Maxim Integrated Teridian V.22 bis Linux Softmodem for 73M1822/73M1922 MicroDAA - Manual (Page 7)

UG_1x22_043 V.22 bis Linux Softmodem for 73M1x22 MicroDAA User Guide
Rev. 1.5 7
2 User Guide
The modem firmware supports a variation of the Hayes AT command set as its DTE interface.
Originating, answering and setting up the various options are performed by sending one or more AT
commands to the modem from the DTE. A brief description of the AT command syntax and the AT
commands supported follows.
2.1 The AT Command Format
Instructions sent to the modem are referred as “AT commands” because they are always preceded by a
prefix composed of the two characters “AT” that are used to get the “ATtention” of the modem.
Provided that the correct connections have been made (refer to the data sheet), the TSC Softmodem will
use those two characters to determine the transmission rate, the data length as well as the parity used by
the DTE. Most of the AT commands have selectable parameters and related values. Every AT command
will have the following format:
{Argument}{=n}
AT - Attention code
Command - A command consists of one letter
Argument - Optional information that further defines the command
=n - Used when setting a register
You may "string" commands together in one command line as long as the total length of the command
line does not exceed 63 bytes. The attention code, AT, is only required at the beginning of the command
line. If no argument is provided with a command that takes a numerical argument, an argument of zero is
assumed. For example, the following commands are identical:
ATH or ATH0
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.
NOTE: the +++ and A/ commands are neither preceded by AT nor followed by .
The TSC Softmodem requires time before it is ready to accept another command after responding
with “OK”. When multiple AT commands are used back to back, the user must wait until after the
‘OK_’ response from the modem from the previous command before the modem is ready
to take another command. This wait time should be a least 10 ms. All commands except “D”, “A”,
and “O” return an “OK”.
The following description uses these conventions:
• All allowed parameters are shown.
•  specifies the default value when applicable.
A Answer
Causes the modem to immediately go on-line (off-hook) in the Answer mode and attempt
to handshake regardless of the value of register S0. This command gives you a method of
manually answering an incoming phone call. For restrictions, see also the R command.