SI2457FS18-EVB Silicon Laboratories Inc, SI2457FS18-EVB Datasheet - Page 18

• Manufacturer Part Number: SI2457FS18-EVB
• Description: BOARD EVAL SI2457 + SI3018 16PIN
• Manufacturer: Silicon Laboratories Inc
• Series: ISOmodem®r

Specifications of SI2457FS18-EVB

• Main Purpose: Telecom, Data Acquisition Arrangement (DAA)
• Utilized Ic / Part: Si2457
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Si2457/34/15/04-Si3008
4.8. Data Compression
The modem can achieve DTE (host-to-ISOmodem)
speeds greater than the maximum DCE (modem-to-
modem) speed through the use of a data compression
protocol. The compression protocols available are the
ITU-T V.42bis and MNP5 protocols. Data compression
attempts to increase throughput by compressing the
data before actually sending it. Thus, the modem is able
to transmit more data in a given period of time.
4.9. Error Correction
The Si2457/34/15/04 ISOmodem can employ error
correction (reliable) protocols to ensure error-free
delivery of asynchronous data sent between the host
and the remote end. The Si2457/34/15/04 supports V.42
and MNP2-4 error correction protocols. V.42 (LAPM) is
most commonly used and is enabled by default.
4.10. Wire Mode
Wire mode is used to communicate with standard non-
error correcting modems. When optioned with \N3, the
Si2457/34/15/04 falls back to wire mode if it fails in an
attempt to negotiate a V.42 link with the remote modem.
Error correction and data compression are not active in
wire mode.
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.
18
Preliminary Rev. 0.7
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). 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 7 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 8 on page 19. Upon
detecting an intrusion, the ISOmodem alerts the host of
the condition via the INT pin.
®
is able to detect when another