Programmable array basics The two basic building arrays inside standard programmable logic devices (such as PALs and GALs) are composed of which gates?

Introduction / Context:Classic programmable logic devices (PLDs) implement sum-of-products logic using structured arrays. Understanding the internal AND–OR organization helps when mapping Boolean expressions to device architectures (PAL, GAL, CPLD) and optimizing resource use.

Given Data / Assumptions:

• We consider the canonical PAL/GAL architecture.
• Product terms are generated by an AND plane.
• Sum terms are formed by an OR plane.

Concept / Approach:

Sum-of-products (SOP) form is F = P1 + P2 + ... where each Pi is a product term (AND of literals). PLDs realize this by first creating many product terms in a programmable AND array; selected products feed a programmable OR array to form logic outputs. Some devices then offer optional output inversion or registered outputs.

Step-by-Step Solution:

Verification / Alternative check:

Datasheets for PAL/GAL families depict a programmable AND matrix feeding fixed or programmable OR gates. Some architectures share product terms among outputs for efficiency, but the core remains AND–OR.

Why Other Options Are Wrong:

• Only AND or only OR is incomplete; both are required for SOP realization.
• NAND/NOR alone are not the standard description, even though NAND/NOR universality exists.
• XOR/XNOR are useful but not the foundational planes in PAL/GAL.

Common Pitfalls:

• Confusing internal universality (NAND/NOR) with the architectural abstraction (AND–OR planes).

Final Answer:

AND gates and OR gates