Correct Answer - Option 3 : 6
Concept:
A MOD-N counter is also called a divide by N counter as the input frequency is divided by the number of states of the counter.
For a counter with ‘n’ flip flops:
- The total number of states = 2n (0 to 2n – 1)
- The largest number that can be stored in the counter = 2n – 1
To construct a counter with any MOD number, the minimum number flip flops required must satisfy:
Modulus ≤ 2n
Where n is the number of flip-flops and is the minimum value satisfying the above condition.
Calculation:
We are required to construct a counter which divides the input frequency by 40, i.e. we require a MOD-40 counter.
Number no. of flip – flops are required to construct mod-40 counter, must satisfy:
2n ≥ 40
The minimum value of n satisfying the above is:
n = 6 bits