DMA Transfers and DMA Controller

DMA Transfers:
- DMA stands for Direct Memory Access.
- It is a method of transferring data between peripherals and memory without the involvement of CPU.
- DMA transfers are used to reduce the burden on CPU and to increase the speed of data transfer.
- In DMA transfers, data is transferred directly from the source peripheral to the destination peripheral through the memory.

DMA Controller:
- DMA transfers are performed by a control circuit called DMA controller.
- It is a special hardware device that controls the transfer of data between peripherals and memory.
- DMA controller is also known as DMA engine or DMA module.
- It is a complex circuit that consists of registers, counters, and control logic.
- DMA controller communicates with the peripherals, memory, and CPU through the system bus.
- DMA controller is capable of handling multiple DMA transfers simultaneously.

Working of DMA Controller:
- DMA controller works in the following steps:
1. The DMA controller is initialized by the CPU by setting the transfer parameters such as source address, destination address, transfer size, and transfer mode.
2. The DMA controller requests the control of the system bus from the CPU.
3. The CPU grants the control of the system bus to the DMA controller.
4. The DMA controller transfers the data between the peripherals and memory without the intervention of CPU.
5. Once the transfer is complete, the DMA controller releases the control of the system bus to the CPU.

Advantages of DMA Transfers:
- DMA transfers have the following advantages:
1. They reduce the burden on CPU and increase the speed of data transfer.
2. They allow the CPU to perform other tasks while the data transfer is in progress.
3. They enable the peripherals to transfer data directly to the memory, which is useful in real-time applications such as video and audio processing.