatibility with older systems running under older operating software.) S26 0 Reserved. S27 0 Bit-mapped register. To set the register see the instructions for S13. Bit Value Result 0 1 Enables ITU-T V.21 modulation at 300 bps for overseas calls; in V.21 mode, the modem answers both overseas and domestic (U.S. and Canada) calls, but only originates V.21 calls. 1 2 Enables unencoded (non-trellis coded) modulation in V.32 mode; rarely used part of ITU-T Recommendation V.32. 2 4 Disables V.32 modulation. 3 8 Disables 2100 Hz answer tone to allow two V.42 modems to connect more quickly. 4 16 See next page. 5 32 See next page. 6 64 Reserved. 7 128 This setting disables the codes and displays the 9600 code instead. The actual rate of the call can be viewed on the ATI6 screen. Used for unusual software incompatibilities. Some software may not accept 7200, 12000 and 14400 bps result codes. Register Default Function S27 (cont'd) Error control handshaking options: select the total values of bits 4 and 5. Bit 4 Bit 5 Result 0 0 Complete handshaking sequence: V.42 Detection, LAPM error control, MNP. 16 0 Disable MNP. 0 32 Disable V.42 Detection and LAPM. 16 32 Combined value of 48 negotiates LAPM without Detection phase. Choose this value if the remote modem uses LAPM but does not support the Detection phase. S28 8 Sets the duration, in tenths of a second, of the EIA-specified Multimode Training. Default = 8 (.8 seconds). This gives V.32 bis,V.FC and V.34 modems additional time to connect with most U.S./Canadian modems at 9600 bps or higher before falling back to attempt a V.23 connection (some U.K. and European phone systems, 1200 bps) or a V.21 connection (U.K. and European, 300 bps). If calling/answering low-speed, overseas modems under V.21 or V.23 modulation, setting S28 to zero eliminates the delay, giving a faster connect time. S29 20 Reserved S30-S33 0 Reserved. S34 (6)(0) Default=0 on V.FC and V.34 modems; default=6 on V.32 bis modems. Allowable values for non-V.FC modems are S34=6, S34=7, S34=14, and S34=15. Set this register by adding 6 to the value of the bit or bits you want enabled. Bit Value Result 0 1 Disable V.32 bis. Used for troubleshooting; U. S. Robotics' Technical Support may require that you disable V.32 bis for testing purposes. 1-2 Reserved. 3 8 Enable V.23 modulation. 4-7 Reserved. S35 0 Reserved. S36 14 Reserved. S38 0 Sets an optional delay, in seconds, before a forced hang-up and clearing of the Transmit buffer when DTR drops during an ARQ call. This allows time for a remote modem to acknowledge receipt of all transmitted data before it is disconnected. Default 0: the modem immediately hangs up when DTR drops. This option only applies to connections terminated by dropping DTR. If the modem receives the ATH command, it ignores S38 and immediately hangs up. Register Default Function S39-44 0 Reserved S51 0 Bit mapped register. To set the register see the instructions for S13. Bit Value Result 0 1 MNP/V.42 disabled in V.22. 1 2 MNP/V.42 disabled in V.22bis. 2 4 MNP/V.42 disabled in V.32bis. 3-7 - Reserved. S54 0 Bit mapped register. To set the register see the instructions for S13. Bit Value Result 0 1 Disable 2400 symbol rate. 1 2 Disable 2743 symbol rate. 2 4 Disable 2800 symbol rate. 3 8 Disable 3000 symbol rate. 4 16 Disable 3200 symbol rate. 5 32 Disable 3429 symbol rate. 6 64 Disable Call Indicate (V.34 only). 7 128 Disable V.8 (V.34 only) S55 0 Bit mapped register. To set the register see the instructions for S13. Bit Value Result 0 1 Disable 8S-2D map. 1 2 Disable 16S-4D map. 2 4 Disable 32S-2D map. 3 8 Disable 64S-4D map. 4-7 - Reserved. Register Default Function S56 0 Bit mapped register. To set the register see the instructions for S13. Bit Value Result 0 1 Disasble non-linearing coding. 1 2 Disable TX level deviation. 2 4 Disable pre-emphasis. 3 8 Disable pre-coding. 4 16 Disable shaping. 5 32 Reserved. 6 64 Disable V.34 (V.34 only). 7 128 Disable V.FC. S57 0 Reserved. Result Codes Four commands control the result codes that the modem returns to the screen. Vn Numeric/verbal response mode Qn Display/suppress all result codes Xn Result code options &An Display/suppress additional result code options These commands are explained in the following sections. Response Modes (Vn) You can select whether result codes are sent to the screen in words (Verbal mode) or numbers (Numeric mode). Use the Vn command to select verbal or numeric result codes for a current session. This command may not be stored in NVRAM. V0 Numeric mode. Numeric result codes are displayed on the same line as your AT command, as in the following example, where a 3 is returned (for NO CARRIER). ATD1234567 becomes 3TD1234567 V1 Verbal mode. Default. Verbal responses are displayed on the next line after your command, as shown below. ATD1234567 NO CARRIER Quiet Mode (Qn) Enable/suppress the display of result codes. Use the Qn command to control the display for your current session. NOTE: This command may not be stored in NVRAM. Q0 Result codes are displayed. Default. Q1 Result codes are suppressed. Q2 Result codes are suppressed only in Answer mode. Result Code Options (Xn) You have five options, X0 through X4, for selecting the result-code set best suited to your applications, as shown in the following tables. X0 Basic set, returns the first five codes (0-4) in the following table. X1 Extended set, codes 0–5, 10, 13 and 18, that adds rate-specific CONNECT messages to the Basic set. This set also includes all &An result codes. X2-4 The default is X4. These options include the X1 set, call-progress codes 6 or 7, and 8, and the functions listed in the following table. NOTE: By default, the modem is also set to &A3, which selects additional results that report the protocols used in the connection. More CONNECT messages indicate an error control connection, the call modulation, or the error control and data compression used. See Additional Result Code Options (&An), after this section. Result Code Options Setting Result Codes X0 X1 X2 X3 X4 0/OK · · · · · 1/CONNECT · · · · · 2/RING · · · · · 3/NO CARRIER · · · · · 4/ERROR · · · · · 5/CONNECT 1200 · · · · 6/NO DIAL TONE · · 7/BUSY · · 8/NO ANSWER · · 10/CONNECT 2400 · · · · 13/CONNECT 9600 · · · · 18/CONNECT 4800 · · · · 20/CONNECT 7200 · · · · 21/CONNECT 12000 · · · · 25/CONNECT 14400 · · · · 43/CONNECT 16800 · · · · 85/CONNECT 19200 · · · 91/CONNECT 21600 · · · · 99/CONNECT 24000 · · · · 103/CONNECT 26400 · · · · 107/CONNECT 28800 · · · · Functions Adaptive Dialing · · · Wait for 2nd Dial Tone (W) · · Wait for Answer (@) · · Fast Dial · · Result Code Definitions Result Code Meaning 0/OK Command has been executed. 1/CONNECT Connection established with another modem; if X0 is selected, connection may be 30028,800bps; if X1 or higher, connection is at 300 bps. 2/RING Incoming ring detected. 3/NO CARRIER Carrier has not been detected or carrier has been dropped due to disconnect. 4/ERROR Command is invalid. 5/CONNECT 1200 Connection established with another modem at 1200 bps. 6/NO DIAL TONE Dial tone not detected during the normal 2 seconds, set in Register S6. 7/BUSY Busy signal detected; modem hangs up. 8/NO ANSWER After waiting 5 seconds for an answer, modem hangs up; returned instead of NO CARRIER when the @ dialing option is used. 10/CONNECT 2400 Connection at reported rate. Same for results of 4800 (18), 9600 (13), 7200 (20), 12K (21), 14.4K (25), 16.8K (43), 19.2K (85), 21.6K (91), 24K (99), 26.4K (103), 28.8K (107). Adaptive Dialing (HUNT) The modem attempts to use tone dialing and, if that doesn't work, reverts to rotary (pulse) dialing. Wait for Another The modem halts dialing until it detects another Dial Tone dial tone. Wait for an The modem does not continue dialing until it Answer (@) detects 5 seconds of silence on the line. Fast Dial The modem dials immediately after detecting a dial-tone, instead of waiting the normal 2 seconds set in Register S6. Additional Result Code Options (&An) Use this command to enable/disable one of the following sets of error control, modulation, or protocol result codes. If you encounter software problems, it may be because your software expects to find different result codes from those the modem is sending. (The modem defaults to &A3.) Review your software documentation or try &A2, &A1, or &A0. You may need to call your software's technical support to find out which &An setting they support. &A0 ARQ (error control) codes are disabled. This setting does not affect an error control connection; the modem returns standard CONNECT messages if result codes are enabled. &A1 ARQ codes are enabled. CONNECT/ARQ is displayed if the modem is set to X0 and the connection is 1200 bps and above. If the modem is set to X1 or above, the results indicate the connection rate. If your software cannot handle the ARQ codes, select &A0. &A2 V.32 modulation codes are enabled. These results require a setting of X1 or higher. If your software cannot handle the added modulation information, select &A1 or &A0. &A3 Protocol codes are enabled. Default. Error control protocols reported are LAPM or MNP. When the call is not under one of those protocols (and ARQ is not included in the result code), the modem reports NONE, for no protocol. If the modems are using data compression, the type of compression—V42BIS or MNP5—is added to the result code. If your software cannot handle the added protocol information, select &A2, &A1, or &A0. Although these codes will return numeric identifiers if you've set the modem to V0, they are the same numeric identifiers used for &A2 result codes. If you want &A3 protocol indicators, use verbal mode (V1), and not numeric mode (V0). ERROR CONTROL (&Mn) By default, the modem first attempts a connection using V.42 (LAPM) error control and, if that doesn't succeed, it attempts an MNP connection. If that doesn't succeed, the modem tries to connect without error control. Error control is possible at rates of 1200 bps and above. The following options are available. NOTE: ARQ is a term for error control protocols that include error detection and automatic retransmission of corrupted blocks of data. &M0 Normal mode, no error control. Because of the nature of phone-line channels, this is never recommended for calls above 2400 bps unless you're using an error-correcting file-transfer protocol. Disables Digital SVD. &M1 Reserved. &M2 Reserved. &M3 Reserved. &M4 Normal/ARQ mode. Default. If the remote modem doesn't recognize your modem's error control signals (V.42 or MNP), your modem will operate in normal mode, as though it were set to &M0. &M5 ARQ mode. If the remote modem doesn't recognize the error control request (V.42 or MNP) the modem hangs up. Always set the modem for error control, &M4 (default) or &M5, for calls at speeds over 2400 bps. Most users communicating with V.42- or MNP-compatible modems will want error control at 2400 and 1200 bps, as well. If you're dialing and have trouble connecting, it may be because the remote modem doesn't have MNP capability, and it misinterprets your modem's MNP error control request. If you know the remote modem doesn't support MNP, disable MNP handshaking by setting Register S27 to 16 (ATS27=16). The modem still connects, but without MNP error control. To reset the modem for normal operations after the call, issue the ATZ (reset) command, or set Register S27 to zero. Auto Answer with Error Control When set to &M4 or &M5 and a call comes in, your modem goes off hook and responds to received error control signals. If the modem doesn't receive those signals and is set to normal/ARQ mode (&M4), it answers the call in normal mode (&M0). If it doesn't receive the signals and is set to ARQ mode (&M5), it hangs up. DATA COMPRESSION (&Kn) When data compression is enabled, the transmitting modem detects redundant units of data and recodes them into shorter units of fewer bits. The receiving modem decompresses the redundant data units before passing them to the receiving computer. Compression does not occur unless the modems can establish an error control connection. If the modem makes a V.42 connection, it negotiates V.42 bis compression. If V.42 bis is not feasible, the connection remains under error control, but without data compression. If the modem makes an MNP connection, it negotiates for MNP level 5 (MNP5) data compression. If the remote modem does not have MNP5 capability, the connection remains under MNP error control, but without compression. &K0 Data compression disabled. &K1 Auto enable/disable. Default. The modem enables compression if the serial port rate is fixed (&B1) and disables compression if the serial port rate varies, by following the the connection rate (&B0). (Compression offers no throughput advantage when serial port and connection rates are equal, and may even degrade throughput.) &K2 Data compression enabled. Use this setting to keep the modem from disabling compression. &K3 Selective data compression. The modem negotiates only for V.42 bis compression, and disables MNP level 5 (MNP5) compression. See the following note. NOTE: MNP5 compression is not useful when transferring already compressed files, such as the .ZIP files downloaded from computer bulletin boards (BBS) and 8-bit binary files that appear already compressed to the modem. MNP5 tends to add data to these files, and, as a result, throughput over the phone link degrades. V.42 bis compression detects when data is already compressed and turns off until it detects that compression will be advantageous. The special &K3 setting allows the best throughput for already compressed and 8-bit binary files. DATA RATE COMMANDS The &Bn and &Nn commands control data rates at the serial port and phone line interfaces. Your Digital SVD modem defaults to a fixed rate at the serial port interface (&B1) to keep the serial port rate higher than the connection rate. You'll get greater throughput regardless of the connection rate. Your software, however, must support this feature and you must set your software to use a fixed rate. For the phone line, however, we recommend variable connection rates (&N0). This lets the modem switch its connection rate to match the rate of a remote modem, no matter what that rate is. If the connection rate is fixed, for example, at 9600 bps (&N6), the modem only connects with modems operating at that rate. Of course, if your application requires connections with modems at only one rate, you may wish to set the modem to a fixed connection rate. Software Requirements Both variable and fixed serial port rates require communications software support. Most communications programs support variable or fixed rates. Check your software manual. Set your software before making calls. Serial Port Rate (&Bn) Initially, the modem's serial port rate is dependent on your software setting. The modem detects the rate at which it receives the AT command to determine the serial port rate; after that the modem depends on its &B setting. &B0 Variable serial port rates. The modem switches its serial port rate to follow the connection rate your local modem established with a remote modem. If your software has Auto Baud Detect, turn it on. The software will switch its serial port rate to match the connection rate. &B1 Fixed serial port rate. Default. The modem detects its serial port rate from your last AT command and maintains it, whatever the connection rate. Set your software to 115.2K, 57.6K, 38.4K, or 19.2 Kbps, then set the modem to &B1 for the best throughput. Some programs require that you turn off Auto Baud Detect to fix the serial port rate. Others use the term Serial Port Lock (yes or no). The serial port rate must equal or exceed the connection rate. Also, this setting requires flow control, preferably hardware flow control (&H1), to avoid buffer overflow. &B2 Fixed for ARQ calls/Variable for non-ARQ calls, Answer mode only. When the modem goes off hook and answers in ARQ mode, it shifts its serial port rate to the one written to NVRAM, for example, 38.4 Kbps. In non-ARQ mode, it acts as if set to &B0 when answering, and switches its serial port rate to match the call's connection rate. This option is designed for installations such as Bulletin Boards that receive calls from a wide variety of modems, ranging from the very slow to those with the modem 's advanced design. Connection Rate (&Nn) Use the &Nn command to select variable or fixed rates at the phone-line interface. Variable rates let the modem connect with a variety of remote modems, while fixed rates limit calls to one connection rate. &N0 Variable rates. Default. Your modem negotiates with the remote modem for the highest possible connection rate, depending on the capabilities of the remote modem. This is the recommended setting. &N Fixed rate. Your modem only connects if the remote modem 1-8 is operating at the same rate. If not, the modem hangs up. The fixed rate options are as follows. &N1 300 bps &N2 1200 bps &N3 2400 bps &N4 4800 bps &N5 7200 bps &N6 9600 bps &N7 12,000 bps &N8 14,400 bps &N9 16,800 bps &N10 19,200 bps &N11 21,600 bps &N12 24,000 bps &N13 26,400 bps &N14 28,800 bps By fixing the connection rate, you can filter out calls at other than a specific rate, for security or other reasons. Use the &U command in conjunction with &N to set a floor connect speed when &Un is set greater than 0. &N is the ceiling connect speed. &U0 Disabled &U1 300 bps &U2 1200 bps &U3 2400 bps &U4 4800 bps &U5 7200 bps &U6 9600 bps &U7 12,000 bps &U8 14,400 bps &U9 16,800 bps &U10 19,200 bps &U11 21,600 bps &U12 24,000 bps &U13 26,400 bps &U14 28,800 bps RS-232 SIGNAL OPERATIONS &Cn Carrier Detect operations. At power-on and reset, the modem operates according to the setting of DIP switch 6. This command is not stored in nonvolatile memory as a power-on/reset default. &C0 CD override, CD always ON. &C1 Normal CD operations. The modem sends a CD signal when it connects with another modem and drops the CD when it disconnects. Default. &Dn Data Terminal Ready (DTR) operations. At power-on and reset, the modem operates according to the setting of DIP switch 1. This command is not stored in nonvolatile memory as a power-on/reset default. &D0 DTR override. The modem operates as though the DTR is always ON. &D1 Advance usage: If issued before connecting with another modem, the modem can enter online command mode during a call by toggling DTR. (Most communications software packages have a method for toggling DTR.) &D1 functions similarly to the escape code (+++), except that this setting is independent of DIP switch 9. If DIP Switch 1 is ON (DTR override) when you issue the &D1 command, the DTR override is automatically turned off. However, if you change the setting of DIP switch 1 after issuing &D1, the DIP switch setting takes precedence. Return online with the On command, or hang up with the Hn command. &D2 Normal DTR operations. The terminal or computer must send a DTR signal for the modem to accept commands. Dropping DTR terminates a call. Default. &Sn The modem sends the computer or terminal a Data Set Ready (DSR) signal via the RS-232 interface. (Data Set is industry jargon for modem.) Few, if any, commercial communications programs require the modem to control DSR, &S1. Leave the modem set for DSR overridden, &S0, unless you know that your installation requires a different setting. &S0 DSR is always ON (override). Default. &S1 In Originate mode, the modem sends the DSR after it dials, when it detects the remote modem's answer tone. In Answer mode, the modem sends the DSR after it sends an answer tone. FLOW CONTROL The modem uses either hardware or software flow control to manage the amount of data stored in the buffers, thus preventing buffer overflow. Your Digital SVD modem defaults to hardware flow control. This type of flow control is performed between the modem and computer via discreet signals sent through the serial port. Software flow control uses the standard ASCII Transmit OFF (XOFF) character, Ctrl-S, and the Transmit ON (XON) character, Ctrl-Q. ASCII definitions are as follows. XON Ctrl-Q ASCII 17 Decimal, 11 Hex XOFF Ctrl-S ASCII 19 Decimal, 13 Hex NOTE: Both your software and computer must support the flow control you select. All 100% IBM PC-compatible computers support hardware flow control. However, hardware flow control requires software support. Refer to your software documentation to see what flow control your software supports. Be sure to set your software appropriately before transferring files. Warning on Software Flow Control In ordinary operations, the only characters the modem recognizes during a call are the three plus symbols (+++) of the escape code that return it to Command mode. But when software flow control is enabled, the modem or computer also recognizes Ctrl-S or Ctrl-Q characters. If these characters occur in a file or as part of a protocol, the modem interprets them as XON/XOFF characters and acts on them. For example, XON/XOFF characters occur in binary files, and are used by Xmodem-type protocols. They may also come from the remote system. An XON from the remote system, after your modem has sent an XOFF, can result in buffer overflow. Software flow control may prove satisfactory if you're only transferring text files; however, you may lose data if XON/XOFF characters occur in the data stream from other sources. To select software flow control, write the &F2 configuration template to Y1. AT &F2 &W1 Software Flow Control Precautions If you can't use hardware flow control and are doing Xmodem-type protocol or binary file transfers, select a protocol that performs error correction, and turn off the modem's error control (AT&M0). Transmit Data Flow Control (&Hn) This type of flow control regulates data your computer transmits to your modem for transmission over the phone link. The modem monitors its Transmit Data buffer as data comes in from the computer. If the buffer nears 90% capacity, the modem signals the computer to stop transmitting. When the modem has sent enough data over the phone link to empty half the buffer, the modem signals the computer to resume transmitting. When it is Required Transmit Data flow control should be enabled in the following situations. - You're using error control (any allowable rate above 300 bps), with or without data compression. If data is resent due to errors, a continuous stream of data from the computer could overflow the modem's buffer. - The serial port rate is higher than the connection rate. For example, the serial port rate is 38.4K bps and the connection rate is 14.4 Kbps. NOTE: Set your software to either hardware or software flow control. Some programs also require that you turn off the type you are not using. &H0 Transmit Data flow control disabled. &H1 Hardware flow control. Default. Your computer and software must support the Clear to Send (CTS) signal. The modem drops the Clear to Send (CTS) signal to the computer when its buffer nears 90% capacity, and starts sending CTS again when the buffer is about half full. &H2 Software flow control. Your software must support XON/XOFF signaling. The modem sends an XOFF to the terminal when its buffer nears 90% capacity, and sends an XON when the buffer is about half full. Default in the &F2Software Flow Control template. &H3 Use both hardware and software flow control. Select this option if you're not sure what your computer supports. NOTE: If possible, use hardware flow control. See Warning on Software Flow Control, earlier in this guide for details. Received Data Flow Control Two commands - &Rn (hardware) and &In (software) - control the flow of received data passed by the modem to your computer. Because computers handle incoming data more quickly than the modem receives it over the phone line, most applications won't need this. Hardware Control (&Rn) When your computer drops its Request to Send (RTS) signal, the modem stops passing along received data to the computer. The computer sends RTS again when it is ready to receive more data. Your computer and software must support RTS. You cannot use this type of flow control, however, if your software requires a constant RTS signal. NOTE: Use hardware flow control only for ARQ (error control) calls, because the V.42 and MNP protocols control the data flow across the phone link. During non-ARQ calls, however, there is no way to signal the remote modem to stop sending data. If your modem stops passing data to your computer and the remote modem keeps sending, your modem's Received Data buffer will overflow. &R0 Reserved. &R1 The modem ignores Request to Send (RTS). This setting is required if your software does not support RTS. &R2 Hardware flow control of received data enabled. Default. The modem passes received data to your computer only on receipt of the RTS signal. Software Control (&In) When you send your modem a Ctrl-S (XOFF) command from the keyboard, the modem stops passing received data to your computer. When you send a Ctrl-Q (XON) command, your modem resumes. NOTE: Because of the risk of data loss, &I15 are recommended only if your data does not have XON/XOFF control characters. See Warning on Software Flow Control for details. &I0 Disables XON/XOFF flow control of received data. Recommended for non-ARQ calls. Default. &I1 Your modem acts on your typed Ctrl-S/Ctrl-Q commands and passes them to the remote computer. Not recommended for non-ARQ calls. Use in ARQ mode only, but keep in mind that XON/XOFF characters sent to the remote computer may interfere with XON/XOFF signaling between it and the remote modem. &I2 is preferred for ARQ calls. &I2 Your modem reacts to your XON/XOFF commands, but removes them before sending data to the remote computer. This is the default in the &F2 (Software Flow Control) template. Recommended setting for ARQ mode, only. It ensures that the remote computer does not confuse its modem's XON/XOFF characters with yours. If the call is not in ARQ mode, there is no flow control on the phone link. If you send an XOFF to your modem and it stops passing data, it has no way to tell the remote computer and modem to stop sending for a while, and your modem's buffer may overflow. See &I5 for another alternative. &I3 Reserved. &I4 Reserved. &I5 Enables phone link flow control when the connection is not under error control. Both modems must use &I5. In ARQ mode, the modem operates as if set to &I2. It acts on XON/XOFF commands, but does not pass them on to the remote system. In non-ARQ mode, the modem acts as if set to &I0. It does not look for local XON/OFF commands, but does look for any XON/XOFF characters coming in over the phone link from the remote computer. The modem acts upon them and drops them from the data stream. Operators can signal the other modem to stop sending and control phone link data flow to keep their modem's buffer from overflowing, if both are set to &I5. GETTING HELP Checking the Help screens is the first step in troubleshooting. These screens give you the information you'll need to identify a problem. Once a problem is identified, it can easily be solved. INQUIRIES (In) The Inquiry command has eight options. The most commonly used options display the following information. ATI4 Current settings ATI5 NVRAM settings ATI6 Link diagnostics I0 The modem returns a product code. If you have a problem and call Technical Support, you will be asked for this product code. I1 The modem performs a checksum of its read-only memory (ROM) and returns the result to the screen. This function is used only in factory testing. The modem should always read the same number. I2 The modem performs a test of its random-access memory (RAM) and returns either the OK (0) or ERROR (4) result code, followed by OK when the test is completed. Use this command as a checkpoint if the modem appears to be malfunctioning. I3 The modem returns a product identification string. I4 The modem displays its current configuration. I5 The modem displays the stored phone numbers and two templates (Y0 and Y1) stored in nonvolatile random access memory (NVRAM). Activate the second screen by pressing any key. I6 During a connection, the modem monitors and stores information about link operations. When the call is ended, you can request a diagnostic summary. For calls under data compression, the number of characters sent may be less than the number of octets sent, due to buffering operations. Most terms used in the display are self explanatory except for the following: Octets: Compressed data units. If the number of octets is greater than the number of characters sent, the modems probably used MNP5 compression on an already compressed file, and the result was expanded data. Blers: Errors in data and protocol blocks. If there were many block errors, your modem may have experienced problems receiving data from the line. Blocks Resent: These represent blocks the remote modem resent due to the previous category, Blers. Link Timeouts: Protocol detection problems; communications were severed momentarily and the modems probably recovered. This does not indicate the retry timeout. Link Naks: Negative acknowledgments (one or more blocks). Data Compression: Indicates the type of data compression negotiated for the call (V42BIS or MNP5) or NONE. A V42BIS response includes the size of the dictionary and the maximum string length used, for example, 2048/32. Fallback: Enabled/Disabled: indicates whether the modems negotiated online fallback during the connection sequence. Protocol: Indicates the error control protocol negotiated (LAPM, MNP, NONE). Speed: The last rates at which the receiver/transmitter were operating before disconnecting. Disconnect Reason: Possible reasons the modem hung up are as follows: -DTR dropped - The DTE dropped the Data Terminal Ready signal, terminating the call. -Escape code - You sent the modem the +++ escape code. -Loss of carrier - The modem detected loss of the remote modem's carrier and waited the duration specified in Register S10 (default is 0.7 seconds). Inactivity timeout—The modem detected no activity on the line for the duration specified in Register S19 (default is 0, timer disabled). -MNP incompatibility - The modem is set to &M5 and the remote modem does not have MNP compatibility, or there was an MNP negotiation procedure error. -Retransmit limit - The modems reached the maximum of 12 attempts to transfer a data frame without error. -LD received - The remote modem sent an MNP error control link disconnect request. -DISC - The remote modem sent a V.42 disconnect frame. -Loop loss disconnect - The modem detected a loss of current on the loop connecting it with the telephone company central office. This usually occurs because the remote modem has hung up. The central office drops current momentarily when there is a disconnect at the other end of a call. Unless Register S38 is set higher than 0, the modem immediately hangs up at loop loss. -Unable to retrain - After several attempts, disturbances on the phone line prevented the modems from retraining (resynchronizing), and they could no longer transmit or receive data. -Invalid speed - The modem is set to &N1 or higher, for a fixed link rate, and the remote modem is not operating at the same rate. -XID timeout - The modems failed to negotiate the V.42 detection (XID exchange) phase. -SABME (Set asynchronous balance mode extended) timeout - The modems failed this part of V.42 link negotiation. -Break timeout - Incompatible processing of a Break signal occurred. -Invalid codeword- The modem received an invalid V.42 bis (compression) frame. -A rootless tree - The modem received an invalid V.42 bis (compression) frame. -Illegal command code - The modem received an invalid V.42 bis (compression) frame. -Extra stepup - The modem received an invalid V.42 bis (compression) frame. I7 The modem returns a product configuration. If you have a problem and call Technical Support, you may be asked to read this screen. S-REGISTER QUERY (Sr?) This command allows you to view the contents of a particular S-register, as in the following example that requests the contents of Register S0 ("On what ring will the modem answer?"). ATS0? STORED PHONE NUMBER QUERY (&Zn?) Use this command to display the phone number stored in NVRAM at position n, as in the following example that includes a sample modem response. AT&Z3? 5551234 LAST-DIALED NUMBER QUERY (DL?) Use this command to display the number stored in the last-dialed number buffer. ATDL? HELP SCREENS Your modem provides four Help screens: summaries of the basic AT command set, extended ampersand (&) AT command set, Dial command options, and S-register functions. Stop/Restart Display The following command stops the display. Hold down the Control key and type S. S To restart the display, use the same command or press . Cancel Display Either of the following commands cancels the display. C K Basic Command Set Help ($) Use AT$ to display a partial summary of the command set. A second screen, activated by pressing any key, shows the remaining commands. Ampersand Command Set Help (&$) Use AT&$ to display a partial summary of the extended ampersand command set. A second screen, activated by pressing any key, shows the remaining command set. Dialing Help (D$) Use ATD$, to display the Dial command summary. S-register Functions Help (S$) Use ATS$, to display a partial summary of the S-register functions. A second screen, activated by pressing any key, shows the remaining registers. TESTING THE MODEM Modem testing is available with the &Tn command and register S16 (Dial test). All loopback testing conforms to ITU-T Recommendation V.54. NOTE: Only one test can be performed at a given time. If you send a test command while the modem is already in Test mode, you'll receive an ERROR message. TESTING WITH &Tn The tests supported through the &Tn command include analog loopback, digital loopback, and remote digital loopback. You can key in your own data during testing, or use the modem's internal test pattern and error detector. Always disable error control before testing. If the modem is detecting errors and, as a result, retransmitting the affected data, your test results will be invalid. Ending a Test - &T0, S18 Issue the &T0 command to terminate a test. Alternatively, set Register S18 to a specified number of seconds, for example, S18=10. When the 10 seconds are up, the modem automatically ends the test and returns to Command mode. If the test was Analog Loopback, the &T0 command hangs the modem up. If the test was Digital or Remote Digital Loopback, issue an ATH command to hang up the modem, or an ATZ command to hang up the modem and reset it to its defaults. NOTE: If you use the S18 test timer, but in the process of testing you issue an ATZ command, S18 resets to zero and the timer is disabled. Also, you cannot store a value for S18 in nonvolatile memory; its power-on and reset default is always zero. Analog Loopback - &T1, &T8 This test checks the operation of the modem's transmitter and receiver. &T1 Command This analog loopback option requires that you type data you can later verify at your screen. 1. The modem should be on hook in Command mode. If you wish, set Register S18 as a test timer. For example, insert S18=10 in the following command string before &T1. AT &M0 S18=10 &T1 This command instructs the modem to disable error control, set the timer, enter analog loopback (AL) mode, and send a CONNECT message. 2. Type recognizable data so that you can verify it when it is looped back to the screen. 3. End the test. If you set S18, the modem automatically stops the test at the timeout, exits AL mode, and responds OK. If you didn't set Register S18, wait one second and type +++ to end the test and return the modem to Command mode. When the modem responds OK, type AT&T0 to terminate AL mode and hang up the modem. (Typing ATH has the same effect. Typing ATZ also has the same effect, but also resets the modem and restores your &M Default.) The modem responds OK. If the modem sends an ERROR message, you have issued an invalid command. 4. If there were no errors, reset the modem to &M4 (enables error control) unless you've issued the ATZ reset command. NOTE: If the modem is in Online-Command modethat is, still connected to a remote modemand you send it an &T1 or &T8 command, it drops the call, enters AL mode, sends a CONNECT result and waits for loopback characters.&T8 CommandThis analog loopback(AL) option causes the modem to send an internal test pattern to its transmitter and loop it back to the receiver. An internal error detector counts any errors and, when the test is ended, sends the number of errors or 000 (no errors) to the screen. Since you don't type anything during this test, and the modem does not send anything to the screen, this option verifies only the modem. If there are no errors but your problem continues, it may be at the computer interface. 1. The modem should be on hook in Command mode. If you wish, set Register S18 as a test timer. For example, insert S18=10 in the following command string before &T8. AT &M0 S18=10 &T8 This command instructs the modem to disable error control, set the timer, and enter AL mode. The modem sends its internal test pattern to the transmitter, and loops the pattern back to the receiver. You will not see any data on your screen. 2. End the test. If you set S18, the modem automatically stops the test at the timeout. If you didn't set Register S18, type AT&T0 to end the test. Or use ATH or the command that resets the modem, ATZ. Both of the latter end the test and hang up the modem. When the modem hangs up, it returns a three-digit code, followed by OK. A code of 000 indicates no errors were found. A code of 255 indicates 255 or more errors. An ERROR message indicates that you issued an invalid command. 3. If there were no errors, reset the modem to &M4 (enables error control) unless you issued the ATZ command. Digital Loopback - &T3 Command If your modem has passed the analog loopback (AL) test, the digital loopback test can help you locate a problem with a remote modem or the telephone channel. 1. Set the modem to &M0 to disable error control. Establish a connection with the remote modem. 2. Bring the modem back to Online-Command mode with the +++ escape code. Then send it the AT&T3 command. The modem enters digital loopback (DL) mode. 3. The remote user should type a short message. It will be looped back by your modem for verification on the remote screen. You will not see the message or any other data. 4. When the remote user has completed the test, issue the AT&T0 command to end the test. If you wish, return the modem online (ATO) to resume Data mode. Or type either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. The modem responds OK. If the modem sends an ERROR message, you have issued an invalid command. &T4, &T5 Commands The &T4 option grants a remote modem's request for a Remote Digital Loopback test. The &T5 option cancels &T4 and your modem will not recognize a request for a Remote Digital Loopback test from a remote modem. This is the default so that your modem isn't subject to another user calling and tying up your modem without your permission. Remote Digital Loopback - &T6, &T7 Commands This test, like the Local Digital Loopback test, verifies the condition of both modems and the phone link. The request for and granting of Remote Digital Loopback testing requires that both modems use ITU-T V.54 standard signaling. The test must be performed at 2400 or 1200 bps. If the remote modem does not have the capability or is not set to respond, you will get an ERROR result code. &T6 Command This remote digital loopback (RDL) option requires that you send keyboard data to the modem and verify it when it is returned over the phone lines and to your screen. 1. Set your software to 2400 or 1200 bps. Set the modem to &M0 (disables error control). If you wish, set the S18 timer. Establish a connection with the remote modem. If you haven't already done so, arrange with the remote user to cooperate with your testing. The remote user should set his or her modem to acknowledge the RDL request, for example, AT&T4. 2. Bring the modem back to Online-Command mode with the +++ escape code. Send the modem the AT&T6 command. The modem enters RDL mode. 3. Type a short message. It will be looped back to your modem by the remote modem and to your screen for verification. (The remote user will not see your data.) 4. End the test. If you set Register S18, the modem automatically ends the test when the test timeout is reached. If you didn't set S18, type AT&T0 to end the test. If you wish, return the modem online (ATO) to resume Data mode. Or send either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. The modem responds OK. If you issue an invalid command, the modem sends an ERROR message. Data errors indicate a problem with the remote modem or the phone link. If you have not performed analog loopback testing with your modem, the problem may also lie with your modem. 5. Reset the modem to &M4 (enables error control) unless you used the reset command, ATZ. &T7 Command This test option causes the modem to send an internal test pattern through the remote digital loopback path. An internal error detector counts any errors and, when the test is ended, sends the number of errors or 000 (no errors) to the screen. You don't need to type anything during this test. The modem sends only its final error count to your screen. 1. Set your software to 2400 or 1200 bps. Set the modem to &M0 (disables error control). If you wish, set the S18 timer. Establish a connection with the remote modem. If you haven't already done so, arrange with the remote user to cooperate with your testing. The remote user should set his or her modem to acknowledge the RDL request, for example, AT&T4. 2. Bring the modem back to Online-Command mode with the +++ escape code. Then send it the AT&T7 command. The modem enters RDL mode. The modem sends its internal test pattern to the remote modem, which loops it back to your modem. You will not see the data on your screen. 3. End the test. If you set S18, the modem automatically stops the test when the timer times out. If you didn't set Register S18, type AT&T0 to end the test. After you view the test results (next paragraph), return the modem online if you wish (ATO) and resume Data mode. Or send either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. When you terminate the test, the modem returns a three-digit code, followed by OK. A code of 000 indicates no errors were found. A code of 255 indicates 255 or more errors. If you issue an invalid command, the modem sends an ERROR message. If you've performed an analog loopback and know your modem is working properly, errors indicate a problem with either the phone connection or the remote modem. 4. Reset the modem to &M4 (enables error control) unless you've sent it the ATZ reset command. DIAL TEST - S16=2 The dial test is used for factory-testing the frequencies of tone dialing values. When S-register 16 is set to 2 and a single tone is dialed (for example, ATD7 ), the modem continues to transmit that tone until you press again. OTHER OPERATIONS FAX OPERATIONS Fax modem Guidelines Fax operations require facsimile-compatible software that can send or receive Group III faxes. To send or receive faxes, follow the instructions in your fax software manual. The modem's normal operating mode is data mode. If your fax software is typical, it automatically switches the modem to fax mode when you run the program, and resets the modem to data mode when you exit the program. If you have a problem, however, and think the modem may be in the wrong mode, you can use one of the following AT commands to manually switch the modem. Most users will never need to use these commands. AT+FCLASS=0 (Switch to data mode) AT+FCLASS=1 (Switch to Class 1 fax mode) AT+FCLASS=2.0 (Switch to Class 2.0 fax mode) If you are not sure whether the modem is in data or fax mode, type the following command. AT+FCLASS? The modem returns a 0 to indicate data mode, a 1 to indicate Class 1 fax mode or a 2.0 to indicate Class 2.0 fax Class mode. Your Digital SVD modem is not compliant with TR-29 (SSP-2388-A) Class 2 facsimilie control. NOTE: Whenever you reset the fax modem by using the ATZ command, toggling the DTR signal, or turning the power off and on, the modem will be set to data mode. Fax Mode Flow Control Setting Many facsimile software products use software flow control when the modem is in fax mode. To be compatible with software products that use software flow control by default, your Digital SVD modem switches to software flow control when entering fax mode. For the best information on modem settings, see your fax software manual. FCC Notice FCC part 68, rules regarding fax operation, has been amended as follows: Telephone facsimile machines - identification of the sender of the message: It shall be unlawful for any person within the United States to use a computer or other electronic device to send any message via a telephone facsimile machine unless such a message clearly contains, in a margin at the top or bottom of each transmitted page or on the first page of the transmission, the date and time it is sent and an identification of the business, other entity, or individual sending the message and the telephone number of the sending machine or of such business, other entity, or individual. Telephone facsimile machines manufactured on and after December 20, 1992 must clearly mark such identifying information on each transmitted page. A Note to Programmers If you want to know more about the supported fax commands, refer to the standard for the Service Class 1 fax protocol. ANSI/EIA/TIA-578-1990 (EIA-578) Asynchronous Facsimile DCE Control Standard November, 1990 Approved: October 22, 1990 You can obtain a copy of this standard by contacting Global Engineering Documents, at 1-800-854-7179. For more information on supported Class 2.0 fax commands, refer to the standard for the Service Class 2.0 fax protocol. ANSI/EIA/TIA-592-1993 (EIA-592) Asynchronous Facsimile DCE Control Standard May, 1993 TECHNICAL SPECIFICATIONS COMPATIBILITY Your Digital SVD modem conforms to the following standards, ensuring compatibility with a wide base of installed modems. The ITU-T (formerly CCITT) is an international standards body. Digital SVD Market-based standard developed by Intel, U.S. Robotics, Rockwell, Hayes, and Creative Labs. for sharing voice and data simultaneously over a single telephone line. V.34 28.8K/26.4K/24K/21.6K/19.2K/16.8K/14.4K/12K/9600/ 7200/4800 /2400 bps V.Fast Class 28.8K/26.4K/24K/21.6K/19.2K/16.8K bps (V.FC/V.34 only) ITU-T V.32 bis 14.4K/12K/9600/7200/4800 bps ITU-T V.32 9600/4800 bps ITU-T V.22 bis 2400 bps ITU-T V.22 1200 bps Bell 212A 1200 bps (also ITU-T V.22) ITU-T V.23 1200 bps with 75 bps back channel (some United Kingdom and European phone systems) Bell 103 300 bps (ITU-T V.21 optional) ITU-T V.42 LAPM error control, 1200 bps and higher ITU-T V.42 bis Data compression, 1200 bps and higher MNP levels 2, 3 and 4 error control, level 5 data compression, 1200 bps and higher ITU-T V.54 Analog, digital, and remote digital loopback testing FAX MODEMS EIA/TIA-592 Service Class 2.0 Asynchronous Facsimile DCE Control Standard EIA/TIA-578 Service Class 1 Asynchronous Facsimile DCE Control Standard ITU-T V.17 14.4K/12K bps ITU-T V.29 9600/7200 bps ITU-T V.27 ter 4800/2400 bps ITU-T V.21 300 bps DEFAULT SETTINGS Data Format Both your software and the remote system must use the same 10-bit data format. If you don't know the setup of the remote computer's modem, phone ahead to find out what combination of word length, parity, and Stop bit is required. Set your communications software to the required scheme. Some communications programs use a kind of shorthand for word length, parity, and stop bit setting, such as 7-E-1 or 8-N-1. Your modem detects the format you are using when you send an AT command from your computer to the modem. Allowable Data Formats Word Parity Stop Length (1 Bit) Bits 7 Even, Odd, 1 Mark, Space 7 None 2 8 None 1 Template Settings You can create one or two customized configurations and store one of them at a time in nonvolatile random-access memory (NVRAM) to use as your power-on/reset default using the &Wn command. To view your NVRAM settings, use the I5 command. Your modem is preconfigured in the factory for the &F1 (hardware flow control) template settings in NVRAM as Y0, and the &F2 (software flow control) template settings in NVRAM as Y1. The following tables list the settings of the permanent configuration templates &F1 (default), &F2, and &F0, as well as parameters you can modify and store in the NVRAM configuration templates. &F1Hardware Flow Control Template Factory Default Feature &F1 Settings ITU-T/Bell Answer Sequence B0 ITU-T sequence Online Echo F1 Online Echo OFF Volume Control (internal) L2 Medium volume Speaker Control M1 Speaker ON until CONNECT Pulse/Tone Dialing P Pulse Dialing Result Code Options X4 All Result codes ARQ Result Codes &A3 All protocol codes enabled Serial port Rate &B1 Fixed serial port rate Guard Tone &G0 No guard tone Transmit Data Flow Control &H1 Hardware flow control Received Data Software Flow Control &I0 Disabled Data Compression &K1 Auto enable/disable Error Control &M4 Auto select Connection Rate &N0 Variable connection rate Make/Break Ratio &P0 U.S./Canada ratio Received Data Hardware Flow Control &R2 Enabled Data Set Ready (DSR) &S0 DSR always on Modem Testing &T5 Deny remote digital loopback Break Handling &Y1 Break clears buffer; break then goes to remote modem The following parameters are changed via your communications software: Word Length 8 bits* Parity None* Serial port Rate 38.4 Kbps* * Initial Settings; match software settings of subsequent &W commands. The &F2 and &F0 templates differ from the &F1 template for only a few commands. The tables below list only those settings that differ from the &F1 template. &F2Software Flow Control Template Feature &F2 Setting Transmit Data Flow Control &H2 Transmit data software flow control Receive Data Flow Control &R1 Received data hardware flow control disabled &I2 Received data software flow control enabled &F0 - Low Performance Template Feature &F0 Settings Result Code Options X1 Basic subset ARQ Result Codes &A1 ARQ codes enabled Serial port Rate &B0 Variable serial port rate Transmit Data Flow Control &H0 Disabled Receive Data Flow Control &R1 Disabled The following parameters are changed via your communications software: Word Length 7 bits* Parity Even* Serial port Rate 9600 bps* * Initial Settings; match software settings of subsequent &W commands. NVRAM S-register Options NVRAM S-register Options Factory Setting S0* Number of rings to answer on 0 S2 Escape code character 43 S3 Carriage return character 13 S4 Line feed character 10 S5 Backspace character 8 S6 Dial wait-time, sec. 2 S7 Carrier wait-time, sec. 60 S8 Dial pause, sec. 2 S9 Carrier detect time, 1/10th sec. 6 S10 Carrier loss wait-time, 1/10th sec. 7 S11 Tone duration, spacing, msec. 70 S12 Escape code guard time, 1/50th sec. 50 S13 Bit-mapped functions 0 S14 Bit-mapped functions 0 S15 Bit-mapped functions 0 S19 Inactivity/hang up timer, min. 0 S21 Break length, 1/100th msec. 10 S22 XON character 17 S23 XOFF character 19 S25 DTR recognition time, 1/100th sec. 5 S27 Bit-mapped functions 0 S28 V.21/V.23 fallback delay, 1/10th msec.8 S34 Bit-mapped functions 0 S38 Disconnect wait time, sec. 0 S51 Bit-mapped functions 0 S54 Bit-mapped functions 0 S55 Bit-mapped functions 0 S56 Bit-mapped functions 0 NOTE: Bit-mapped registers have up to eight functions. See instructions for register S13 in Chapter 5 of the Modem Installation and User's Guide. * The valid range of rings that can be stored in NVRAM for S0 is 1 - 255. S0=0 cannot be stored in NVRAM. MODEM CONCEPTS HOW MODEMS WORK The word "modem" derives from the words "modulation" and "demodulation". A modem modulates (converts) digital data (computer information) to analog data (fluctuations in tones carried over a copper telephone wire). The information is carried over a telephone network until it reaches its destination, where another modem demodulates the analog signals and converts them back to digital data so the computer there can use the information. This ability to use the telephone network for quick, inexpensive data exchange makes a modem a powerful tool that can be used by businesses and individuals worldwide to expand business and personal networks. MODEM CONNECTIONS Modems come in all shapes and sizes and their ability to communicate is based on the protocols they use (the rules they follow) to perform operations in identical ways. They may be preset or reset logically (using communications software) to best communicate with the modem they are transferring information to and receiving information from. When the modems initially contact each other, the calling modem contacts the answering modem and introduces itself. The modems communicate via a series of signals to identify the appropriate protocol and speed for efficient data transfer. The answering modem either accepts the call or rejects the call. This transaction is called a handshake. Successful handshaking results in a carrier signal. When modems establish a carrier signal, your modem sends a Carrier Detect signal to your computer, indicating that the modems are ready to transfer data. If they fail to connect, your modem sends your computer a No Carrier message. LINE TRAVEL Poor telephone line quality may cause a decrease in efficient data transmission. In order to ensure the data sent and received is reliable, error control was introduced by modem manufacturers. The modems check each data block received, and if something went wrong between locations, the receiving device instructs the sending device to resend the affected block. Modems send information at different rates, measured in bits per second (bps). Today, the figures can be staggering. In the most optimal situation, your Digital SVD modem can exchange data as fast as 115,200 bps in data only mode. In most cases, though, the speed relies heavily on the ability of the modem to adapt to line conditions at high speed. This adaptability is the most important feature of your modem. DIGITAL DATA The smallest data unit modems send is made up of a defined word length (7 or 8 bits each), a start bit (a 0 that indicates where the data unit begins), and one or two stop bits. FLOW CONTROL Another important aspect of modem communications is flow control, which manages the amount of data stored in buffers (temporary memory locations). Buffers are used to store information before it is passed on to a computer or modem. Flow control is used to prevent buffer overflow. The system uses either hardware or software (using control characters) flow control. We recommend the use of hardware flow control, because actual data may be mistaken for the control characters used in software flow control and the data may be distorted. ERROR CONTROL Error control protects the integrity of data transferred over phone channels and is available for calls at 1200 bps and above. It can be disabled, although high-speed calls (above 2400 bps) should always be made using error control. The operations defined in an error control protocol include the following. - Establishment of compatibility. - Data formatting into blocks. - Error detection through Cyclic Redundancy Checking (CRC). CRC is based on algorithms that calculate a value for an entire block of data. The CRC value attached to each block sent must match the receiving modem's calculation. If not, the remote modem sends a negative acknowledgment to the sending modem. - Positive acknowledgment of error-free blocks and negative acknowledgment of corrupted data blocks. - Retransmission of corrupted data blocks. Always set your Digital SVD modem for error control, &M4 (by default) or &M5, for calls at speeds over 2400 bps. Most users communicating with V.42- or MNP-compatible modems will want error control at 2400 and 1200 bps, as well. Your Digital SVD modem is set at the factory to &M4, causing it to try for an error control connection and, if that isn't possible, to proceed with the call in Normal mode. The modem first tries for a V.42 connection, then an MNP connection. The information below assumes a modem setting of &M4. ITU-T V.42 Handshaking The exchange of signals between two devices in order to establish a communications link is called handshaking. ITU-T V.42 includes a two-stage handshaking process. - A detection phase that is based on an exchange of predefined characters. - LAPM (Link Access Procedures for modems) Negotiation. In this phase, the modems identify their capabilities concerning maximum data-block size and the number of outstanding data blocks allowed before an acknowledgment is required. MNP Handshaking This protocol is supported by the ITU-T V.42 recommendation. It was originally developed by Microcom, Inc., and is now in the public domain. MNP handshaking begins with an MNP link request sent by the calling modem. If the remote modem doesn't recognize the request, error control isn't possible. Data Compression If the modems successfully establish a V.42 connection, they also negotiate for the associated V.42 bis data compression. If a V.42 connection is not established, but an MNP connection is established, they negotiate for MNP5 data compression. Modems using V.42 bis compression negotiate the following options. - Dictionary size - the amount of memory available for compression table entries. (Entries in the table are codes devised for redundant data. The data is packed into shorter data units, called code words, and unpacked by the receiving modem.) Possible sizes are as follows. Your Digital SVD modem uses 11-bit, or 2048-entry dictionaries, but drops down if the remote modem uses a 512- or 1024-entry dictionary. Bits Entries 9 512 10 1024 11 2048 - Maximum string length of each entry. As the dictionary fills, the modem deletes the oldest, unused strings. V.42 bis compression is more efficient than MNP5 compression, in part because it dynamically deletes unusable strings. In addition, it works better with files that are already compressed. These include .ZIP files downloaded from many Bulletin Boards and 8-bit binary files, which appear to the modem to be compressed. MNP5 compression should not be used with such files because it adds data to them, which lessens throughput. (The additional data is stripped when the file is decompressed by the remote modem.) When transferring such files, it's best to set the modem to &K3. This allows V.42 bis compression to work dynamically with the compressed data, but disables MNP5. Flow Control Flow control of data from the computer is required when modems use error control for two reasons. 1. The transmitting modem stores a copy of each frame it transmits to the remote end until it is acknowledged by the receiving modem. 2. If errors are encountered, the transmitting modem must resend the corrupted data. This retransmission activity, combined with the steady stream of data from the computer, can overflow the buffer. Online Fallback/Fall Forward Under error control, if a disturbance on the phone line causes an error to a data block, the receiving modem replies with a negative acknowledgment. In response, the transmitting modem retrieves a copy of the original data block from its transmit buffer, and every block it sent after that block, and retransmits them. This keeps the data error-free and in sequence. However, there is a retransmission limit: the modems hang up if line disturbances are so severe that one of the modems has retransmitted the same block of data twelve times without a positive acknowledgment. Because high-rate calls are more vulnerable than transmissions at 2400 bps and below, V.34 modems (such as your 28.8 Digital SVD modem) risk reaching the retransmit limit and hanging up. To prevent this, one of the modems requests that they fall back to a slower rate if necessary. When line conditions improve, the modems fall forward to the next higher rate, up to the original connection rate of the call. THROUGHPUT GUIDELINES The following guidelines should help you to make the most of your modem's advanced performance features. In many instances, experimentation and experience will indicate what works best for your applications. Throughput is the volume of user information transferred per second, without Start and Stop bits and other overhead information. You'll obtain optimal throughput under the following conditions. 1. Your communications software supports a fixed serial port rate (between your modem and the computer) higher than the connection rate (between the two connecting modems). An example of this would be setting your software to lock into the 38.4 Kbps rate, and retaining the default &B1 setting. 2. The call uses data compression. 3. You're transmitting text files. Throughput is higher for text files than other types of files, such as .EXE or .COM binary files. 4. File transfer may be slowed down by a file-transfer protocol. Many non-text files require a file-transfer protocol, but throughput results vary. For example, certain public domain file-transfer protocols have the following effects. Kermit Newer versions of Kermit support packets up to 9 Kbps and a sliding window design to eliminate turnaround delay. With earlier versions, however, throughput may be severely reduced due to short block lengths (possibly under 128 bytes) and acknowledgment turnaround time. Xmodem Throughput may be reduced if your version uses short block lengths, for example 128 bytes. Some versions use blocks of 1K byte, which is much better, although overhead (error control protocol information) still affects overall throughput. Ymodem This protocol is similar to Xmodem with 1K byte block lengths, and allows multiple files to be sent in one transfer. The above protocols further reduce throughput during error control (ARQ) connections. The accuracy of the data is checked twice, by the file-transfer protocol and by the modem. To avoid redundancy, disable modem error control by setting the modem to &M0. The most current version of Zmodem can yield the most efficiency. Leave the modem at its error control default (&M4) and data compression default, &K1. Zmodem performs the same kind of compression as V.42 bis; it turns off its compression if files are already compressed. An alternative protocol is Ymodem-G, with the modem left at its error control default, &M4. Ymodem-G assumes the modems are using error control. Overhead is minimal, with throughput almost equal to that obtained with no file-transfer protocol. However, keep in mind that Ymodem-G is only useful if the modems are using error control. In addition, follow this recommendation only if your machine and software are set to hardware flow control. NOTE: Both modems must use the same protocol for data transfer to take place. WARNING: If you are using an X-, Y- or Zmodem-type protocol, do not use the modem's software flow control. Achievable Throughput Statistics The table below indicates the maximum throughput, in characters per second (cps), that can be expected under the following conditions: - Serial port rate set at 115.2 Kbps; modem set to &B1 (Your software and computer must support 57.6 Kbps in order to use that rate.) - Connection (link) rate of 28.8 Kbps (assuming no protective fallback to a lower speed is necessary) - V.42 bis compression negotiated for the call, and the default size 11-bit, 2048-entry dictionary - Straight data (that is, not already compressed, and no file-transfer protocol) - Transmission from a fast (386, 486 or Pentium) computer Maximum Throughput (cps) if set to 14.4 Kbps File Type MNP5 V.42 bis Assembler or Compiler listing 2880 3840 Text file 2325-2625 3400-5760 Binary file: .EXE 2175-2400 2030-2600 Binary file: .COM 2100-2250 2050-2300 .ZIP files (common on BBS's)* 1500-1650 1700 Random binary 8-bit* 1460-1575 1700 * These files are already compressed or appear to the modem to be compressed. Additional MNP5 compression causes throughput lower than what can be expected using MNP without compression. We recommend setting the modem to &K3 when transferring these files, to allow V.42 bis but disable MNP5. The following table indicates the maximum throughput, in characters per second (cps), that can normally be expected in the same conditions as the previous table, but with a serial port rate of 38.4K bps. Maximum Throughput (cps) if set to 14.4 Kbps File Type MNP5 V.42 bis Assembler or Compiler listing 2880 3840 Text file 2325-2625 3400-3840 Binary file: .EXE 2175-2400 2030-2600 Binary file: .COM 2100-2250 2050-2300 .ZIP files (common on BBS's)* 1500-1650 1700 Random binary 8-bit* 1460-1575 1700