Demystifying FPGAs: What Are They, How Do They Work and Where Are They Heading?

Have you heard of FPGAs but aren‘t quite sure what they are or what makes them such a big deal? You‘re not alone! Though growing rapidly in use across many industries, field programmable gate arrays remain a mystery to many.

In this comprehensive guide, we‘ll lift the veil on FPGA technology – from unraveling exactly what FPGAs are at a hardware level to how their flexible architecture empowers real-world applications today and into the future. You‘ll gain a clear understanding of what makes them such a versatile accelerator chip.

So What Exactly is an FPGA?

At the highest level, an FPGA is an integrated circuit that can be programmed and reconfigured after manufacturing to implement custom hardware functionality. They provide the flexibility of software with the speed and efficiency of hardware.

But how do they merge attributes from both realms so seamlessly? The key lies in their underlying field programmable architecture:

  • Configurable logic blocks act as basic logic "atoms" that can be connected in massive flexible arrays
  • Interconnect "glue" that allows blocks to be wired arbitrarily to form advanced logic circuits
  • I/O interfaces to communicate with external components and processors
  • Embedded memories, DSP blocks, transceivers and other hardened cores tailored to accelerate functions

FPGA Architecture

FPGA Hardware Architecture (Image credit: Xilinx)

By incorporating programmable building blocks that span from transistor-level gates to complex functional units like arithmetic cores, FPGAs can take on radically different personalities as needed.

Think of them like blank silicon canvases that can be painted upon with any digital masterpiece imaginable. Yes…it‘s that magical!

Bit of History: When Did This FPGA Magic Originate?

The concepts behind field programmable logic stretch back to pioneering work in the 1960s on programmable read-only memory and logic arrays.

But it wasn‘t until 1985 that Xilinx co-founders Ross Freeman and Bernard Vonderschmitt (pictured below) nicely commercialized FPGA technology and incorporated the original company. The debut Xilinx XC2064 chip implemented a mere 64 configurable logic blocks – miniscule by today‘s standards but revolutionary at the time!

FPGA Pioneers

FPGA Trailblazers: Xilinx Founders Freeman (left) and Vonderschmitt (right)

Shortly after in 1987, another Silicon Valley startup called Altera (now part of Intel) brought their first CMOS FPGA to market. These earliest FPGAs used static RAM bits to program user logic into the hardware – an approach still dominant and proven today.

Over the ensuring decades, innovation in underlying FPGA fabrics, toolchains, microarchitectures and applications has progressed enormously. Some key milestones advancing capabilities:

  • 1990s – Growth in telecom fuels density needs
  • 1996 – First million gate FPGA demonstrated
  • 2004 – 90nm process allows FPGAs to integrate multi-gigabit transceivers
  • 2010 – Integrated hard CPU cores and future bus interfaces arrive
  • 2020 – Chiplets help connect multi-die solutions with advanced packaging

Today spanning from tiny, power-efficient mobile variants to data center behemoths packing over 9 million logic cells, FPGAs now saturate a $5 billion per year semiconductor industry growing at 8% CAGR.

FPGA History Timeline

FPGA Technology Key Events Timeline

Clearly the industry has come a very long way from humble beginnings!

So how did these bits of silicon actually work their magic to make such incredible progress possible?

Hardware Architecture: What‘s Under the FPGA Hood?

The hardware foundations enabling field programmability stems from ingenious use of SRAM memory fused with generic logic resources that can be "rewired" together. This architecture lets engineers re-map functionality cycle after cycle to tackle vastly different applications.

Zooming inside a modern FPGA reveals a dense grid of key ingredients like:

Configurable Logic Blocks (CLBs)

The CLB is the central element that provides basic computation and storage. Think of it like a tiny chip within the big chip. Each block typically contains:

  • 4-6 Input Look-Up Tables (LUTs) – logic mapper
  • Multiplexers – input/output signal routers
  • Flip-flops – 1-bit registers to hold state
  • Misc. gates for expansion

FPGA Configurable Logic Block

Simplified Configurable Logic Block (CLB)

By cleverly arranging multiple LUTs (which are really just small memories) together with muxes and flip-flops, each CLB forms a flexible foundation to digitally model advanced logic circuits.

Interconnect Network

Surrounding the CLBs is a routing network that ties everything together. Like major city roads and highways, interconnect consists of:

  • Local/express lines between nearby CLBs
  • High-speed bus routes across long distances
  • Switch matrices exchanging traffic

This infrastructure stitches CLBs into more complex functions and pipes data around optimized pathways. Modern interconnect is extremely high bandwidth to prevent congestion.

I/O Resources

Ringing the chip periphery are banks of I/O logic blocks, allowing external components to both control the FPGA and move data in/out. Standard interfaces like PCIe, Ethernet, memory controllers and high speed serial make integration easy.

DSP Slices & Block RAM

For frequently used functions like multipliers and local memory, dedicated hardware resources save space and power. Hundreds of DSP slices perform math in parallel while tens of megabits of distributed RAM stores data.

Hard Processor Systems

Many high-end FPGAs embed hardcore ARM or PowerPC cores for control functions instead of "soft processor" IP programming. This frees up logic cells for custom acceleration tasks.

Clock Management Tiles (CMTs)

Like a heartbeat synchronizing activity across the FPGA, clock manager circuits distribute timing signals while minimizing skew and jitter.

Finally, by overlaying all these hardware components with a flexible, programmable wiring framework, the amazing canvas of an FPGA emerges!

Programming FPGA Magic: Conjuring the Silicon Genie

But magically bringing silicon to life requires more than just exotic hardware. After all, it‘s called a field programmable gate array for good reason!

To conjure the genie from its bottle, engineers use special design languages describing hardware behavior rather than software algorithms. Want to make the FPGA dance? Better brush up on those hardware description language programming skills!

Popular languages to master include:

  • VHDL – VHSIC Hardware Description Language. Somewhat similar to Ada or Pascal syntax. Strong type checking to catch errors.

  • Verilog – Initially created by Gateway Design to prototype chips efficiently. C-like syntax makes it easy to learn and fast to code.

  • SystemVerilog – Superset of Verilog adding classes, constrained random testing and functional verification features to enhance productivity.

By describing components like logic gates, multiplexers, registers, buses and other constructs used in chip design, the HDL source code defines everything the FPGA needs to implement application-specific hardware behavior.

A downstream toolchain then synthesizes this high-level code into a low-level bitstream that configures all the actual silicon programmable elements. Finally, loading the bits into the FPGA memory brings the custom digital circuit to life!

FPGA Toolflow

FPGA Programming Software Toolflow

Additional frameworks like OpenCL can also simplify programming complex parallel functions across FPGA resources.

Demystified now, let‘s explore some of the magic FPGAs enable across industries when expertly conjured!

FPGA Applications: Where Silicon Sorcery Shines

From powering clinical diagnostics machinery to serving up financial risk models at lightning speeds, FPGAs accelerate a diverse range of verticals with their hardware customization prowess:


A vital cog across all network infrastructure from 3G/4G to the emerging 5G, FPGAs handle up to 100Gbps line rates for functions like:

  • Data plane processing – packet inspection, routing, tagging, forwarding
  • Control plane decision making – traffic management, congestion avoidance
  • Forward error correction – coding gain improves signal quality
  • Encryption/compression – secure voice/video with minimal bandwidth

FPGAs keep data flowing smoothly through their parallel processing pipelines specialized for network algorithms.

Aerospace and Defense

Mission-critical guidance systems, radar, communications, image recognition and other applications must meet extreme environmental resilience and functional safety specifications. Rugged antifuse FPGAs deliver:

  • Design security – crypto cores prevent tampering
  • Radiation tolerance – immunity from space particles
  • Reliability – withstand shock/vibe during flight

Reconfigurability also allows updating functionality without physical access which is perfect for remote satellites and weapons systems.

Automotive Safety

Self-driving cars demand an enormous amount of sensor data be fused and analyzed in real time – often faster than round trip latency to the cloud allows. In-vehicle processing on FPGAs tackle tasks like:

  • Sensor aggregation – fuse LiDAR, cameras, radar and other inputs
  • Object detection – identify pedestrians, signs, vehicles, animals, etc.
  • Path planning – plot safe, efficient routes to destinations

Low power consumption and small form factors also make FPGAs feasible for embedded ADAS.

Financial Trading

Shaving every microsecond of latency can yield competitive advantages and bigger profits in rapid high frequency trading systems. FPGAs accelerate quant models for:

  • Ultra low latency orders – race other algorithms
  • Complex risk analysis – Monte Carlo simulations
  • Vector processing – analytics on market data history
  • High speed connectivity – network traffic at 20Gbps+

And much more in other industries like video broadcasting, medical devices, IoT, robotics and scientific computing leveraging FPGA performance and determinism!

FPGA Design Considerations: Plan Before Programming!

With great reprogrammability comes great responsibility to engineer FPGA systems thoughtfully.

Attempting to code raw HDL without much architectural planning is akin to building a skyscraper without blueprints – a recipe for confusion!

Follow these hardware design best practices for FPGAs:

  • Thoroughly plan requirements, interfaces and system diagram first
  • Architect data flow and control units top down hierarchically
  • Encapsulate reusable logic clusters as parametrized modules
  • Develop robust stimulus testbenches for verification
  • Analyze timing performance to meet strict constraints
  • Add overlays and redundancy to guarantee reliability

Strong up front design methodologies prevent getting lost in overwhelming density unique to FPGAs.

FPGA Design Flow

Overview of FPGA Hardware Design Flow Steps

With smart planning and programming, your custom accelerator will efficiently utilize hardware resources.

Now that we‘ve toured the FPGA landscape, what does the future hold?

The Exciting Road Ahead: FPGA Projections

As computational demands in AI, genomics research, autonomous mobility and other explode, FPGAs are poised to grow in several directions:

  • Heterogenous computing with tighter coupling to CPUs, GPUs, domains specific accelerators
  • RISC-V open source processor implementations for fast prototyping
  • 3D architectures and advanced packaging for next gen interconnect
  • Embedded FPGA (eFPGA) IP reuse improving density and productivity
  • Secure enclaves keeping data safe across clouds

Ideally positioned between the ultimate flexibility of software and maximized performance of specialized hardware, FPGAs adaptive nature makes them a perfect fit to propel future innovation.

Conclusion: FPGAs Unlocked

By now you should have a much clearer picture of field programmable gate arrays – those ingeniously flexible silicon canvases underpinning acceleration across so many industries.

We lifted FPGA hoods to reveal the inner reconfigurable mechanisms that bestow hardware superpowers. We followed the brief but brilliant history of commercial FPGAs that now drive a >$5B semiconductor sector. And we previewed the road ahead as FPGAs become further embedded to meet voracious data processing demands.

FPGAs marry software control with hardware performance for a compelling computing paradigm delivering the best of both worlds. Need to mold the perfect custom silicon solution? Call upon FPGA magic!

I hope this guide illuminated FPGAs so they seem far less mysterious devices. Please drop me additional questions in the comments section below if curious about any other aspects. Now go unleash some FPGA power in your own projects!

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