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The device that holds the bus at a given time is called bus master. Typical Block Diagram of DMA Controller Working of DMA ControllerÄMA controller has to share the bus with the processor to make the data transfer. The typical block diagram of the DMA controller is shown in the figure below. When the transfer is completed, DMA informs the processor by raising an interrupt. It also contains the control unit and data count for keeping counts of the number of blocks transferred and indicating the direction of transfer of data.
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DMA controller contains an address unit, for generating addresses and selecting I/O device for transfer.
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