Question

Given below are two statements :
one is labelled as
Assertion (A) and the other is labelled as
Reason (R).
Assertion (A) :
During memory interfacing, address decoding is required to select the desired memory chip.
Reason (R) :
Each memory chip has unique address range that must be enabled using chip select signals.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Address decoding is like the operator in an old telephone exchange—they look at the "number" (address) you dialed and connect your call to the specific "house" (memory chip) meant for that range.

Answer 1

The Correct Option is A

Memory interfacing is the process of connecting a microprocessor to various memory ICs (RAM, ROM) so they can be addressed individually. 1. The Role of Address Decoding: A microprocessor has a set number of address lines (e.g., 16 lines for 64KB). However, a system usually consists of multiple smaller memory chips. To ensure that the processor communicates with only one chip at a time, we use address decoding to interpret the high-order bits of the address bus. Thus, Assertion (A) is correct. 2. The Chip Select (CS) Mechanism: Every memory chip has an input pin called Chip Select (CS) or Chip Enable (CE). When this pin is active, the chip "wakes up" to read or write. Each chip is assigned a specific, non-overlapping range in the system's memory map. Thus, Reason (R) is correct. 3. Linkage: The need for address decoding (A) exists because we must generate those specific CS signals based on the unique address ranges assigned to each chip (R). Therefore, (R) is the correct explanation of (A).