What is dma why is it needed

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Please contact us. This adds load on the processor and most of the time it stays in the ideal state, thus decreasing the efficiency of the system. DMA controller transfers data with minimal intervention of the processor. The term DMA stands for direct memory access.

The hardware device used for direct memory access is called the DMA controller. DMA controller provides an interface between the bus and the input-output devices. Although it transfers data without intervention of processor, it is controlled by the processor. The processor initiates the DMA controller by sending the starting address, Number of words in the data block and direction of transfer of data. More than one external device can be connected to the DMA controller.

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. When the transfer is completed, DMA informs the processor by raising an interrupt. The typical block diagram of the DMA controller is shown in the figure below. Connect with us. Sign up. Term of the Day. Best of Techopedia weekly. News and Special Offers occasional. Techopedia Explains Direct Memory Access DMA A defined portion of memory is used to send data directly from a peripheral to the motherboard without involving the microprocessor, so that the process does not interfere with overall computer operation.

Memory addresses. Interrupt request numbers IRQ. Direct memory access DMA channels. DMA is a method of data transfer between main memory and peripheral devices. DMA controller transfers the data to and from memory without the participation of the processor. The processor provides the start address and the word count of the data block which is transferred to or from memory to the DMA controller and frees the bus for DMA controller to transfer the block of data.

DMA controller transfers the block of data to and from memory in three modes burst mode , cycle steal mode and transparent mode. Comments it is usefull for us and thanku.

Thanks for this useful information and simple way of explanation. Too easy and understandable Thanku.