DMA• Direct Memory Access transfers data to or from the

processor’s memory without the involvement of the processor itself.

• DMA is commonly used to provide improved performance with input/output devices.

• Rather than have the processor read data from an I/O device and copy the data into memory or vice versa, a separate DMA controller can handle such transfers in parallel.

• The processor loads the DMA controller with control information including the starting address for the transfer, the number of words to be transferred, the source and the destination.

• The DMA controller uses the bus request pin to notify the DSP core that it is ready to make a transfer to or from external memory.

• The DSP core completes its current instruction, releases control of external memory and signals the DMA controller via the bus grant pin that the DMA transfer can proceed.

• The DMA controller then transfers the specified number of data words and optionally signals completion through an interrupt.

• Some processor can also have multiple channels DMA managing DMA transfers in parallel.