si2493 Silicon Laboratories, si2493 Datasheet - Page 20

• Manufacturer Part Number: si2493
• Description: V.92 Isomodem With Global Daa
• Manufacturer: Silicon Laboratories

Si2493
4.11. V.92 PCM Upstream
The Si2493 supports the ITU-V.92 PCM upstream data
protocol. This protocol allows the ISOmodem to connect
at speed up to 48 kbps upstream. Previously the
upstream connection rate was limited to 33.6 kbps. The
PCM upstream mode is enabled by default; to disable,
issue the AT command +PIG = 1 (see Table 8 on
page 23). To view both downstream and upstream
connect speeds in the connect result message, issue
the command “AT \V4” or “AT+MR”.
4.12. V.92 Quick Connect
The Si2493 supports the ITU-V.92 quick connect
protocol. Quick connect enables the modem to save
and reuse line condition parameters to reduce startup
negotiation time.
The quick connect feature is enabled by default in the
Si2493. For information on changing the quick connect
settings, see the +PSS and +PQC commands shown in
Table 8 on page 23.
4.13. V.92 Modem-on-Hold
The modem-on-hold (MOH) feature allows the modem
user to answer an incoming call while connected online
without dropping the internet connection. The modem
will remain “on hold” for a period of time determined by
the host and the ISP. There are four AT commands that
control the operation of MOH. The commands are as
follows: +PCW, +PMH, +PMHT, +PMHR. By changing
these parameters, the user can enable/disable call
waiting and MOH, set the MOH request timeout, and set
the MOH initiate timeout. For further details and syntax
on these commands see Table 8 on page 23. The MOH
feature is most useful when the Si2493 is connected to
a central office that allows call waiting.
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Rev. 1.3
4.14. Caller ID Operation
The Si2493 supports full type I and type II caller ID
detection and decode. Caller ID is supported for the US
Bellcore, European ETSI, UK, and Japanese protocols
and is enabled via the +VCID, +VCDT, and +PCW
commands.
4.15. Parallel Phone Detection
The ISOmodem
telephone, modem, or other device is using the phone
line. This allows the host to avoid interrupting another
phone call when the phone line is already in use and to
intelligently handle an interruption when the ISOmodem
is using the phone line.
4.15.1. On-Hook Line-in-use Detection
When the ISOmodem is sharing the telephone line with
other devices, it is important that it not interrupt a call in
progress. To detect whether another device is using the
shared telephone line, the host can use the ISOmodem
to monitor the TIP-RING dc voltage with the line voltage
sense (LVS) register (U6C, bits 15:8). The LVS bits
have a resolution of 1 V per bit with an accuracy of
approximately ±10%. Bits 0 through 6 of this 8-bit
signed twos complement number indicate the value of
the line voltage, and the sign bit (bit 7) indicates the
polarity of TIP and RING. The ISOmodem can also
monitor the TIP-RING dc voltage using the LVCS
register (U79, bits 4:0). See Figure 9 on page 21. See
also the %Vn commands for automatic line-in-use
detection.
4.15.2. Off-Hook Intrusion Detection
When the ISOmodem is off-hook, an algorithm is
implemented in the ISOmodem to automatically monitor
the TIP-RING loop current via the LVCS register. During
the off-hook state, the LVCS register switches from
representing the TIP-RING voltage to representing the
TIP-RING current. See Figure 10 on page 21. Upon
detecting an intrusion, the ISOmodem alerts the host of
the condition via the INT pin.
®
is able to detect when another