****************************************************************************** ************ This Document is for the Aus.Linx International ************ ************ Kookaburra 33.6pc PCMCIA fax/modem ************ ************ This is identified on the top left front of the modem ************ ****************************************************************************** ______________________________________________________________________________ Table of Contents - Rockwell Chip Set 1**Extended AT Command Set 2**AT Command Result Codes 3**S-Registers 4**Bit Mapped and S-Registers 5**Error Correction, Data Compression, and Flow Control 6**Fax Operation 7**Diagnostic Tests ______________________________________________________________________________ 1**Extended AT Command Set**************************************************** AT Commands A/ Re-execute previous command. A Answer. Bn Select CCITT or Bell standard B0 CCITT operation at 300 or 1200 b/s B1 Bell operation at 300 or 1200 b/s (default) Cn Carrier control. The only valid parameter is 1. D Dial 0-9 Dial DTMF digits 0 to 9. * Dial the "star" symbol (tone dialing only). # Dial the "pound" symbol (tone dialing only). A-D Dial DTMF digits A, B, C, and D. Some countries may prohibit sending these digits during dialing. L Re-dial last number. L must immediately follow D; all further characters are ignored. P Select pulse dialing; affects current and subsequent dialing. T Select tone dialing; affects current and subsequent dialing. R Not currently implemented. S=r Dial stored number r (see &Z for storing numbers). ! Flash: go on-hook for a time defined by S29. Country requirements may limit the time. W Wait for dial tone. If no dial tone is detected within the time specified by S7, the modem aborts the rest of the sequence, goes on-hook, and generates an error message. @ Wait for silence. The modem waits for at least 5 seconds of silence in the call-progress frequency band before continuing with the next dial string parameter. If the modem does not detect these 5 seconds of silence before the expiration of the call abort timer S7, it terminates the call attempt with a NO ANSWER message. If busy detection is enabled, the modem may terminate the call with a BUSY result code. If answer tone arrives during execution of this parameter, the modem handshakes with the remote modem. & Wait for credit card dial tone then dial rest of string. If the modem waits for the time specified by S7 then aborts the call. , Pause. The modem pauses for a time specified by S8 before dialing the following digits. Most often used when dialing an outside line through a PBX. ; Return to command mode after processing command. This character allows the user to issue additional AT commands while remaining off-hook, either on the original command line or on subsequent command lines. The modem monitors call progress only after an additional dial command is issued without the ; terminator. Useful for issuing long dialing strings that would otherwise overflow the command buffer. Use H to abort the dial in progress and go back on-hook. ^ Disable calling tone transmission; applicable to current dial attempt only. ( ) Ignored; can be used to format the dial string. - Ignored; can be used to format the dial string. Spaces are ignored; can be used to format the dial string. Invalid characters are ignored. > If enabled by a country-specific parameter, the modem generates a grounding pulse on the GND output. En Command echo E0 Disables command echo. E1 Enables command echo (default). Fn Select line modulation (14.4 Modems only) The line modulation is fixed unless automode is selected. This command interacts with S37 and the N command. The parameter value, if valid, is written to S31 bit 1. To select line modulation, use either the F command or a combination of S37 and the N command, but not both. F0 Selects auto-detect mode. Sets N1 and S31 bit 1. In this mode, the modem configures for automode operation. All connect speeds supported by the modem are possible, according to the remote modem's preference. The contents of S37 are ignored, as is the sensed DTE speed. F1 Selects V.21 or Bell 103, according to the B setting, as the only acceptable line modulation resulting in a subsequent connection. Sets N0, sets S37 to 1, and clears S31 bit 1. Equivalent to the command string ATN0S37=1. F2 Not supported. F3 Selects V.23 as the only acceptable line modulation for a subsequent connection. Originator is at 75 b/s and answerer is at 1200 b/s. Sets N0, sets S37 to 7, and clears S31 bit 1. Equivalent to the command string ATN0S37=7. F4 Selects V.22 1200 or Bell 212A, according to the B command setting, as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 5, and clears S31 bit 1. Equivalent to the command string ATN0S37=5. F5 Selects V.22 bis as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 6, and clears S31 bit 1. Equivalent to the command string ATN0S37=6. F6 Select V.32 bis 4800 or V.32 4800 as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 8, and clears S31 bit 1. Equivalent to the command string ATN0S37=8. F7 Selects V.32 bis 7200 as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 12, and clears S31 bit 1. Equivalent to command string ATN0S37=12. F8 Selects V.32 bis 9600 or V.32 9600 as the only acceptable line modulations for a subsequent connection. Sets N0, sets S37 to 9, and clears S31 bit 1. Equivalent to the command string ATN0S37=9. F9 Selects V.32 bis 12000 as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 10, and clears S31 bit 1. Equivalent to command string ATN0S37=10. F10 Selects V.32 bis 14400 as the only acceptable line modulation for a subsequent connection. Sets N0, sets S37 to 11, and clears S31 bit 1. Equivalent to command string ATN0S37=11. Hn Disconnect (hang up) H0 (Default.) The modem releases the line if currently on-line and terminates any test in progress. Country-specific, modulation-specific,and error-correction-protocol-specific (S38) processing is handled outside the H0 command. H1 If on-hook, the modem goes off-hook and enters command mode. The modem returns on-hook after a period of time determined by S7. In Identification I0 Product code (e.g., "14400"). I1 Calculates the ROM checksum and reports the least significant byte of the checksum. I2 Calculates the ROM checksum and compares it with the prestored checksum. Reports "OK" is it compares and "ERROR" if it does not compare. I3 Reports the firmware version, basic model, application code, and interface type code. I4 Reports OEM defined identifier string. I5 Reports Country Code parameter I6 Reports modem data pump model and internal code revision. I7 Reports the DAA code resulting from MCU interrogation of the DAA for auto DAA recognition. Ln Speaker volume L0 Off or low volume. L1 Low volume (default). L2 Medium volume. L3 High volume. Mn Speaker control M0 Speaker is always off. M1 Speaker is on during call establishment, but goes off when carrier is detected (default). M2 Speaker is always on. M3 Speaker is off during dialing and when receiving carrier, but on during answering. Nn Automode enable. N0 Automode detection is disabled. A subsequent handshake is conducted according to the contents of S37 or, if S37 is zero, according to the most recently sensed DTE speed. N1 Automode detection is enabled (default). A subsequent handshake is conducted according to the automode algorithm supported by the modem. This command is equivalent to F0. On Return to on-line data mode O0 Enters on-line data mode without a retrain. Handling is determined by the call establishment task. Generally, if a connection exists, this command connects the DTE back to the remote modem after escape. O1 Enters on-line data mode with a retrain. Qn Quiet results codes control Q0 Enables result codes to the DTE (default). Q1 Disables result codes to the DTE. Sr Read or write to S-register r r Establishes S-register r as the default register. r=n Sets S-register r to the value n. r? Reports the value of S-register r. Following country restrictions, some commands may be accepted but the value limited and replaced by a maximum or minimum value. Vn Result code form V0 Enables short-form (terse) result codes. V1 Enables long-form (verbose) result codes (default). Wn Connect Message Control W0 Upon connection, the modem reports only the DTE speed (default). W1 Upon connection, the modem reports the line speed, the error correction protocol, and the DTE speed, respectively. W2 Upon connection, the modem reports the DCE speed. Xn Error correction message control X0 Disables monitoring of busy tones unless forced otherwise by country requirements; sends only OK, CONNECT, RING, NO CARRIER, ERROR, and NO ANSWER result codes. Blind dialing enabled or disabled by country parameters. If busy tone detection is enforced and busy tone is detected, NO CARRIER is reported. If dial tone detection is enforced and dial tone is not detected, NO CARRIER is reported instead of NO DIAL TONE. The value 000b is written to S22 bits 6, 5, and 4 respectively. X1 Disables monitoring of busy tones unless forced otherwise by country requirements; sends only OK, CONNECT, RING, NO CARRIER, ERROR, NO ANSWER, and CONNECT rate. Blind dialing enabled or disabled by country parameters. If busy tone detection is enforced and busy tone is detected, NO CARRIER is reported instead of BUSY. If dial tone detection is not detected, NO CARRIER is reported instead of NO DIAL TONE. The value 100b is written to The value 100b is written to S22 bits 6, 5, and 4 respectively. X2 Disables monitoring of busy tones unless forced otherwise by country requirements; sends only OK, CONNECT, RING, NO CARRIER, ERROR, NO DIALTONE, NO ANSWER, and CONNECT rate. If busy tone detection is enforced and busy tone is detected, NO CARRIER is reported instead of BUSY. If dial tone detection is enforced or selected and dial tone is not detected, NO CARRIER is reported instead of NO DIAL TONE. The value 101b is written to S22 bits 6, 5, and 4 respectively. X3 Enables monitoring of busy tones; sends only OK, CONNECT, RING, NO CARRIER, ERROR, NO DIALTONE, NO ANSWER, and CONNECT or CARRIER rate. Blind dialing enabled or disabled by country parameters. If dial tone detection is enforced and dial tone is not detected, NO CARRIER is reported. The value 110b is enforced or selected and dial tone is written to S22 bits 6, 5, and 4 respectively. X4 Enables monitoring of busy tones; sends all messages. The value 111b is written to S22 bits 6, 5, and 4 respectively. (Default.) Yn Long space disconnect Y0 Disables long space disconnect (default). Y1 Enables long space disconnect. Zn Soft reset and restore profile Z0 Soft reset and restore stored profile 0. Z1 Soft reset and restore stored profile 1. AT& Commands &Cn Data Carrier Detect (DCD) option &C0 DCD remains ON at all times. &C1 DCD follows the state of the carrier (default). &Dn DTR option &D0 Default. DTR drop is interpreted according to the current &Q setting as follows: &Q0, &Q5, &Q6: DTR is ignored (assumed ON). Allows operation with DTEs that don't provide DTR. &Q1, &Q4: DTR drop causes the modem to hang up. Auto- answer is not affected. &Q2, &Q3: DTR drop causes the modem to hang up. Auto- answer is inhibited. &D1 DTR drop is interpreted according to the current &Q setting as follows: &Q1, &Q4, &Q5, &Q6: DTR drop is interpreted by the modem as if the asynchronous escape sequence had been entered. The modem returns to asynchronous command mode without disconnecting. &Q2, &Q3: DTR drop causes the modem to hang up. Auto- answer is inhibited. &D2 DTR drop is interpreted according to the current &Q setting as follows: &Q0 through &Q6: DTR drop causes the modem to hang up. Auto- answer is inhibited. &D3 DTR drop is interpreted according to the current &Q setting as follows: &Q0, &Q4, &Q5, &Q6: DTR drop causes the modem to perform a soft reset as if the Z command were received. The &Y setting determines which profile is loaded. &Q2, &Q3: DTR drop causes the modem to hang up. Auto- answer is inhibited. &Fn Restore factory configuration (profile) &F0 Recall factory profile 0 (default). &F1 Recall factory profile 1. &Gn Select guard tone &G0 Disables guard tone (default). &G1 Disables guard tone. &G2 Enables 1800-Hz guard tone. &Jn Telephone jack control &J0 Single phone line, RJ-11 jack (default). &J1 Multiple phone lines, RJ-12 or RJ-13 jack. &Kn Flow control &K0 Disables flow control. &K3 Enables RTS/CTS flow control (default for data modem modes). &K4 Enables XON/XOFF flow control. &K5 Supports transparent XON/XOFF flow control. &K6 Enables both RTS/CTS and XON/XOFF flow control (default for fax modem modes). &Pn Select pulse dial make/break ratio &P0 39/61 make/break ratio at 10 pulses per second (default). &P1 33/67 make/break ratio at 10 pulses per second. &P2 39/61 make/break ratio at 20 pulses per second. &P3 33/67 make/break ratio at 20 pulses per second. &Rn RTS/CTS option &R0 In synchronous mode, CTS tracks the state of RTS; the RTS-to-CTS delay is defined by S26. In asynchronous mode, CTS acts according to V.25 bis handshake. &R1 In synchronous mode, CTS is always ON (RTS transitions are ignored). In asynchronous mode, CTS drops only if required by flow control. (Default.) &Sn DSR override &S0 DSR remains ON at all times (default). &S1 DSR becomes active after answer tone has been detected and inactive after carrier has been lost. &Tn Test and diagnostics &T0 Terminates test in progress and clears S16. &T1 Initiates local analog loopback, V.54 Loop 3. Sets S16 bit 0. If a connection exists when this command is issued, the modem hangs up. The CONNECT rate message is displayed upon the start of the test. &T2 Returns ERROR. &T3 Initiates local digital loopback, V.54 Loop 2. Sets S16 bit 2. If no connection exists, ERROR is returned. Sets S16 bit 4 when the test is in progress. &T4 Enables digital loopback acknowledgment for remote request, i.e., a remote digital loopback (RDL) request from a remote modem is allowed. Sets S23 bit 0. (Default.) &T5 Disables digital loopback acknowledgment for remote request, i.e., a remote digital loopback (RDL) request from a remote modem is denied. Clears S23 bit 0. &T6 Requests a remote digital loopback (RDL), V.54 Loop 2, without self-test. If no connection exists, ERROR is returned. Sets S16 bit 4 when the test is in progress. The CONNECT or CARRIER rate message is displayed upon the start of the test. &T7 Requests a remote digital loopback (RDL), V.54 Loop 2, with self-test. (In self-test, a test pattern is looped back and checked by the modem.) If no connection exists, ERROR is S18 or the &T0 or H command, the number of detected errors is reported to the DTE. Sets S16 bit 5 when the test is in progress. &T8 Initiates local analog loopback, V.54 Loop 3, with self-test. (In self-test, a test pattern is looped back and checked by the modem.) If a connection exists, the modem hangs up before the test is initiated. When the test is terminated by expiration of S18 or the &T0 or H command, the number of detected errors is reported to the DTE. Sets S16 bit 6 when the test is in progress. This command may not be available in some countries due to PTT restrictions. &V Display current configuration and stored profiles &Wn Store current configuration &W0 Store the current configuration as profile 0. &W1 Store the current configuration as profile 1. &Xn Select synchronous timing &X0 Internal timing. The modem generates the transmit clock signal and applies it to the TXCLK output at the serial interface. &X1 External timing. The local DTE sources the transmit clock signal on the XTCLK input of the serial interface. The modem applies this clock to the TXCLK output at the serial interface. &X2 Slave receive timing. The modem derives the transmit clock signal from the incoming carrier and applies it to the TXCLK output at the serial interface. &Yn Designate a default reset profile &Y0 The modem uses profile 0. &Y1 The modem uses profile 1. &Zn=x Store telephone number in 1 of 4 locations n = 0-3, x = dial string (256-byte NVRAM). AT% Commands %Cn Enable or disable data compression %C0 Disables data compression. Resets S46 bit 1. %C1 Enables MNP 5 data compression negotiation. Resets S46 bit 1. %C2 Enables V.42 bis data compression. Sets S46 bit 1. %C3 Enables both V.42 bis and MNP 5 data compression. Sets S46 bit 1. (Default.) %En Line quality monitor The parameter value, if valid, is written to S41 bits 2 and 6. If enabled, the modem attempts to retrain for a maximum of 30 seconds. %E0 Disable line quality monitor and auto-retrain (default). %E1 Enable line quality monitor and auto-retrain. %E2 Enable line quality monitor and fallback/fall-forward. %L Line signal level Returns a value that indicates the received signal level. For example, 009 = -9 dBm, 043 = -43 dBm, and so on. %Q Line signal quality Reports line signal quality (DAA-dependent). Returns higher order byte of the EQM value. Based on EQM value, retrain or fallback/fall-forward may be initiated if enabled by %E1 or %E2. %TTn PTT testing utilities %TT00-%TT009 DTMF tone dial digits 0 to 9. %TT0A DTMF digit *. %TT0B DTMF digit A. %TT0C DTMF digit B. %TT0D DTMF digit C. %TT0E DTMF digit #. %TT0F DTMF digit D. %TT10 V.21 channel 1 mark (originate) symbol. %TT11 V.21 channel 2 mark symbol. %TT12 V.23 backward channel mark symbol. %TT13 V.23 forward channel mark symbol. %TT14 V.22 originate (call mark) signaling at 600 b/s. %TT15 V.22 originate (call mark) signaling at 1200 b/s. %TT16 V.22 bis originate (call mark) signaling at 2400 b/s. %TT17 V.22 answer signaling (guard tone if PTT-required). %TT18 V.22 bis answer signaling (guard tone if required). %TT19 V.21 channel 1 space symbol. %TT1A V.21 channel 2 space symbol. %TT1B V.23 backward channel space symbol. %TT1C V.23 forward channel space symbol. %TT20 V.32 9600 b/s. %TT21 V.32 bis 14400 b/s. %TT30 Silence (on-line), i.e., go off-hook. %TT31 V.25 answer tone. %TT32 1800-Hz guard tone. %TT33 V.25 calling tone (1300 Hz). %TT34 Fax calling tone (1100 Hz). %TT40 V.21 channel 2. %TT41 V.27 ter 2400 bps. %TT42 V.27 ter 4800 bps. %TT43 V.29 7200 bps. %TT44 V.29 9600 bps. %TT45 V.17 7200 bps long train. %TT46 V.17 7200 bps short train. %TT47 V.17 9600 bps long train. %TT48 V.17 9600 bps short train. %TT49 V.17 12000 bps long train. %TT4A V.17 12000 bps short train. %TT4B V.17 14400 bps long train. %TT4C V.17 14400 bps short train. %TT5R, S, C, A, P V.FC modulation, where the R, S, C, A, and P parameters are shown below. %TT6R, S, C, A, P V.34 modulation, where the R, S, C, A, and P parameters are shown below. R Data Rate 0 2400 (V.34 only) 1 4800 (V.34 only) 2 7200 (V.34 only) 3 9600 (V.34 only) 4 12000 (V.34 only) 5 14400 6 16800 7 19200 8 21600 9 24000 A 26400 B 28800 S Symbol Rate (Baud) 0 2400 1 Reserved 2 2800 3 3000 4 3200 5 3429 C V.FC Carrier Bias (V.FC Only) 2B -100 2C -95 ... ... 3E -10 3F -5 40 0 (default) 41 +5 42 +10 ... ... 53 +95 54 +100 A Auxiliary (secondary) Channel Enable/Disable 0 Disabled (default) 1 Enabled P Amount of Upper Band Edge Atten. Comp. (dB) (V.FC) 0 0 (default) 1 1 ... ... 8 8 9 9 A 10 B 12 C 13 D 14 E 15 F 22 AT\ Commands \An Select maximum MNP block size \A0 64 characters. \A1 128 characters (default). \A2 192 characters. \A3 256 characters. \Bn Transmit break to remote modem \B1-\B9 Break length in 100-ms units. (Default = 3.) Non-error- corrected mode only. \Kn Break control Determines how modem handles a break. If the break is received from the DTE while the modem is in data mode: \K0 Enter command mode; no break sent to remote modem. \K1 Clear data buffers and send break to remote modem. \K2 Same as 0. \K3 Send break to remote modem immediately. \K4 Same as 0. \K5 Send break to remote modem in sequence with transmitted data (default). If the break is received from the DTE while the modem is in command mode: \K0 Clear data buffers and send break to remote modem. \K1 Same as 0. \K2 Send break to remote modem immediately. \K3 Same as 2. \K4 Send break to remote modem in sequence with data. \K5 Same as 4 (default). If the break is received from a remote modem during a non-error- corrected connection: \K0 Clears data buffers and sends break to the DTE. \K1 Same as 0. \K2 Send a break immediately to DTE. \K3 Same as 2. \K4 Send break to DTE in sequence with received data. \K5 Same as 4 (default). \Ln MNP block/stream mode select \L0 Use stream mode for MNP connection (default). \L1 Use interactive block mode for MNP connection. This command accepts block mode but implements stream mode. \Nn Operating mode \N0 Normal speed-buffered mode; disables error-correction mode. (Forces &Q6.) \N1 Not used. \N2 Reliable (error-correction) mode. The modem first attempts a LAPM connection and then an MNP connection. Failure to make a reliable connection results in the modem hanging up. (Forces &Q5, S36=4, and S48=7.) \N3 Auto-reliable mode. Identical to \N2 except that failure to make a reliable connection results in the modem falling back to the speed- buffered normal mode. (Forces &Q5, S36=7, and S48=7.) \N4 LAPM error-correction mode. Failure to make a LAPM error- correction connection results in the modem hanging up. (Forces &Q5 and S48=0.) The MNP 10 command -K1 can override the \N4 command. \N5 MNP error-correction mode. Failure to make an MNP error- correction connection results in the modem hanging up. (Forces &Q5, S36=4, and S48=128.) \Vn Single Line Connect Message Enable \V0 Connect messages are controlled by the single command setings X, W, and S95. \V1 Connect messages are displayed in the single line format described below subject to the command settings V and Q. In Non-Verbose mode, single line connect messages are disabled and a single numeric result code is generated for CONNECT DTE. MNP 10 Commands *Hn Link Negotiation Speed Controls the connection speed for link negotiatons before upshift occurs between two MNP 10 modems. The parameter value, if valid, is written to S28 bits 6 and 7. *H0 Link negotiation occurs at the highest supported speed (default). *H1 Link negotiation occurs at 1200 b/s; used primarily for establishing cellular connections. *H2 Link negotiation occurs at 4800 b/s; used primarily to negotiate an MNP 10 connection on poor-quality phone lines. Do not use with )M1. -Kn MNP extended services -K0 Disables V.42 LAPM to MNP 10 conversion. -K1 Enables V.42 LAPM to MNP 10 conversion (default). -K2 Enables V.42 LAPM to MNP 10 conversion; inhibits MNP Extended Services initiation during V.42 LAPM answer mod detection phase. )Mn Enable or disable automatic adjustment of the transmit power level to accommodate the signaling requirements of cellular telephone equipment. )M0 Disables power level adjustment during MNP 10 link negotiation (defualt). Allows transmitter adjustment if cellular operation is requested by remote modem. )M1 Enables power level adjustment during MNP 10 link negotiation. Do not use with *H2. -Qn Enable fallback to V.22 bis/V.22 -Q0 Disables fallback to 2400 b/s (V.22 bis) and 1200 b/s (V.22). Fallback is enabled only to 4800 b/s. -Q1 Enables fallback to 2400 b/s (V.22 bis) and 1200 b/s (V.22) (default). -SEC=n Enable/Disable MNP10-EC -SEC0 Disable MNP10-EC. -SEC1,x Enable MNP10-EC with the transmit level of 0 to 30 (0 dB to -30 dB). ______________________________________________________________________________ 2**AT Command Result Codes**************************************************** The modem responds to commands from the DTE and to activity on the line by signaling to the DTE in the form of result codes. Display of these messages is controlled by the Qn command. Q0 (the default) enables result codes. Q1 disables all result codes; no messages are returned to the DTE. Two forms of each result code are available: the long form, a "verbose" English-like response, and the short form, a "terse" numeric response. The long-form code is preceded and terminated by a carriage return-line feed sequence; it is enabled by V1 (the default). The short form is terminated by a carriage return only, and there is no preceding sequence. It is enabled by V0. The Xn command controls monitoring of busy tone and dial tone and reporting of DTE speed and line speed. The following table shows how the value of n in this command affects result code reporting. An X indicates that the message is generated for that value of n. If the entry is blank, no message is generated for that value of n. For certain messages and values of n, a less explicit result code is substituted for the one listed; a numerical entry indicates the short form of this substitute message. Short (Terse) Long (Verbose) 00 OK 01 CONNECT 02 RING 03 NO CARRIER 04 ERROR 05 CONNECT 1200 06 NO DIALTONE 07 BUSY 08 NO ANSWER 09 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 CONNECT 16800 61 CONNECT 21600 62 CONNECT 24000 63 CONNECT 26400 64 CONNECT 28800 66 COMPRESSION: CLASS 5 67 COMPRESSION: V.42 bis 69 COMPRESSION: NONE 76 PROTOCOL: NONE 77 PROTOCOL: LAPM 80 PROTOCOL: ALT 81 PROTOCOL: ALT-CELLULAR +F4 +FCERROR ______________________________________________________________________________ 3**S-Registers**************************************************************** Hayes-compatible modems store most of their configuration information in 8-bit status registers, or S-registers. For instance, S-register 7 (S7 for short) determines the length of time the modem waits for carrier before going back on-hook. You can modify many features of the modem's operation by writing directly to these registers, using AT commands provided for this purpose. NOTE: Many AT commands that do not expressly invoke S-registers nonetheless write to them. For instance, the Fn command, which selects line modulation, writes to S31, and the &Tn test commands write to S16. For further examples, see Appendix A. The following table shows a summary of your modem's S-registers. Section 4 contains a detailed description of bit-mapped and coded S-registers. S-registers are volatile and are not preserved after a power-off or reset. However, the contents of the registers marked * in Table 7.1 can be saved permanently in nonvolatile RAM as part of a configuration profile, using the &Wn command. The S-register values of factory configuration profiles are stored permanently in the modem's ROM. You can also configure most communications programs to issue a series of AT commands, including those that write to S-registers, automatically as part of a macro or command string associated with specified operations. Writing to S-Registers The command to write the value n to S-register r is Atr=n Since the S-registers hold 8 bits, n must be an integer from 0 to 255. Although for many S-registers the value of the separate bits is meaningful, you cannot write directly to individual bits, and you must always enter values as decimal numbers. S-Register Summary No. Function Range Units Default *0 Rings to auto-answer 0-255 rings 0 1 Ring counter 0-255 rings 0 *2 Escape character 0-255 ASCII 43 3 Carriage-return character 0-127 ASCII 13 4 Line-feed character 0-127 ASCII 10 5 Backspace character 0-255 ASCII 8 *6 Wait time for dial tone 2-255 s 2 *7 Wait time for carrier 1-255 s 50 *8 Pause for dial delay modifier 0-255 s 2 *9 Carrier detect response time 1-255 0.1 s 6 *10 Carrier loss disconnect time 1-255 0.1 s 14 *11 DTMF tone duration 50-255 0.001 s 95 *12 Escape code guard time 0-255 0.02 s 50 13 Reserved _ _ _ *14 General bit-mapped options _ _ _ 15 Reserved _ _ _ 16 Test mode bit-mapped options _ _ 0 17 Reserved _ _ _ *18 Test timer 0-255 s 0 19 Reserved _ _ _ 20 Reserved _ _ _ *21 V.24/general bit-mapped options _ _ _ *22 Speaker/Results bit-mapped opt. _ _ _ *23 General bit-mapped options _ _ _ *24 Sleep inactivity timer 0-255 s 0 25 Delay to DTR off 0-255 s or 0.01 s 5 26 RTS-to-CTS delay 0-255 0.01 s 1 *27 General bit-mapped options _ _ _ *28 General bit-mapped options_ *28 General bit-mapped options - - 0 29 Flash dial modifier time 0-255 10 ms 70 30 Disconnect inactivity timer 0-255 10 s 0 *31 General bit-mapped options _ _ 2 32 XON character 0-255 ASCII 17 33 XOFF character 0-255 ASCII 19 34 Reserved _ _ _ 35 Reserved _ _ _ *36 LAPM failure control _ _ 7 *37 Line connection speed _ _ 0 38 Delay before forced hangup 0-255 s 20 *39 Flow control bit-mapped options _ _ 3 *40 General bit-mapped options _ _ _ *41 General bit-mapped options _ _ _ 42 Reserved _ _ _ 43 Reserved _ _ _ 44 Reserved _ _ _ 45 Reserved _ _ _ *46 Data compression control _ _ _ 48 V.42 negotiation control _ _ 7 82 LANM break control _ _ _ 86 Call failure reason code 0-14 _ _ 91 PSTN transmit attenuation level 0-15 dBm 10 92 Fax transit attenuation level 0-15 dBm 10 *95 Result code messages control _ _ 0 *Can be saved as part of a configuration profile. For example, S0 determines the number of rings before the modem auto-answers. The default is 0. To change the number of rings to 1, give the command ATS0=1 S7 determines the time that the modem waits for carrier. The default is 50, in units of seconds. To change this value to 60 seconds, give the command ATS7=60 Pointing to a Default Register The command ATSr points to S-register r as the default register. When this has been done, AT=n writes the value n to S-register r. The command to change the number of rings before auto-answering to 1 could therefore also be given as ATS0 AT=1 Reading S-Registers The command ATSr? reports the value of S-register r. For instance: ATS0? 000 OK reads the value of S0. Like other AT commands, multiple read commands can be given together: ATS3?S5? 013 008 OK ______________________________________________________________________________ 4**Bit-Mapped and Coded S-Registers******************************************* This section describes the options coded in bit-mapped S-registers, and certain other S-registers whose contents does not represent a measurement or a character. For a summary of all S-registers, including registers 1 to 12, see the last section. S14 General bit-mapped options Bit 0 This bit is ignored. Bit 1 Command echo (En) 0 = Disabled (E0) 1 = Enabled (E1) (default) Bit 2 Quiet mode (Qn) 0 = Send result codes (Q0) (default) 1 = Do not send result codes (Q1) Bit 3 Result codes (Vn) 0 = Numeric (V0) 1 = Verbose (V1) (default) Bit 4 Reserved Bit 5 Tone (T)/Pulse (P) 0 = Tone (T) (default) 1 = Pulse (P) Bit 6 Reserved Bit 7 Originate/Answer 0 = Answer 1 = Originate (default) S16 General bit-mapped test options Bit 0 Local analog loopback 0 = Disabled (default) 1 = Enabled (&T1) Bit 1 Not used Bit 2 Local digital loopback 0 = Disabled (default) 1 = Enabled (&T3) Bit 3 Remote digital loopback (RDL) status 0 = Modem not in RDL (default) 1 = RDL in progress Bit 4 RDL requested (AT&T6) 0 = RDL not requested (default) 1 = RDL requested (&T6) Bit 5 RDL with self-test 0 = Disabled (default) 1 = Enabled (&T7) Bit 6 Local analog loopback (LAL) with self- test 0 = Disabled (default) 1 = Enabled (&T8) Bit 7 Not used S21 V.24/general bit-mapped options Bit 0 Set by &Jn command but ignored otherwise. 0 = &J0 (default) 1 = &J1 Bit 1 Reserved Bit 2 CTS behavior (&Rn) 0 = CTS always on (&R0) 1 = CTS tracks RTS (&R1) (default) Bit 3,4 DTR behavior (&Dn) 0 = &D0 selected (default) 1 = &D1 selected 2 = &D2 selected 3 = &D3 selected Bit 5 RLSD (DCD) behavior (&Cn) 0 = &C0 selected 1 = &C1 selected (default) Bit 6 DSR behavior (&Sn) 0 = &S0 selected (default) 1 = &S1 selected Bit 7 Long space disconnect (Yn) 0 = Y0 (default) 1 = Y1 S22 Speaker/results bit-mapped options Bit 0,1 Speaker volume (Ln) 0 = Off (L0) 1 = Low (L1) (default) 2 = Medium (L2) 3 = High (L3) Bit 2,3 Speaker control (Mn) 0 = Disabled (M0) 1 = Off on carrier (M1) (default) 2 = Always on (M2) 3 = On during handshake (M3) Bit 4,5,6 Limit result codes (Xn) 0=X0, 4=X1, 5=X2, 6=X3, 7=X4 (default) Bit 7 Reserved S23 General bit-mapped options Bit 0 Grant remote digital loopback (RDL) 0 = RDL not allowed (&T5) 1 = RDL allowed (&T4) (default) Bit 1,2,3 Assumed DTE rate 0 = 0-300 b/s 1 = 600 b/s 2 = 1200 b/s 3 = 2400 b/s 4 = 4800 b/s 5 = 9600 b/s 6 = 19200 b/s 7 = 38400 b/s or higher (default) Bit 4,5 Assumed DTE parity 0 = even 1 = not used 2 = odd 3 = none (default) Bit 6,7 Guard tone (&Gn) 0 = None (&G0) (default) 1 = None (&G1) 2 = 1800 Hz (&G2) S27 Bit-mapped options Bit 0-3 Reserved Bit 4,5 Internal clock select (&Xn) 0 = Internal clock (&X0) (default) 1 = External clock (&X1) 2 = Slave clock (&X2) Bit 6 CCITT/Bell mode select (Bn) 0 = CCITT mode (B0) 1 = Bell mode (B1) (default) Bit 7 Reserved S28 Bit-mapped options Default: 0. Bit 0 V.23 split speed (\Wn) 0 = Disabled (\W0) (default) 1 = Enabled (\W1) Bit 1 V.23 split-speed direction 0 = 75Tx/1200Rx (%F1) (default) 1 = 1200Tx/75Rx (%F2) Bit 2 Reserved (always 0) Bit 3,4 Pulse dialing (&Pn) 0 = 39/61 make/break ratio at 10 pulses per second (&P0) (default) 1 = 33/67 make/break ratio at 10 pps (&P1) 2 = 39/61 make/break ratio at 20 pps (&P2) 3 = 33/67 make/break ratio at 20 pps (&P3) Bit 5-7 Reserved S31 Bit-mapped options Bit 0 Single line connect message control (\Vn) 0 = Message controlled by S95, Wn, Vn (\V0) (default) 1 = Single line connect message (\V1) Bit 1 Controls auto line-speed detection (Nn) 0 = Disabled (N0) 1 = Enabled (N1) (default) Bit 2,3 Controls error correction progress messages (Wn) 0 = DTE speed only (W0) (default) 1 = Full reporting (W1) 2 = DCE speed only (W2) Bit 4-7 Reserved S36 LAPM failure control (ECC models only) Bit 0-2 Indicates what should happen upon LAPM failure. These fallback options are initiated immediately upon connection if S48=128. If an invalid number is entered, the number is accepted into the register, but S36 acts as if the default value had been entered. 0 = Modem disconnects. 1 = Modem stays on-line and a direct mode connection is established. 2 = Reserved. 3 = Modem stays on-line and a normal mode connection is established. 4 = An MNP connection is attempted and if it fails, the modem disconnects. 5 = An MNP connection is attempted and if it fails, a direct mode connection is established. 6 = Reserved. 7 = MNP connection attempted; if it fails, normal mode connection is established (default). Bit 3-7 Reserved S37 Desired line connection speed Bit 0-4 Desired line connection speed. This is interlinked with the Fn command. If an invalid number is entered, the number is accepted into the register, but S37 acts as if the default value had been entered. 0 = Attempt auto-mode connect (F0) (default) 1-3 = Attempt to connect at 300 b/s (F1). 4 = Reserved. 5 = Attempt to connect at 1200 b/s (F4). 6 = Attempt to connect at 2400 b/s (F5). 7 = Attempt to connect at V.23 (F3) 8 = Attempt to connect at 4800 b/s (F6). 9 = Attempt to connect at 9600 b/s (F8). 10 = Attempt to connect at 12000 b/s (F9). 11 = Attempt to connect at 14400 b/s (F10). 12 = Attempt to connect at 7200 b/s (F7). Bit 5-7 Reserved S39 Flow control (&Kn) Bit 0-2 Status of command options 0 = No flow control (&K0) 3 = RTS/CTS (&K3) (default) 4 = XON/XOFF (&K4) 5 = Transparent XON (&K5) 6 = Both methods (&K6) Bit 3-7 Reserved S40 General bit-mapped options Bit 0,1 MNP extended services (-Kn) 0 = Disable extended services (-K0) (default) 1 = Enable extended services (-K1) 2 = Enable extended services (-K2) Bit 2 Reserved Bit 3-5 Break Handling (\Kn) 0 = \K0 1 = \K1 2 = \K2 3 = \K3 4 = \K4 5 = \K5 (default) Bit 6-7 MNP block size (\An) 0 = 64 chars (\A0) 1 = 128 chars (\A1) (default) 2 = 192 chars (\A2) 3 = 256 chars (\A3) S41 General bit-mapped options Bit 1,0 Compression selection (%Cn) 0 = Disabled (%C0) 1 = MNP 5 (%C1) 2 = V.42 bis (%C2) 3 = MNP 5 and V.42 bis (%C3) (default) Bit 6,2 Auto retrain and fallback/fall-forward (%En) 00 = Retrain and fallback/fall-forward disabled (%E0) (default) 01 = Retrain enabled (%E1) 10 = Fallback/fall-forward enabled (%E2) Bit 3-7 Reserved S48 V.42 negotiation action The V.42 negotiation process determines the capabilities of the remote modem. When the capabilities of the remote modem are known and negotiation is unnecessary, this process can be bypassed if desired. Range: 0, 7, or 128. If an invalid number is entered, it is accepted into the register, but S48 acts as if 128 had been entered. Default: 7. 0 Disable negotiation, bypass the detection and negotiation phases, and proceed with LAPM. 7 Enable negotiation. (default). 128 Disable negotiation; bypass the detection and negotiation phases; and proceed at once with the fallback action specified in S36. Can be used to force MNP. S86 Call failure reason code When the modem issues a NO CARRIER result code, a value is written to this S-register to help determine the reason for the failed connection. S86 records the first event that contributes to a NO CARRIER message. Range: 0-14. 0 Normal disconnect, no error occurred. 4 Loss of carrier. 5 V.42 negotiation failed to detect an error-correction modem at the other end. 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. S95 Extended result codes A bit set to 1 in this register enables the corresponding result code regardless of the Wn setting. Default: 0. Bit 0 CONNECT result code indicates DCE speed instead of DTE speed. Bit 1 Append /ARQ to CONNECT rate result code in error-correction mode Bit 2 Enable CARRIER rate result code Bit 3 Enable PROTOCOL identifier result code Bit 4 Reserved Bit 5 Enable COMPRESSION type result code Bit 6 Reserved Bit 7 Reserved ______________________________________________________________________________ 5**Error Correction, Data Compression, and Flow Control*********************** Your modem is compatible with the latest standards for error correction and data compression. This chapter explains basic concepts of error correction, data compression, and flow control. Error Correction Your modem supports the CCITT V.42 standard for error correction, including LAPM (link access procedure for modems) and MNP 4. In ordinary asynchronous transmission, each eight-bit sequence of data is framed by a start bit and a stop bit. In an error-correction protocol, the transmitting modem strips off the start and stop bits and divides the data into larger blocks. (The size of the blocks can vary according to the amount of data and the quality of the connection, and can be as great as 256 bytes.) For each block it calculates a polynomial checksum, and transmits both the block and the checksum synchronously. The receiving modem must also be an error-correcting modem. It recalculates the checksum and compares it with the value it received. If they match, the block is considered good; if they do not match, the receiving modem asks for the block to be retransmitted. The chance that the checksum will accidentally match a corrupted block is extremely small_so small that in practice the transmission can be considered 100-percent error-free. The most reliable and efficient error-control protocol is CCITT V.42, but your modem can also use MNP (Microcom Networking Protocol) Level 4, or it can fall back to MNP 4 or to a non-error-corrected transmission. The error-control mode is selected by the \N command. Normal Mode Normal, asynchronous non-error-correcting mode is used to communicate with non-error-corrected modems. It is selected by \N0. Auto-reliable mode also falls back to this mode if error correction is not possible. Normal mode includes speed buffering, so the local DTE-to-modem speed and the modem-to-modem line speed can differ. (This is desirable to ensure efficient data transmission, as discussed under "Flow Control" later in this chapter.) Direct Mode Direct mode is similar to normal mode, except that no speed buffering takes place. DTE speed and line speed must therefore be the same. This mode is selected by \N1. Reliable Mode "Reliable" means an error-correcting mode. In this mode, selected by \N2, the originating modem first attempts a V.42 LAPM connection (by looking for the LAPM character during modem handshaking). If the attempt fails, because the answering modem does not support V.42 or is set for the wrong mode, or because the line quality is extremely bad, it falls back to an MNP connection (again by looking for MNP characters). If the MNP connection also fails (for similar reasons), the originating modem hangs up. You should therefore use this mode only when error correction is essential and you are certain that the remote modem supports V.42 or MNP. Otherwise auto-reliable mode is a better choice. Auto-Reliable Mode Auto-reliable mode is identical to reliable mode, except that if the modem fails to make a reliable connection it falls back to normal speed-buffered mode. For most users, this is the most flexible and convenient mode. It is selected by \N3, and is the default error-correcting mode. V.42 Mode The originating modem attempts to negotiate a V.42 LAPM error-correction connection. If it fails, it hangs up without falling back to MNP or to normal mode. This mode is selected by \N4. Like reliable mode, this mode should be used only when error correction is essential and you are certain that the remote modem supports V.42. MNP Mode The originating modem attempts to negotiate an MNP error-correction connection. If it fails, it hangs up without falling back to normal mode. This mode is selected by \N5. Like reliable mode, this mode should be used only when error correction is essential and you are certain that the remote modem supports MNP. **Software Error-Correction Protocols** V.42 and MNP error correction are performed by the modem hardware and firmware. Since data integrity is essential for executable files, most file transfer protocols, such as XMODEM, used with communications software also incorporate error-correcting features. These protocols operate similarly to V.42 and MNP, except that the block length is usually shorter and the checksum may not be so robust. When used with an error-correcting modem, software error correction is redundant and adds overhead, reducing the efficiency of the transfer. On connections where hardware performs the error correction, you may want to use a non-error-correcting file transfer protocol such as YMODEM-G or IMODEM. The ZMODEM protocol offers other desirable features, such as resumption of an interrupted file transfer, and imposes only a small penalty for error correction; it may be a good choice when you cannot be sure of achieving a hardware-corrected connection. **Data Compression** Many forms of data, such as text, word-processing files, spreadsheet. or database files, are highly redundant_that is, they contain repeated characters, or sequences of characters that recur frequently. By removing the redundancy, such data can be encoded in a shorter form for transmission over a telephone line and then reconstructed at the remote site, effectively raising the data throughput of the connection. Like error correction, hardware data compression must be supported by modems at both ends of the link. Executable files usually contain much less redundancy and benefit less from compression techniques. Files that have already been compressed by an archiving program, such as PKZIP for DOS or StuffIt on the Macintosh, allow little or no further compression. Files on computer bulletin boards and on- line services are often stored in this compressed form. Your modem supports two data compression standards, V.42 bis and MNP 5. V.42 bis generally achieves greater compression, and has an additional advantage over MNP 5: it does not attempt to compress already-compressed files. MNP 5 tries to compress all files; if the file is already compressed, this attempt adds processing overhead, and in some cases actually increases the length of the file (because the protocol must add header information). Data compression requires simultaneous error correction, since corruption of even one bit could destroy an entire block of compressed data. V.42 bis data compression can be used only in conjunction with V.42 error correction. MNP 5 error compression can be used only in conjunction with MNP 4 error correction. Data compression is controlled through the %C command. The default, %C3, is to enable both V.42 bis and MNP 5 data compression; the choice depends on the type of error correction the modem negotiates. %C1 enables only MNP 5, and %C2 enables only V.42 bis; data compression is used only if the modem negotiates the corresponding error correction protocol. %C0 disables data compression altogether. **Flow Control** During a data transfer, the two modems at the ends of the connection are constantly exchanging data. A personal computer used as a DTE, on the other hand, may also be reading from or writing to disk, and its microprocessor has many other tasks to perform simultaneously. The speed with which it can send data to or receive data from the modem therefore varies. Obtaining Maximum Throughput If the maximum data transfer rate between DTE and modem (the serial port speed or DTE speed) is set to the same value as the data transfer rate between the local modem and the remote modem (the modem speed or line speed), there will be times when the DTE is unable to send data to or receive data from the modem as fast as the modem can process it. The modem therefore fails to achieve its rated throughput. Since your modem can transmit uncompressed data as fast as either 14,400 or 28,800 b/s, for maximum throughput you should set your DTE speed (usually controlled by the communications software) to 38,400 b/s (or higher if you are using data compression). In its default configuration, your modem permits DTE speed and line speed to differ (\J0). To force the DTE speed to match the line speed, use \J1. Data Buffers Of course, if the DTE speed is higher than the line speed, the DTE may send data to the modem faster than the modem can process it. To deal with this situation, the modem maintains transmit data buffers in RAM that temporarily store the extra characters. (The data buffers are also used for error correction and data compression.) At any DTE speed, there may be times when the modem sends data to the DTE faster than the DTE can accept it (for instance, if the DTE is busy writing to disk). The 16550 UART chip, found in many personal computers, buffers data received on the serial port, which helps to make high-speed downloads reliable; this chip is desirable for high-speed data communications. Communications software may also maintain its own data buffers. No matter how large a buffer is, however, it can overflow, and if that happens data is lost. The DTE and the modem must therefore have some way to stop the flow of data before the buffers overflow. There are two types of flow control: hardware and software. NOTE: Modem-to-modem flow control is handled by either the hardware error- correction protocol or the file transfer protocol. Hardware Flow Control Hardware flow control uses the RS-232 RTS (Ready to Send) and CTS (Clear to Send) signals. If the modem's transmit data buffer is about to overflow, it drops CTS, signaling the DTE to halt its flow of data. When the buffer is ready to accept more data, the modem raises CTS and the flow resumes. In the same way, if the UART's receive buffer or the communications software's buffer is full, the software can drop characters, XON and XOFF are treated as commands by a modem in data mode, and are ordinarily not passed along in the data stream to the remote modem. XOFF is the signal to the modem from the DTE or the DTE from the modem to stop data flow; it is normally ASCII 19d (13h), which is equivalent to v-S, but it can be changed through S33. XON is the signal to resume data flow; it is normally ASCII 17d (11h), which is equivalent to v-Q, but it can be changed through S32. The drawback to software flow control is that the XON and XOFF characters may unintentionally appear in binary data, aborting a file transfer. Software flow control is enabled by &K4. &K6 enables both hardware and software flow control. &K0 disables all flow control. Software flow control must also be enabled in your communications software. ______________________________________________________________________________ 6**Fax Operation************************************************************** To send and receive fax messages over your modem, you need a personal computer and fax software. When you receive a fax message, the modem performs protocol handshaking with the remote fax machine or fax modem and passes the incoming data to the fax software, which decodes it to a bit-mapped image and stores the image as a disk file. When you send a message, the fax software codes a file as a bit-mapped image and passes the corresponding data to the modem, which sends it out over the telephone line to a remote fax machine or fax modem. EIA Class 1 and Class 2 fax commands are a set of extended AT commands defined by the EIA/TIA (Electronic Industries Association-Telecommunications Industry Association) for controlling a fax modem over the EIA RS-232 serial interface. These commands and responses are described briefly in the table below. Except for the standard AT commands D and A to originate and answer a call, all fax commands begin with +F. The user does not normally need to understand the details of these commands, which are hidden by the fax software interface. Fax Class 1 & 2 Commands Command Function +FCLASS= Service class Fax Class 1 Commands +FTS=n Stop transmission and wait +FRS=n Receive silence +FTM=n Transmit data +FRM=n Receive data +FTH=n Transmit data with HDLC framing +FRH=n Receive data with HDLC framing Class 2 Action Commands D Originate a call A Answer a call +FDT Data transmission +FET=N Transmit page punctuation +FDR Begin or continue phase C receive data +FK Session termination Class 2 DCE Responses +FCON Facsimile connection response +FDCS: Report current session +FDIS Report remote identification +FCFR Indicate confirmation to receive +FTSI: Report the transmit station ID +FCSI: Report the called station ID +FPTS: Page transfer status +FET: Post page message response +FHNG Call termination with status Class 2 Session Parameters +FMFR? Identify manufacturer +FMDL? Identify model +FREV? Identify revision +FDCC= DCE capabilities parameters +FDIS= Current sessions parameters +FDCS= Current session results +FLID= Local ID string +FCR Capability to receive +FPTS= Page transfer status +FCR= Capability to receive +FAE Adaptive answer +FBUF? Buffer size (read only) +FPHCTO Phase C time-out +FAXERR Fax error value +FBOR Phase C data bit order ______________________________________________________________________________ 7**Diagnostic Tests*********************************************************** Your modem offers several diagnostic tests that you can perform to test its operation, its link to your DTE, and its link to another modem: Local analog loopback Local digital loopback Remote digital loopback These tests can help you locate and isolate a failure in the local modem, a remote modem, the serial interface, the telephone connection, or the computer and communications software. All tests are initiated by AT&Tn commands entered from the keyboard of a terminal or a computer running communications software in terminal mode. The modem should be off-line and in direct, unbuffered mode (&Q0 or &M0) before beginning the test. It is a good idea to start by typing AT to test the operation of the terminal or communications software, the integrity of its link to the modem, and the modem's ability to respond to commands. If everything is working, the modem responds OK Test Timer The value of the S18 register determines the duration of a test in seconds, from 0 to 255. It is usually convenient to specify the value of this timer as part of the test command. The default for S18 is 0, meaning that the test runs indefinitely. To terminate an indefinite test (or to terminate a timed test before it is over), type AT&T0 This command terminates the test in progress. Alternatively, you can type ATH to hang up. Self-Test Some tests include a self-test, which is simply a test pattern generated by the modem and checked for errors. If you do not run the self-test, you have to enter test data yourself at the terminal. Single-Modem Tests There are two tests you can perform without the aid of another modem: local analog loopback with and without self-test. Local Analog Loopback In the local analog loopback test, digital data from the DTE is sent to the modem's transmitter, modulated into analog form, looped back to the modem's receiver, demodulated, and returned to the DTE. This test therefore tests the modem, the DTE, and the connections between them. This test is initiated by the command ATS18=duration&T1 where duration is the length of time you want the test to run. If instead you type simply AT&T1 then the length of the test is determined by the current value of the S18 timer. If a connection exists when you issue the test command, the modem terminates it and begins the test. When the test begins you see a message giving the connect rate. Type any characters. To pass the test, the modem should echo them back to the screen exactly as you typed them. (You see the characters only once, not twice.). Local Analog Loopback with Self-Test This test is identical to the previous one, except that the modem itself generates the data, which you can see on-screen as printable ASCII characters. The command to begin the test is ATS18=duration&T8 When the test is terminated by expiration of S18 or the &T0 or H command, the modem reports the number of errors detected to the DTE. For the modem to pass the test, this number should be zero. Two-Modem Tests The remaining tests require a second modem (called the remote modem, although it does not have to be far away from the test modem, only connected to it through a telephone line). Local Digital Loopback In the local digital loopback test, the local modem receives analog data from the remote modem, demodulates it into digital form, loops it back to its own transmitter, remodulates it into analog form, and retransmits it to the remote modem. This test therefore tests your local modem, the telephone line, and the remote modem and DTE (presumed to be good). The remote modem does not need to have any special capabilities, but you need the cooperation of someone at the remote site. To perform this test, establish a connection with another modem, and then give the command ATS18=duration&T3 to begin local digital loopback. The actual testing is done at the remote site: any characters typed on the remote keyboard should be echoed back to the remote screen exactly as they were typed. There is no self-test available for this test. Remote Digital Loopback The remote digital loopback test can be performed with an unattended remote modem, but the remote modem must have CCITT V.54 remote digital loopback capability. In this test, the local modem sends a remote digital loopback request to the remote modem. If the remote modem has this capability and it is configured to accept the request, it establishes a connection. The local modem modulates digital data from its local DTE into analog data and transmits it to the remote modem. There it is received, demodulated into digital form, looped back to the remote transmitter, remodulated into analog form, and retransmitted to the local modem. The local modem in turn demodulates it and sends the resulting digital data to the local DTE. This test therefore tests your local DTE and modem, the connections between them, the telephone line, and the remote modem (presumed to be good). The command for this test is ATS18=duration&T6 As in the local analog loopback test, all characters you type at the local keyboard should be echoed perfectly back to the screen. The modem remains on-line after the test terminates. By default, a V.54-compliant modem is configured to accept requests for remote digital loopback from another modem. Requests can be denied by entering the command AT&T5 and re-enabled by AT&T4 Remote Digital Loopback with Self-Test This test is identical to the previous one, except that the local modem itself generates the data, which you can see on-screen as printable ASCII characters. The command to begin the test is ATS18=duration&T7 When the test is terminated by expiration of S18 or the &T0 or H command, the modem reports the number of errors detected to the DTE. For the modem to pass the test, this number should be zero. The modem remains on-line after the test terminates. When you issue the test command, the modem terminates it