Altera FLEX10K architecture — replacement for AND/OR arrays In the Altera (Intel) FLEX10K family of PLDs/CPLDs/FPGAs, what logic element is used in place of traditional sum-of-products AND and OR arrays?

Introduction / Context:
Classic PAL/GAL devices implement logic as a programmable AND array feeding a fixed OR array (sum-of-products). More advanced programmable logic families migrated to look-up tables (LUTs), which store truth tables in small RAM-like structures. This question asks you to identify the core logic primitive used by Altera’s FLEX10K architecture instead of fixed AND/OR planes.

Given Data / Assumptions:

• The device family uses fine-grained logic elements grouped into larger blocks.
• LUTs are typically implemented with SRAM cells to realize arbitrary Boolean functions of a small number of inputs.
• Modern FPGAs favor LUTs over hard-wired sum-of-products arrays.

Concept / Approach:

A k-input LUT directly encodes 2^k output values, enabling the device to implement any Boolean function of up to k variables by loading the appropriate configuration bits. This replaces the need for dedicated AND/OR matrices and allows flexible routing and packing of logic into logic array blocks within the fabric.

Step-by-Step Solution:

Verification / Alternative check:

Vendor literature and architecture overviews consistently describe logic elements built around LUTs with optional flip-flops, carry chains, and routing resources.

Why Other Options Are Wrong:

“Nothing, it uses AND/OR arrays” contradicts standard FPGA architecture practice.

“SRAM-based memory” is a technology detail used to implement LUTs but is not the logic primitive itself.

“HPLD architecture” is not a standard logic primitive and does not identify the function element.

Common Pitfalls:

Confusing implementation technology (SRAM) with the logical abstraction (LUT). The LUT is the building block; SRAM stores its content.

Final Answer:

Look-up tables