Direct Memory Access (DMA)

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Direct memory access (DMA) is a new feature of modern computer systems that allows certain hardware subsystems to read/write data to/from memory without microprocessor intervention, allowing the processor to do other necessary work. It is used in disk controllers, video/sound cards etc, or between memory locations. Typically, the CPU initiates DMA transfer, does other operations while the transfer is in progress, and receives an interrupt from the DMA controller once the operation is complete.

So in other words the direct memory access (DMA) is a method that allows an input/output (I/O) device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations. The whole process is look after by an another controller called as DMA controller. Whenever there is a transfer of data from/to memory from the peripheral devices that the DMA controller comes into working and sends the BR (Bus request) to the central processing unit. The CPU then gives the go ahead signal by sending the BG (Bus grant) back to the DMA controller. Once the DMA controller receives the signal then the control of all buses (data bus, address bus, control bus and I/O bus) are under DMA controller.

The college of computer science and applications of IIMT University, Meerut having courses like BCA, MCA and its MCA course is ranked as top MCA courses in Uttar Pradesh is having best faculty to teach the basics of computer. Now the DMA controller can initiate the required data transfer between memory and peripheral devices and the CPU is now free to do its own processing i.e. the CPU is not kept busy in just overlooking the data transfer.

The DMA controller transfers the data in two modes Single-cycle mode and Burst-mode, in single cycle mode DMA data transfer is done one byte at a time while in burst-mode DMA transfer is finished when all data has been moved. The college of computer science and applications of IIMT University, Meerut having courses like BCA, MCA and its MCA course is ranked as top MCA courses in Uttar Pradesh because the teaching aim of the university is to practical knowledge to its students.

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