What is Field Programmable Gate Array?

Catalog

Ⅰ Introduction

FPGA

FPGA design is not simple chip research but mainly uses the FPGA model to design products in other industries. Unlike ASIC, FPGA is widely used in the communications industry. Compared with traditional chip design, FPGA chips are not limited to research and design chips but can be optimized for products in many fields with the help of specific chip models. From the perspective of chip devices, FPGA itself constitutes a typical integrated circuit in semi-custom circuits, which contains digital management modules, embedded units, output units, and input units. On this basis, it is necessary for FPGA chips to focus on comprehensive chip optimization design, and to add new chip functions by improving the current chip design, thereby achieving the simplification and performance improvement of the overall chip structure.

Ⅱ Basic structure

FPGA chip

FPGA devices are a kind of semi-custom circuit in the application-specific integrated circuit, which is a programmable logic array. It can effectively solve the problem of fewer gate circuits in the original device. The basic structure of FPGA includes programmable input and output units, configurable logic blocks, digital clock management modules, embedded block RAM, wiring resources, embedded dedicated hard cores, and underlying embedded functional units. Because FPGA has the characteristics of rich wiring resources, repeatable programming, high integration, and low investment, it has been widely used in the field of digital circuit design. The FPGA design process includes algorithm design, code simulation, and design, board debugging, designers and actual needs to establish the algorithm architecture, use EDA to establish a design plan or HD to write design code, through code simulation to ensure that the design plan meets actual requirements, and finally board Level debugging, using the configuration circuit to download the relevant files to the FPGA chip to verify the actual operation effect.

Ⅲ Working principle

FPGA in the circuit

FPGA adopts the concept of logic cell array LCA, which includes configurable logic modules CLB (Configurable Logic Block), input and output module IOB (Input Output Block), and internal wiring (Interconnect) three parts. Field programmable gate array (FPGA) is a programmable device that has a different structure compared with traditional logic circuits and gate arrays (such as PAL, GAL, and CPLD devices). FPGA uses a small look-up table (16×1RAM) to implement combinational logic. Each look-up table is connected to the input of a D flip-flop, and the flip-flop drives other logic circuits or I/O, thus forming the basic logic unit module that can realize the combination logic function and the sequential logic function. These modules are connected to each other or I/O modules by metal wires. FPGA logic is realized by loading programming data into the internal static storage unit. The value stored in the memory unit determines the logic function of the logic unit and the connection between modules or between modules and I/O, and finally determines the function that FPGA can realize. FPGA allows unlimited programming.

Ⅳ Chip design

Compared with other types of chip design, FPGA chips usually need to set a higher threshold and draft a more rigorous basic design process. Specifically, when designing, it should be closely integrated with the relevant schematic diagrams of the FPGA to realize a large-scale specialized chip design. Through the use of Matlab and the special design algorithm of C language, it should be possible to achieve smooth conversion in all directions, so as to ensure that it conforms to the current mainstream chip design ideas. Under this premise, if you choose the above design ideas, you usually need to focus on the orderly integration of various components and corresponding design languages, thereby ensuring the availability and readability of chip programming. The use of FPGA can realize board debugging, code simulation, and other related design operations to ensure that the current code-writing methods and design schemes can meet specific design requirements. In addition, regarding the design algorithm, rationality should be put in the first place, so that the optimized project design effect is realized and the effectiveness of the chip operation is optimized. Therefore, as a designer, the first thing is to build a specific algorithm module to complete the related chip code design. This is because the pre-designed code helps to ensure the reliability of the algorithm, and the overall chip design effect can also be significantly optimized. On the premise of comprehensively completing the board debugging and simulation test, it should be possible to shorten the cycle of designing the entire chip consumption at the root, and at the same time, it is also committed to optimizing the current existing hardware overall structure. For example, when it comes to developing some non-standard hardware interfaces, the above-mentioned new product design patterns are usually used.

The main difficulty in FPGA design is to be familiar with the hardware system and internal resources, to ensure that the language of the design can achieve effective coordination between components, and to improve the readability and utilization of the program. This also puts forward relatively high requirements for designers.

In the algorithm design, it is necessary to focus on rationality, to ensure the final effect of the project, and to propose solutions to the problem based on the actual situation of the project to improve the operating efficiency of the FPGA. After determining the algorithm, the module should be constructed reasonably to facilitate the later code design. In the code design, the pre-designed code can be used to improve work efficiency and enhance reliability. Write a test platform, perform code simulation testing and class debugging, and complete the entire design process. FPGA is different from ASIC because the development cycle is relatively short, and the hardware structure can be changed according to the design requirements. When the communication protocol is immature, it can help enterprises quickly launch new products to meet the needs of non-standard interface development.

Ⅴ Advantages and Disadvantages

1 Advantages

(1) FPGA is composed of hardware resources such as logic unit, RAM, multiplier, etc. By rationally organizing these hardware resources, hardware circuits such as multipliers, registers, and address generators can be realized.

(2) FPGA can be designed by using a block diagram or Verilog HDL, from a simple gate circuit to FIR or FFT circuit.

(3) FPGA can be reprogrammed indefinitely, and it only takes a few hundred milliseconds to load a new design. Reconfiguration can reduce hardware overhead.

(4) The operating frequency of FPGA is determined by the FPGA chip and design, and certain demanding requirements can be met by modifying the design or replacing faster chips (Of course, the operating frequency is not unlimited, but is affected by the current IC technology).

2 Disadvantages

(1) All the functions of FPGA are realized by hardware, and operations such as branch condition jump cannot be realized.

(2) FPGA can only realize fixed-point operations.

Summary: FPGA relies on hardware to implement all functions, and its speed can be compared with dedicated chips, but its design flexibility is far from general-purpose processors.

Ⅵ Industry Application

1 Video segmentation system

In recent years, large-scale master control systems have been increasingly widely used, and the level of related video segmentation technology is gradually improving. This technology uses multi-screen splicing to display a video signal.

With the advancement of technology, video segmentation technology gradually matures to meet people's basic needs for clear video images. FPGA chip hardware structure is relatively special. You can use pre-edited logical structure files to adjust the internal structure, and use constrained files to adjust different connections and locations of the logic unit. When processing video signals, FPGA chips can make full use of their own speed and structural advantages to realize ping-pong technology and pipeline technology. In the process of external connection, the chip adopts a data-parallel connection method to broaden the bit width of image information and use internal logic functions to increase the speed of image processing. Through the cache structure and clock, management to achieve control of image processing and other equipment. In the overall design structure, the FPGA chip is at the core. The interpolation processing, extraction, and storage of complex data also play a role in overall control to ensure the stable operation of the system. In addition, video information processing is different from other data processing and requires the chip to have a special logic unit and a RAM or FIFO unit to ensure sufficient data transmission speed.

2 Data delay and storage design

FPGA has a programmable delay digital unit, which is widely used in communication systems and various electronic devices, such as synchronous communication systems, time digitization systems, etc. The main design methods include numerical control delay line method, memory method, and counter method And so on, the memory method is mainly realized by using FPGA RAM or FIFO.

Using FPGA to read and write relevant data of SD card can carry out programming according to the low demand of specific algorithms and FPGA chip, and realize the continuous update of reading and write operations according to the changes of actual conditions. Under this mode, only the original chip can be used to effectively control the SD card, which significantly reduces the cost of the system.

3 Communications industry

Under normal circumstances, the communication industry comprehensively considers various factors such as cost and operation. In locations where the number of terminal equipment is relatively large, the amount of FPGA is relatively large, and the base station is most suitable for using FPGA. Almost every board of the base station needs to use an FPGA chip. The model is relatively high-end, which can handle complex physical protocols and realize logical control. At the same time, due to the logical link layer of the base station, the protocol part of the physical layer needs to be updated regularly, and FPGA technology is also more suitable. At present, FPGA is mainly used in the initial and mid-term applications of the communication industry, and gradually replaced by ASIC in the later period.

4 Other applications

FPGAs are also widely used in security, industry, and other fields. For example, protocols such as video encoding and decoding in the security field can be processed by FPGA in the process of front-end data acquisition and logic control. The industrial field mainly uses small-scale FPGAs to meet the needs of flexibility. In addition, because FPGAs have relatively high reliability, they are also widely used in military and aerospace fields. In the future, with the continuous improvement of technology, related processes will be upgraded. In many new industries such as big data, FPGA will have a wider application prospect. With the construction of 5G networks, FPGAs will be widely used in the initial stage, and new fields such as artificial intelligence will also use FPGAs more.