Application of EDA Technology in Digital Circuit Design

With the marketization of scientific research and technology development, it has become increasingly difficult to complete complex electronic system design in a short period of time using traditional electronic design methods. EDA (EleCTRonICs Design Automation) technology is an advanced, fast and effective electronic design automation tool with the rapid development of integrated circuits and computer technology.

1 EDA technology

EDA (Electronic Circuit Design Station Automation) is based on computer as the working platform, hardware description language (VHDL) as the design language, programmable device (CPLD/FPGA) as the experimental carrier, and ASIC/SOC chip as the target device. Component modeling and system simulation electronics automation design process. EDA is a revolution in the field of electronic design, which stems from computer-aided design, computer-aided manufacturing, computer-aided testing, and computer-aided engineering. Using EDA tools, electronic designers start designing electronic systems from concepts, algorithms, and protocols, from circuit design to performance analysis to IC layout or PCB layout generation. EDA represents the latest development direction of today's electronic design technology. Its basic feature is that the designer uses the computer as a tool, according to the top-down design method, the whole system is designed and functionally divided, and the system description level is completed by the hardware description language. The use of advanced development tools to automatically complete logic compilation, simplification, segmentation, synthesis, optimization, place and route, simulation and specific target chip adaptation and programming download, which is called high-level design method of digital logic circuit.


1.1 Introduction to EDA Software

"EDA" is Electronic Design AutomaTIon, which helps people design electronic circuits or system software tools that make it possible to design more complex circuits and systems. Currently entering China and has a wide range of influences on EDA software: muhisim7, OW_AD, Protel, Viewlogio, Mentor, Synopsys, PCBW Id, Cadence, MicmSim, etc. These softwares have their own characteristics, which are roughly divided into chip-level design tools and board-level design. Tools, programmable logic device development tools and circuit simulation tools, etc.; Protel is the most popular and widely used software for printed circuit board design in China. It is produced by Australian protd Technology and used to be used for schematics. Input and PCB layout design, starting with Protel 98, adding analog and digital hybrid circuit simulation module and programmable logic device design module. In 1999, Protel launched a more powerful EDA integrated design environment Protel 99, which integrates all EDA content into one. As a complete EDA software, the software has great potential, but its most distinctive and powerful features are still schematic input and PCB layout design.

1.2 Main content of EDA technology

EDA technology covers a wide range and rich in content. From the perspective of teaching and practicality, it should mainly master the following four aspects: one is large-scale programmable logic device; the other is hardware description language; the third is software development tool; the fourth is experiment development system. Among them, large-scale programmable logic device is the electronic system design carrier using EDA technology, hardware description language is the main expression means of electronic system design using EDA technology, software development tool is the intelligent automatic design tool for electronic system design using EDA technology. The experimental development system is an electronic system design download tool and hardware verification tool using EDA technology.

1.3 Main features of EDA technology

As the leading technology in modern electronic system design, EDA has several distinct features:

1.3.1 Designing Hardware with Software Design Methods

The hardware system conversion is automatically completed by the relevant development software. The design input can be the schematic VHDL language. The software design method is used to test the specific function hardware circuit design, and the hardware design modification work is as fast and convenient as modifying the software program. The process involves almost no hardware, and the operability and product interchangeability are strong.

1.3.2 based on chip design method

The EDA design method, also known as the chip-based design method, has a higher degree of integration, enabling on-chip system integration, more complex circuit chip design and ASIC design, resulting in small size, low power consumption, and high reliability. In system programming or field programming, the device programming, reconstruction, and modification are simple and convenient, and online upgrade can be realized; various simulations can be performed, the development cycle is short, the design cost is low, and the design flexibility is high.

1.3.3 High degree of automation

EDA technology automatically processes the electronic product from the circuit function simulation, performance analysis, optimization design to the result test according to the design input file, and automatically generates the target system, so that the designer does not have to learn a lot of in-depth professional knowledge, and can also be exempted. Many derivation operations can achieve optimized design results, high degree of design automation, reduced designer workload, and high development efficiency.

1.3.4 Automatic product design

EDA technology automatically performs logic compilation, simplification, synthesis, simulation, optimization, layout, routing, adaptation, and download programming to generate target systems based on design input files (HDL or schematics), ie, electronic product simulation from circuit functions. , performance analysis, optimization design to the results of the test process is automatically processed on the computer;

1.4 EDA technical points

1.4.1 Programmable Logic Device - PLD

The development of digital logic devices directly reflects the transition from discrete components, small and medium-sized standard chips to programmable logic devices. ISP technology and HDPLD devices enable designers to easily develop dedicated integrated digital circuit chip ASICs in the lab. Currently, many well-known 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 choose a standard integrated circuit "Bottom-Up" to construct a new system. This design method, such as building a building with the same brick and tile, is not only inefficient, costly and error-prone, but the high-level design provides us with a new “Top-Down” design method. The system starts with functional block diagram division and structure design at the top level, simulates and corrects errors at the block diagram level, describes the high-level system with hardware description language, performs verification at the system level, and then uses the integrated optimization tool to generate the specific gate network. The corresponding physical implementation level of the table may be a printed circuit board or an application specific integrated circuit. Since the main simulation and debugging process of the design is completed at a high level, it is advantageous for early detection of structural design errors, avoiding design waste, and reducing The logic function simulates the workload and improves the design success rate.

2 digital circuit design

Since the 1990s, the development of electronic information products has clearly shown two characteristics: First, the product complexity is deepened; second, the time limit for product launch is urgent. With the improvement of computer cost performance and the emergence of programmable logic devices, the traditional digital electronic system design method has been revolutionized. The modern electronic system design method is that the designer designs the chip to realize the electronic system function, and selects the traditional firmware and the circuit board design. Work is done in the chip design. However, circuit design is essentially based on gate-level description of single-level design (mainly based on digital circuits). Designing all work (including design input, simulation and analysis, design modification, etc.) is performed at the level of basic logic gates. Obviously, this design method can not adapt to the new situation, for which a high-level electronic design method, also known as system design method, is introduced.

The design of digital circuit itself is a comprehensive design. The design circuit generally contains different types of circuits. In the design process, there are inevitably many errors and shortcomings. If the design circuit is directly installed and debugged on the circuit board. The result often makes the circuit debugging time-consuming and laborious, and even causes problems such as damage to components and equipment, resulting in the design not achieving the desired results. Using EDA technology to design digital circuits on the simulation software platform can help familiarize with and master the most advanced circuit design methods and skills. In the rapid development of electronic technology, new devices and new circuits are constantly emerging, and the design conditions are subject to financial constraints and other factors, and generally cannot be updated in time. Using software simulation method, virtualized an advanced test instrument and complete electronic workbench on the computer, which can carry out experimental training for verification, testability and design, and cultivate the ability to use computers and analyze, apply and innovate circuits. "To be a substitute for reality" and "soft to hard" should become one of the trends in contemporary design development.

3 Digital circuit design based on EDA technology

EDA technology is applied in digital systems. The digital clock design based on ALTEraEPM7128SLC84-15 chip and MAX PlusII 10.0 software platform is taken as an example to discuss the specific application of EDA technology in digital systems.

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, transforming the traditional "circuit design hardware test debugging" mode into automatic completion on the computer.

3.2 Design requirements

With hour, minute, second, count display function, with 24-hour cycle timing. It has the function of clearing and adjusting hours and minutes. With hourly chime function.

3.3 Input design source file

A design project consists of one or more source files, which can be schematic files, hardware description language files, mixed input files, click on the Source/New menu, select the type of source file you want to design, enter the design state, and complete the source file design. Save, exit; in a schematic editor window, through the File / Matching Symbol menu, create a schematic symbol, generate a logical macro component with the same name and the same function as the schematic file, it is automatically added to the component In the list, you can call it repeatedly in higher layer drawings;

3.3 logical compilation

The logic compiles the selection device EPM7128SLC84-15, compiles the design project with the MAX PlusII compiler, and automatically performs error checking, netlist extraction, logic synthesis, device adaptation through the compiler, and finally generates the device programming file (.jed).

3.4 Comprehensive

The integration is to use the EDA software system synthesizer to link the VHDL software design with the hardware implementability, which is a key step in turning the software into a hardware circuit. Synthesizer-to-source file synthesis is for a range of FPGA/CPI D vendors. Therefore, the combined results have hardware achievability. EDA provides a good logic synthesis and optimization function, which can automatically convert the designer's design logic level circuit diagram into gate level circuit, and generate corresponding netlist files, timing analysis files and various reports. If there is no error in the design, it can be generated. Can be programmed to download. SOF file.

3.5 device adaptation

After the integration, the integrated network table file must be logically mapped to a specific target device by using the FPGA/CPLD layout/wiring adapter, including the underlying device configuration, logic segmentation, logic optimization, place and route operations, and so on. After adaptation, generate netlist files and download files for timing simulation, such as JED or POF files. The adaptation object corresponds directly to the device structure details.

3.6 function simulation

Usually, simulations are performed at each stage of the design process to verify its correctness. Before the synthesis, the behavior simulation is performed, and the VHDI source program is directly sent to the VHDI simulator for simulation. At this time, the simulation is only performed according to the VHDI semantics, and has no relationship with the specific circuit. After synthesis, the function of generating a netlist file can be used to simulate the design description and design intent. Functional simulation only tests and describes the design description logic function to understand 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 simulated according to the generated netlist file after adaptation. It is close to the real device running 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 simulation is determined to be basically successful, the design project can be downloaded to the device in JTAG mode through the Byteblaster download cable to complete all the design work. According to the design flow of this example, EDA technology and its tools are playing an increasingly important role in digital circuit systems (including analog circuit systems), and its application depth and breadth are extending to a deeper level.

3.8 target system

The coding circuit is described in the VHDL language. The decoding circuit uses the CASE statement to complete the lookup table decoding, and there are nearly 40 possible cases. By finding the syndrome value, the error data is reversed, and the signal is given in other cases, indicating that there is an error. The encoding and decoding circuit selects EPF1OK10TC144-3, which is produced by ALTERA Company. The encoding circuit occupies 32 logical units, and the decoding circuit occupies 163 logical units. Functional simulation of the coding and decoding circuit. Test use seems to be when the data input is all ‘1, if the bus uploads the last bit of data error. 0, the correct data is XORed to the data check line DC so that the decoder can 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 indicates an uncorrectable error; if the data is correctly transmitted, the decoder indicates that there is no error.

4 Conclusion

At present, the development of modern integrated circuit technology makes the number of equivalent gates of large-capacity programmable logic devices represented by field-programmable gate arrays rapidly increase, and its scale is almost equal to the standard gate array, reaching the level of system integration. Especially after entering the 1990s, with the emergence of field programmable logic devices such as CPLD and FPGA, VHDL, Verilog and other common versatility, portability of strong hardware description languages, ASIC technology continues to improve, EDA technology in modern digital Systems and microelectronics applications play an increasingly important role. In the usual sense, modern electronic system design is no longer inseparable from the help of EDA technology.