AT Commands

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This chapter discusses the following topics:

Direct Command
AT Commands
MNP 10 Commands
Fax Class 1 Commands
AT+ Commands/V.25ter Operation Controls

This chapter describes your modem's data mode commands. Each of these commands should be preceded by AT, except for the A/, AT command, and Escape Code.

Direct Command A/ Re-execute command.

AT Commands A Go off-hook and attempt to answer a call. B0 Select V.22 connection at 1200 bps. B1 Select Bell 212A connection at 1200 bps. C1 Return OK message. Dn Dial modifier. E0 Turn off command echo. E1 Turn on command echo. F0 Select auto-detect mode (equivalent to N1). (RC144) F1 Select V.21 or Bell 103. (RC144) F2 Reserved. (RC144) F3 Select V.23 line modulation. (RC144) F4 Select V.22 or Bell 212A 1200 bps line speed. (RC144) F5 Select V.22 bis line modulation. (RC144) F6 Select V.32 bis or V.32 4800 line modulation. (RC144) F7 Select V.32 bis 7200 line modulation. (RC144) F8 Select V.32 bis or V.32 9600 line modulation. (RC144) F9 Select V.32 bis 12000 line modulation. (RC144) F10 Select V.32 bis 14400 line modulation. (RC144) H0 Initiate a hang-up sequence. H1 If on-hook, go off-hook and enter command mode. I0 Report product code. I1 Report pre-computed checksum. I2 Report OK. I3 Report firmware revision, model, and interface type. I4 Report response programmed by an OEM. I5 Report the country code parameter. I6 Report modem data pump model and code revision. I7 Reports the DAA code (W-class models only). L0 Set low computer speaker volume. L1 Set low computer speaker volume. L2 Set medium computer speaker volume. L3 Set high computer speaker volume. M0 Turn computer speaker off. M1 Turn computer speaker on during handshaking and turn speaker off while receiving carrier. M2 Turn computer speaker on during handshaking and while receiving carrier. M3 Turn computer speaker off during dialing and receiving carrier and turn computer speaker on during answering. N0 Turn off automode detection. N1 Turn on automode detection. O0 Go on-line. O1 Go on-line and initiate a retrain sequence. P Force pulse dialing. Q0 Allow result codes to DTE. Q1 Inhibit result codes to DTE. Sn Select S-Register as default. Sn? Return the value of S-Register n. =v Set default S-Register to value v. ? Return the value of default S-Register. T Force DTMF dialing. V0 Report short form (terse) result codes. V1 Report long form (verbose) result codes. W0 Report DTE speed in EC mode. W1 Report line speed, EC protocol and DTE speed. W2 Report DCE speed in EC mode. X0 Report basic call progress result codes, i.e., OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER and ERROR. X1 Report basic call progress result codes and connections speeds (OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER, CONNECT XXXX, and ERROR. X2 Report basic call progress result codes and connections speeds, i.e., OK, CONNECT, RING, NO CARRIER (also, for busy, if enabled, and dial tone not detected), NO ANSWER, CONNECT XXXX, and ERROR. X3 Report basic call progress result codes and connection rate, i.e., OK, CONNECT, RING, NO CARRIER, NO ANSWER, CONNECT XXXX, BUSY, and ERROR. X4 Report all call progress result codes and connection rate, i.e., OK, CONNECT, RING, NO CARRIER, NO ANSWER, CONNECT XXXX, BUSY, NO DIAL TONE and ERROR. Y0 Disable long space disconnect before on-hook. Y1 Enable long space disconnect before on-hook. Z0 Restore stored profile 0 after warm reset. Z1 Restore stored profile 1 after warm reset. &C0 Force RLSD active regardless of the carrier state. &C1 Allow RLSD to follow the carrier state. &D0 Interpret DTR ON-to-OFF transition per &Qn: &Q0, &Q5, &Q6 The modem ignores DTR. &D1 Interpret DTR ON-to-OFF transition per &Qn: &Q0, &Q5, &Q6 Asynchronous escape. &D2 Interpret DTR ON-to-OFF transition per &Qn: &Q0 through &Q6 The modem hangs up. &D3 Interpret DTR ON-to-OFF transition per &Qn:. &Q0, &Q5, &Q6 The modem performs soft reset. &F0 Restore factory configuration 0. &F1 Restore factory configuration 1. &G0 Disable guard tone. &G1 Disable guard tone. &G2 Enable 1800 Hz guard tone. &J0 Set S-Register response only for compatibility. &J1 Set S-Register response only for compatibility. &K0 Disable DTE/DCE flow control. &K3 Enable RTS/CTS DTE/DCE flow control. &K4 Enable XON/XOFF DTE/DCE flow control. &K5 Enable transparent XON/XOFF flow control. &K6 Enable both RTS/CTS and XON/XOFF flow control. &L0 Select dial up line operation. &M0 Select direct asynchronous mode. &P0 Set 10 pps pulse dial with 39%/61% make/break. &P1 Set 10 pps pulse dial with 33%/67% make/break. &P2 Set 20 pps pulse dial with 39%/61% make/break. &P3 Set 20 pps pulse dial with 33%/67% make/break. &Q0 Select direct asynchronous mode. &Q5 Modem negotiates an error corrected link. &Q6 Select asynchronous operation in normal mode. &R0 CTS tracks RTS (async) or acts per V.25 (sync). &R1 CTS is always active. &S0 DSR is always active. &S1 DSR acts per V.25. &T0 Terminate any test in progress. &T4 Allow remote digital loopback. &T5 Disallow remote digital loopback request. &V Display current configurations. &V1 Diagnostics: &W0 Store the active profile in NVRAM profile 0. &W1 Store the active profile in NVRAM profile 1. &X0 Select internal timing for the transmit clock. &X1 Select external timing for the transmit clock. &X2 Select slave receive timing for the transmit clock. &Y0 Recall stored profile 0 upon power up. &Y1 Recall stored profile 1 upon power up. &Zn=x Store dial string x (to 34) to location n (0 to 3). %E0 Disable line quality monitor and auto retrain. %E1 Enable line quality monitor and auto retrain. %E2 Enable line quality monitor and fallback/fall forward. %G1 Monitor line quality and automatically request a rate renegotiation if line conditions are bad (default). %L Return received line signal level. %Q Report the line signal quality. %Un Control u-law/A-law settings (n=0 for u-law; 1 for A-law). * Serial interface operation only. \Kn Controls break handling during three states:
When modem receives a break from the DTE: \K0,2,4 Enter on-line command mode, no break sent to the remote modem. \K1 Clear buffers and send break to remote modem. \K3 Send break to remote modem immediately. \K5 Send break to remote modem in sequence with transmitted data.
When modem receives \B in on-line command state: \K0,1 Clear buffers and send break to remote modem. \K2,3 Send break to remote modem immediately. \K4,5 Send break to remote modem in sequence with transmitted data.
When modem receives break from the remote modem: \K0,1 Clear data buffers and send break to DTE. \K2,3 Send a break immediately to DTE. \K4,5 Send a break with received data to the DTE. \N0 Select normal speed buffered mode. \N1 Select direct mode. \N2 Select reliable link mode. \N3 Select auto reliable mode. \N4 Force LAPM mode. \N5 Force MNP mode. \V0 Connect messages are controlled by the command settings X, W, and S95. \V1 Connect messages are displayed in the single line format.

MNP 10 Commands
-K0 Disable MNP 10 extended services. -K1 Enable MNP 10 extended services. -K2 Enable MNP 10 extended services detection only. -SEC=0 Disable MNP10-EC. -SEC=1,[<tx level>] Enable MNP10-EC and set transmit level <tx level> 0 to 30 (0 dBm to -30 dBm).

Fax Class 1 Commands
+FCLASS=n Service class. +FAE=n Data/fax auto answer +FRH=n Receive data with HDLC framing. +FRM=n Receive data. +FRS=n Receive silence. +FTH=n Transmit data with HDLC framing. +FTM=n Transmit data. +FTS=n Stop transmission and wait.

AT+ Commands/V.25ter Operation Controls
+DS Data Compression This command controls the V.42bis data compression function if provided in the DCE.

The format for AT+DS is:

AT+DS=<direction>,<compression_negotiation>, <max_dict>, <max_string>

The Direction parameter specifies the desired direction(s) of operation of the data compression function from the DTE point of view. The Direction parameters are:

The compression_negotiation parameter specifies whether or not the DCE should continue to operate if the desired result is not obtained. The compression_negotiation parameters are:

The max_dict parameter specifies the maximum number of dictionary entries which should be negotiated. This parameter may be used by the DTE to limit the codeword size transmitted, based on its knowledge on the nature of the data to be transmitted. The max_dict parameter has a range of 512 to 65535.

The max_string parameter specifies the maximum string length to be negotiated (V.42bis P2). The max_string parameter has a range of 6 to 250. The default is 6.

+ES Error Control Selection This command contols the manner of operation of the V.42 protocol in the DCE (if present).

The format for AT+ES is:

AT+ES=<orig_rqst>, <orig_fbk>, <ans_fbk>

The orig_rqst parameter specifies the initial requested mode of operation when the DCE is operating as the originator. The orig_rqst parameters are:

The orig_fbk parameter specifies the acceptable fallback mode of operation when the DCE is operating as the originator. The orig_fbk parameters are:

The ans_fbk parameter specifies the acceptable fallback mode of operation when the DCE is operating as the answerer. The ans_fbk parameters are:

+ES V.80 Synchronous Access Mode Configuration To enable, use AT+ES=6 (Originator), AT+ES=,,8 (Receiver.) The modem can be issued T+ES=6,,8 which will cover both of the above commands. This configures the modem to initiate Synchronous Access Mode when connection is completed and Data State is entered.

+ESA Synchronous Access Mode Configuration This command is used to control the manner of operation of the Synchronous Access Mode in the DCE (if present). The format for AT+ESA is:

AT+ESA=<trans_idle>,<framed_idle>,<framed_un_ov>,<hd_auto>,<crc_type>,<nrzi_en>, <syn1>, <syn2>

The trans_idle parameter specifies the bit sequence transmitted by the DCE when a transmit data buffer underrun condition occurs. This is while operating in Transparent sub-Mode. The trans_idle parameters are:

The framed_idle parameter specifies the bit sequence transmitted by the DCE when a transmit data buffer underrun condition occurs immediately after a flag. This is while operating in Framed sub-Mode. The framed_idle parameters are:

The framed_un_ov parameter specifies the actions undertaken by the DCE when a transmit data buffer underrun or overrun condition occurs immediately after a non-flag octet. This is while operating in Framed sub-Mode. The framed_un_ov parameters are:

The hd_auto parameter specifies whether or not, in V.34 half-duplex operation, additional procedures besides those specified in section 12/V.34 shall be performed by the DCE when switching from primary channel to secondary channel operation and vice versa. The hd_auto parameters are:

The crc_type parameter specifies the CRC polynomial used while operating in Framed sub-Mode. The crc_type parameters are:

The nrzi_en parameter specifies if Non Return to Zero Inverted (NRZI) encoding is to be used by the DCE for transmit and receive data. The nrzi_en parameters are:

The syn1 parameter specifies the octet value(s) to be used while performing character-oriented framing. When trans_idle=0, syn1 specifies the 8 bit transmit idle sequence to be used by the DCE. When trans_idle=1, syn1 specifies the 8 bit synchronization sequence to be used by the DCE. When trans_idle=2, syn1 specifies the first 8 bits of 16 bit synchronization sequence to be used by the DCE. The default setting for syn1 is 255.

The syn2 parameter specifies the octet value(s) to be used while performing character-oriented framing. When trans_idle=2, syn2 specifies the last 8 bits of 16 bit synchronization sequence to be used by the DCE. The default setting for syn2 is 255.

+ESR Selective Repeat This command controls the use of the selective repeat (SREJ) option in V.42 (if present in the DCE).

The format for AT+ESR is: AT+ESR=<value> The Value parameters are:

+FCCLASS Service Class Identification

+GCAP Request Complete Capabilities List This command causes your modem to display one or more lines of information reporting the +n commands available in your modem.

+ITF Transmit Flow Control Thresholds This command allows the DTE to determine the input buffer size in the DCE for data on curcuit 103 from the DTE, to control the thresholds used for folw control of such data, and to control how often the DCE reports to the DTE the number of octets in this buffer. This parameter is ignored in Direct and Synchronous Modes, shere flow control is not used. The Off and On parameters are applicable in Synchronous Access, Frame Tunneling, Buffered V.14, and error control modes. The Report Period parameter is applicable only in Synchronous Access mode. The format for AT+ITF is: AT+ITF=<off>,<on>,<report_period>

+MS Select Modulation This command allows you to select a specific modulation, enable or disable automode, and specify the highest and lowest connection rates for your modem.

The command format for AT+MS is: AT+MS = <mod>,<automode>,<minimum rate>,<maximum rate> <x_law>, <rb_signal>, <Maxup_rate>

You can leave a parameter at its current value by leaving that parameter's place blank and entering a comma to separate the parameters or by entering a carriage return ([CR]) if it is the last parameter. To specify a preferred modulation, enter a character designation from the <mod> column of the following table. The Mod parameter defined:

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