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FPGA Concepts

Basic — FPGA fundamentals
Intermediate — architecture & timing
Advanced — system-level & optimization
FPGA interview questions test both your theoretical knowledge of the architecture and your practical experience with tools and constraints. Understanding the "why" behind design choices is what separates good answers from great ones.

Basic Questions

Basic 7 questions
1

What are some of the primitive elements inside an FPGA?

FPGA Architecture Answer in Book →
2

What is the difference between an FPGA, a CPLD, and a Microcontroller? What are the typical applications for each of these devices?

FPGA Architecture Answer in Book →
3

What clocking blocks are available in a typical Xilinx FPGA?

Clocking Answer in Book →
4

What are the different types of memory elements available inside a Xilinx UltraScale+ family of FPGAs?

Memory Read Answer →
5

What are the most basic types of design constraints required for any FPGA design?

Constraints Read Answer →
6

What sort of debugging tools are available in the Xilinx Toolkit?

Debug Answer in Book →
7

ASIC designs frequently use clock gating to turn off the clock to certain sections of the design. How is similar functionality handled on an FPGA?

Clocking Answer in Book →

Intermediate Questions

Intermediate 8 questions
1

What does Stacked Silicon Interconnect (SSI) mean?

FPGA Architecture Answer in Book →
2

What are Super Logic Regions (SLRs) in some Xilinx devices?

FPGA Architecture Answer in Book →
3

What precautions need to be taken while using SSI devices or while handling signals crossing SLR boundaries?

FPGA Architecture Answer in Book →
4

What are some of the considerations while using resets in Xilinx FPGA designs?

Design Practice Read Answer →
5

What is Retiming? What are the typical scenarios where it might be useful?

Timing Closure Answer in Book →
6

What are Timing Exceptions? Why is it important to specify them?

Constraints Read Answer →
7

What are Synthesis Directives? Explain with some common examples.

Synthesis Answer in Book →
8

What is the difference between the directives KEEP and DONT_TOUCH?

Synthesis Read Answer →

Advanced Questions

Advanced 9 questions
1

On a Xilinx UltraScale+ device, there are two differential clock inputs — a 400 MHz clock on a GC pin and a 312.5 MHz MGTREFCLK. How would you generate 50 MHz, 200 MHz, and 156.25 MHz clocks for internal use?

Clocking Answer in Book →
2

Two of the most common hindrances in Timing Closure are high-fanout nets and excessive levels of logic. How should either of these problems be handled in the design?

Timing Closure Answer in Book →
3

A register stores an 8-bit value that must be shifted left by 4 bit positions. How many levels of logic will be needed to implement this operation?

Synthesis Answer in Book →
4

What are XPMs (Xilinx Parameterizable Macros) and where are they typically used?

FPGA Architecture Answer in Book →
5

What is Floorplanning? Explain the thought process and the steps involved in floorplanning a design.

Floorplanning Answer in Book →
6

Xilinx IP Library has FIFOs designated as First Word Fall Through (FWFT). Explain the design significance and use cases of these FIFOs.

Memory Answer in Book →
7

Xilinx Dual Port BlockRAMs have two flavors — Simple Dual Port and True Dual Port. What are the differences between the two types?

Memory Answer in Book →
8

What are IOSTANDARDs in FPGA design? Why are they needed and how are they specified?

IO Design Read Answer →
9

A module implemented on a Xilinx FPGA needs to send out source synchronous data along with the clock. How should the data and the clock be handled at the FPGA IOs?

IO Design Answer in Book →

Want detailed answers with full explanations?

All questions are covered in depth in the book — with context, design rationale, and follow-up discussion.

View the Book →