Importance

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Abstract

Embodiments of a method and system for conserving power used in a central processing unit (CPU) are described. An embodiment uses direct memory access (DMA) fetch suspend logic to allow the CPU to stay in a sleep state indefinitely until a break event occurs. Embodiments include power management monitoring and Universal Serial Bus (USB) descriptor monitoring logic. Power management monitor logic monitors the CPU sleep state and sets a status flag to the USB descriptor monitoring logic whenever the CPU is in a predefined sleep state. The USB descriptor monitoring logic monitors the fetching of linked descriptor lists. When the CPU status flag is raised, it causes monitoring of the descriptor fetch by the USB descriptor monitoring logic. If the USB controller has completed all of the descriptor fetches while the CPU sleep flag is true, this logic sets a flag to cause the USB controller to suspend DMA fetch operations.

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First Claim