Question

Which type of counter requires 5 flip-flops to implement a MOD-31 operation?

• A. Synchronous counter
• B. Asynchronous (Ripple) counter
• C. Ring counter
• D. Johnson counter

Hint:

Number of flip-flops needed = $2^n \geq N$
MOD-31 → $2^5 = 32$ → 5 flip-flops required

Answer 1

The Correct Option is B

Concept:
A MOD-N counter is a digital counter that cycles through N distinct states before repeating the sequence. The number of flip-flops required depends on the number of states that must be represented.
Step 1:Determining the number of flip-flops.
The number of flip-flops required is determined by the smallest integer $n$ satisfying: \[ 2^n \geq N \] where $N$ is the modulus of the counter.
Step 2:Applying the formula for MOD-31.
For a MOD-31 counter: \[ 2^5 = 32 \] Thus, 5 flip-flops are required to represent at least 31 states.
Step 3:Type of counter implementation.
A commonly used implementation for such counters is the asynchronous (ripple) counter, where flip-flops toggle sequentially based on the output of the previous stage. Conclusion:
Therefore, a MOD-31 counter requires 5 flip-flops, and it is typically implemented using an asynchronous (ripple) counter.