When Bus Grant (BG) = 1 in direct memory access (DMA) transfer, then what…
2021
When Bus Grant (BG) = 1 in direct memory access (DMA) transfer, then what function read line and write lines perform?
- A.
Read line and write line act as input line allowing CPU to communicate with internal DMA register
- B.
Read line act as input line and write line act as output line from DMA
- C.
Read line act as output line and write line act as input line from DMA controller
- D.
Read line and write line act as output lines from DMA controller
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Correct answer: D
When Bus Grant (BG) = 1, the DMA controller gains control of the system bus. During this state, the DMA manages data transfer between memory and I/O devices without CPU intervention. The read line and write line are used to transfer data. The read line outputs data from the DMA controller to memory, while the write line inputs data from memory to the DMA controller. This means both lines function as output lines from the DMA controller's perspective during the transfer.