The choice of FPGA devices is different from other general-purpose logic devices. In addition to considering the performance of the device itself, software is also important. At present, there are more than 20 FPGA device manufacturers on the market, and there are more than 50 kinds of design software in addition to the software developed by the manufacturer. The price of FPGA devices is already high, not to mention the price of design software. So how to choose the right FPGA device is not only a one-off work, but also the selection of design software and the further development in the future.
First of all, users should choose a suitable software tool according to their technical environment, technical conditions, usage habits, etc., and at the same time take into account the development of EDA technology. The dominant software vendors have established good partnerships with most chip manufacturers. Therefore, having a design software, further selecting different tool libraries, or adding some configurations, can be different types of FPGAs from different manufacturers. The product is designed.
Second, the user can determine which type of FPGA device to select based on the needs of the design. If used in aerospace, military, anti-fuse technology, a programming FPGA is the first choice; if you want to complete a variety of arithmetic operations, or require higher speed, FPGA / CPLD is a better choice; In terms of sequential logic, standard gate array cell type FPGAs have the advantages of high integration, flexibility, and low power consumption. Of course, this is only a general guideline. The key is that the selected device can meet all the functions of the design requirements. Based on this, the above criteria can be used to determine a specific device.
Third, the selection of a certain manufacturer's products, a large number of manufacturers producing similar devices, generally based on the following criteria to choose.
(1) Select a chip from a manufacturer with design software support to reduce capital investment and reduce costs.
(2) Choose a product design performance improvement with a margin. If the selected chip is the capacity of a certain manufacturer's product: the largest, or the highest speed, then once the design needs to be improved, it is possible to select the appropriate one in the manufacturer's chip.
(3) Continuity and scalability of design applications. If the product of the selected manufacturer has great limitations, it may be applied to only a small part of the design, resulting in waste of design software investment.
(4) Choose the performance price ratio to be optimal. Although device manufacturers such as Xilinx and Altera are marketing through price cuts, the price of most FPGA chips is still relatively high, and it is necessary to properly consider the price in case of meeting the above criteria.
The development of FPGA devices is very fast. The above statistics are carried out from the market point of view for some manufacturers with large market share and leading position in the industry. They are representative, but not very comprehensive. Only by continuously tracking the technological development and market dynamics in this field can we have a more comprehensive and constantly updated understanding of FPGA products, and make better use of FPGAs in future designs to improve the design level of products.
Because FPGA has the advantages of flexible design and reprogrammable, it has been widely used in the field of electronic product design. In engineering projects or product design, the following strategies and principles can be referred to for selecting an FPGA chip.
Try to choose a mature product line
The technology of FPGA chips has been at the forefront of chip design, and the product update speed is very fast. Stability and reliability are key factors in product design considerations. The latest FPGA series products from manufacturers are generally not verified by high-volume applications. Choosing such a chip increases the risk of design. Moreover, due to the relatively small output of the newly introduced FPGA chip, the general supply situation will not be ideal, and the price will be higher. If a mature product meets the design specifications, it is best to choose such a chip to complete the design. For example, design a data acquisition card with an FPGA. This feature can be achieved with three series of chips from Altera's Cyclone, Cylone II and Cyclone III. Considering that Cyclone and Cylone II are mature products, and Cylone II is an upgraded product of Cyclone, choosing Cylone II is an ideal solution.
Try to choose a compatible package
FPGA system design generally uses hardware description language (HDL) to complete the design. This is very different from CPU-based software development. Especially when the algorithm is implemented, it is difficult to estimate how much FPGA logic resources this algorithm needs before designing. As a code designer, I hope that the model of the FPGA will be selected after the algorithm is implemented. However, the current design process is generally started in parallel with software and hardware. That is to say, before the design of the HDL code, the design of the hardware board is started. This requires a hardware board with certain compatibility, and can be compatible with FPGA chips of different sizes. Fortunately, FPGA chip manufacturers have taken this into account. At present, the same series of FPGA chips can generally be compatible with devices of different sizes in the same physical package. For example, Xilinx's Spartan3 series FPGAs, in the BGA456 package, can choose 4 types of FPGAs: 3S200, 2S400, 3S1000, and 3S1500. Because of this, future products have very good scalability, and can continuously add new features or improve performance without modifying the design files of the board.
Try to choose a company's products
If you need multiple FPGA devices in your entire electronic system, try to choose a company's product. This benefit not only reduces costs, but also reduces development difficulty. Because the development environment and tools are consistent, the chip interface levels and characteristics are also consistent, making it easy to interconnect.
Many designers who have been exposed to FPGAs for the first time have had this question when selecting chips. In fact, the two largest FPGA manufacturers are located in the same city in the United States. The personnel and technical exchanges are very frequent. Therefore, the advantages and characteristics of each product are difficult to tell who is good or who is bad.
In different regions of the world, the market performance of the FPGA chips of the two companies will be different. In the Chinese market, the two companies can be said to be equally divided, and Altera's customers in colleges and universities will be slightly more. For specific applications, the right series or model can be found in both manufacturers' catalogs.
For example, for low-cost applications, Altera's Cyclone series and Xilinx's Spartan3 series are compatible. For high-performance applications, Altera's StraTIx series and Xilinx's Virtex series are compatible. Therefore, the choice of the company's products is still to see the developer's habits.
Pay attention to the actual working temperature of the chip when selecting the chip.
Recently, the instruments completed by the project always have data inaccuracy during the test, but there has never been a similar situation in the past, and all the indicators meet the requirements during the indoor test, but once the outdoor test (in the instrument application, the outdoor open space) ), the test data will be inaccurate, puzzling, and finally we judge that the actual environment temperature is beyond the normal operating temperature range of the chip. At this time, the outdoor temperature in Beijing is often lower than 0 degrees, and the FPGA chip I use is commercial grade, and its operating temperature range is 0°~70°, so it is very likely that the problem is here, and the equipment is warmed. After that, the test results have been significantly improved.
By the way, the operating temperature range of various grades of chips
Commercial grade: 0°~70°
Industrial grade: -40°~85°
Military grade: -55°~125°
The nature of Altera's FPGA model naming can also be seen. For example, the FPGA I use is EP2C8Q208C8.
2C: Representative is the Cyclone II series
8: the number of logical units, 8 means that there are about 8000 logical units
Q: indicates package, Q stands for QFP package
208: represents the number of pins, there are 208 pins
C: The representative is commercial grade, and I stands for industrial grade.
8: indicates the chip speed, generally there are 6, 7, 8 three, 6 highest, 8 slowest
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