SPLD nomenclature — meaning of “16H8” An SPLD (e.g., PAL/GAL) listed as 16H8 most likely indicates which output polarity characteristic?
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Aactive-HIGH outputs
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Bactive-LOW outputs
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Cvariable-level outputs
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Dlatches at the outputs
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Etristate-only outputs
Answer
Correct Answer: active-HIGH outputs
Explanation
Introduction / Context:Older SPLD parts (PALs/GALs) often use letter codes to denote output behavior and resources. For instance, R, L, and H letters can indicate Registered outputs, active-Low outputs, or active-High outputs, respectively. Understanding these codes helps interpret datasheets and choose pin-compatible replacements.
Given Data / Assumptions:
- Device code format “16H8”.
- “16” typically refers to available input terms; “8” refers to the number of outputs.
- Letter “H” indicates a polarity characteristic of the outputs.
Concept / Approach:Historically, families such as PAL16L8 (L = active-Low outputs), PAL16H8 (H = active-High outputs), and PAL16R8 (R = registered outputs) follow a naming convention where the letter conveys output style. Therefore, “H” denotes active-High outputs for that device variant.
Step-by-Step Reasoning:
Decode numeric fields: 16 inputs, 8 outputs (typical interpretation).Interpret letter “H” per convention: High-true outputs.Conclude: 16H8 devices have active-HIGH outputs.Verification / Alternative check:Check part tables listing PAL16H8 vs PAL16L8. The latter explicitly states active-Low outputs, while the former specifies active-High, confirming the polarity implication of the letter code.
Why Other Options Are Wrong:
- active-LOW outputs: would be “L” variant.
- variable-level / tristate-only: not standard SPLD naming implications.
- latches at the outputs: would be indicated by other letters or specific part numbers; “R” generally denotes registered outputs (flip-flops), not latches.
Common Pitfalls:
- Assuming all PAL/GAL codes are identical across vendors; always confirm in the specific datasheet.
Final Answer:active-HIGH outputs