FPGA building blocks In field-programmable gate arrays (FPGAs), which section of embedded logic forms the fundamental programmable element used to implement combinational functions?

Introduction / Context:
The core of modern FPGA architecture is a highly regular fabric composed of small, repeatable logic elements. Understanding what these elements are and how they map HDL code into hardware is essential for designers targeting efficient, portable implementations across device families.

Given Data / Assumptions:

• The question concerns the fundamental combinational logic resource inside an FPGA.
• Focus is on general-purpose logic used to realize Boolean expressions.
• We distinguish between embedded hard blocks (such as DSP slices) and soft, programmable logic.

Concept / Approach:
A lookup table (LUT) is a small truth-table memory that outputs a value based on its input address bits. For example, a 4-input LUT implements any Boolean function of four variables by storing the appropriate 16-bit truth table. Synthesis tools decompose HDL expressions into networks of LUTs and registers, then pack these into configurable logic blocks (CLBs/ALMs/logic elements). While FPGAs also include embedded memories, PLLs, and DSP blocks for multiply-accumulate operations, the LUT remains the basic “universal gate” resource for combinational logic.

Step-by-Step Solution:

Verification / Alternative check:
Review any vendor architecture overview (for example, Xilinx CLB/SLICE, Intel Logic Array Block). All describe LUT-based logic elements as the base combinational resource, confirming this answer across vendors and families.

Why Other Options Are Wrong:

• core: Vague term; not a specific logic primitive.
• DSP: A specialized hard block for arithmetic acceleration, not the general-purpose element.
• PI: Not a standard FPGA primitive acronym in this context.

Common Pitfalls:
Confusing LUTs with block RAM (both store bits) and assuming DSP slices replace LUTs for all arithmetic; in reality, many arithmetic and control functions still synthesize to LUT networks.

Final Answer:
LUT