UGC NET CSE | December 2007 | Part 2 | Question: 8

Question

In order to build a $\text{MOD - 18}$ counter, the minimum number of flip flops needed is equal to :

• A. $18$
• B. $9$
• C. $5$
• D. $4$

Answer 1

$18$ can be represented by using $5$ bits in binary. So to uniquely identify every state of MOD-$18$ counter, we need $5$ flip flops.

Alternatively,  $log_{2}\left ( \left \lceil 18 \right \rceil \right )$  $=$  $5$ flip flops are required.

Option C is correct.