Specifications

AN93
28 Rev. 0.9
The modem has a 48-character buffer, which makes it
possible to enter multiple AT commands on a single
line. The multiple commands can be separated with
spaces or linefeed characters to improve readability.
Neither the AT nor the space (or linefeed characters)
are loaded into the buffer and are not included in the 48
characters. The command must end with a carriage
return character to instruct the modem to process the
command. The modem ignores command lines greater
than 48 characters and reports “ERROR”.
Table 16 shows examples of multiple AT commands on
a single line.
Consecutive U-Registers can be written in a single
command as “AT:Uhh,xxxx,yyyy,zzzz” where hh is the
first U-Register address in the three register
consecutive series. This command writes a value of
xxxx to Uhh, yyyy to Uhh+1, and zzzz to Uhh+2.
Additional consecutive values may be written up to the
48 character limit.
Caution: Some U-Register addresses are reserved for
internal use and are not available. Consequently, there
are gaps in the addresses of available U-Registers.
Writing to reserved registers can cause unpredictable
results. Be certain the U-Register addresses written
with a consecutive write command have consecutive
addresses. Only one :U or :R command is allowed per
AT command line.
If a command line has multiple commands, there can be
only one :U or :R command, and it must be the last
command in the string. For example,
ATS0=3M1X1:U42,0022.
This restriction also applies to all commands beginning
with the “+” character (eg. +VCID).
For example, AT:U42,0022:U43,0010<CR> is an illegal
command and causes unpredictable behavior. Also, \Tn
commands may not be used on the same command line
as a :U or :R command.
The AT command execution time is approximately
300 ms. The host must wait for a response after each
command (e.g., “OK”) before issuing additional
commands. The reset recovery time (the time between
a hardware reset or the carriage return of an ATZ
command and the time the next AT command can be
executed) is approximately 300 ms.
Characters must not be sent between the ATDT
command and the protocol message. During this time,
the modem is in a transition between command and
data modes. Any characters sent during this time will
cause the connection attempt to fail.
Blind dialing (dialing without waiting for dial tone) is
enabled by ATX0, ATX1, and ATX3. Whether or not
blind dialing is enabled, use of the W dial modifier
causes the modem to look for a dial tone before dialing
the number string after the W. For example, an AT
command string, “ATX1 DT 9, W123456<CR>”, causes
the modem to dial 9 immediately without detecting a dial
tone but does not dial 123456 until a dial tone is
detected. AT commands and result codes are listed in
Tables 18–22. The default settings are shown in bold.
Table 15. Command Examples
Command Result Comment
AT$ E = 001 Configuration status of basic
AT commands.
M=000
Q = 000
V=001
X=004
Y=000
AT&$ &D = 001
&G = 017
Configuration of &AT
commands.
&H = 000
(Si2457)
&P = 000
ATS2? 043 S-Register 2 value—Escape
code character (+).
AT:R2C 00A0 Value stored in register U2C.
Table 16. Multiple AT Commands on a
Single Line
Command Result
ATS0=4M1X1<CR> The modem auto-answers on
the fourth ring. The speaker
is on during dial and hand-
shake only. Blind dialing is
enabled.
AT S0=4 M1 X1 <CR> Same as above (spaces do
not matter).
ATS0=4<CR> Same as above.
ATM1<CR>
ATX1<CR>
Table 17. Consecutive U-Register Writes on a
Single Line
Command Result
AT:U00,0078,67EF,C4FA 0x0078 written to U00
0x67EF written to U01
0xC4FA written to U02