Finishing: FPGA selection

FPGA selection problem under targeted arrangement

First, access to chip information:

To do the selection of the chip, the first is to have the potential to face the chip has a holistic understanding, that is, as much as possible first to obtain the information of the chip. Now there are 4 main FPGA manufacturers, Altera,xilinx,lattice and Actel. The most convenient way to get information is the official website of these manufacturers (http://www.altera.com.cn/,http://china.xilinx.com/,http://www.lattice.com/,http:// www.actel.com/intl/china/). In general, the official website will be listed in accordance with the product line or application of all products, intuitive to tell you a series of applications. For example, in Altera's website, it will clearly identify its three categories of FPGA products, high-end Stratix series, mid-end Arria series and low-cost Cyclone series.

Each factory will launch a product selection manual every year, many companies also provide evaluation tools on the website, is the Altera2012 version of the selection manual:

Often stroll around the official website of these manufacturers, see some overview of the document, when the FPGA manufacturers of product series have a more extensive understanding of the selection will not become too big a problem. Before determining the direction to be done, if you can find similar products, you can study the following products used in the scheme, if not found, can be retrieved through the database and other databases, but also to look at other people to do similar directions adopted by the scheme, which is a very good reference, It is important to note that many academic research-based programs are not product-proven, and some are relatively lagging, requiring a comprehensive assessment.

Second, the choice of FPGA manufacturers

As mentioned above, the production of FPGA manufacturers are mainly altera,xilinx,lattice and Actel. Each manufacturer's products have their own characteristics and areas of application. Selection of manufacturers is a relatively complex, to consider the following several factors:

1. To meet the specific needs of the project. For example, if you want to choose the small size of the 4mmx4mm package without the need to configure the chip FPGA, then maybe Actel is your only choice. If you need an FPGA chip with an ADC, you may be able to select only some FPGAs and Actel with ADCs.
2. Look at the supply, good supply channels for the production of products will have a better guarantee, if there is no special channel or choose those better buy and widely used models
3. Look at the price, the lower price will effectively improve the competitiveness of the product
4. is the technical personnel to all meet the requirements of the manufacturers of the product familiarity degree. The use of the most familiar products, can effectively shorten the development of the difficulty, reduce development time, improve product time to market.
5. See the maturity of the chip, is not a good development software platform, is not a better technical support, is not a large number of applications, whether it can be easier to obtain resources and so on.

Three, the choice of chip series

Each FPGA manufacturer has multiple series of products to meet different performance and price requirements for different applications. For example, Altera's FPGA products are mainly divided into three series, namely high-end Stratix, mid-end Arria and low-end cyclone.

Each series of FPGA specific performance features can also be found on Altera's official website of the corresponding documents. Select the appropriate series according to the actual project needs. For example, if you need to implement a relatively simple control function, the resource requirements are relatively low, and the cost control requirements are relatively high, then you need to start from the Cyclone series of FPGAs to evaluate whether this series of FPGA can meet the requirements. However, if you want to do larger ASIC chip validation, FPGA logic resources, bandwidth and operating frequency requirements are relatively high, then to evaluate the Stratix series of FPGA. There is a basic principle to note that can be done with the low-end chip work, do not use high-end chips, the goal is to achieve the best balance of performance and cost.

Each series of FPGA chips, may also be divided into several generations of products, such as Altera's Cyclone series, has now developed the CYCLONE,CYCLONEII,CYCLONEIII and CYCLONEIV four generations of products. The upgrading of this product is largely due to the upgrading of the semiconductor process. With the upgrading of semiconductor technology, FPGA chip also in the process of upgrading, providing more powerful functions, lower power consumption and better cost-effective. After deciding on a series of FPGAs, it becomes a problem to choose which generation of products. My personal advice is to choose the more new products in the case of price and availability without problems. Must not choose the manufacturers have been or will be discontinued chips. Any product has a life cycle, the goal is to try to ensure that the life cycle of the product, the life cycle of the chip used is not over. In the initial stage of product planning to do chip selection, to choose as far as possible manufacturers just mass production or mass production of products soon, even in the case of the exact supply channels, you can choose the production of the chip manufacturers will be.

Four, the choice of chip

In the CYCLONEIII series of FPGAs, it is divided into two different sub-series, ordinary CYCLONEIII and CYCLONEIII LS. In each sub-series, according to the different on-chip resources are divided into more models, such as the ordinary CYCLONEIII sub-series, including the Ep3c5,ep3c10,ep3c16,ep3c25,ep3c40,ep3c55, Ep3c80 and ep3c120 8 types of chips. Each model of the chip is based on the number of general-purpose I/O port and the packaging area of different chips. For example, EP3C5 chips have ep3c5e144,ep3c5m164,ep3c5f256 and ep3c5u256 four different kinds of chips. And each kind of chip, also has the different speed grade, for example ep3c5e144 has the C7,c8,i7 and A7 four speed grade.

The table below lists the parameters of the FPGA for the common CYCLONEIII series from different angles, which are derived from the official documentation for the CYCLONEIII chip:

1, the on-chip resource table of each model chip. This table shows the on-chip resources for each model chip, where maximum user I/Os gives the number of user I/Os that the model has, but it is important to note that the number of user I/Os in different packages is not the same.

2, the table below gives the package information for each type of chip, and the number of available I/O to the chip and the number of check signal channels under the package.

In selecting specific chip models and packages, the following aspects should be considered as a comprehensive consideration:

1, on-chip resources, mainly based on the information given in table 1. Select the appropriate on-chip resources based on the size of the design. This is a more difficult to determine a parameter, the design of their own how much, how much resources needed, it is difficult to determine the next. One of the recommended way is to take the previous design to the synthesis after mapping to a certain chip, to see how much of the on-chip resources, and then evaluate the new design to do with the previous size, do the conversion to get the amount of resources needed on-chip. Another way is to complete the new design, directly integrated to map to different models of the chip, and then evaluate which kind of chip suitable. There is also a need to pay attention to the point is that you can not choose on-chip resources just enough chips, to leave a certain margin, so that the late design error correction and upgrade.

2, package, mainly according to table 2 and table 3 gives the information. Select the package, the main need to consider in two aspects, the first is the number of available I/O ports. The second one is the dimensions of the package. The number of I/O is a necessary condition, first of all to filter out the available chips according to this condition. Then in the selected chip, according to the package type, size and pitch size to choose the right chip. In case the package size meets the requirements, choose the package which is advantageous to PCB design and production. For example, if there is a chip in the TQFP package, the size meets the requirements of the project, then do not choose BGA Package. For BGA package chip, if there is pitch 1.0mm can meet the requirements, do not choose pitch for 0.5mm. This directly affects PCB design difficulties, manufacturing costs and yield.

3, the speed level, mainly according to the information given in table 4. The speed level is a relatively independent parameter. According to the actual design can be integrated out of the highest operating frequency and demand for the operating frequency of comparison, as far as possible to choose the speed of slow-grade chip. When all the speed levels are not enough, more need to be optimized from the angle of design to improve the design itself can achieve the highest operating frequency.

Five, the choice of FPGA beginners

For an FPGA beginner, how to choose a company's product of a series as the basis for learning? This is a problem, but it is not the most important issue.

Beginners in the study of FPGA, to solve the first problem is to master the basic knowledge of digital circuit technology, and then the Hardware Description Language Mastery (Veirlog or VHDL). As for the FPGA chip itself, it is just a carrier. When really mastered the nature of FPGA design, need to use a certain manufacturer of some kind of FPGA, only need to do some understanding of this model of the FPGA manufacturer, the basis of the design is the same, the previous accumulation of most of the experience can be applied.

However, in the choice of time, but also to select mainstream manufacturers of popular models, so that more easily access to learning resources.

Finishing: FPGA selection