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Abstract

A direct memory access and direct register access (DMA/DRA) controller and method are used on microprocessors, microcontrollers and digital signal processors which incorporate shadow register sets or register windows or both. The DMA/DRA controller is coupled to the processor's data paths so as to transfer data between the registers and memory in burst and in cycle-steal modes. The DMA/DRA controller enables the processor to perform single-cycle register set save and restore operations by extending the effective depth of the shadow register set by creating virtual register sets in memory. The DMA/DRA subsystem interacts with the caches and other memory traffic controllers to perform the register set transfers before they are needed making use of otherwise unused external memory cycles. Using this invention, delays associated with register saving and restoring can be largely eliminated without the need for unduly large and costly internal sets of register files.

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First Claim