si2439-a-gm Silicon Laboratories, si2439-a-gm Datasheet - Page 19

• Manufacturer Part Number: si2439-a-gm
• Description: V.92 And V.34 Isomodem With Global Daa
• Manufacturer: Silicon Laboratories

Si2494/39
This device is ideal for embedded modem applications due to its small board space, low power consumption, and
global compliance. The Si2494/39 solution includes a silicon DAA using Silicon Laboratories’ proprietary third-
generation DAA technology. This highly-integrated DAA can be programmed to meet worldwide PTT specifications
for ac termination, dc termination, ringer impedance, and ringer threshold. In addition, the Si2494/39 has been
designed to meet the most stringent worldwide requirements for out-of-band energy, billing-tone immunity, surge
immunity, and safety requirements.
The Si2494/39 allows for rapid integration into existing modem applications by providing a serial interface that can
directly communicate to either a microcontroller via a UART interface or a PC via an RS-232 port. This interface
allows for PC evaluation of the modem immediately upon powerup via the AT commands using standard terminal
software.
4.1. Host Interface
The Si2494/39 interfaces to the host processor through either an asynchronous serial interface, a synchronous
Serial Peripheral Interface (SPI), or a parallel interface.
The default is asynchronous serial communication.
Selection of either SPI or parallel interface is done on power-up with reset strapping.
Please refer to “AN93:
®
ISOmodem
Chipset Family Designer's Guide” for details.
4.1.1. Asynchronous Serial Interface
The Si2494/39 supports asynchronous serial communication with data terminal equipment (DTE) at rates up to
307.2 kbps with the standard serial UART format. Upon powerup, the UART baud rate is automatically detected
using the autobaud feature.
4.1.2. Serial Peripheral Interface (SPI)
The serial peripheral interface (SPI) provides a flexible synchronous serial bus for host processor and Si2494/39
ISOmodem communication. When the Si2494/39 is powered up with SPI mode enabled the modem becomes an
SPI slave, and the pins are configured to SS (slave select input, active low), MOSI (serial data input to modem),
MISO (serial data output from modem) and SCLK (serial data clock input).
Each SPI operation consists of a
control-and-address byte and a data byte.
4.1.3. Parallel Interface
The Si2494/39 can also communicate via a parallel interface. The parallel interface is an 8-bit data bus with a
single bit address to memory mapped registers.
Rev. 1.0
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