4. AT Command Set and S-Registers
4-3
3830-A2-GB91-20
November 1996
Command Guidelines
Review the following guidelines before using any AT Commands.
•
The escape sequence (+ + +) is used to enter online Command
mode from Data mode.
•
The asynchronous character format for the AT command set
must be one of the following:
– 8 data bits + no 1 stop bit.
– 7 data bits + no 2 stop bits.
– 7 data bits + 1 stop bit (parity can be odd, even,
mark, or space).
•
All commands (except A/ (repeat last command) and (+ + +)
must begin with the characters AT and end by pressing the Enter
key. The AT (or at) prefix clears the command buffer and
matches the modem speed and parity to that of the DTE.
Commands can be upper- or lowercase, but the modem will not
recognize mixed case prefixes (At or aT).
•
Commands can be entered one at a time or in strings. Strings can
have up to 40 characters after the AT prefix. You can use spaces,
hyphens (-), and parentheses ( ) as fillers to make the commands
easier to read; the modem ignores these fillers and they are not
counted among the characters which make up the command
string. Commands must be entered on one line and end with the
carriage return character (Enter key).
•
Commands with the suffix n have several options associated
with them. For example, in the Ln command, L1 sets the speaker
volume to Low and L3 sets the speaker volume to High. If no
value is entered for the n suffix, the modem assumes a zero (0)
value.
•
The A/ command (without pressing the Enter key) causes the
modem to repeat the last command entered.
•
Valid commands are acknowledged with numeric or word result
codes (unless the result codes have been disabled using the Q1
command).
Table 4-1 lists all available result codes with numeric and word
equivalents.
