DMA controller :

Steps include in transferring a block of data from I/O devices (for example a disk) to memory:

1. CPU sends a signal to initiate disk transfer through I/O interface

2. CPU sends starting address of the block

3. Disk driver reads starting address, and then reads one block of data and puts it in its own buffer

4. Disk driver sends interrupt signal to the CUP

5. CPU reads the datum into its registers (accumulator)

6. CPU examine if there is more to transfer, if answer is yes, the CPU signals the disk driver to do so meanwhile

7. CPU transfer the datum from registers to memory and increments its pointer to memory

8. DMA controller takes care of the last few steps (from signalling disk to transfer) .