The CIA World Factbook 1992

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Text File | 1991-12-02 | 14.3 KB | 376 lines

"AT" COMMANDS: PROTOCOL SUMMARY -------------------------------- Hayes compatible modems autodialing protocol use the industry standard "AT" command set. Each command in the autodialing protocol follows the format below (with the exception of the A/ command and the +++ command, which will be discussed later). <AT><Command>{Argument}{=n}{More}<Return> Each element of the command line shown above is described below. Note: Information in "angle" brackets <> must be included as part of the command line, while information in "curly" braces {} may or may not be necessary as part of the command line. AT This is the attention code to let the modem know that a command will follow. The AT must be in capital letters. Command A command consists of one or two letters. Argument Optional information that further defines the command. =n Used when setting a register. These registers are used to change certain of the modem's operating parameters. More You may "string" commands together in one command line as long as the total length of the command line does not exceed 40 characters. The attention code, AT, is only required at the beginning of the command line. Therefore, the "more" command sequence follows the following format: <Command>{Argument}{=n} <Return> This is the carriage return or enter key on your computer's keyboard. Pressing RETURN at the end of the command line will tell the modem to execute the command(s) in that command line. For example, let's look at the command line AT DT 555-1234 ; <return> Here, AT is the attention code; DT is the command to dial a number using the tone method; 555-1234 is the argument (a phone number); ; is "more" (another command, this one instructing the modem to return to the command state after dialing); and <return> is the carriage return terminating the command line. In the following commands, r and n are used as variables and can have the values that are explained with the associated command. "n...n" means that an item may be repeated as many times as necessary, as long as the entire command line does not exceed 40 characters. "AT" COMMAND SET SUMMARY ------------------------ A Tells the modem to immediately answer an incoming call. A/ Causes the modem to re-execute the last command that was issued. For example, this command can be used to redial a number if the previous command was a dial command. A/ and +++ are the only commands that are neither preceded by AT nor followed by <return>. B[n] n=0 or 1 (default=1) B0 Selects CCITT V.22 operation at 1200 bps. B1 Selects Bell 212A operation at 1200 bps. C[n] n=0 or 1 (default=1) This command instructs the modem to turn the carrier signal ON or OFF. C0 Carrier OFF C1 Carrier ON D[n...n] This command instructs the modem to dial the phone number expressed by the string argument n...n. The number will be dialed with either tones or pulses depending on how the last number was dialed. On power up, this command will default to pulse dialing. (See note in DT[n...n] command). The allowable arguments for n...n differ for pulse and tone dialing, see the detailed descriptions under DT[n..n]. DP[n...n] n=0 to 9, P T R ;@ ! W / This command instructs the modem to dial the phone number expressed by the argument n...n using pulse dialing. See the detailed description of the arguments under DT[n...n] below). DT[n...n] n=0 to 9, P T R ;@ ! W / A B C D * # This command instructs the modem to dial the phone number expressed by the argument n...n using tone dialing. The [n...n] arguments consist of three groups: In addition to the numerals 0-9, there are some special characters that can be included in a dialing string. They are called dial string modifiers, and they both define the phone number to be dialed, and certain other specific dialing operations. These characters are P R T ; , @ ! W / A B C D * #. These characters have the following functions: P Causes the MODEM to pulse dial the digits that follow. R Causes the modem to go into the Answer mode after dialing the number. This character must only be at the end of the dialing string. T Causes the modem to tone dial the digits, characters, and symbols that follow. ; A ; (semicolon) causes the modem to go back into the Command State, allowing you to enter other commands while online. , When inserted in a dialing string, a , (comma) causes the modem to pause. The default time for the pause is two seconds, and can be changed by modifying register S8. @ A @ (commercial "at") causes the modem to wait for a specified period of quiet before proceeding. This is often used to detect the end of a prerecorded message. The default is 30 seconds, and can be changed by modifying register S7. Result code 8 will be reported regardless of which result code set is selected. ! A ! (exclamation mark) causes a "hookflash." This simulates hanging up for 1/2 second and then reconnecting. It is typically used for transferring calls. W Causes the modem to wait for a dial tone for a specified length of time before proceeding. The default is 30 seconds, and can be changed by modifying register S7. Result code 6 will always be included regardless of which result code set is selected. / A / (slash) causes the modem to wait for 0.125 second before proceeding with the rest of command line. A-D, *, # The characters A B C D and the symbols * # can be used only during tone dialing. They are typically used to access the newer features of modern telephone systems. E[n] n=0 or 1 (default=1) Causes the modem to either echo characters or not to echo characters while in the Command State. E0 Echo is OFF E1 Echo is ON F[n] n=0 or 1 (default=1) The F[n] command selects either Full- or Half-Duplex operation. This causes the modem to either echo or not to echo characters while online. F0 Half-Duplex; echo is ON F1 Full-Duplex; echo is OFF H[n] n=0 or 1 (default=0) Causes the modem to go offhook or onhook. (Going offhook means that the modem "picks up" the telephone; going onhook means that the modem "hangs up" the telephone.) H0 Onhook H1 Offhook I[n] n=0-2 (default=0) The I[n] command requests that the modem respond with certain product information. I0 Returns product identification code of the format 24X. I1 Returns ROM checksum I2 Runs memory (ROM) test and returns with OK or ERROR result code message L[n] n=0 to 7 (default=3) The L[n] command selects the speaker volume (0 is the softest; 7 is the loudest). M[n] n=0-3 (default=1) The M[n] command controls the ON/OFF function of the speaker. M0 Speaker always OFF M1 Speaker ON until carrier is detected M2 Speaker always ON O[n] n=0-2 The O[n] command causes the modem to go offhook in the same mode (originate or answer) as in the previous call, and controls whether or not the Remote Digital Loopback mode is ON or OFF. O0 Causes the modem to go off hook in the same mode (originate or answer) as in the previous call. O1 Remote digital loopback OFF O2 Remote digital loopback ON P Causes the modem to pulse dial until tone dialing is selected or the modem is reset. Q[n] n=0 or 1 (default=0) The Q[n] command tells the modem to either send the Result Codes or to remain quiet. Q0 Send Result Codes Q1 Stay quiet S[r]? r=0 to 16 The S[r]? command requests the modem to respond with the value of any of the modem's 17 registers. These registers are used to set up various operating parameters of the modem. S[r]=[n] r=0 to 16 n=0 to 255 The S[r]=[n] command allows you to set (modify) the value of any of the 17 registers. T Causes the modem to touch-tone dial until pulse dialing is selected or the modem is reset. V[n] n=0 or 1 (default=1) The V[n] command either verbal (whole words) or numerical Result Codes. V0 Result Codes sent as digits (numerals) V1 Result Codes sent as whole words X[n] n=0 to 4 (default=0) The X[n] command selects normal or extended Result Codes. X0 Includes Result Codes 0-4 X1 Includes Result Codes 0-5 X2 Includes Result Codes 0-6 X3 Includes Result Codes 0-5, 7 X4 Includes Result Codes 0-8 Dial string modifiers W and @ cause result codes 6 and 8, respectively, to always be included. Result Codes are summarized at the end of this document. Y[n] n=0 or 1 (default=1) The Y[n] command enables or disables long space disconnect. Y0 Long space disconnect disabled Y1 Long space disconnect enabled Z The Z command resets the modem. All commands and registers are returned to their default values. +++ During a data connection, the escape command +++ returns you to Command State without terminating the data connection so you can enter commands. (Do not type AT before the pluses or <return> after them. You must wait for one second of inactivity before and after typing the pluses.) RESULT CODES ------------ Digit Word Code Code Meaning ────── ────────── ────────────────────────────────────── 0 OK Command was executed without error 1 CONNECT Carrier detect at 300 or 1200 bps (basic Result Code) 2 RING Ring signal detected 3 NO CARRIER Carrier was lost or connection was not made 4 ERROR Invalid command or error in command line 5 CONNECT 1200 Connection established at 1200 bps 6 NO DIALTONE No dialtone was detected on the telephone line 7 BUSY Busy signal detected after dialing 8 NO ANSWER The "wait for quiet answer" dial modifier @ was issued, and five seconds of silence was not detected S-REGISTER SUMMARY ------------------ Register Range Units Function Default ──────── ────── ──────── ─────────────────────── ─────── S0 0-255 rings Number of rings on which 00 the modem answers the call S1 0-255 rings Number of rings occurred 00 S2 0-127 ASCII Escape Code character 43 S3 0-127 ASCII Carriage return character 13 S4 0-127 ASCII Line feed character 10 S5 0-32 ASCII Backspace character 08 & 127 S6 2-255 seconds Wait time for dial tone 02 S7 1-255 seconds Wait time for carrier 30 S8 0-255 seconds Length of pause (caused 02 by comma) S9 1-255 1/10 sec Carrier detect response 06 time S10 0-255 1/10 sec Lost carrier to hang-up 07 delay S11 50-255 milli- Duration and spacing of 70 seconds touch-tones. S12 0-255 1/50 sec Escape Code guard time 50 S13 ------ -------- UART Status Register -- S14 ------ -------- Option Register -- S15 ------ -------- Flag Register -- S16 0-2, 4 -------- Self test 00