Introduction / Context:
Tri-state output buffers provide three states—drive HIGH, drive LOW, or high-impedance (Hi-Z)—and are essential for bus sharing. Inputs, however, are receivers; they do not drive buses and therefore do not require tri-state output drivers.
Given Data / Assumptions:
- PAL devices offer output macrocells with optional tri-state control via an output-enable equation.
- Dedicated input pins terminate in input buffers and protection networks, not output drivers.
- Some pins may be configurable as I/O; tri-state applies when the pin is used as an output.
Concept / Approach:
The phrase “driving the input pins” is contradictory: input pins do not drive; they are driven by external sources. Tri-state drivers belong to output paths (and bidirectional pins when configured as outputs). Hence, saying that PALs have tri-state buffers on input pins is incorrect.
Step-by-Step Solution:
Define tri-state → attribute of output drivers to enter Hi-Z.Identify input pins → receive signals via input buffers; no output driver present.Conclude statement is false: tri-state buffers do not “drive” inputs.
Verification / Alternative check:
Examine PAL pin function tables: outputs have OE equations; inputs do not.
Why Other Options Are Wrong:
Correct: Would wrongly assign output hardware to inputs.Only true for Schmitt-trigger inputs: Schmitt inputs shape edges; they do not add output drivers.True for power pins only: Power pins are neither inputs nor outputs.
Common Pitfalls:
Confusing “bidirectional pins” configured as outputs with dedicated inputs.Assuming every pad cell contains a tri-state driver regardless of direction.
Final Answer:
Incorrect
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