si2401 Silicon Laboratories, si2401 Datasheet - Page 25

• Manufacturer Part Number: si2401
• Description: V.22bis Isomodem With Integrated Global Daa
• Manufacturer: Silicon Laboratories

5.3. AT Command Set Description
A
The “A” command makes the modem go off-hook and
respond to an incoming call. This command is to be
executed after the Si2401 has indicated a ring has
occurred. (The Si2401 indicates an incoming ring by
echoing an “R”.)
This command is aborted if any other character is
transmitted to the Si2401 before the answer process is
completed.
Auto answer mode is entered by setting S00 (NR) to a
non-zero value. NR indicates the number of rings before
answering the line.
Upon
whatever protocol has been determined via the modem
control registers in S07 (MF1).
If no transmit carrier signal is received from the calling
modem within the time specified in S39 (CDT), the
modem hangs up and enters the idle state.
D
The D commands make the modem dial a telephone
call according to the digits and dial modifiers in the dial
string following the command. A maximum of 64 digits is
allowed. A DT command performs tone dialing, and a
DP command performs pulse dialing.
The ATH1 command can be used to go off-hook without
detecting a dial tone or dialing.
The dial string must contain only the digits “0–9”, “*”, “#”,
“A”, “B”, “C”, “D”, or the modifiers “ ; ”, “ / ”, or “ , ”. Other
characters are interpreted incorrectly. The modifier “ , ”
causes a two-second delay (added to the spacing value
in S04) in dialing. The modifier “ / ” causes a 125 ms
delay (added to the spacing value in S04) in dialing. The
modifier “ ; ” returns the device to command mode after
dialing and must be the last character.
If any character is received by the Si2401 between the
ATDT#<CR> (or ATDP#<CR>) command and when the
connection is made (“c” or “d” is echoed), the extra
DT#
DP#
Table 12. AT Command Set Summary
V0
V1
q#
Z
z
answering, the modem communicates by
Answer
Dial
Tone Dial Number.
Pulse Dial Number.
Read S-Register in binary
Result code with no carriage return
Result code with added carriage
returns
Software reset
Wakeup on ring
Rev. 1.0
character is interpreted as an abort, and the Si2401
returns to command mode ready to accept AT
commands. A line feed character immediately following
the <CR> is treated as an “extra character” and aborts
the call.
If the modem does not have to dial (i.e., “ATDT<CR>” or
“ATDP<CR>” with no dial string), the Si2401 assumes
the call was manually established and attempts to make
a connection.
5.3.1. Automatic Tone/Pulse Dialing
The Si2401 can be configured to attempt DTMF dialing
and automatically revert to pulse dialing if it determines
that the line is not DTMF-capable. This feature is best
explained by the following example.
If it is desired that the telephone number, 12345, be
dialed, it is normally accomplished through either the
ATDT12345 or the ATDP12345 command. In the force
pulse dialing mode of operation, the following string
should be issued instead: ATDT1,p12345
If the result code returned is “t,”, this indicates that the
dialing was accomplished using DTMF dialing. If the
result code returned is “tt,”, it indicates that the dialing
was accomplished using pulse dialing.
In the above example, the Si2401 dials the first digit “1”
using DTMF dialing. The “,” is used to pause in order to
ensure that the central office has had time to accept the
DTMF digit “1”. When the Si2401 processes the “p”
command, it attempts to detect a dial tone. If a dial tone
is detected, the DTMF digit “1” was not effective; hence,
the line does not support DTMF dialing. Conversely, if
the dial tone is not detected, the DTMF digit “1” was
effective, and the line supports DTMF dialing. The
character after the “p” may or may not be dialed
depending on whether the DTMF digit “1” was effective.
If the “1” was effective (DTMF mode), the character after
the “p” is skipped. The next DTMF digit to be dialed is
“2”. Subsequent digits are all DTMF. If the “1” was not
effective, the first character after the “p” (the “1”) is
pulse-dialed, and subsequent digits are all pulse-dialed.
E
Tells the Si2401 whether or not to echo characters sent
from the terminal.
Does not echo characters sent from the terminal.
Echoes characters sent from the terminal.
H0
Hang up and go into command mode (go offline).
H1
Go off-hook and remain in command mode.
EO
E1
Command Mode Echo
Hangup
Off-hook
Si2401
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