Chips and Technologies, Llc.

Brian Verstegen

Cheng Kai Chen

George A Vlantis

Rashid N Khan

Aurav R Gollabinnie

Win-Sheng Cheng

Chien-Feng Cheng

Lance King

A system for assisting the scanning of a keyboard associated with a personal computer. The system comprises a logic circuit which interacts with the microcontroller and the keyboard to reduce power consumption by the personal computer as well as freeing the microcontroller to do other tasks. The logic circuit 'interrupts' the microcontroller whenever keyboard activity is detected. An image RAM stores a pattern of current key closures to be compared in subsequent keyboard scans. A subsequent miscompare between the keyboard and the Image RAM indicates that keyboard activity has occurred. When no keys are pressed, scanning may be stopped. Any key closure will then generate an interrupt, and the microcontroller will restart scanning.

Interrupt-generating keyboard scanner using an image RAM

A circuit for waking a microprocessor from a sleep mode and providing it with its microprocessor clock long enough for a refresh, direct memory access (DMA) or master cycle operation to be done by external circuitry. The clock signal is then removed from the microprocessor to put it back into the sleep mode, thereby conserving energy. A hold signal is provided to the microprocessor to cause the microprocessor outputs to be put into a tri-state, high impedance condition, and thus relinquish control of the external bus to the external refreshing circuitry.

Sleep mode refresh apparatus

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Sunnyvale, CA, United States of America

Brian Verstegen