With the marketization of scientific research and technology development, it is becoming more and more difficult to complete the design of complex electronic systems in a short time by using traditional electronic design methods. EDA (EleCTRonICs Design Automation) technology is an advanced, rapid and effective electronic Design Automation tool with the rapid development of integrated circuits and computer technology.
1 EDA technology
EDA (electronic circuit design automation) is the computer as the working platform, to the hardware description language (VHDL) as the design language, to the programmable device (CPLD/FPGA) as the experimental carrier, to ASIC/SOC chip as the target device, the necessary component modeling and system simulation of electronic product automation design process. EDA is a revolution in electronic design. It originated from computer-aided design, computer-aided manufacturing, computer-aided testing and computer-aided engineering. Using EDA tools, electronic designers from the concept, algorithm, protocol design of electronic systems, from circuit design, performance analysis until IC layout or PCB layout generation process can be completed automatically on the computer. EDA represents a new development direction of the modern electronic design technology, its basic characteristics are the designers to the computer as the tool, according to the top-down design method, the solution to the whole system design and functional division, designed by hardware description language to complete the system behavior level, using advanced development tools automatically logic compilation, reduction, segmentation, integration, optimization, layout, simulation, and a specific target chip adapter to compile and download programming, this is called the digital logic circuit design method of high level.
1.1 introduction to EDA software
EDA stands for Electronic Design AutomaTIon, which is a software tool that helps people Design Electronic circuits or systems, making it possible to Design more complex circuits and systems. At present, EDA software has been widely used in China, such as: muhisim7, OW_AD, Protel, Viewlogio, Mentor, Synopsys, PCBW Id, Cadence, MicmSim, etc. These software have their own characteristics, which can be divided into chip-level design tools, pcb-level design tools, programmable logic device development tools and circuit simulation tools. Protel is the most popular, the most widely used software, a printed circuit board design choice for the Australian protd Technology company, in the past is only used for schematic diagram input and PCB layout design, starting from Protel 98, joined the analog digital mixing circuit simulation module and the programmable logic devices design module, Protel 1999 introduced a more powerful EDA Protel 99 integrated design environment, it will be an EDA all content integration for an organic whole, complete the EDA software, and the software development potential is very big, But its most distinctive and powerful features are still schematic input and PCB layout design.
1.2 main contents of EDA technology
EDA technology involves a wide range of content, from the point of view of teaching and practical, should master the following four aspects: first, large-scale programmable logic devices; Second, hardware description language; Third, software development tools; Fourth, the experimental development system. Among them, the large-scale programmable logic devices is the use of EDA technology in electronic system design carrier, hardware description language is to use EDA technology in electronic system design main expressive means, software development tools is the use of EDA technology in electronic system design of intelligent automatic design tools, experimental development system is to use EDA technology in electronic system design download tools and hardware validation tool.
1.3 main features of EDA technology
As the leading technology of modern electronic system design, EDA has several obvious characteristics:
1.3.1 use software design method to design hardware
Hardware system transformation is developed by the software automatically, design principle diagram of the input can be a VHDL language, through testing the software design, implementation of specific functions, hardware circuit design and hardware design modification work and convenience also like modify the software program, design the whole process does not involve almost any hardware and maneuverability strong interchangeability and products.
1.3.2 chip design method
EDA design method, also known as chip-based design method, has a higher degree of integration, which can realize on-chip system integration, carry out more complex circuit chip-based design and special integrated circuit design, making the product small size, low power consumption, high reliability; Can be in the system programming or field programming, so that device programming, reconstruction, modification is simple and convenient, can realize online upgrade; Can carry on each kind of simulation, the development cycle is short, the design cost is low, the design flexibility is high.
1.3.3 high degree of automation
EDA technology, according to the design input file from electronics circuit function simulation, performance analysis and optimization design to the whole process test results on computer automatic processing, automatic generation of the target system, make the designers don’t have to learn to play many deep professional knowledge, can also be exempted from many derivation operation can obtain optimal design results, design a high degree of automation, reduce the workload of the designers, the development of high efficiency.
1.3.4 automatic product face design
EDA technology according to the design input file (HDL, or circuit schematic diagram), automatically logic compilation, reduction, comprehensive, simulation, optimization, layout, wiring, adaptation, and download the program to generate the target system, the electronic products from the circuit function simulation, performance analysis and optimization design to the whole process test results on the computer automatic processing is complete;
1.4 EDA technology highlights
1.4.1 PLD (programmable logic device)
The development of digital logic devices directly reflects the transition from discrete components and small and medium scale standard chips to programmable logic devices. ISP technology and HDPLD devices enable designers to easily develop ASIC in the lab. At present, many famous manufacturers at home and abroad have developed a new generation of ISP devices and corresponding development software (such as Synario, EXPERT, FundaTIon, MAX Plus2, etc.).
1.4.2 “top-down” design method
Ten years ago, the basic idea of electronic design was to build a new system “bottom-up” from standard integrated circuits. Design method such as a brick construction building, not only low efficiency, high cost and easy to get wrong, high-level design provides us with a “top-down” (Top – Down), a new design method, this method first, from the perspective of the system, on the Top floor for functional block diagram and structure design, simulation, error correction in the block diagram level, and describe with the hardware description language to high-level system, at the system level verification, and then use integrated optimization tools to generate specific gate netlist, the corresponding physical implementation level can be a printed circuit board or application-specific integrated circuit, Since the design of the main simulation and debugging process is completed at a high level, this is not only conducive to the early detection of structural design errors, to avoid design time waste, but also reduce the workload of logical function simulation, improve the success rate of design a time.
Digital circuit design
Since the 1990s, the development of electronic information products has two obvious characteristics: one is the deepening of product complexity; Second, the product time limit is urgent. With the improvement of computer cost performance and the appearance of programmable logic devices, the traditional design method of digital electronic system has been revolutionized. The modern design method of electronic system is that designers design chips to realize the functions of electronic system, and put the traditional firmware selection and circuit board design in the chip design. Circuit design, however, is essentially based on gate-level description sheer level (mainly composed of digital circuit design, design all work (including design input, simulation and analysis, design, modification, etc.) are in the basic logic gates on this level, obviously this design method can’t adapt to the new situation, and therefore introduced a high-level electronic design method, also known as the system design method.
Sex itself is a kind of comprehensive design digital circuit design, circuit design in general contains different types of circuits, in the design process, inevitably there are many mistakes and shortcomings if according to the design circuit on the circuit board directly for installation, debugging, the results are often make circuit debugging time-consuming, even can cause components and equipment damage and other problems, lead to design can not achieve the desired effect. The application of EDA technology in the design of digital circuit on the simulation software platform can help familiar with and master the most advanced circuit design methods and skills. Today, with the rapid development of electronic technology, new devices and new circuits are emerging constantly. However, design conditions are limited by funds and other factors, so they cannot be updated in time. By means of software simulation, an advanced testing instrument and electronic worktable with various components are simulated on the computer, which can be used for experimental training such as verification, testing and design, so as to cultivate the ability to use the computer and analyze, apply and innovate circuits. “Copy instead of reality”, “soft instead of hard” should become one of the trends of contemporary design development.
Digital circuit design based on EDA technology
Taking alteraepm7128slc84-15 chip and MAX PlusII 10.0 software platform digital clock design as examples, the application of EDA technology in digital system is discussed.
3.1 EDA technology design process
In terms of design methods, EDA technology has brought about fundamental changes in the field of digital electronic circuit design. It has transformed the traditional mode of “circuit design hardware commissioning and welding” into automatic completion on the computer.
3.2 design requirements
With time, minutes, seconds, counting display function, with 24 hours cycle time. It has functions of clearing zero and adjusting hour and minute. With the hour function.
3.3 input design source files
A design project is composed of one or more Source files, they can be schematic files, hardware description language files, mixed input files, click Source/New menu, select the Source file type you want to design, enter the design state, complete the Source file design, save, exit; In another schematic editor window, through the File/Matching Symbol menu, a schematic Symbol is established to generate a macro Symbol with the same name and the same function logic as the schematic File, which is automatically added to the list of symbols and can be repeatedly invoked in higher level drawings.
3.3 logical compilation
Logic compilation selection device EPM7128SLC84-15, the MAX Plus Ⅱ compiler design projects, through the compiler automatically error checking, netlist extraction, logic synthesis, device adapter, eventually produce device programming (file. Jed).
Synthesis is the use of EDA software system integrator VHDL software design and hardware realizability hook, this is the software into the hardware circuit key steps. Synthesizer for source file synthesis is for a certain FPGA/CPI D supplier product series. Therefore, the result is hardware realizable. EDA provides a good logic synthesis and optimization function, it can be designed by the designer logic level circuit automatically converted to the gate level circuit, and generate the corresponding network table files, timing analysis files and various reports, if the design is not wrong, the final generation can be programmed to download. SOF file.
3.5 device adaptation
After passing the synthesis, the FPGA/CPLD layout/wiring adapter must be used to conduct the logical mapping operation of the integrated backlist file for a specific target device, including the operation of the underlying device configuration, logical segmentation, logical optimization, layout and wiring, etc.. After adaptation, network table files and download files, such as JED or POF files, are generated for sequential simulation. The adaptation object corresponds directly to the structural details of the device.
3.6 functional simulation
Usually, in the design process, each stage must carry on the simulation to verify its correctness. Before synthesis, conduct behavior simulation and send the VHDI source program directly to the VHDI emulator for simulation. At this time, the simulation is only conducted according to the VHDI semantics and has nothing to do with the specific circuit. After synthesis, the generated netlist file can be used for functional simulation to understand the consistency of design description and design intention. Functional simulation only tests and simulates the design description logic function to find out whether its implementation function meets the original design requirements. The simulation process does not involve specific device hardware characteristics, such as delay characteristics. The timing simulation is conducted according to the network table file generated after adaptation, which is close to the real device operation simulation. The hardware characteristics of the device have been taken into account in the simulation process, so the simulation accuracy is much higher. The timing simulation netlist file contains more accurate delay information.
3.7 programming download
After the design is confirmed to be basically successful through simulation, the design project can be downloaded to the device in the way of JTAG through Byteblaster cable, and all the design work can be completed. According to the design process of this example, EDA technology and its tools are playing an increasingly important role in digital circuit system (including analog circuit system).
3.8 target system
Using VHDL language to describe the coding circuit. Decoding circuit USES CASE statement to complete table lookup decoding, which has nearly 4O possible cases. By finding the adjoint value, the data with one error is reversed and corrected. In other cases, the signal is given to indicate the error. The device epf1ok10tc144-3 produced by ALTERA company was selected as the coding and decoding circuit, in which 32 logic units were occupied by the coding circuit and 163 logic units were occupied by the decoding circuit. The function of the decoding circuit is simulated. Test use appears when data is all entered as’ 1 ‘if the last bit of data from the bus goes wrong. Is 0, the correct data xor and the data check line DC enables the decoder to change the last bit to 1; If the data input is “00000001”, the encoder DC is “19” and two errors occur. For example, the highest bit and the lowest bit, the decoder indication is uncorrectable error; If the data is transmitted correctly, the decoder indicates no error.
At present, with the development of modern integrated circuit technology, the equivalent gate number of large capacity programmable logic devices (PLDS) represented by field programmable gate array (fpga) is increasing rapidly, and its scale is close to that of standard gate array, reaching the level of system integration. Especially after the 1990s, with the rise of CPLD, FPGA and other field programmable logic devices, VHDL, Verilog and other universality, strong portability of hardware description language popularity, ASIC technology constantly improve, EDA technology in modern digital systems and microelectronic technology applications are playing an increasingly important role. In a general sense, the design of modern electronic systems can no longer do without the help of EDA technology.