Historia del Conjunto de Comandos AT A comienzos de los 80s, una compañía llamada Hayes dio inicio a la fabricación de su módem (modulador-demodulador) Hayes Smartmodem 1200. Este era un módem de 1200 baudios por segundo. Al muy poco tiempo se comenzó a comercializar una nueva tecnología: la de los módems de 2400 baudios. Estos ofrecían el doble de velocidad, y la demanda por el último modelo de Hayes se evaporó de la noche a la mañana. No era para menos: los nuevos aparatos reducían a la mitad el tiempo de conexión telefónica (y su costo). Si querían siendo relevantes en la industria, Hayes debia completar de apuro un nuevo modelo. Los tiempos productivos requeridos no alcanzaban para proponer un nuevo producto que superase una tecnología ya dominada por su competencia. Esto obligó incluso a Hayes a dejar de lado cualquier tipo de consideración para hacer cambios fundamentales o embellecer al nuevo diseño. Se decantaron por a un producto igual al que tenían, pero que fuese capaz de ofrecer el doble de velocidad, y que pudiesen industrializarlo inmediatamente bajo el nombre de Smartmodem 2400. De esta forma y sin advertirlo Hayes terminó creando la nueva tendencia de estandarización en módems, una que - increíblemente - que continúa hasta el día de hoy. Podríamos decir que la afirmación de que dichos módems eran "inteligentes" como afirmaba su marca comercial, es estirar un poco a la realidad... incluso si los comparamos con los módems de aquel entonces. Lo usual por entonces era que el usuario cumpliese un papel ineludible para establecer el enlace de comunicación. Debía usar un aparato de teléfono conectado a la extensión de línea, discar el número deseado y oír la portadora de respuesta del módem remoto, para luego presionar un botón "Comienzar", y luego colgar el tubo. Sólo entonces se podía estableecer la conexión de datos. Este proceso de discado manual era bastante común en los módems concebidos para ser utilizados con las líneas telefónicas del sistema público conmutado (PSTN) de comienzos de la década de 1980. Los módems con autodiscado eran bastante raros, esta la capacidad discar números telefónicos solía ofrecerse sólo como una opción a costo extra. Por ejemplo, el módem Radio Shack DC-1200 de 1200 baudios por segundo (un módem Ventel de 1983) costaba la friolera de U$S 699 de la época, y su módulo opcional de autodiscado (que sólo podía efectuar el más antiguo marcado por pulsos en lugar de los más modernos marcado por tonos) requería desembolsar unos unos U$S 150 adicionales. Incluso una tarea común como podía ser colgar la llamada requería que el usuario pasara el módem en estado de espera ("hold") y colgara la línea, o bien apagara el módem. Los Smartmodem 1200 y 2400 - por lo pronto - ya eran capaces de discar por sí mismos. Estaban provistos de un altavoz interno, ya que se consideró realmente necesario oir los tonos de discado. Aún así, tanto el Smartmodem 1200 como el Smartmodem 2400 eran realmente incapaces de reconocer un tono de línea ocupada o bien detectar la presencia del tono de discado, ni tampoco contaban con ninguna de las docenas de otras características consideradas estándares en los módems producidos desde finales de los 80s. Estos Smartmodems Hayes incluía varias características especiales (capacidad nativa de transmitir código morse, trabajar como radioteletipos, y operar con repetidores de radio amateur). Sin embargo, estas funcionalidades de nicho no generaron interés para la mayoría de los usuarios, y terminarían desapareciendo en años posteriores, Lo que terminó haciendo realmente únicos al Smartmodem Hayes 1200 y al 2400 fue la introducción - por vez primera - de la noción que un fabricante concibiera producir dos modelos diferentes de módems para el POTS/PSTN que hicieran uso del mismo conjunto de comandos de operación. Esto significó que cualquier programa de software que entendía cómo hacer que un Smartmodem 1200 discara un número telefónico, pudiese funcionar también con el Smartmodem 2400 sin que tuviese que modificarse. Como se ha mencionado, esto sucedió más por necesidad y accidente que por intencionalidad de diseño para poder afrontar la velocidad de 2400 baudios por segundo que demandaban los usuarios. En ese momento, había muy pocos servicios telemáticos en el mundo, y Compuserve era un exponente mayor, por mucha diferencia. Toda vez que un fabricante sacaba un nuevo módem al ruedo, sus compradores solían tener que aguardar hasta varios meses para que los programadores de las aplicaciones de software pudiesen escribir un controlador específico que les permitiese compatibilizar cada nuevo modelo de módem con algunas determinadas marcas o modelos de computadora, y ésta fuese capaz de conectarse a Compuserve. Por tal motivo, para el momento en que el Smartmodem 2400 salió al mercado, ya existía un controlador operativo para el Smartmodem 2400: se trataba del controlador para el Smartmodem 1200, que ya estaba disponible - y para muchas plataformas de computadoras - desde hacía tiempo. Aquel quien compró al nuevo Smartmodem 2400 no se vio en la necesidad de aguardar la preparación de un nuevo controlador; podía utilizar aquél que ya estaba hecho para el Smartmodem 1200. El soporte especial que había que dar al Smartmodem 2400 no iba más allá de agregar a la documentación una nota que explicara que el Smartmodem 2400 funcionaba también usando el controlador del Smartmodem 1200. Los demás fabricantes de módems entendieron rápidamente la ventaja de hacer nuevos modelos de módems que compartieran el mismo conjunto de comandos similares a modelos ya existentes, algo que pocos vendedores se habían molestado en hacer. Incluso había diseñadores de módems individuales que habían tendido a desarrollar rutinariamente conjuntos de comandos completamente nuevos y diferentes para cada modelo sucesivos de módems que creaban. El Smartmodem 1200 y 2400 cesaron esta práctica industrial, y en meros seis meses, ya eran varios los fabricantes que ofrecían conjuntos de comandos "compatibles con Hayes" como una opción, o como la única opción de sus respectivos módems. Hayes disputó en las cortes con estas compañías por usar la marca "Hayes" en su literatura de producto y empaque, de forma tal que el resto de los fabricantes se vieron en la necesidad de describir colectivamente a sus módems como "Compatibles con el Conjunto de Comandos AT", y continuaron imitando el conjunto de comandos Hayes. Ya para 1986 prácticamente habñian desaparecido los módems de consumo que no contaran - al menos - un modo emulado del conjunto de comandos AT. Años después, la TIA/EIA introdujo un estándar formal títulado "Data Transmission Systems and Equipment - Serial Asynchronous Automatic Dialing and Control" (Sistemas y Equipamiento de Transmisión de Datos, Discado Automático Asíncrono Serial), también conocido como TIA/EIA-602. El estándar TIA/EIA-602 era casi idéntico a los comandos de datos específicos que se podían encontrar en los Smartmodems 1200 y 2400 originales. Naturalmente, para el momento en que el estándar TIA/EIAA-602 comenzó a aplicarse, los fabricantes de la industria ya comercializaban módems con corrección de errores, compresión y velocidades mucho mayores. Ninguna de esas nuevas capacidades (o los comandos que hacían falta para controlarlas) estaban contempladas en el estándar TIA/IAE-602 (si bien otros estándares o borradores de estándares ya existían tanto para los comandos específicos requeridos para operaciones de Fax en los módems que los soportaban, así como comandos específicos para operaciones de voz). Para cumplimentar con estas nuevas características de los módems, muchos fabricantes eligieron copiar las extensiones del conjunto de comandos Hayes original ya existentes - las cuales se habñian integrado al modelo Hayes Ultra de 14.400 baudios. Estas extensiones eran mayormente una creación de Rockwell, quien por entonces era la principal proveedora de microchips para Hayes por entonces. Aún así, no todos los fabricantes de chipsets para módems siguieron la práctica de utilizar los comandos extendidos del Ultra al pie de la letra. Esto terminó provocando ciertas incompatibilidades que se mantivieron largos años sin resolver al intentar usar los comandos Hayes más sofisticados. Estas incompatibilidades suelen salir aún a superficie cuando el fabricante de chipset no es Rockwell o un licenciatario del código fuente para módems de Rockwell. Aún así, varios licenciatarios terminaron alterando el código distribuído por Rockwell, e incluso en algunos casos Rockwell misma terminó introduciendo incompatibilidades por sí misma. ========== Hayes AT Commands ============== AT or at always precedes a command. The modem needs these two letters to adjust itself to the settings of the PC’s comport. The modem then switches automatically to the defined baud rate and parity, until the next command is issued or the modem is turned off. The modem will not respond to any commands not preceded by an AT. The modem recognises following formats : 1 or 0 start bits, 7 or 8 data bits, no, odd or even parity and 1 or 2 stop bits. The commands can be issued at a rate between 300 and 115,000bps. In V.23 mode, the commands are sent at 1,200bps. The modem’s replies are then sent at 75bps to the PC. The command interpreter recognizes AT and at, but not At or aT. Both characters have to be sent in upper- or lowercase and must be sent directly after one another. +++ Switch from data mode to command mode without dropping the line. A second before and after this command, no other character may be sent to the modem, including a . A/ Repeat last command, no ATA Answer incoming call When you want to answer a call manually, you type this command after a ring has appeared on the screen of your Terminal emulator. D Dial a telephone number ATDTn After issuing this command, the modem will attempt to establish a connection and dial the number n. Options to the command D: W Wait for dialtone. When using a PABX this is used to wait for the second dialtone. Note: not all PABXs give a second dialing tone. Consider using "@" instead. @ Wait for silence for 5 seconds. , Pause for 2 seconds (S8) ! Flash ( on-hook for value in S29 ) ; Return to command mode after dialing. P Pulse dial T Tone dial n The telephone number to be dialed Sn Dial number stored in directory entry &Zn where n=0..19. The selected number is shown on the screen for verification. J Perform MNP10 link negotiation at highest supported speed (for this call only). L Redial last number. ^ Disable calling tone, this call only. The call can be aborted at any stage before the connect message appears, by entering any character except Linefeed. ATE Command echo to host E0 Commands are not echoed E1 Commands are echoed With this command you can select if the modem should return all the commands to the screen or not. This is useful to check if all characters are received by the modem. If characters appear double on the screen, disable echoing by the modem or by your terminal. The value of ATE can be written in the RAM of the modem using AT&W. ATFn Select transmission mode/speed F0 Auto mode F1 V.21 300bps F3 V.23 75Tx/1200Rx with AT%F1 V.23 1200Tx/75Rx with AT%F2 F4 V.22 1,200bps F5 V.22bis 2,400bps F6 V.32bis 4,800bps F7 V.32bis 7,200bps F8 V.32bis 9,600bps F9 V.32bis 12,000bps F10 V.32bis 14,400bps These commands are not valid for V.34 modems. The equivalent command for the V.34 modems is +MS, please refer to this command. ATH Go on-hook, hang up. H0 Go on-hook ( Hang up ) H1 Go off-hook ATI Identifiers I0 Product code I1 Pre-computed Checksum I2 Returns OK I3 Returns OK I4 OEM String I5 - I11 Returns OK I12 ROM Checksum I13 RC Version number I14 Shows Firmware version I15 Shows selected country I17 GSM option I18 Shows Supported GSM Kit (GSM-ready™ only) ATL Speaker volume settings L0 Lowest speaker volume L1 Low speaker volume L2 Medium speaker volume L3 Highest speaker volume With this command the speaker volume can be set. ATM Speaker control M0 Speaker always off M1 Speaker on until carrier detected M2 Speaker always on M3 Speaker on only while answering ATNn Select Auto mode N0 Auto mode disabled N1 Auto mode enabled This command is not longer valid for the V.34 modems. ATOn Return to data mode O0 Return to data mode from command mode, only if on-line. O1 Return on-line and initiate retrain (2400bps or higher) ATQn Result codes Q0 Modem returns result codes Q1 Quiet mode enabled. Modem gives no result codes. If the quiet mode is enabled, the responses from the modem are not sent to the PC. ATSn Sets and reads the selected register Sn=x Sets register n to the value x Sn? Reads the value of register n n is a numeric value, varying between 0 and 255 (depending on the register). ATVn Result codes in numerical or verbose form V0 Returns the code in numerical form V1 Full-word result codes ATWn Connect messages formatting W0 DTE rate ( connect rate ) W1 Hayes 4 line format : Carrier, Protocol, Compression, DTE rate W2 Result code is DCE rate ( carrier rate ) ATXn Extended Result codes X1 Ignore dialtone and busy tone X2 Ignore busy tone X3 Inner dialtone X4 Modem recognises dialtone and busy tone X3 and X1 set the modem for Blind Dialing. This option is country specific, because some countries do not allow blind dialing. ATYn Long Space disconnect Y0 Disable long space disconnect Y1 Enable long space disconnect If the modems receives after activating this function, a BREAK-signal of at least 1.6 seconds coming from the remote PC, it will send a BREAK-signal of 4 seconds back to the remote PC before hanging up the telephone line. ATZn Resetting the modem Z0 Restore stored profile 0 Z1 Restore stored profile 1 If this command is issued to the modem during a connection, the modem will drop the line. According to the parameter n, the modem will restore the values stored in the non-volatile RAM (See also &W ). AT&Cn Carrier-detect &C0 DCD is always active &C1 DCD is active if modem is on-line Data Carrier Detect (DCD) is a hardware signal that notifies the software that the modem is in communication with another modem. Most software’s will not start-up properly if the DCD is active. Default is &C1. AT&Dn Data Terminal Ready settings &D0 Modem ignores DTR &D1 Go to command mode on ON-to-OFF DTR transition. &D2 Hang up on DTR-drop and go to command mode &D3 Reset (ATZ) on DTR-drop. Modem hangs up. AT&F Restore Factory Settings &F0 Use profile 0 &F1 Use profile 1 The modem is reset to the default firmware settings. If the modem is on-line, the command will not be executed. AT&Gn Select guard tone &G0 Disables guard tone &G1 Disables guard tone &G2 Selects 1800Hz guard tone This command may not be permitted in some countries. AT&Kn Flow Control &K0 Flow control disabled &K3 RTS/CTS flow control (Hardware) &K4 XON/XOFF flow control (Software) &K5 Transparent XON/XOFF flow control &K6 RTS/CTS and XON/XOFF flow control Flow control is the use of characters or RS232 signals to start and stop the flow of data to avoid data loss during buffering. This is extremely important when the DTE/DCE rate is different from the line speed, e.g. when data compression is used. The DTE/DCE rate must be higher then the line speed. RTS/CTS flow control (Hardware flow control) The PC will send data to the modem. The modem will store this data in a buffer. When this buffer is full, the modem will drop the CTS-line, telling the PC that it has to stop transmitting data until the signal raises again. If the RTS-signal is OFF, transmitting data to the PC is stopped until the signal switches to ON. XON/XOFF flow control (Software flow control) If the modem receives a XON-character (S32) from the PC, it stops transmitting data to the PC until it receives a XOFF-character (S33). The process is similar if the PC is sending data to the modem. NOTE : The preferable setting is RTS/CTS flow control AT&Pn Pulse dial make-break &P0 : 61/39 ratio at 10pps &P1 : 67/33 ratio at 10pps &P2 : 39/61 ratio at 20pps &P3 : 33/67 ratio at 20pps Settings may be locked depending on country selection. Default is also country dependent. AT&Qn Sync/Async Mode &Q0 : Selects direct async operation. &Q1 : Selects synchronous connect mode with async off-line command mode. &Q2 : Selects synchronous connect mode with async off-line command mode and enables DTR dialing. &Q4 : Selects Autosync™ mode &Q5 : The modem will try to negotiate an error corrected link. &Q6 : Selects async operation in normal mode. This command is used to control the connection modes permitted. AT&Rn CTS/RTS option &R0 : In sync mode, CTS tracks the state of RTS. In async mode, CTS acts according V.25bis handshake. &R1 : In sync mode CTS is always on. In async mode, CTS will drop only if required by flow control. This selects how the modem controls CTS. CTS operation is modified if hardware FC is selected ( AT&Kn ). AT&Sn DSR Override &S0 : DSR will remain on at all times. &S1 : DSR will become active after answer tone has been detected and inactive after the carrier has been lost. This command selects how the modem will control DSR. AT&Tn Test and diagnostics &T0 : Terminates test &T1 : Initiates local analogue loop back &T2 : Returns ERROR &T3 : Initiates local digital loop back &T4 : Enables digital loop back acknowledgment for remote request. &T5 : Disables digital loop back acknowledgment for remote request. &T6 : Requests a remote digital loop back without self test. &T7 : Requests a remote digital loop back with self test &T8 : Initiates local analogue loop back with self test. The modem will perform selected test and diagnostic functions according to the parameter supplied. A test can be run only when in an asynchronous operation in non-error-correction mode. To terminate a test in progress, the escape sequence must be entered first, except for parameters 7 and 8. AT&Vn Display current configuration and stored profiles Reports the current (active) configuration, the stored (user) profiles, and the first four stored telephone numbers. AT&Wn Store current configuration &W0 : Store current configuration in profile 0 &W1 : Store current configuration in profile 1 AT&Xn Select Synchronous Clock Source &X0 : Selects internal timing &X1 : Selects external timing &X2 : Selects slave receive timing Selects the source of the transmit clock for the synchronous mode of operation. AT&Yn Designate a default reset profile &Y0 : The modem will use profile 0 &Y1 : The modem will use profile 1 Selects which user profile will be used after a hard reset. AT&Zn Store telephone number &Zn=x n=0 to 3 and x=dial string AT%En LQM and Auto-retrain or FB/FF %E0 : Disable Line Quality Monitor and auto-retrain %E1 : Enable Line Quality Monitor and auto-retrain %E2 : Enable Line Quality Monitor and fall back/fall forward. (V.34 only) Controls whether or not the modem will automatically monitor the line quality and request a retrain or fall back / fall forward depending on the line quality. AT%Cn Enable/Disable data compression %C0 : Disables data compression %C1 : Enables MNP5 %C2 : Enables V.42bis %C3 : Enables both V.42bis and MNP5 data compression. Enables or disables data compression negotiation. The modem can only perform data compression on an error corrected link. AT\Gn Modem to modem flow control \G0 : Disables modem-to-modem flow control \G1 : Enables modem-to-modem flow control In non-error correction mode, the modem enables or disables the generation or recognition of modem to modem XON/XOFF flow control according to the parameter supplied. In error correction mode, the setting of \G is ignored. AT\Nn Operating mode \N0 : Normal speed buffered mode. (&Q6) \N1 : Serial interface selected. (&Q0) \N2 : Reliable connection ( First V.42 the MNP4). Failure to make a reliable connection results in modem hanging up. \N3 : Auto reliable mode ( First V.42, then MNP4 then speed buffered ) \N4 : V.42 (LAPM) . If connection fails, modem hangs up. \N5 : MNP4 EC mode. Failure results in hanging up. This command controls the preferred error correcting mode to be negotiated in a subsequent data connection. \An Select maximum MNP block size \A0 64 characters \A1 128 characters \A2 192 characters \A3 256 characters )Mn Enable cellular power level adjustment )M0 : Disables transmit power level adjustment during MNP10 link negotiation. )M1 : Enables transmit power level adjustment during MNP10 link negotiation. V.34 : Uses the @Mn value to establish initial cellular connection. After connection power level is determined by modem. )M2 : Enables transmit power level adjustment during MNP10 link negotiation. Uses the @Mn value to establish initial cellular connection. After connection power level is fixed. (V.34 only) Enables or disables automatic adjustment of the transmit power level to accommodate the signaling requirements of cellular telephone equipment. -Kn MNP Extended Services -K0 Disables V.42 LAPM to MNP10 conversion -K1 Enables V.42 LAPM to MNP10 conversion -K2 Enables V.42 LAPM to MNP10 conversion, inhibits MNP ES initiation during V.42 LAPM answering mode detection Phase (V.34 only) Enables or disables conversion of a V.42 connection to a MNP10 connection. V.34 Commands Following commands are valid only for the V.34 modems. @Mn Initial Cellular Power Level setting @M0 -26dBm (Default) @M1 -30dBm @M2 -10dBm @M3-@M10 -10dBm @M11 -11dBm ... @M31 -31dBm Sets the initial power level for up shift at connect until line conditions can be determined. :En Compromise Equalizer Enable command :E0 Disables the equalizer :E1 Enables the equalizer Enables or disables the V.32 compromise equalizer. This command can be used when the modem is attached to either a flat line or a cellular connection. +MS Select Modulation Note : The use of the Nn command is not recommended for speeds higher than 14.400. Syntax: +MS=[,[][,[][,[max_rate>]]]] +MS? Reports selected options response : +MS:11,1,300,33600 (example) +MS=? Reports supported options response : +MS:(0,1,2,3,8,9,10,13,64,69,74),(0,1),(300-33600),(300-33600) Sub parameter definitions: 1. Mod Modulation Bps 0 V.21 300 1 V.22 1200 2 V.22bis 2400 or 1200 3 V.23 1200/75 9 V.32 9600,4800 10 V.32bis 14400,9600,7200, 4800,1200 11 V.34 33600,32100,28800, 26400,24000, 21600, 19200, 16800, 14400,9600,7200, 4800, 2400 64 Bell 103 300 69 Bell 212 1200 74 V.FC 28800,26400,24000,21600, 19200, 16800, 14400,9600,7200,4800,2400 2. is an optional numeric value which enables or disables automatic modulation negotiation using V.8 or V.32bis Annex A. The options are : 0 Auto mode disabled 1 Auto mode enabled using V.8 or V.32bis Annex A The default value is 1, which enables auto mode. Note, however, there are modulations for which there is no automatic negotiation, e.g., Bell 212. =1 The modem connects at the highest possible rate in accordance with V.8 or V.32bis Annex A if V.8 is not supported by the remote modem. A. If is greater than the highest speed supported by then modulation specified by , the modem auto modes down from the highest rate to the selected modulation. For example : +MS=10,1,1200,24000 selects auto moding down from V.32bis 14400bps. B. To emulate issuance of the N1 command, specify the modulation and the rate to start auto moding down from using and , respectively. Examples : +MS=11,1,300,16800 auto mode at V.34 16800bps +MS=9,1,300,12000 auto mode at V.32bis 12000bps 3. is an optional number which specifies the lowest rate at which the modem may establish a connection. The value is decimal coded, in units of BPS, e.g. 2400 specifies the lowest rate to be 2400. The default is 300 for 300bps. 3. is an optional number which specifies the highest rate at which the modem may establish a connection. The value is decimal coded, in units of BPS, e.g. 14400 specifies the lowest rate to be 14400. The default is 33,600 for 33,600bps. AT Command Result Codes The modem responds to commands from the DTE ( PC ) and to activity on the line by signaling to the DTE in the form of result codes. The result codes that the modem can send are described below. Value Verbose 0 OK 1 RING 3 NO CARRIER 4 ERROR 5 CONNECT 1200 6 NO DIALTONE 7 BUSY 8 NO ANSWER 9 CONNECT 0600 10 CONNECT 2400 11 CONNECT 4800 12 CONNECT 9600 13 CONNECT 7200 14 CONNECT 12000 15 CONNECT 14400 16 CONNECT 19200 17 CONNECT 38400 18 CONNECT 57600 19 CONNECT 115200 22 CONNECT 75TX/1200RX 23 CONNECT 1200TX/75RX 24 DELAYED 32 BLACKLISTED 33 FAX 35 DATA 40 CARRIER 300 44 CARRIER 1200/75 45 CARRIER 75/1200 46 CARRIER 1200 47 CARRIER 2400 48 CARRIER 4800 49 CARRIER 7200 50 CARRIER 9600 51 CARRIER 12000 52 CARRIER 14400 53 CARRIER 16800 54 CARRIER 19200 55 CARRIER 21600 56 CARRIER 24000 57 CARRIER 26400 58 CARRIER 28800 59 CARRIER 31200 60 CARRIER 33600 61 CONNECT 16800 62 CONNECT 21600 63 CONNECT 24000 64 CONNECT 26400 65 CONNECT 28800 66 CONNECT 33600 67 COMPRESSION: CLASS 5 68 COMPRESSION: V.42 bis 69 COMPRESSION: NONE 70 PROTOCOL: NONE 77 PROTOCOL: LAPM 80 PROTOCOL: ALT 81 PROTOCOL: ALT-CELLULAR +F4 +FCERROR Supported countries To change the country settings, use followingfollow next procedure : AT*NCnn Modem responds with OK ATZ Modem responds with OK Note : Some counties do not allow their country settings to be altered. *NCnn Country select 40 Australia 1 Austria 2 Belgium 3 Denmark 4 Finland 5 France 6 Germany 17 Greece 10 Netherlands 7 Ireland 8 Italy 43 Japan 26 Namibia 11 Norway 12 Portugal 27 South Africa 13 Spain 14 Sweden 15 Switzerland 16 UK 19 Czech Republic 24 Poland 25 Russia 22 United States Note : Use the Interactive Manual™ to setup the country. S-Registers S0 Auto-answer Sets the number of the rings required before the modem automatically answers a call. Setting this register to zero disables auto-answer mode Range : 0 to 255 S1 Ring counter S1 is incremented each time the modem detects a ring signal on the telephone line. Range : 0 to 255 S2 Escape character S2 holds the decimal value of the ASCII character used as the escape sequence. A value over 127 disables the escape process. Range : 0 to 127 (Default = 43) S3 Carriage Return Character Sets the command line and result code terminator character. Pertains to asynchronous operation only. Range : 0 to 127 ASCII decimal (Default=13) S4 Line feed Character Sets the character recognised as a line feed. Pertains to asynchronous operation only. Range : 0 to 127 ASCII decimal (Default=10) S5 Backspace Character Sets the character recognised as a backspace. Range : 0 to 32 ASCII decimal (Default=8) S6 Wait for dialtone Sets the time in seconds that the modem will try to detect a dialtone (if set) and wait before starting to dial. Range : 2 to 255 seconds S7 Wait for Carrier after dial Sets the time in seconds that the modem will wait for a carrier before hanging up. Range : 1 to 255 seconds S8 Pause time for delay Sets the time the modem must pause when the ‘,’ dial modifier is used. Range : 0 to 255 seconds S9 Carrier detect response time Sets the time in 10th of a second, that the carrier must be present before the modem considers it valid and turns on RLSD. Range : 1 to 255 tenths of a second. S10 Lost carrier to Hang-up delay Sets the time in 10th of a second, that the modem waits before hanging up after a loss of carrier. Range : 1 to 255 S11 DTMF Tone duration Range : 50 to 255 milliseconds (Default=95) S12 Escape Prompt Delay Defines the maximum period, in fifties of a second, allowed between receipt of the last character of the three escape character sequence and the sending of the OK message. Range : 0 to 255 1/50 of a second S18 Test timer Sets the length in seconds that the modem conducts a test. Range : 0 to 255 seconds S25 Delay to DTR Sets the time that the modem will ignore DTR before taking action specified by &Dn. Range : 0 to 255 seconds S26 RTS to CTS delay Sets the time delay, before the modem turns on CTS after detecting an OFF-ON transition on RTS when &R0 is commanded. Range : 0 to 255 hundredths of a second S32 XON Character Range : 0 to 255 ASCII decimal (Default=17) S33 XOFF Character Range : 0 to 255 ASCII decimal (Default=19) S38 Delay Before Forced Hang-up This register sets the delay between the modem’s receipt of the H command to disconnect and the disconnect operation. Range : 0 to 255 seconds S86 Call Failure Reason Code When the modem issues a NO CARRIER result code, a value is written to this S-register. Range : 0,4,5,9,12,13 or 14 0 Normal disconnect, no error occurred 4 Loss of carrier 5 V.42 negotiation failed 9 The modems could not find a common protocol 12 Normal disconnect initiated by the remote modem 13 Remote modem does not respond after 10 re-transmissions of the same message. 14 Protocol violation S91 PSTN Transmit level Attenuation Sets the transmit level attenuation level from 0 to 15dBm for the PSTN mode. Some countries may not permit changing the transmit level. Range : 0 to 15dBm (Corresponding to 0 to -15dBm transmit level) Default : 10dBm S95 Extended Result Codes The bits in this register can be set to override some of the Wn command options. A bit set to a 1 in this register will enable the corresponding result code regardless of the Wn setting. Bit 0 Connect message indicates DCE speed Bit 1 Append /ARQ to CONNECT XXXX Bit 2 Enable CARRIER XXXX message Bit 3 Enable PROTOCOL message Bit 4 Reserved Bit 5 Enable COMPRESSION XXXX Bit 6 Reserved Bit 7 Reserved