PAL architecture clarification: Evaluate the statement — “A PAL uses a programmable OR array followed by a fixed AND array.”

Introduction / Context:
Programmable Array Logic (PAL) devices are classic SPLDs whose internal structure every digital designer should know. This question tests whether you can correctly identify which array is programmable and which is fixed inside a PAL device.

Given Data / Assumptions:

• PAL devices implement sum-of-products logic.
• Two core arrays exist: AND array and OR array.
• Only one of these arrays is programmable in a standard PAL.

Concept / Approach:
In a PAL, the AND array is programmable (you can form the needed product terms), while the OR array is fixed (each output has a fixed number of product-term inputs it can sum). This is the reverse of a PLA, which has both arrays programmable. Therefore, the statement claiming a programmable OR and fixed AND is wrong.

Step-by-Step Solution:

Verification / Alternative check:
Consult typical PAL16L8/PAL16R8 block diagrams: fusible links appear at the AND plane, not the OR plane. OR resources are predetermined per output macrocell.

Why Other Options Are Wrong:

• Correct: Not correct because it reverses PAL internals.
• True only for GAL: GALs mimic PAL behavior while adding reprogrammability, not swapping array roles.
• Tri-stated outputs / fuse polarity: Output options and fuse polarity do not change which array is programmable.

Common Pitfalls:
Confusing PAL with PLA; assuming both arrays are programmable in every SPLD; ignoring fixed product-term limits per output.

Final Answer:
Incorrect