SI2404-D-FT Silicon Laboratories Inc, SI2404-D-FT Datasheet - Page 19

• Manufacturer Part Number: SI2404-D-FT
• Description: IC ISOMODEM SYSTEM-SIDE 24TSSOP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2404-D-FT

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.11. Caller ID Operation
The Si2457/34/15/04 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.
4.12. 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.
4.12.1. 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).
LVC S
BITS
30
25
20
15
10
5
®
0
0 3 6
is able to detect when another
9 12 15 18 21 24 28 30 33 36 39 42 45 47 51 54 57 60 63 66 69 72
Figure 9. Loop Voltage
Rev. 1.3
Loop Voltage (V)
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 19. See
also the %Vn commands for automatic line-in-use
detection.
4.12.2. 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 20. Upon
detecting an intrusion, the ISOmodem alerts the host of
the condition via the INT pin.
Si2457/34/15/04
75 78 81 84 87
100
19