US Patent 8117475 Direct memory access controller

A system has a central processing unit (CPU) operable to operate in a sleep or low power mode and in an active mode, a plurality of system components operable to operate in a sleep or low power mode and in an active mode, and a direct memory access (DMA) controller operating independently from the CPU and operable to operate in a sleep or low power mode and in an active mode, wherein the DMA controller is further operable to transfer data from and to a memory or peripheral device, wherein when the system is in a sleep or low power mode, only the DMA controller and any system component which is necessary to perform a DMA transaction are switched into active mode.