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What is FPGA?

FPGA (field programmable gate array) is the product of further development on the basis of pal (programmable array logic), gal (general array logic) and other programmable devices. As a semi custom circuit in the field of application specific integrated circuits (ASIC), it not only solves the shortcomings of custom circuits, but also overcomes the shortcomings of the limited number of programmable devices.

Basic structure

FPGA device is a kind of semi customized circuit in ASIC. It is a programmable logic array, which can effectively solve the problem of less number of original device gates. The basic structure of FPGA includes programmable input and output unit, configurable logic block, digital clock management module, embedded block ram, wiring resources, embedded special hard core, and bottom embedded functional unit. FPGA has been widely used in the field of digital circuit design because of its rich wiring resources, high reprogrammability, high integration and low investment. The FPGA design process includes algorithm design, code simulation and design, board debugging. The designer and the actual needs establish the algorithm architecture, use EDA to establish the design scheme or HD to write the design code, ensure that the design scheme meets the actual requirements through code simulation, and finally carry out board level debugging, and use the configuration circuit to download the relevant files to the FPGA chip to verify the actual operation effect.

working principle

FPGA adopts the concept of logic cell array (LCA), which includes configurable logic block (CLB), input output block (iob) and interconnect. Field programmable gate array (FPGA) is a programmable device. Compared with traditional logic circuits and gate arrays (such as pal, gal and CPLD devices), FPGA has different structures. FPGA uses small look-up table (16 × 1ram) to realize combinatorial logic. Each look-up table is connected to the input of a D trigger, and the trigger then drives other logic circuits or drives i/o, thus forming a basic logic unit module that can realize both combinatorial logic functions and sequential logic functions. These modules are interconnected or connected to i/o modules by metal wires. The logic of FPGA 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 mode between modules or between modules and i/o, and finally determines the function that FPGA can realize. FPGA allows unlimited programming.

Industry application

Video segmentation system

In recent years, large-scale master control system has been widely used, and the level of video segmentation technology related to it is also gradually improving. This technology uses the way of multi screen splicing display to display a video signal, which is widely used in some scenes that need to use large screen display. [2] With the progress of technology, video segmentation technology has gradually matured, meeting people's basic needs for clear video images. FPGA chip hardware structure is relatively special. You can use the pre edited logic structure file to adjust the internal structure, use the constrained file to adjust the connection and position of different logic units, and properly handle the data line path, Its own flexibility and adaptability facilitate the development and application of users. When processing video signals, FPGA chip can make full use of its own speed and structural advantages to realize ping-pong technology and pipeline technology. In the process of external connection, the chip adopts the method of data parallel connection to broaden the bit width of image information and improve the speed of image processing by using the internal logic function. The control of image processing and other devices is realized through the cache structure and clock management. In the overall design structure, FPGA chip is at the core. The interpolation processing, extraction and storage of complex data also play the role of overall control to ensure the stable operation of the system. In addition, unlike other data processing, video information processing requires a special logic unit and ram or FIFO unit on the chip to ensure sufficient data transmission speed.

Data delayer and storage design

FPGA has programmable delay digital units, which are 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, counter method, etc., of which the memory method is mainly realized by using FPGA ram or FIFO. Using FPGA to read and write SD card related data can be programmed according to the needs of specific algorithms, and the continuous updating of reading and writing operations can be realized according to the changes of more actual conditions. Under this mode, the effective control of SD card can be realized only by using the original chip, which significantly reduces the cost of the system.

Communication industry

Generally, the communication industry takes into account the cost, operation and other factors. In the location with a large number of terminal equipment, 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 FPGA chip, and the model is relatively high, which can handle complex physical protocols and realize logic control. At the same time, because the logical link layer and the physical layer protocol of the base station need to be updated regularly, it is also more suitable to use FPGA technology. At present, FPGA is mainly used in the initial and medium-term construction of the communication industry, and it is gradually replaced by ASIC in the later stage

Other applications

FPGA is also widely used in security, industry and other fields. For example, protocols such as video coding and decoding in security field can be processed by FPGA in the process of front-end data acquisition and logic control. In the industrial field, small-scale FPGA is mainly used to meet the needs of flexibility. In addition, due to its high reliability, FPGA is also widely used in military and aerospace fields. In the future, with the continuous improvement of technology, the 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 network, FPGA will be widely used in the initial stage, and more FPGA will be used in new fields such as artificial intelligence.