In Direct Memory Access (DMA) data transfer, what happens during 'Cycle Stealing' mode?

Subject: Computer Architecture and Organization

Topic: Input-Output (I/O) Organization & DMA

Options:

1. Option A: DMA controller takes control of the system bus for the entire block transfer duration
2. Option B: DMA controller steals one bus cycle from the CPU to transfer a single word of data
3. Option C: CPU halts permanently until peripheral power is disconnected
4. Option D: I/O device bypasses main RAM memory and writes directly into CPU instruction registers

Correct Answer:

Option B: DMA controller steals one bus cycle from the CPU to transfer a single word of data

Explanation:

In Cycle Stealing mode, the DMA controller requests control of the system bus from the CPU for just one clock cycle to transfer a single data word, after which control is immediately yielded back to the CPU.