The 21st century is an era of information. All kinds of electronic technologies are updating and developing rapidly. Computers, mobile phones and DVS have become an indispensable part of contemporary life. The functions of these electronic products are increasing day by day, the performance is getting better and better, but the price is decreasing or not increasing. Explore the reasons, The development of integrated circuit manufacturing technology and the improvement of electronic design technology are two mainstream factors. Integrated circuit manufacturing technology is mainly micro machining, and electronic design technology is centered on EDA technology. EDA technology has become one of the forefront of today’s electronic technology development, which is the result of the joint efforts of more advanced countries. The application of CPLD and FPGA programmable logic devices undoubtedly brings great flexibility and applicability to electronic design.
1. Concept and characteristics of EDA Technology
EDA technology is electronic design automation technology. It is developed from PLD technology. The application and integration scale expansion of PLD brings great convenience and flexibility to the design of digital system, and changes the traditional design concept, process and method of digital system. Through the continuous improvement of PLD technology, EDA technology came into being.
EDA technology is a new technology based on large-scale programmable devices, which takes computer as a tool and completes the expression according to Hardware Description Language HDL to realize the objectives of logic compilation, simplification, segmentation, layout and optimization. With the help of EDA technology, the operator can realize a description of hardware functions by using software, Then the final design result can be obtained by using FPGA / CPLD.
New design method: top-down
The traditional electronic design method is generally “bottom-up”. Generally speaking, it is to determine the standard general integrated circuit chip, then carry out module design, and finally complete the system design. For a long time, this design has insurmountable defects, low efficiency, easy failure, too many components and large consumption… EDA technology is a breakthrough and reform of traditional electronic design methods. Its design is “top-down”, that is, taking system design as the starting point, At the time of design, divide the functional block diagram and complete the structure planning of each part, complete the simulation and error correction in the block diagram division stage, and complete the logical description of the high-level system with the help of HDL. After verification, complete the electronic design 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, Then the final design result can be obtained by using FPGA / CPLD.
In this way, we can find that both simulation and debugging are completed at a high level in the early stage. In this way, it not only helps to find possible errors in structural design in time, reduce errors in design work, but also effectively improves the efficiency and success rate of electronic design.
1.3. Unique description language: Hardware Description Language
EDA technology takes 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 to design hardware electronic systems. It also belongs to computer language. It describes the logic function, circuit function and connection mode of electronic systems. ABEL-HDL and VHDL are two widely used hardware description languages, and the latter is more used than the former.
Abel can support various input modes. The so-called input mode refers to the expression of circuit system design, including truth table and state diagram. Its description has strong independence. At the same time, it can complete the description from wide aperture to system, so it can adapt to programming design of different scales. Using standard format design can also convert the design environment. Compared with VHDL, its application area is much wider, its operation is flexible and simple, its requirements are loose and easy to be completed quickly.
1.4. Typical design: ASIC
Nowadays, electronic products are updated very quickly and the complexity is also increasing. Sometimes a seemingly simple electronic system may consist of tens of thousands of small and medium-sized integrated circuits, which makes the electronic system often encounter the challenges of high energy consumption and low reliability. ASIC chip is an effective way to improve this problem.
It includes FPGA and CPLD devices. FPGA / CPLD is not only the basis of EDA, but also the final expression means of EDA thought. It belongs to high-density programmable logic devices. Generally, they can be applicable to the development of samples or the development of products in small quantities, and greatly shorten the design cycle, reduce expenses, avoid risks, so that the products can be listed as soon as possible.
The structures of FPGA and CPLD are different. The former is a standard gate array, while the latter is an and or array, but their integration and ease of use are quite similar, so they can keep pace. Of course, they also have their own characteristics, and their differences are shown in the following aspects:
(1) The particle size is different. Compared with CPLD, the particles of FPGA are relatively fine. One of its particles is only logical macro unit, while CPLD is logical macro block.
(2) Applicable structures are different. FPGA is more suitable for the structure with relatively rich flip flops, and CPLD is more suitable for the structure with limited flip flops but particularly rich product terms.
(3) Different programming methods. FPGA can be programmed under the logic gate. It mostly adopts the way of changing internal wiring, which has strong flexibility. GPLD can be realized only when the logic is fast. It is faster by modifying the logic function of the fixed internal circuit.
(4) Different function consumption. FPGA consumption is small and CPLD consumption is relatively large.
2. Application of EDA Technology in electronic design
EDA technology belongs to a high-level electronic design method, which can also be called system level design method. It is driven by concepts. Electronic designers do not need to use gate level schematic diagram, but can describe the circuit according to the determined design objectives. In this way, the constraints and restrictions on circuit details are reduced, So that the design can be more open and more creative. After the designer has the conceptual idea, the high-level description can be input into the computer, and the EDA system will automatically complete the whole electronic design driven by rules. In this way, the new concept can become a product in a period of time. The electronic design process based on EDA technology is shown in Figure 1:
The first step of 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 which input form to choose, it is not necessarily. The schematic diagram of general design is relatively intuitive, so it is not difficult to master and accept. Moreover, there are many unit devices available in the editor. At this time, it provides the designer with the opportunity to choose the expression mode according to their own needs, If the compiled file is a VHDL file, an important work before synthesis is simulation, that is, sending the original design program into the VHDL simulator. This simulation process can help to find the possible errors in structural design in time.
The third step is to integrate and communicate the software and hardware design. After integration, the 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 actually only detects the electronic design from the logical function, and does not involve some hardware characteristics of the device, For example, some typical designs with delay characteristics and less strict design can usually be omitted from this layer of simulation. The last step is programming download. After the design is confirmed to be correct through simulation, FPGA / CPLD is used to complete the logic mapping operation and adaptation. Finally, JTAG programmer or other download design items are used to the target device PFGA to complete the system level design.
3. Matters needing attention in electronic design based on EDA Technology
First, considering that the delay time of electronic circuit is uncertain and some automatic compilation may be simplified by redundant circuits, when EDA technology is applied to electronic design, it is not suitable to use even inverters and connect them in parallel to form a “delay circuit”; Second, the input pin cannot be placed in the suspended state. On the one hand, there must be an active signal to drive, and on the other hand, some unused pins must be grounded at all times; 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 them; Fourth, in order to make the design expansion and modification easier and more convenient, there must be a redundant amount of both logic units and pins in the process of using the device; Fifth, environmental problems should also be vigilant to avoid overheating of devices 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 manufacturing of large-scale integrated circuits. On the contrary, the development needs of modern integrated circuit technology put forward higher requirements for EDA technology. It can be predicted that in the near future, EDA technology will become the leading force in electronic design.