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; (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;, continue by sending ATDTW; 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 (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;, the line requires pulse dialing. Pulse dial the
entire telephone number using ATDP12345.
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