Shift-register counters and reset logic: Evaluate the statement: “Shift register counters use logic functions to reset the registers when the desired count is reached,” as in ring and Johnson counters implemented with shift registers.

Introduction / Context:Shift-register-based counters, such as ring and Johnson counters, generate sequences by shifting bits through flip-flops. To maintain a specific sequence length (modulus), the circuit often uses feedback or decoding logic to initialize or recycle the pattern when a terminal condition is detected. This item asks whether logic functions are used to cause that reset or recycling action.

Given Data / Assumptions:

• Shift registers can be wired into counters by feeding back selected taps.
• Ring counters circulate a single 1; Johnson counters circulate a complemented pattern.
• Decoding logic can detect illegal states or a terminal state to reinitialize the sequence.

Concept / Approach:In practice, logic gates monitor the register contents. When a particular combination appears (desired terminal count or illegal state), a pulse is generated to clear/load the register. This ensures a stable, repeatable modulus and quick recovery if power-up places the register in an unintended state.

Step-by-Step Solution:

Verification / Alternative check:Example designs include a NAND of particular Q outputs to drive an asynchronous clear, or a synchronous load that inserts the seed pattern, confirming the role of logic functions in resetting.

Why Other Options Are Wrong:

Common Pitfalls:Failing to include a recovery path from illegal states; assuming power-up always sets a valid pattern without supervisory logic.

Final Answer:Correct