Question

What registers are significantly incremented and decremented respectively for the transmission of each byte by Direct Memory Access (DMA)?

• A. \( \text{Address Register \& Byte Count Register} \)
• B. \( \text{Control Register \& Byte Count Register} \)
• C. \( \text{Transmitter Register \& Byte Count Register} \)
• D. \( \text{Status- Register \& Byte Count Register} \)

Hint:

DMA controllers are essential for efficient data movement in modern computer systems. Remember the three primary registers in a DMA controller: \textbullet \ Address Register Points to the memory location and increments (or decrements) for sequential access. \textbullet \ Byte/Word Count Register Tracks the amount of data remaining to be transferred and decrements with each transfer. \textbullet \ Control Register Configures the DMA operation (e.g., source/destination, transfer direction, mode).

Answer 1

The Correct Option is A

To solve this problem, we need to identify the registers that are significantly incremented and decremented during the transmission of each byte in Direct Memory Access (DMA) operations.

1. Understanding DMA (Direct Memory Access):

- DMA is a method used for transferring data between memory and I/O devices without involving the CPU, thus allowing faster data transfer. During DMA operations, two main registers play a crucial role:

• Address Register: This register holds the memory address where the next byte of data will be transferred to or from.
• Byte Count Register: This register keeps track of the number of bytes remaining to be transferred. It is decremented after each byte is transferred.

2. Analysis of the Options:

- Option 1: "Address Register & Byte Count Register" – This is correct. The address register is incremented to point to the next memory location, and the byte count register is decremented after each byte is transferred. 
- Option 2: "Control Register & Byte Count Register" – This is incorrect. The control register manages the control signals for the DMA, but it is not significantly incremented or decremented during each byte transfer. The byte count register is the one that is decremented. 
- Option 3: "Transmitter Register & Byte Count Register" – This is incorrect. The transmitter register holds data to be sent out, but it is not incremented or decremented in the same way as the address or byte count register. 
- Option 4: "Status Register & Byte Count Register" – This is incorrect. The status register provides information about the current state of the DMA but is not incremented or decremented during the byte transfer process.

3. Final Answer:

The registers that are significantly incremented and decremented during the transmission of each byte by DMA are Address Register & Byte Count Register.