Method and apparatus for local and distributed data memory access (DMA) control

摘要

An apparatus for local direct memory access control includes a processor unit for generating a direct memory access designator when needed data is not available and continuing processing which does not require the unavailable data. A memory access designator holder receives the memory access designator, and a local data memory access controller performs a data memory access transaction in accordance with the content of a descriptor. Staging registers hold components of a data memory access designator and transfer the components to a selected portion of the data memory access designator holder. The data memory access controller transfers the contents of the staging registers to the data memory access designator holder when one of the staging registers is written to by the processor unit. The processor unit stalls if a write to the staging register occurs when the data memory access designator holders contain a data memory access designator, and ceases the stall when one of the plurality of data memory access designator holders ceases to contain a data memory access designator.