BEE Digital Logic and Microprocessors 2

Question 1

Which Boolean expression represents the output of a 2-input XNOR gate?

Accepted Answer

A·B + A'·B'

Answer

XNOR outputs 1 when both inputs are equal, expressed as A·B + A'·B'.

Question 2

In a JK flip-flop, what happens when both J=1 and K=1 on the active clock edge?

Accepted Answer

Output toggles

Answer

When J=K=1, the JK flip-flop toggles its output on each active clock edge.

Question 3

A 4-bit ripple carry adder adds two 4-bit numbers. What is the maximum propagation delay if each full adder has a carry propagation delay of 10 ns?

Accepted Answer

40 ns

Answer

In a ripple carry adder, carry propagates through all 4 stages, giving 4 × 10 ns = 40 ns total delay.

Question 4

What is the purpose of the program counter (PC) in a microprocessor?

Accepted Answer

Holds the address of the next instruction to fetch

Answer

The program counter holds the memory address of the next instruction to be fetched and executed.

Question 5

Which addressing mode uses the content of a register as the memory address?

Accepted Answer

Register indirect

Answer

Register indirect addressing uses the value stored in a register as the effective memory address.

BEE - Bachelor of Electrical Engineering Practice Test