Comtrol AT Commands for SmartACFL - Manual (Page 13)

Command Reference Manual
100722A Conexant 2-1
2. SYNTAX AND PROCEDURES
The command and response syntax and procedures generally conform to referenced recommendations and standards. Since
these recommendations and standards describe characteristics universal to a large installed base of modems to a maximum
degree, there may be syntax and procedural differences due to extensions and behavioral differences in implemented
commands, parameters, and responses beyond that described in these recommendations and standards.
The syntax and procedures described in this section are based on V.250 and V.253 with additional information included for
implemented extensions, behavioral differences beyond V.250, and legacy commands.
2.1 Alphabet
The T.50 International Alphabet 5 (IA5) is used in this document. Only the low-order seven bits of each character are
significant to the modem; any eighth or higher-order bit(s), if present, are ignored for the purpose of identifying commands
and parameters. Lower-case characters are considered identical to their upper-case equivalents when received by the
modem from the DTE. Result codes from the modem are in upper case.
2.2 DTE Commands Lines
Words enclosed in <angle brackets> are references to syntactical elements. The brackets are not used when the words
appear in a command line, the brackets are not used. Words enclosed in [square brackets] represent optional items which
may be omitted from the command line at the specified point. The square brackets are not used when the words appear in
the command line. Other characters that appear in syntax descriptions must as included as shown.
Any modem responses are mentioned in terms of their alphabetic format; the actual response issued will depend on the
setting of parameters that affect response formats, e.g., Q and V commands (see 2.7).
2.2.1 Command Line General Format
A command line is made up of three elements: the prefix, the body, and the termination character.
The command line prefix consists of the characters "AT" or "at" or, to repeat the execution of the previous command line, the
characters "A/" or "a/".
The body is made up of individual commands described in this document. Space characters (IA5 2/0) are ignored and may be
used freely for formatting purposes, unless they are embedded in numeric or string constants. The termination character may
not appear in the body. The modem can accept at least 50 characters in the body.
The termination character may be selected by a user option (parameter S3), the default being CR.
2.2.2 Command Line Editing
The character defined by parameter S5 (default, BS) is interpreted as a request from the DTE to the modem to delete the
previous character. Any control characters (IA5 0/0 through 1/15, inclusive) that remain in the command line after receipt of
the termination character are ignored by the modem.
The modem checks characters from the DTE first to see if they match the termination character (S3), then the editing
character (S5), before checking for other characters. This ensures that these characters will be properly recognized even if
they are set to values that the modem uses for other purposes. If S3 and S5 are set to the same value, a matching character
will be treated as matching S3 (S3 is checked before S5).
2.2.3 Command Line Echo
The modem may echo characters received from the DTE during command state and online command state back to the DTE,
depending on the setting of the E command. If enabled, characters received from the DTE are echoed in the same format as
received. Invalid characters in the command line or incomplete or improperly-formed command line prefixes may not be
echoed.