A 5-stage ring counter (one-hot) is built using 5 flip-flops connected in a ring. How many unique states does it cycle through?
Electronics and Communication Engineering
Digital Electronics
Difficulty: Easy
Choose an option
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A5 states
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B10 states
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C32 states
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DInfinite states
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E2^5 - 1 = 31 states
Answer
Correct Answer: 5 states
Explanation
Introduction / Context:Ring counters are widely used for sequence generation, time-slot selection, and simple state machines in digital systems. They are “one-hot” by design.
Given Data / Assumptions:
- 5 flip-flops wired as a ring (one-hot configuration).
- Exactly one flip-flop is high at any time; the “1” circulates.
Concept / Approach:
In a ring counter, the number of stable, recurring states equals the number of flip-flops, provided proper initialization to a one-hot state.
Step-by-Step Solution:
Start with 10000, then 01000, 00100, 00010, 00001.After 5 clocks, the pattern repeats. Hence 5 unique states.Verification / Alternative check:
Simulate the ring on paper or HDL; the single “1” advances one stage per clock, cycling through five states before repeating.
Why Other Options Are Wrong:
- 10 or 32 states: confuse with Johnson counters or general 5-bit counters.
- Infinite: the sequence is finite and periodic.
- 2^5 - 1: applies to maximal-length LFSRs, not ring counters.
Common Pitfalls:
Confusing ring counters with Johnson (twisted ring) counters, which have 2N states.
Final Answer:
5 states