Difficulty: Easy
Correct Answer: external logic circuits that decode the various states of the counter to apply the correct logic levels to the J-K inputs
Explanation:
Introduction / Context:
Synchronous counters change state on a common clock edge, enabling precise custom sequences that are not simple powers of two. Building a nonbinary (arbitrary MOD) synchronous counter relies on steering the flip-flop inputs so that only the desired state transitions occur, while undesired states are skipped or reset predictably.
Given Data / Assumptions:
Concept / Approach:
The canonical method is to derive next-state equations from a state table or Karnaugh maps. External combinational logic decodes the present state (and possibly inputs) to generate the required control levels for the flip-flop inputs (e.g., J and K). This logic ensures that on each clock the counter advances to exactly the next desired state, creating the specified sequence and modulus.
Step-by-Step Solution:
Verification / Alternative check:
Simulate the counter or step through states manually to verify that every present state transitions to the correct next state and that unintended states self-correct to the sequence (if needed via reset gating).
Why Other Options Are Wrong:
Modifying BCD or asynchronous counters to “every second pulse” does not generalize to arbitrary sequences and misses the synchronous design principle.
Eliminating counter stages is impossible; the flip-flops are what store state. Combinational logic alone cannot “count.”
Common Pitfalls:
Forgetting to analyze unused states (self-start or self-correcting behavior), neglecting hazards in the decode logic, or not meeting setup/hold timing on the synchronous inputs.
Final Answer:
external logic circuits that decode the various states of the counter to apply the correct logic levels to the J-K inputs
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