Specifications

AN93
118 Rev. 0.8
Receiving Modem On Hold Requests
If Modem On Hold is enabled via the +PMH=1
command, the Si2493 may be placed on hold by a
remote modem. The maximum time the modem will
remain on hold is configured with the +PMHT setting.
Possible values of +PMHT are given in Table 84. Upon
receipt of a Modem On Hold request, the Si2493 will
indicate +PMHR: followed by the code corresponding to
the timeout granted. The DCD pin will de-assert while
the modem is on hold and the CONNECT result code
will indicate a return to data mode. A modem disconnect
due to a timeout or failed negotiation will result in a NO
CARRIER result code.
V.92 Quick Connect
The Si2493 supports ITU-T V.92 shortened phase 1 and
phase 2 to decrease the time required to connect to a
server modem using the V.90 modulation. After the first
call, the Si2493 will retain line parameters that allow it to
use shortened phase 1 and 2 to reduce the total
negotiation time. If line conditions change or the
remote server does not support the shortening of these
phases, the modem will automatically connect with the
normal phase 1 and phase 2 negotiation unless
specifically commanded not to. Two AT commands
control this feature, AT+PQC and AT+PSS.
The AT+PQC command controls the enabling and
disabling of shortened phase 1 and phase 2 individually
according to Table 85. It is recommended that both
shortened phases be used to realize the maximum
reduction in connect time. The possible settings of the
AT+PSS command are shown below in Table 86. The
AT+PSS command may be used to force quick connect
by setting AT+PSS = 1; however, this is not
recommended as calling a server that does not support
this feature will result in a failed connection.
Table 84. Possible +PMHT Settings
<value> Description
0 Deny V.92 Modem-on-Hold Request
1 Grant MOH with 10 second timeout
2 Grant MOH with 20 second timeout
3 Grant MOH with 30 second timeout
4 Grant MOH with 40 second timeout
5 Grant MOH with 1 minute timeout
6 Grant MOH with 2 minute timeout
7 Grant MOH with 3 minute timeout
8 Grant MOH with 4 minute timeout
9 Grant MOH with 6 minute timeout
10 Grant MOH with 8 minute timeout
11 Grant MOH with 12 minute timeout
12 Grant MOH with 16 minute timeout
13 Grant MOH with indefinite timeout
Table 85. AT+PQC Parameters
<value> Description
0 Enable Short Phase 1 and Short Phase 2
1 Enable Short Phase 1
2 Enable Short Phase 2
3 Disable Short Phase 1 and Short Phase 2