# VLSI Questions and Answers – Cellular Automata

This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “Cellular Automata”.

1. Cellular automata produce
a) exhaustive patterns
b) exhaustive pseudo random patterns
c) random patterns
d) pseudo random patterns

Explanation: Cellular automata is similar to linear feedback shift register and it generates pseudo-random patterns.

2. In which method the effect of bit shifting is not observed or visible?
a) internal feedback LFSR
b) external feedback LFSR
c) cellular automata
d) counters

Explanation: The effect of bit shifting is not observed in cellular automata as it is done in linear feedback shift register.

3. The patterns produced using ______ is less random.
a) LFSR
b) Cellular automata
c) NAND gates
d) Shift registers

Explanation: The patterns produced by cellular automata is more random in nature than those produced using LFSR.

4. Which method needs more number of EX-OR gates?
a) internal feedback LFSR
b) counters
c) external feedback LFSR
d) cellular automata

Explanation: The construction of cellular automata is not as simple as LFSR and thus cellular automata needs more number of EX-OR gates.

5. The construction of CA register is based on
a) logical relationship of flip-flop
b) EX-OR gate
c) primitive polynomial
d) degree of the polynomial

Explanation: The construction of cellular automata is based on the logical relationship of each flip-flop to its two neighbours.
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6. The next state for rule 150 is obtained by
a) x(t)
b) x(t+1)+x(t)+x(t-1)
c) x(t+1)+x(t-1)
d) x(t)+x(t-1)

Explanation: The next state for rule 150 is obtained by exploring three current state values – itself, previous flip-flop and next flip-flop.

7. The next state for rule 90 is obtained by
a) x(t)
b) x(t+1)+x(t)+x(t-1)
c) x(t+1)+x(t-1)
d) x(t)+x(t-1)

Explanation: The next state for rule 90 is obtained by exploring two current values – the state value of previous and the next flip-flop.

8. Which occupies lesser area?
a) internal feedback LFSR
b) external feedback LFSR
c) null condition CA
d) cyclic boundary CA

Explanation: The area occupied by null boundary cellular automata is comparatively lesser than that used by cyclic boundary CA.

9. The maximal length sequence is given by
a) 2n
b) 2n + 1
c) 2n – 1
d) 2n

Explanation: The maximal length sequence is given by 2n – 1 in null condition boundary cellular automata.

10. Rule 90 CA minimizes area when compared to rule 150.
a) true
b) false

Explanation: Maximizing the use of rule 90 cellular automata minimizes area overhead when compared to using rule 150 cellular automata.

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