Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 170)

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170 Rev. 1.3
6.10.2. Method 2: Single Off-Hook Transition
Use this method if it is undesirable for the modem to go off-hook more than once or to DTMF dial a single digit. This
method is somewhat more complicated and is best illustrated with an example, dialing the number 1234 below.
Set bit 7 of U-register 7A (U7A [7] (DOP) = 1) and send ATDT1;<CR> (Dial the first digit using DTMF and wait for a
response). A response of OK indicates that DTMF digit 1 was sent, and the rest of the digits can be dialed. If a
response of NO DIALTONE is received, the command failed because there was no dial tone (no line available),
and the call cannot be completed.
If a response of OK is received after sending ATDT1;<CR>, continue by sending ATDTW;<CR> to perform the
second dial tone detection and wait for a response. A response of NO DIALTONE indicates that no dial tone was
detected for two seconds, and the line is DTMF capable. Complete the dialing by sending ATDT2345<CR> (DTMF
dial beginning with the second number since the first number was successfully sent initially).
If an OK (dial tone present) was received after the ATDTW;<CR>, the line requires pulse dialing. Pulse dial the
entire telephone number using ATDP12345<CR>.
6.10.3. Method 3: Adaptive Dialing
Adaptive dialing attempts to dial with DTMF, then falls back to pulse dialing. It is enabled with bit 6 of U7A. If bit 6 is
set, the first digit is dialed with DTMF, and the ISOmodem waits two seconds. If a dial tone is still present, the first
digit is resent with pulse dialing followed by the other digits in the dial string. If a dial tone is not present, the
remaining digits are dialed with DTMF. Adaptive dialing does not select 10 pps vs. 20 pps dialing. This must be
configured beforehand. In a PBX installation, this method typically results in pulse dialing, because the first digit
dialed, usually 8 or 9, is used to obtain an outside line and therefore results in a dial tone.
6.10.4. Automatic Phone-Line Configuration Detection
The modem may automatically determine the following characteristics of the telephone line:
DTMF or pulse dialing only
 Determine if 20 pps is supported on a pulse dial only line.
 Identify it as an outside line or extension network (PBX).
 If connected to a PBX, determine if the dial tone is constant or make/break.
 If connected to a PBX, determine the number to dial for an outside line.
The AT&X1 command automatically determines the above parameters through a series of off-hooks and dialed
digits.
6.10.5. Line Type Determination
The digit dialed to determine 10 pps vs. 20 pps is programmable through S51. The &X2 command works as
described above; however, only DTMF/20 pps/10 pps determination is made (no PBX). The &X1 and &X2
commands may be aborted by sending the command, AT&X0. The result code will be OK.
Table 106. Automatic Phone Line Configuration
AT
Command
Result Code
&X1
WXYZn
W = 0 line supports DTMF dialing
1 line is pulse dial only
X = 0 line supports 20 pps dialing
1 line supports 10 pps dialing only
Y = 0 extension network (PBX)
1 connected to outside line
Z = 0 continuous dial tone
1 make-break dial tone
n = 0–9, number for outside line