Question

Arrange the following steps for retrieving data from memory unit.
• [A.] The Memory Address Register (MAR) sends the address to memory chips
• [B.] The address is placed on the address bus
• [C.] The control unit sends a signal
• [D.] The data is retrieved and placed into the Memory Data Register (MDR)
Choose the correct answer from the options given below:

• A. D, C, B, A
• B. A, B, C, D
• C. A, C, D, B
• D. B, D, A, C

Hint:

Memory Read Order: MAR → Address Bus → Control Signal → MDR.

Answer 1

The Correct Option is B

Concept: Memory read operation follows a structured sequence involving registers, buses, and control signals. The main components involved are:
• MAR (Memory Address Register) – holds address
• Address Bus – carries address to memory
• Control Unit – initiates read operation
• MDR (Memory Data Register) – stores fetched data

Step 1: MAR sends address to memory chips.
The process begins when the processor places the required memory address into the MAR.
The MAR then forwards this address toward the memory system.
\[ \text{This corresponds to step A.} \]

Step 2: Address placed on address bus.
The address from MAR is transmitted via the address bus to the memory unit.
This ensures the correct memory location is selected.
\[ \text{This corresponds to step B.} \]

Step 3: Control unit sends signal.
The control unit sends a READ signal to memory indicating that data needs to be fetched.
Without this signal, memory will not respond.
\[ \text{This corresponds to step C.} \]

Step 4: Data retrieved into MDR.
Once the memory receives the address and read signal:
• Data from that location is accessed
• Data is transferred to MDR \[ \text{This corresponds to step D.} \]

Step 5: Final correct sequence. \[ A \rightarrow B \rightarrow C \rightarrow D \] \[ \boxed{(2)} \]