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What is an FPGA? Definition, Types, Programming, and More
FPGAs are a type of programmable logic device that have become increasingly popular in recent years. This guide will explain what an FPGA is, how it works, how it compares to other types of circuits, and how to program it.
Data Center Knowledge
August 17, 2023
6 Min Read
Alamy
As data centers continue to evolve to meet the growing demands of modern applications, field-programmable gate arrays (FPGAs) have emerged as popular, versatile, and efficient solutions for enhancing data center performance.
In this article, you’ll gain a foundational understanding of what an FPGA is, learn about the different types of FPGAs, explore the benefits and challenges of using FPGAs, get a high-level overview of how to program an FPGA, and uncover the different types of FPGA programming languages.
What Is an FPGA?
A field-programmable gate array (FPGA) is a type of integrated circuit (IC), or chip, that is customizable through an array of configurable logic blocks (CLB) and that can be reconfigured after manufacturing.
Components of an FPGA
A CLB is the fundamental logic unit of FPGAs that typically contains a combination of flip-flops and lookup tables (LUTs). Flip-flops provide the ability to store and manipulate data in sequential logic circuits, and LUTs are used to implement combinational logic.
FPGAs may include additional components such as:
Interconnects - routing resources that connect the various logic blocks
Input/output (IO) blocks - components that provide the interface between the external world and the internal logic of the FPGA
Digital signal processing blocks (DSP blocks) - units that facilitate specialized functions like filtering or multiplying
FPGA manufacturers can implement custom digital circuits and reconfigure the components to meet the needs of the end user.
FPGA vs. ASIC vs. CPLD: What’s the Difference?
Along with FPGAs, ASICs and CPLDs are also important components in modern computing that are often compared in the industry. Knowing the differences between them – and which one to choose for certain applications – is important for both novice and veteran IT professionals involved in computing decisions.
FPGAs and ASICs are both types of integrated circuits with similar circuit designs, but they differ in purpose and functionality. In general, ASICs are custom designed for a specific application whereas FPGAs are more multi-purpose and able to be refitted for multiple applications. CPLDs are less complex than FPGAs and ASICs and are often used for simpler logic applications.
The below table breaks down the advantages and disadvantages of each circuit type to help you decide which is best for your applications.
What Are the Types of FPGAs?
There are three types of FPGAs: static random-access memory (SRAM)-based, flash-based, and anti-fuse.
SRAM-based
SRAM-based FPGAs use volatile SRAM cells to store configuration data, which must be loaded every time an FPGA powers up. They are commonly used for prototyping, development, and applications where frequent design changes and tests are needed.
Flash-based
Flash-based FPGAs use non-volatile flash memory cells to store configuration data, allowing the FPGA to retain its configuration and remain live at power-up. Flash-based FPGAs are most suitable for applications that need instant-on functionality without needing to reload the configuration data at each power cycle.
Anti-fuse
Anti-fuse FPGAs are non-volatile and remain live at power-up but are one-time programmable and cannot be undone or reconfigured. These traits make anti-fuse FPGAs ideal for applications that require security and do not need additional reprogramming, such as in defense, aerospace, or other high-reliability applications.
What Are the Benefits of Using FPGAs?
FPGAs provide many benefits, including, but not limited to:
Versatility - FPGAs are highly versatile due to their programmability and reconfigurability, allowing them to be used in a wide range of applications.
Speed & Efficiency - FPGAs are capable of parallel processing, allowing them to offer faster speeds, higher processing power, better response times, and overall improved performance when compared to other types of hardware.
Cost - Compared to ASICs, FPGAs provide lower upfront costs because of their ability to be reprogrammed over and over again. This is especially beneficial for low to medium production volumes where the upfront costs of a long ASIC design and development cycle may not be justifiable.
Configurability - The primary advantage of FPGAs is that they are reprogrammable. This quality allows FPGAs to be modified quickly and easily to meet a user’s needs when compared to ASICs, which cannot be reconfigured after manufacturing.
Integration - Due to their flexible nature, FPGAs can be seamlessly integrated and quickly upgraded into larger systems more easily than ASICs, which may require additional engineering costs to update.
What Are the Challenges of Using FPGAs?
Some challenges of using FPGAs, include, but are not limited to:
Cost - Although FPGAs require a lower upfront cost than ASICs because of shorter development times, FPGAs can be more expensive in the long run for high-volume production.
Power Consumption - The reconfigurability overhead of FPGAs leads them to consume more power than ASICs, which consume less power because their design is highly customized and optimized for specific tasks.
Complexity - FPGAs require a complex programming process involving specialized knowledge of hardware design, HDL, synthesis, and place-and-route tools, especially for large and intricate designs.
Time Constraints - The configuration data must be loaded every time an FPGA powers up, which can lead to a longer startup time when compared to ASICs.
How Do You Program an FPGA?
Step 1: Select an FPGA bitstream
It can be helpful to first familiarize yourself with terms and concepts such as logic gates, boolean, and logic circuits and their various types.
An FPGA bitstream is a binary file containing the configuration information for the FPGA. The FPGA bitstream should specify the configurable logic blocks, interconnects, and other necessary components that should work together for the desired digital circuit.
Step 2: Write an HDL program
Learn and use an HDL, such as Verilog or VHDL, to write code for an FPGA design flow that describes the desired behavior of your logic, including interconnections between components, registers, control signals, and data paths.
Step 3: Verify and compile the program
Debug and verify the correctness of the HDL code through simulation and testing. Once verified, use synthesis tools to convert your code into a netlist representation of the logic gates and interconnects.
Step 4: Configure the FPGA device
Convert the synthesized netlist into a format that is compatible with your FPGA device. The configuration files define how the FPGA's resources should be interconnected based on your HDL code.
Step 5: Run the program
Load the generated bitstream onto the FPGA device using programming hardware. The bitstream will configure the FPGA to implement the logic described in the HDL program.
What Are the Different Types of FPGA Programming Languages?
Verilog and VDHL (VHSIC hardware description language) are the most commonly used FPGA programming languages.
Verilog is a simple, easy-to-learn, text-based language and is widely accepted as an industry standard. It was designed to resemble the C programming language, is more commonly used in the US, and is characterized by a flexible syntax.
VHDL is known for its strongly typed, hardware description language best suited for complex digital systems. It has syntax reminiscent of the Ada programming language, is more commonly used in Europe, and is characterized by rigorous logic and prudence.
Other FPGA programming languages include lucid, C and C++, python, and AI frameworks like TensorFlow and PyTorch.
Popular FPGA Vendors
Popular vendors in the FPGA space include Xilinx (acquired by AMD in 2022), Altera (acquired by Intel in 2015), Lattice Semiconductor, Microchip (formerly Microsemi), and QuickLogic Corporation.
FPGA Outlook
The FPGA’s unique versatility and processing power make it an excellent solution to meet the growing demands of modern data center infrastructure needs, characterized by the increasing popularity of cloud computing, the explosion of data creation, and the rise of new computing-intensive applications, like machine learning.
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