Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 57)

AN93
Rev. 1.3 57
5.2. DSP
The DSP (data pump) is primarily responsible for modulation, demodulation, equalization, and echo cancellation.
Because the ISOmodem is controller-based, all interaction with the DSP is via the controller through AT
commands, S registers, and/or U registers.
5.3. Memory
The user-accessible memory in the ISOmodem includes the S registers, accessed via the ATSn command, and the
U registers, accessed via the AT:Rhh and AT:Uhh commands. These memory locations allow the modem to be
configured for a wide variety of functions and applications and for global operation.
5.4. AT Command Set
AT commands begin with the letters AT, end with a carriage return, and are case-insensitive. However, case cannot
be mixed in a single command. The only exception to this format is the A/ command. This command is neither
preceded by AT nor followed by a carriage return but re-executes the previous command immediately when the “/”
character is typed. Generally, AT commands can be divided into two groups: control commands and configuration
commands. Control commands, such as ATD, cause the modem to perform an action (in this case, dialing). The
value of this type of command is changed at a particular time to perform a particular action. For example, the
command ATDT1234<CR> causes the modem to go off-hook and dial the number 1234 via DTMF. No change is
made to the modem settings during the execution of an action command. Configuration commands change
modem characteristics until they are modified or reversed by a subsequent configuration command or the modem
is reset. Modem configuration status can be determined with the use of ATY$, ATSn?, or AT:Rhh commands where
Y is a group of AT command arguments, n is an S-register number (decimal), and hh is the hexadecimal address of
a U register.
The AT commands for reading configuration status are listed in Table 35. Each command is followed by a carriage
return.
The examples in Table 36 assume the modem is reset to its default condition. Each command is followed by a
carriage return.
Table 35. Configuration Status
Command Action
ATY$ settings Displays status of a group of
settings.
AT$ Basic AT command settings.
AT&$ AT& command settings.
AT%$ AT% command settings.
AT\$ AT\ command settings.
ATSn? Displays contents of S-register n
ATS$ Displays contents of all S registers
AT:Rhh Displays contents of U-register hh
AT:R Displays the current contents of all U registers.
AT+VCID? Displays Caller ID setting.