Conexant Chip Combines Set-Top, Modem

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Chip manufacturer Conexant Systems Inc. last week bowed a new digital cable set-top transceiver that combines digital set-top and cable-modem functionality into a single silicon chip.

"By integrating onto one chip the functions that once were on separate chips, we can raise performance while lowering the price point on the bill of materials for consumer cable products," said Conexant marketing director Anthony Simon.

The new Conexant "CX24420" chip features three downstream 16-256 quadrature amplitude modulation (QAM) demodulator channels-two personal video recorder channels (one for viewing, the other for recording) and a third for cable-modem traffic-along with two upstream channels (broad in-band and narrow out-of-band).

The chip also incorporates upgradable media-access control (MAC) software architecture to support such standards as Data Over Cable Service Interface Specification 1.0 and 1.1, EuroDOCSIS and DVB/DAVIC 1.2 and 1.5.

The unusual integration of these international transmission standards gives Conexant an opportunity to seek a worldwide market for just one chip. Until now, Conexant rival Broadcom Corp. has dominated MAC technology.

Conexant's new chip also is designed to work with the company's "CN2811" silicon-based cable tuner and "CX24490" series of single-chip MPEG-2 (Moving Picture Expert Group) decoders, creating an "end-to-end silicon solution for interactive digital set-top box applications," said Simon.

The eventual goal, he added, is to consolidate these three chips (transceiver, tuner and decoder) into one piece of silicon.

"Once we can have an entire set-top box on a single chip, then we'll no longer be limited on where the chip can be placed," such as mobile or portable devices or even desktop computers, he said.

Conexant's plan is to work the new chip into high-end cable boxes at first, then lower costs so that it can be "mainstreamed" into medium and low-end boxes.

Broadcom has led the market with its integrated "7100" chip for digital boxes. But the chipmaker has not introduced a single chip like Conexant's latest entrant, said a Broadcom spokesperson who declined further comment.

Mark Samuel, marketing director for Philips Semiconductors' "Nexperia" line, is not optimistic on consolidating all cable functions into a single chip.

"Because of innovation and standards not yet being finalized, you'll need to keep some functions on separate chips, at least for the next three of four production cycles," he said. A cycle typically runs about three years.

Texas Instruments Inc. isn't presently working on an integrated set-top/cable modem chip, said Eric Dewannain, general manager of TI's cable broadband communication group.

"Our strategy is to go from data over cable modems and then IP (Internet protocol) voice-over-cable, and then video-over-cable modems," he said. "We don't believe in integration just for the sake of integration. You first have to future-proof your products."

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