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What is an FPGA?

Date: Apr 20, 2023

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An FPGA (Field Programmable Gate Array) is a product that has evolved further based on programmable devices such as PAL (Programmable Array Logic) and GAL (Generic Array Logic). It emerged as a type of semi-custom circuit in the application-specific integrated circuit (ASIC) domain, addressing the limitations of custom circuits while overcoming the drawback of limited gate circuit numbers in existing programmable devices.

Abbreviation: FPGA

Full Name: Field Programmable Gate Array

Category: AI Chip



FPGA design is not merely about chip research; it mainly involves designing products for other industries using FPGA patterns. Unlike ASICs, FPGAs are widely used in the communication industry. By analyzing the global FPGA product market and related suppliers and considering the actual situation and domestic leading FPGA products, we can identify the future development direction of related technologies, which play a vital role in promoting the overall improvement of national technological levels.

FPGA chips are not strictly limited to research and design compared to traditional chip design models. Instead, they can optimize designs for various domain products using specific chip models.

From the perspective of chip devices, FPGAs themselves constitute typical integrated circuits in semi-custom circuits, including digital management modules, embedded units, output units, and input units.

On this basis, focusing on comprehensive chip optimization design for FPGA chips is essential. This approach simplifies the overall chip structure and enhances performance by improving the current chip design to add new chip functions.

Basic Structure

FPGA devices belong to a type of semi-custom circuit in application-specific integrated circuits. They are programmable logic arrays capable of effectively addressing the issue of having too few gate circuits in existing devices.

The basic structure of an FPGA includes the following:

  • Programmable input/output units.

  • Configurable logic blocks.

  • Digital clock management modules.

  • Embedded block RAM.

  • Wiring resources.

  • Embedded dedicated hard cores.

  • Underlying embedded functional units.

Due to their abundant wiring resources, programmability, high integration, and low investment, FPGAs have been widely applied in digital circuit design.

The FPGA design process involves algorithm design, code simulation and design, and board debugging. Designers establish algorithm architectures based on actual needs, use EDA to create design schemes or write design code in HD, and perform code simulations to ensure the design meets practical requirements. Finally, board-level debugging is carried out, and configuration circuits download the relevant files to the FPGA chip to verify actual performance.

Working Principle

FPGAs employ a concept called Logic Cell Array (LCA), which consists of three internal components: Configurable Logic Blocks (CLBs), Input-Output Blocks (IOBs), and Interconnects.

what is an FPGA.jpgwhat is an FPGA?

Field Programmable Gate Arrays (FPGAs) are programmable devices with a different structure than traditional logic circuits and gate arrays (such as PAL, GAL, and CPLD devices).

FPGAs use small lookup tables (16x1 RAM) to implement combinational logic, with each lookup table connected to the input of a D flip-flop. The flip-flop drives other logic circuits or I/Os, forming basic logic unit modules that implement combinational and sequential logic functions. These modules are interconnected using metal wiring or connected to I/O modules.

The logic of an FPGA is implemented by loading programming data into internal static storage units. The values stored in the memory units determine the logic functions of the logic units, the connection methods between the modules or between the modules and the I/Os, and ultimately the functions that the FPGA can perform. FPGAs allow for unlimited programming.

Chip Design

FPGA chip design usually requires a higher entry barrier and a more stringent basic design process than other types of chip design. During the design stage, it is essential to closely follow the relevant schematics of the FPGA to achieve large-scale specialized chip design. A comprehensive smooth conversion can be achieved by utilizing specialized design algorithms in Matlab and C language, ensuring conformity with the current mainstream chip design ideas. Under this premise, if the design above approach is chosen, it is generally necessary to focus on the orderly integration of various components and corresponding design languages, ensuring a highly usable and readable chip program design.

Chip Design.png
chip design

FPGA can be used to perform board debugging, code simulation, and other related design operations, ensuring that the current code-writing methods and design schemes meet specific design requirements.

In addition, the design algorithm should prioritize rationality to achieve optimized project design results and enhance the practical effectiveness of chip operation.

Therefore, the first step as a designer is constructing specific algorithm modules to complete the related chip code design. This is because pre-designed code helps ensure algorithm reliability and significantly optimizes the chip design effect. Upon completing board debugging and simulation testing, the design cycle of the entire chip should be shortened at its root while optimizing the existing hardware structure.

For instance, the aforementioned new product design pattern is often used when developing non-standard hardware interfaces.

The main difficulty in FPGA design is to be familiar with hardware systems and internal resources, ensuring that the design language can effectively coordinate components and improve the readability and utilization of programs. This sets high requirements for designers, who must accumulate experience from multiple projects to meet these demands.

During algorithm design, focusing on rationality, ensuring the project's outcome, and proposing solutions to problems based on the actual project situation to improve FPGA performance is crucial. After determining the algorithm, modules should be reasonably constructed to facilitate later code design.

In code design, pre-designed code can improve work efficiency and enhance reliability. Write a testing platform, perform code simulation testing and board debugging, and complete the entire design process. Unlike ASICs, FPGAs have a shorter development cycle and can change hardware structures according to design requirements. FPGAs can help companies quickly launch new products and meet non-standard interface development needs in situations where communication protocols are immature.

Advantages and Disadvantages of FPGA


The advantages of FPGAs are as follows:

1. FPGAs consist of hardware resources such as logic units, RAM, multipliers, etc. By organizing these hardware resources reasonably, hardware circuits such as multipliers, registers, and address generators can be implemented.

2. FPGAs can be designed using block diagrams or Verilog HDL, from simple gate circuits to FIR or FFT circuits.

3. FPGAs can be reprogrammed indefinitely, and loading a new design scheme takes only a few hundred milliseconds. Reconfiguration can reduce hardware overhead.

4. The FPGA chip and the design determine the working frequency of FPGAs. It can be achieved by modifying the design or replacing it with a faster chip to meet certain demanding requirements (of course, the working frequency is not infinitely improvable and is subject to factors such as current IC technology).


The disadvantages of FPGAs are as follows:

1. All functions of FPGAs rely on hardware implementation, making performing operations such as conditional branch jumps impossible.

2. FPGAs can only implement fixed-point operations.

In conclusion: FPGAs rely on hardware to implement all functions, and their speed can be compared to that of dedicated chips. However, their design flexibility has a significant gap compared to general-purpose processors.

Design Language and Platform

Programmable logic devices are hardware carriers that implement electronic application systems' predetermined functions and technical indicators through EDA technology. As one of the mainstream devices to achieve this, FPGA is user-oriented, highly flexible and versatile, easy to use, and fast in hardware testing and implementation.

Hardware Description Language (HDL) is a language used to design digital logic systems and describe digital circuits. The most commonly used languages include VHDL, Verilog HDL, System Verilog, and System C.

As a comprehensive hardware description language, Very High-Speed Integrated Circuit Hardware Description Language (VHDL) has characteristics independent of specific hardware circuits and design platforms. It has a wide range of descriptive capabilities, does not depend on specific devices, and can describe complex control logic designs with rigorous and concise code. This makes it widely supported by many EDA companies and extensively applied in electronic design.

VHDL is a high-level language for circuit design. Compared to other hardware description languages, it has the characteristics of concise language, strong flexibility, and no dependency on device design. This makes it a general hardware description language for EDA technology, making it more accessible to designers.

Verilog HDL is a widely used hardware description language that can be applied to the hardware design process's modeling, synthesis, and simulation stages.

Advantages of Verilog HDL: Similar to C language, easy to learn, and flexible. It is case-sensitive and has advantages in writing stimulus and modeling.

Disadvantages: Many errors cannot be discovered during compilation.

Advantages of VHDL: Rigorous syntax, clear hierarchical structure.

Disadvantages: It takes longer to become familiar with and is less flexible.

Quartus II software is a complete multi-platform design environment developed by Altera Corporation, meeting various FPGA and CPLD design needs. It is a comprehensive environment for on-chip programmable system design.

Vivado Design Suite is an integrated design environment released by Xilinx, a leading FPGA manufacturer, in 2012. It includes a highly integrated design environment and a new generation of tools from the system to the IC level, all built on a shared, scalable data model and a common debugging environment.

Xilinx Vivado Design Suite provides FIFO IP cores, which can be conveniently applied to designs.

Industry Applications

Video Splitting System

In recent years, large-scale control systems have been increasingly widely used, and the related video-splitting technology level has gradually improved. This technology uses a multi-screen mosaic display method to display a single video signal, widely used in scenarios requiring large-screen displays.

Video splitting technology has gradually matured as technology advances, meeting people's basic needs for clear video images. FPGA chips have a unique hardware structure that allows users to adjust the internal structure using pre-edited logic structure files and constraint files to adjust the connections and positions of different logic units. Properly handling data line paths, flexibility, and adaptability make them convenient for user development and application.

FPGA chips can fully utilize their speed and structural advantages when processing video signals and implementing ping-pong and pipelining technology.

In external connections, the chip adopts a data parallel connection method, widening the bit width of image information and using internal logic functions to improve image processing speed. It controls image processing and other devices through high-speed cache structures and clock management. In the overall design structure, the FPGA chip is at the core, handling complex data interpolation processing, extraction, and storage while also playing a role in overall control, ensuring the system's stable operation. In addition, video information processing differs from other data processing, requiring chips to have special logic units and RAM or FIFO units to ensure sufficient data transmission speed.

Data Delays and Storage Design

FPGAs have programmable delay digital units, which have widespread applications in communication systems and various electronic devices, such as synchronous and time-to-digital systems. The main design methods include digital control delay line, memory, and counter methods, with memory methods primarily using FPGA's RAM or FIFO implementation.

Using FPGA for SD card-related data reading and writing can be programmed based on specific algorithm requirements on the FPGA chip, constantly updating read and write operations as situations change. Under this mode, effective control of the SD card can be achieved using only the existing chip, significantly reducing system costs.

Telecommunications Industry

Under normal circumstances, the telecommunications industry considers costs and operations comprehensively. In locations with a large number of terminal devices, FPGAs are heavily used. Base stations are most suitable for using FPGA chips. Almost every base station board requires FPGA chips, usually high-end models capable of handling complex physical protocols and implementing logic control. At the same time, FPGA technology is also suitable since the protocol parts of the base station's logical link layer and physical layer need to be updated regularly.

FPGA is mainly used in the initial and middle stages of the telecommunications industry's construction, gradually being replaced by ASIC in the later stages.

Other Applications

FPGAs are also widely used in security, industry, and other fields. For example, video encoding and decoding protocols in security can use FPGA processing during front-end data collection and logic control. The industrial sector mainly uses smaller-scale FPGAs to meet flexibility requirements. Additionally, due to the high reliability of FPGAs, they are also widely used in the military and aerospace fields.

In the future, as technology continues to improve, related processes will be upgraded and transformed. FPGAs will have a broader application prospect in many new industries, such as big data. With the construction of 5G networks, FPGA will be heavily used in the early stages, and new fields like artificial intelligence will also increasingly use FPGA.

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