National Semiconductor Corporation

Vimi Pandey

Kenneth C Ma

John D Kenny

Scott Shaw

Leo Jiang

Emilia Vai-Lun Lei

A method and apparatus is disclosed for controlling the application of a clock stopping signal in a processor to limit power consumption. The system controller receives addresses, signals indicative of primary and secondary system activity, and at least one nap timeout signal. Interrupt addresses or programmed addresses are trapped and stored as shadowed addresses. Current addresses may be compared with shadowed addresses. Matching addresses trigger a nap mode. Upon nap mode triggering, the clock stopping signal may be applied during a throttling period. Applying the clock stopping signal with programmable duty cycle during the throttling period ensures that processing necessary for the detection and servicing of primary and secondary activity can occur. A prefetch detect circuit ensures that shadowed addresses loaded in the middle of a prefetch do not trigger the clock stopping signal. Clock stopping signal is removed or inhibited when primary or secondary activity is detected or when a nap timer expires.

Power conservation method and apparatus activated by detecting shadowed

A method and apparatus is disclosed for controlling the application of a clock stopping signal in a processor to limit power consumption. The system controller receives addresses, signals indicative of primary and secondary system activity, and at least one nap timeout signal. Addresses are compared with fixed software interrupt addresses. Matching non-prefetched addresses trigger a nap mode. Upon nap mode triggering, the clock stopping signal may be throttled until a programmable NAP timer expires. Applying the clock stopping signal with programmable duty cycle during the throttling period ensures that processing necessary for the detection and servicing of primary and secondary activity may occur. A prefetch detect circuit ensures that fixed software interrupt addresses loaded in the middle of a prefetch do not trigger the clock stopping signal. The clock stopping signal is removed or inhibited when primary or secondary activity is detected or when a nap mode is terminated by a nap timer timing out.

Power conservation method and apparatus activated by detecting specific

A method and apparatus is disclosed for controlling the application of a clock stopping signal in a processor to limit power consumption. The system controller receives addresses, signals indicative of primary and secondary system activity, and at least one nap timeout signal. Addresses are compared with programmed addresses. Matching addresses trigger a nap mode. Upon nap mode triggering, the clock stopping signal may be applied during a throttling period. Applying the clock stopping signal with programmable duty cycle during the throttling period ensures that processing necessary for the detection and servicing of primary and secondary activity can occur. A prefetch detect circuit ensures that programmed addresses loaded in the middle of a prefetch do not trigger the clock stopping signal. The clock stopping signal is removed or inhibited when primary or secondary activity is detected or when nap mode is terminated by timeout.

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Santa Clara, CA, United States of America

Vimi Pandey