Active-level designation for up/down counting Given a counter designation that specifies the active logic levels for counting direction, what does it mean if the notation states that the up count is active-LOW and the down count is active-HIGH?
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Aup count is active-HIGH, the down count is active-LOW
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Bup count is active-LOW, the down count is active-HIGH
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Cup and down counts are both active-LOW
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Dup and down counts are both active-HIGH
Answer
Correct Answer: up count is active-LOW, the down count is active-HIGH
Explanation
Introduction / Context:Many up/down counters have direction-control inputs whose active level determines the counting direction. Recognizing “active-LOW” or “active-HIGH” notation prevents wiring mistakes and logic inversions when designing control signals.
Given Data / Assumptions:
- One control input selects up or down counting.
- Active level indicates which logic level causes that action.
- Positive-logic system is assumed (0 = LOW, 1 = HIGH).
Concept / Approach:“Active-LOW up count” means the counter increments when the up-control input is at logic 0. “Active-HIGH down count” means the counter decrements when the down-control input is at logic 1, or when the same direction line (with defined polarity) selects down mode at logic 1.
Step-by-Step Solution:
1) Interpret the notation given with the device.2) Map active-LOW to logic 0 and active-HIGH to logic 1.3) Conclude which level selects each direction.4) Apply when wiring the direction control to avoid unintended counting.Verification / Alternative check:Consult a truth table: check that the counter steps up when UP=0 and steps down when DOWN=1 (or when a single DIR line uses the stated polarity).
Why Other Options Are Wrong:
- Options a, c, d contradict the specified active-level conditions.
Common Pitfalls:Ignoring active-LOW labels and assuming all controls are active-HIGH; forgetting required pull-ups/pull-downs.
Final Answer:up count is active-LOW, the down count is active-HIGH