Hewlett-packard Company

Hewlett-packard Corporation

Robert B Puckette

Timothy J Jondrow

Preston D Brown

Michael D Derocher

Steven L Fogle

A clock reference frequency is digitally derived from a base signal, then digitally modulated by ramping the clock reference frequency up and down about a desired frequency. The modulation occurs in periodic fashion at a prescribed modulation frequency. Such modulation spreads the electromagnetic energy of the system signals over a band that is a portion of the desired clock frequency. As a result, energy in harmonics of the respective system signals also are spread. When the energy spreading of any system signal or harmonic of such signal occurs over a bandwidth greater than the 120 kHz bandwidth of conventional communication receivers, adverse EMI emissions are reduced.

Digital method and apparatus for reducing EMI emissions in

The position encoder system requires no keyboard surface area and includes a retractable and extendable handle that is stored inside the computer when not in use. The handle is extended for use near the computer keyboard. The movement of the handle is sensed by a high resolution sensing system that consumes relatively little power.

Position encoder system

Information representing the state of switches carried on a pointing device handle is carried to an associated computer via a capacitive coupling technique.

Switch interconnect for position encoder system

Apparatus for detecting electrostatic discharge events that may affect operation of a calculator and for suspending the operation of an internal calculator chip before the discharge can corrupt the chip's operation. The apparatus includes an edge detector that detects the discharge event and generates a signal to timer circuitry. The timer circuitry in response generates a signal for a predetermined time to WAIT circuitry which suspends operation of the calculator chip before its calculations can be corrupted. The predetermined time is long enough for the electrostatic discharge to dissipate sufficiently so that it can no longer corrupt the calculations. After the predetermined time passes, the calculator chip resumes its operation to complete its calculations.

Method and apparatus for suspending computation due to detection of

The present invention describes a method and apparatus for interconnecting keyboard lines and memory lines to the same pins of a microprocessor or calculator chip. Resistors are placed in series with each keyboard line before interconnection to the memory lines and microprocessor pins to prevent disruption or degradation of the memory signal in the event a key on keyboard is depressed during a memory operation cycle. Means are provided to prevent memory operations during keyboard scan routines and means are provided to prevent keyboard scan routines from operating during memory operation cycles.

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Corvallis, OR, United States of America

Robert B Puckette