SI2457-D-FT Silicon Laboratories Inc, SI2457-D-FT Datasheet - Page 21

• Manufacturer Part Number: SI2457-D-FT
• Description: IC ISOMODEM SYSTEM-SIDE 24TSSOP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2457-D-FT

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

4.13. Overcurrent Detection
The Si2457/34/15/04 includes an overcurrent detection
feature
programmable time after the Si2457/34/15/04 goes off-
hook. This allows the Si2457/34/15/04 to detect if it is
connected to an improper telephone line. The
overcurrent detection feature may be enabled by setting
the OCDM bit (U70, bit 11). OHT (U77, bits 8:0) sets the
delay after off-hook until the loop current is measured.
See “AN93: ISOmodem
Guide” for details.
4.14. Global Operation
The Si2457/34/15/04 chipset contains an integrated
silicon direct access arrangement (Silicon DAA) that
provides a programmable line interface to meet
international telephone line interface requirements.
“AN93: Modem Designer’s Guide” gives the DAA
register settings required to meet international PTT
standards.
Additionally, the user-access registers (via the AT:U and
AT:R commands) may be programmed for country-
specific settings, such as dial tone, ring, ringback, and
busy tone. See AN93 for complete details.
4.15. Firmware Upgrades
The Si2457/34/15/04 contains an on-chip program ROM
that includes the firmware required for the features
listed in this data sheet. In addition, the Si2457/34/15/04
contains on-chip program RAM to accommodate minor
changes to the ROM firmware. This allows Silicon Labs
to provide future firmware updates to optimize the
characteristics of new modem designs and those
already deployed in the field. See AN93 for complete
details.
4.16. DTMF Detection / Generation
The Si2457/34/15/04 provides comprehensive DTMF
tone generation and detection. The ISOmodem can
generate single tones or DTMF tones using the +VTS
command. DTMF tones may also be generated during
dialing using the “ATDT” command. DTMF detection is
only available in voice mode (+FCLASS = 8). DTMF
digits are reported from the modem to the host using
<DLE> shielding.
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4.17. SMS/MMS Support
Short Message Service (SMS) is a service that allows
text messages to be sent and received from one
telephone to another via an SMS service center.
Multimedia Messaging Service (MMS) extends the core
SMS capability to send messages that include
multimedia content. The Fax ISOmodem provides an
interface that offers a great deal of flexibility in handling
multiple SMS standards. This flexibility is possible
because most of the differences between standards are
handled by the host using the raw data itself. The
Si2457/34/15/04 performs the necessary modulation/
demodulation of the data and provides two options for
message packet structure (Protocol 1 and Protocol 2, as
defined in ETSI ES 201 912). The rest of the data link
layer and transfer layer are defined by the host system.
The content of the message is entirely up to the host
including any checksum or CRC. ETSI ES 201 912
describes two standard data and transfer layers that are
commonly used. SMS typically relies on caller
identification information to determine if the call should
be answered using an SMS device or not.
See “6.4. SMS Support” in AN93 for more information
on how to configure the modem for SMS support.
4.18. Codec Interface (24-Pin Version Only)
In order to support a full range of voice and data
applications, the Si2457/34/15/04 includes an optional
serial interface that connects to an external voice codec
(Si3000). See AN93 for complete details.
4.19. EEPROM Interface
The Si2457/34/15/04 supports an optional serial
peripheral interface (SPI) bus serial EEPROM Mode 3
with a 16-bit (8–64 kbit range) address. Upon powerup,
if a pulldown resistor 10 k is placed between D6 and
GND, the ISOmodem attempts to detect an EEPROM.
The EEPROM is intended first for setting custom
defaults, second for automatically loading firmware
upgrades, and third to allow for user-defined AT
command macros for use in custom AT commands or
country codes. See AN93 for complete details.
4.20. AT Commands
At powerup, the Si2457/34/15/04 is in the AT command
mode. In command mode, the modem monitors the
input (serial or parallel) checking constantly for a valid
command (AT commands are described in Table 8.)
(24-Pin Version Only)
Si2457/34/15/04
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