What happens during DMA transfer?

Answer Posted / niaz mohammad

DMA (Direct Memory Access) is a technique that transfers
data between a microprocessor's memory and an I/O device
without involving the microprocessor.

* Working process of DMA controller:

1. The I/O device request DMA operation via the DMA request
lines of the controller chip.

2. The controller chip activates the microprocessor HOLD
pin, requesting the CPU to release the bus.

3. The processor then sends HLDA (Hold Acknowledgement) back
to the DMA controller.

4. The DMA controller completes the DMA transfer and
releases the bus.

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