Ring counter initialization – starting a one-hot sequence To start a ring shift counter so that it operates correctly, what initialization is required?

Introduction / Context:
A ring counter is a shift register configured so that a single 1 circulates through a chain of flip-flops, generating non-overlapping timing phases. Correct startup is essential; otherwise the sequence may be all zeros or multiple ones, breaking the intended timing.

Given Data / Assumptions:

• Ring counter built from N flip-flops with serial feedback.
• We want a one-hot pattern (only one flip-flop set at a time).
• No automatic power-on preset unless designed.

Concept / Approach:
Ring counters require an initial state with exactly one flip-flop at logic 1 and the remaining flip-flops at logic 0. On each clock, the 1 shifts to the next stage, creating a cyclic sequence of length N. If all stages were cleared, the sequence would remain zeros; if more than one stage were set, multiple ones would circulate.

Step-by-Step Solution:
Define desired state: 1000…0 (one-hot).Initialize by presetting one flip-flop = 1 and clearing all others = 0.Apply clock pulses to circulate the single 1 around the ring.

Verification / Alternative check:
Simulate a 4-stage ring: start 1000 → 0100 → 0010 → 0001 → 1000 …; any different initialization (e.g., 0000 or 1100) fails to produce the unique one-hot cycle.

Why Other Options Are Wrong:
Clearing all / presetting all: leads to 0000… or 1111…, neither produces a valid one-hot sequence.Clearing one and presetting all others: creates a many-hot state, not a ring counter.No initialization: most discrete designs need explicit preset/clear at startup.

Common Pitfalls:
Relying on random power-on states. Use synchronous or asynchronous preset/clear, or a reset controller, to guarantee the proper initial one-hot pattern.

Final Answer:
presetting one flip-flop and clearing all others