cx20493-35/app Conexant Systems, Inc., cx20493-35/app Datasheet - Page 26

• Manufacturer Part Number: cx20493-35/app
• Description: With Cx20493 Smartdaa?
• Manufacturer: Conexant Systems, Inc.

2.5.2
2.5.3
2.6
2.6.1
2.6.2
2.6.3
2.6.4
2-6
CX81801-7x/8x SmartV.XX Modem in 128-Pin LQFP with CX20493 in 32-Pin LQFP Data Sheet
Quick Connect
PCM Upstream
Error Correction and Data Compression
V.42 Error Correction
MNP 2-4 Error Correction
V.44 Data Compression
V.42 bis Data Compression
The quick connect function enables the modem to shorten the connect time of subsequent
calls to a server supporting quick connect. The quick connect feature is supported by the
+PQC command.
PCM upstream boosts the upstream data rates between the user and ISP to reduce upload
times for large files and email attachments. A maximum of 48 kbps upstream rate is
supported with PCM upstream enabled, in contrast to a maximum of 32.2 kbps upstream
rate with PCM upstream not enabled. PCM upstream is supported by the +PCM
command. PCM upstream is disabled by default.
V.42 supports two methods of error correction: LAPM and, as a fallback, MNP 4. The
modem provides a detection and negotiation technique for determining and establishing
the best method of error correction between two modems.
MNP 2-4 is a data link protocol that uses error correction algorithms to ensure data
integrity. Supporting stream mode, the modem sends data frames in varying lengths
depending on the amount of time between characters coming from the DTE.
V.44 data compression mode, enabled by the +DS44 command, encodes pages and files
associated with Web pages. These files include WEB pages, graphics and image files,
and document files. V.44 can provide an effective data throughput rate up to DTE rate for
a 56-kbps connection. The improved performance amount varies both with the actual
format and with the content of individual pages and files.
V.42 bis data compression mode, enabled by the %Cn command or S46 register, operates
when a LAPM connection is established.
The V.42 bis data compression employs a “string learning” algorithm in which a string of
characters from the DTE is encoded as a fixed length codeword. Two 2-KB dictionaries
are used to store the strings. These dictionaries are dynamically updated during normal
operation.
Conexant
102247B