si2439-a-gm Silicon Laboratories, si2439-a-gm Datasheet - Page 21

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

4.8. Low-Power Modes
The Si2494/39 provides multiple low power modes. Using the S24 S-register, the Si2494/39 can be set to
automatically enter sleep mode after a pre-programmed time of inactivity with either the DTE or the remote
modem. The sleep mode is entered after (S24) seconds have passed since the last DTE activity, after the transmit
FIFO is empty, and after the last data are received from the remote modem.
Additionally, the Si2494/39 can be placed in wake-on-ring-mode using the command, AT&Z. In either mode, the
ISOmodem remains in the sleep state until one of the following occurs:
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The Si2494/39 may also be placed in a complete powerdown mode. Once the Si2494/39 completely powers down,
it can only be powered back on via the RESET pin.
4.9. 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.44,
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.
4.10. Error Correction
The Si2494/39 ISOmodem can employ error correction (reliable) protocols to ensure error-free delivery of
asynchronous data sent between the host and the remote end. The Si2494/39 supports V.42 and MNP2-4 error
correction protocols. V.42 (LAPM) is most commonly used and is enabled by default.
4.11. Wire Mode
Wire mode is used to communicate with standard non-error correcting modems. When optioned with \N3, the
Si2494/39 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.
A 1-to-0 transition on TXD (UART mode).
A 1-to-0 transition on SS (SPI mode).
A 1-to-0 transition on CS (parallel mode).
An incoming ring is detected.
A parallel telephone is picked up.
Line polarity reversal
Rev. 1.0
Si2494/39
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