FPGA terminology — CLB expansion In field-programmable logic device documentation, the acronym CLB most commonly stands for:

Introduction / Context:
Vendors use a consistent set of acronyms to describe major building blocks in an FPGA architecture. Recognizing these acronyms is key to reading datasheets, understanding resource counts, and mapping HDL logic to hardware. CLB is one of the most ubiquitous terms in the FPGA world.

Given Data / Assumptions:

• We refer to general FPGA documentation (e.g., Xilinx families) where CLB is a standard term.
• CLBs contain LUTs, flip-flops, carry chains, and routing to implement logic functions.
• Other options (buffers) are not standard expansions of CLB.

Concept / Approach:

“Configurable Logic Block” is the canonical expansion of CLB. A CLB groups smaller primitives (LUTs and registers) into a tile that can be configured to perform a wide range of combinational and sequential functions, often with fast carry logic and local routing.

Step-by-Step Solution:

Verification / Alternative check:

Review block diagrams for common FPGA families: CLBs are the tile repeated throughout the fabric, sitting between global routing channels.

Why Other Options Are Wrong:

“Buffer” variants do not match literature; buffers are specific I/O or routing elements, not the main logic tile.

“Critical” or “Constant” are not part of the standard acronym.

Common Pitfalls:

Confusing CLB (a logic tile) with slices or logic cells (subdivisions within a CLB). Different families may group resources differently but keep the CLB name.

Final Answer:

Configurable Logic Block