Frequency counter data path: when is the new count transferred to the display register? Consider the timing of a gated frequency counter in HDL. Identify when the fresh count value is latched into the display register for stable presentation.
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AAfter disabling the counter
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BWhen the count buffer is full
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CAfter the sample interval is set
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DWhen the timing and control block has put it there
Answer
Correct Answer: When the timing and control block has put it there
Explanation
Introduction / Context:In a gated frequency counter, the measurement cycle consists of opening a timing gate, counting input pulses, closing the gate, and then transferring the stable result to a display register while the next measurement begins. This requires coordinated timing and control.
Given Data / Assumptions:
- A dedicated timing/control FSM (finite state machine) orchestrates gate, count, and latch operations.
- Display register must capture the count only when stable (post gate-close).
- Transfer may coincide with a latch/LD signal generated by control logic.
Concept / Approach:The transfer is explicitly commanded by the timing/control block after the counting window ends. This guarantees that the displayed value does not glitch while counting continues internally for the next interval.
Step-by-Step Solution:
Gate opens → counter accumulates pulses.Gate closes → count is stable.Control asserts “load display” → value moves to display register.Display remains steady until next cycle’s transfer.Verification / Alternative check:Simulations show clean latch timing edges aligning with end-of-gate signals.
Why Other Options Are Wrong:
- A/C describe phases but not the authoritative transfer event.
- B: “Buffer full” is not a standard event in simple counters.
Common Pitfalls:Capturing mid-count causes flicker or incorrect readings.
Final Answer:When the timing and control block has put it there