At&t Bell Laboratories

Lucent Technologies Inc.

Michael David Rauchwerk

Daniel Amrany

Hong Y Chung

Velraj Ramaswamy

A personal computer's microprocessor is time-shared to provide the functions formerly provided by a microprocessor dedicated to a modem. This technique is transparent to software applications programs which interact with a modem. The personal computer utilizes an operating system, such as the Microsoft Windows operating system, in which a portion of the operating system, known as the communications driver, provides the interface between the operating system and the personal computer's serial and parallel communication ports. All communications between the communications driver and the rest of the operating system are examined. Those communications destined for a particular port associated with a modem not having a dedicated microprocessor are redirected while other communications destined for other ports are passed to the Microsoft Windows communications driver. The redirected communications are coupled to a software application program which utilizes the PC microprocessor to carry out the functions formerly provided by the modem microprocessor. As a result, the modem's microprocessor and associated RAM and ROM can be eliminated. The software application program can be loaded into the personal computer's memory only when required.

Technique for time-sharing a microprocessor between a computer and a

The present invention addresses a timing synchronization problem which arises in tandem modem operation when a single codec strobed by a common sample clock is used for A/D and D/A signal conversion in a modem. Tandem modem operation is defined as a system application when two modems have their RS-232 interfaces directly connected to one another. In accordance with the present invention, a digital interpolator connected to the A/D converter in the modem effectively alters the timing phase of the A/D converter in response to first and second control signals. The first control signal is generated in response to an externally supplied clock and an internal modem clock and is representative of any perturbations in the externally supplied clock with respect to the internal modem clock. The second control signal is generated in response to digital signals derived from the incoming analog signal from a remote modem and is representative of any residual asynchronism between the transmit sample clock of the remote modem and the modem's transmit sample clock after alteration by the digital interpolator in response to the first control signal alone.

Timing recovery scheme for a transceiver using a single sample clock

Primary and secondary data are communicated from a transmitter to a receiver in a communication system. The value of an individual primary data word is communicated by transmitting an individual one of first plurality of channel symbols associated with that value while the value of a combined data word comprising an individual primary data word and an individual secondary data word is communicated by transmitting an individual one of second plurality of channel symbols associated with that value. In the receiver, both the primary and secondary data word values are recovered from the channel symbols thus transmitted. The approach of alternating two sets of channel symbols for transmission depending on the data word size can further apply to data communications at various fallback speeds.

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Holmdel, NJ, United States of America

Michael David Rauchwerk