The 21st century is the era of information. All kinds of electronic technologies are updated and developed at an unbelievable speed. Computers, mobile phones, DV, etc. have become an indispensable part of contemporary life. The functions of these electronic products are increasing day by day, and their performance is getting better and better. The price has decreased but not increased. To explore the reasons, the development of integrated circuit manufacturing technology and the improvement of electronic design technology are the two mainstream factors. The integrated circuit manufacturing technology is mainly based on micro-processing, and the electronic design technology is based on EDA technology. EDA technology has become one of the frontiers of today’s electronic technology development. This is the result of the joint efforts of countries with advanced technologies. The application of CPLD and FPGA programmable logic devices has undoubtedly brought great benefits to electronic design. Flexibility and applicability.
1. Concept and characteristics of EDA technology
EDA technology is electronic design automation technology, which is developed from PLD technology. The application of programmable logic device PLD and the expansion of integration scale have brought great convenience and flexibility to the design of digital systems, changing the traditional digital System design concept, process, method. Through the continuous improvement of PLD technology, EDA technology came into being.
EDA technology is a new technology based on large-scale programmable devices, using computer as a tool, and completing expression according to hardware description language HDL to achieve the goals of compiling, simplification, partitioning, layout, and optimization of logic. With the help of EDA technology, operation The designer can realize a description of the hardware function by using software, and then use FPGA/CPLD to get the final design result.
A New Design Approach: Top Down
Traditional electronic design methods are generally “bottom-up”. Generally speaking, after the standard general integrated circuit chip is determined, the module design is carried out, and the system design is finally completed. This kind of design has long-term insurmountable defects, such as low efficiency, easy failure, too many components required, and high consumption… EDA technology is a breakthrough and change to traditional electronic design methods. Its design is “Top-down”, that is, taking the system design as the entry point, dividing the functional block diagram and completing the planning of the structure of each part at the time of design, and completing the simulation and error correction in the block diagram division stage, and at the same time with the help of HDL Complete the logic description of the high-level system. After verification, the electronic design is completed with the help of comprehensive optimization tools. With the help of EDA technology, the operator can realize a description of the hardware function by using software, and then use FPGA/CPLD to get the final result. Design results.
In this way, we can find that both simulation and debugging are completed at a high level in the early stage, which not only helps to find possible errors in structural design in time, reduces mistakes in design work, and at the same time effectively It greatly improves the efficiency and success rate of electronic design work.
1.3. Unique description language: hardware description language
EDA technology uses hardware description language HDL as the main expression of system logic description, so what is hardware description language? Compared with general computer languages such as C and Pascsl, it is mostly used in the design of hardware electronic systems. It is also a computer language. It describes the logical functions, circuit functions and connection methods of electronic systems. ABEL-HDL and VHDL are two widely used hardware description languages, and the latter is used more than the former.
ABEL can support various ways of input. The so-called input mode refers to the expression of circuit system design, including truth table and state diagram. Its description is highly independent. At the same time, it can complete descriptions from wide apertures to systems, so it can adapt to programming designs of different scales. It can also convert design environments by using standard format design. Compared with VHDL, it has The applicability of the product is much wider, the use and operation are flexible and simple, and the requirements are also loose, which is easy to implement.
1.4. Typical design: ASIC
Nowadays, electronic products are updated very fast, and the complexity is constantly increasing. Sometimes a seemingly simple electronic system may be composed of tens of thousands of small and medium-sized integrated circuits, so that the electronic system often encounters high energy consumption and low reliability. and other challenges. ASIC chips are an effective way to improve this problem.
It includes FPGA and CPLD devices. FPGA/CPLD is the basis for realizing EDA, and it is also the final expression method of EDA thought. It belongs to high-density programmable logic devices. Generally, they can be used for sample development or small batch product development. Applicable, and greatly shorten the design cycle, reduce overhead, avoid risks, and enable products to be launched as soon as possible.
The structure of FPGA and CPLD is different. The former is a standard gate array, while the latter is an AND or array, but the integration and ease of use of the two are quite similar, so they can keep pace with each other. Of course, the two also have their own characteristics, and their differences are reflected in the following aspects:
(1) The particle size is different. Compared with CPLD, the particle of FPGA is relatively fine. One of its particles is only a logic macrocell, while that of CPLD is a logic macroblock.
(2) The applicable structure is different. FPGAs are more suitable for structures with relatively abundant flip-flops, while CPLDs are more suitable for structures with limited flip-flops but particularly rich product terms.
(3) The programming method is different. FPGA can be programmed under the logic gate, and it is very flexible by changing the way of internal wiring. GPLD can only be realized when the logic is fast, and the method of modifying the logic function of the interconnected circuit that has been fixed is often used, and the speed is faster.
(4) The function consumption is different. FPGA consumption is small, CPLD consumption is relatively large.
2. Application of EDA technology in electronic design
EDA technology belongs to a relatively high-level electronic design method, which can also be called a system-level design method. It is driven by concepts. Electronic designers do not need to use gate-level schematic diagrams, but only for the determined design goals. Realize the description of the circuit. In this way, there are fewer constraints and restrictions on the details of the circuit, so that the design can be more open and more creative. After the designer has a conceptual idea, the high-level description is input to the computer. In the middle, the EDA system will automatically complete the entire electronic design driven by the rules. In this way, new concepts can become products in a period of time. The electronic design process based on EDA technology is shown in Figure 1:
The first step in electronic design is to present the design with the help of text or graphic editing tools, that is, to realize the design description.
The second step is to implement staggered compilation with the help of the compiler, that is, HDL program input. As for the input form to choose, it is not necessarily the same. The schematic diagram of the general design is relatively intuitive, so it is not difficult to master and accept, and the editor There are a lot of unit devices available in the system, and at this time, the designer is provided with the opportunity to choose the way of expression according to their own needs. If the compilation file is a VHDL file, then an important work that needs to be done before synthesis is Simulation is to send the original design program into the VHDL simulator. This simulation process can help to find possible errors in the structural design in time.
The third step is to synthesize and communicate the software and hardware design. After the synthesis, a netlist can be generated. For the netlist, functional simulation can be implemented to ensure that the design description strictly follows and conforms to the design intent. The simulation function is actually only from the logic function. The electronic design is tested on the above, and does not involve some hardware characteristics of the device, such as typical delay characteristics, and some less stringent designs, this layer of simulation can usually be omitted. The last step is programming download. After confirming that the design is correct through simulation, use FPGA/CPLD to complete the logic mapping operation, adaptation, and finally use the JTAG programmer or other download design items to the target device PFGA to complete the system-level design.
3. Matters needing attention in electronic design based on EDA technology
First, considering the uncertainty of the delay time of electronic circuits and the fact that some automatic compilation may be simplified by redundant circuits, it is not appropriate to use an even number of counters when applying EDA technology to electronic design. and connect them in parallel to form a “delay circuit”; second, the input pins cannot be left floating, one must be driven by an active signal, and some unused pins must always be Keep grounding; third, it is necessary to ensure that the power and ground pins of major devices are always connected, and it is necessary to filter and decouple between them; fourth, in order to make design expansion and modification easier and more convenient In the process of using the device, there must be an excess amount of logic cells or pins; fifth, environmental problems should also be vigilant to avoid overheating of the device as much as possible.
In short, EDA technology is a breakthrough and innovation of traditional electronic design technology. Without the support of EDA technology, it is impossible to successfully complete the design and manufacture of large-scale integrated circuits. Conversely, thinking about the development needs of modern integrated circuit technology EDA technology has put forward higher requirements. It is foreseeable that in the near future, EDA technology will become the dominant force in electronic design.