While the microprocessor is executing a program an interface circuit takes over control of address, data, control buses when not in use by microprocessor
The DMA control waiting for the microprocessor to finish execution of the program and then takes over the buses
DMA controller taking over the address, data and control buses while a block of data is transferred between memory and I/O device
Data transfer takes place between the I/O device and memory during every alternate clock cycle
EXAMIANS