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SI2493D Datasheet(PDF) 22 Page - Silicon Laboratories |
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SI2493D Datasheet(HTML) 22 Page - Silicon Laboratories |
22 / 60 page Si2493 22 Rev. 1.31 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® Chipset Family 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. 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 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. 4.21. 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 (24-Pin Version Only) 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.) |
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