si2493 Silicon Laboratories, si2493 Datasheet - Page 22

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

Si2493
4.16. Overcurrent Detection
The Si2493 includes an overcurrent detection feature
that measures the loop current at a programmable time
after the Si2493 goes off-hook. This allows the Si2493
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
Designer's Guide” for details.
4.17. Global Operation
The Si2493 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.
4.18. Firmware Upgrades
The Si2493 contains an on-chip program ROM that
includes the firmware required for the features listed in
this data sheet. In addition, the Si2493 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.
4.19. DTMF Detection / Generation
The Si2493 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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Chipset Family
Rev. 1.3
4.20. 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
Si2493
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.
4.21. Codec Interface (24-Pin Version Only)
In order to support a full range of voice and data
applications, the Si2493 includes an optional serial
interface that connects to an external voice codec
(Si3000). See AN93 for complete details.
4.22. EEPROM Interface
The Si2493 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.
4.23. AT Commands
At powerup, the Si2493 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)
performs
the
necessary
modulation/