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GATE 2025 IN – Question 42

Digital Electronics · Microprocessors and data acquisition · 2 marks · Multiple choice

An 8-bit microprocessor has 16-bit address bus (A15 − A0) where A0 is the LSB. As shown in Figure (a), it has a pre-installed 4 KB ROM whose starting address is 0000 H. The processor needs to be upgraded by adding a 16 KB RAM as shown in Figure (b). The address range for the newly added RAM is

Diagram for GATE 2025 IN question 42
  1. 1000 H – 4FFF H
  2. 3000 H – 6FFF H
  3. 4000 H – 7FFF H
  4. 8000 H – BFFF H

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Show answer and explanation

Correct answer: (C) 4000 H – 7FFF H

Explanation

Active-low chip select is driven by A14bar OR A15.

Selection therefore requires A14=1 and A15=0.

The lower fourteen address bits vary freely, spanning **4000H–7FFFH, C**.

This is exactly 2¹⁴ bytes.