Ring counters vs. Johnson (twisted-ring) counters In digital electronics, ring shift counters and Johnson (twisted-ring) counters are best classified as which type of counters?

Introduction / Context:
Ring counters and Johnson (twisted-ring) counters are special shift-register-based counting circuits used for sequence generation, state machines, timing, and divide-by-N operations. Unlike ripple (asynchronous) counters, they use a common clock to advance through well-defined state sequences. This question checks whether you can correctly classify their timing and nature relative to synchronous/asynchronous and true binary counters.

Given Data / Assumptions:

• A ring counter circulates a single 1 or 0 through a shift register.
• A Johnson counter feeds the inverted output of the last flip-flop back to the input of the first flip-flop.
• Both are clocked shift-register structures.
• “True binary counter” implies natural binary sequences (… 000, 001, 010, 011, …).

Concept / Approach:
Because every flip-flop in these counters receives the same clock edge, their state transitions occur simultaneously. That is the hallmark of synchronous operation. However, their sequences are not natural binary counts; they are coded sequences (one-hot for ring; two-hot patterns for Johnson), so they are not “true binary counters.”

Step-by-Step Solution:
Identify the clocking method: common clock → synchronous.Identify the sequence type: one-hot or twisted ring → not natural binary.Therefore, classification: synchronous counters (but not true binary).

Verification / Alternative check:
Datasheets and textbooks show that a 4-bit ring counter has 4 valid states (one-hot), and a 4-bit Johnson counter has 8 valid states. Both are advanced by one common clock; no ripple path is used, confirming synchronous behavior.

Why Other Options Are Wrong:

• Asynchronous counters: use ripple timing; not applicable here.
• True binary counters: produce natural binary sequences; ring/Johnson do not.
• Synchronous and true binary: incorrect because they are not natural binary.

Common Pitfalls:

• Confusing synchronous clocking with binary coding.
• Assuming any “counter” must be binary; many are coded or one-hot.

Final Answer:
Synchronous counters