Introduction / Context:
Encoders map one-of-N inputs to a binary-encoded output. When multiple inputs might be active, a priority encoder resolves conflicts by selecting the highest-priority input according to a predefined order. Understanding this behavior is essential for interrupt controllers and bus arbitration.
Given Data / Assumptions:
- Priority encoders produce a code for one active input at a time.
- They typically include a valid output and enable signals.
- “Highest and lowest simultaneously” contradicts single-winner resolution.
Concept / Approach:
A priority encoder masks lower-priority inputs when any higher-priority input is active. Its truth table ensures only the top-ranked active line determines the output code, never a combination of highest and lowest simultaneously.
Step-by-Step Solution:
Assume inputs In7..In0 with In7 highest priority.If In7=1 and any lower Ink=1, output encodes 7, not both 7 and k.Therefore, “highest and lowest simultaneously” is not how a priority encoder operates.
Verification / Alternative check:
Inspect a 74148 8-to-3 priority encoder datasheet: the output corresponds to the highest-priority asserted input.
Why Other Options Are Wrong:
Correct / code variants: No mainstream encoder simultaneously reports highest and lowest values on one code output.Thermometer/Gray references: These are coding schemes, not priority mechanisms.
Common Pitfalls:
Confusing a plain encoder with a priority encoder.Expecting multi-winner outputs when the device is designed for single-winner arbitration.
Final Answer:
Incorrect
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