Identifying the PAL structure A device that consists of a programmable array of AND gates feeding a fixed array of OR gates, and that is usually one-time programmable (OTP), is called a:

Difficulty: Easy

Correct Answer: PAL

Explanation:


Introduction / Context:
Programmable logic devices come in many architectural flavors. Two historically important types are PALs and GALs. PALs generally provide a programmable AND plane and a fixed OR plane, while GALs add reprogrammable technology and versatile output macrocells. Understanding the architectural hallmark of a PAL helps you recognize its capabilities and limitations.



Given Data / Assumptions:

  • Structure: programmable AND array, fixed OR array.
  • Programming model: typically one-time programmable (fuse/OTP).
  • Target: choose the device class that best matches the structure and OTP behavior.


Concept / Approach:

The defining characteristic of a PAL (Programmable Array Logic) device is exactly this sum-of-products organization with a programmable AND matrix and fixed OR summation. Many PALs were OTP, distinguishing them from later GALs that used erasable technologies (e.g., EEPROM) and offered per-pin OLMC flexibility.


Step-by-Step Solution:

Match the described architecture to known device types.PAL fits “programmable AND + fixed OR” and “often OTP.”Therefore, select PAL.


Verification / Alternative check:

Historical datasheets and textbooks present classic PAL block diagrams showing an AND matrix with fixed OR gates driving outputs, sometimes with simple output enable/inversion controls.


Why Other Options Are Wrong:

GAL: similar purpose but reprogrammable with more flexible OLMCs.

CPLD: multi-macrocell blocks with wider interconnect; not necessarily fixed OR planes as in classic PALs.

SPLD: a generic category that includes PAL and GAL; not specific enough to match the exact description.


Common Pitfalls:

Confusing the general SPLD category with a specific architecture. Here the exact structure and OTP cue point to PAL.


Final Answer:

PAL

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