introduction Embedded system is a system that integrates application programs and operating systems with computer hardware. It is application-centric, computer-based, software and hardware can be tailored, functions, reliability, cost, volume, and power consumption are strictly required Dedicated computer system. This kind of system has the characteristics of small software code, high automation, fast response speed, etc., and is particularly suitable for systems that require real-time and multi-tasking. Embedded devices refer to computer devices that use embedded systems. In a sense, it is indeed a miniaturization of large-scale computing equipment, and this miniaturization will definitely bring about a relative performance decrease. But it is the convenience brought to people by the miniaturization of this volume that is incomparable. With embedded devices, people can read e-books and book air tickets anytime and anywhere without losing them in any unfamiliar city. They can even watch any movie they want to see in the shortest possible time. Software development for embedded devices In 2001, the IT industry produced 2 billion microcomputers. Among them, 95% will be used for embedded device purposes. Therefore, instead of taking the 150 million networked computers listed each year as the research object, it is better to increase efforts to promote the networking of 8 billion embedded devices and focus on manufacturing software that is compatible with it. David Tennenhouse, the leader of the research department of Intel Corporation in the United States, said at the CompuTIngConTInuumConference conference held in San Francisco, "Research on computers should increase the network of 800 million embedded microprocessor devices than 150 million computers." It has become a top priority to build an environment that can be connected to the network anytime and anywhere, and to develop adaptive software. After carefully examining the status quo of foreign embedded device software and the domestic market potential, embedded device software will set off a software revolution in China! 1 Embedded processor technology The core of an embedded system is an embedded microprocessor. Embedded processors are computer chips used to provide added functionality in devices other than computers, and are often used in the field of control and monitoring. According to the audit report in the Blue Book of World Semiconductor Trade Statistics, from the perspective of unit sales, the market share of processors such as Intel’s PenTIum system, Advanced Micro Devices’ Athlon, and IBM and Motorola’s PowerPC only occupy the world market. 6% of the total and the remaining 94%, or 5 billion chips, are embedded microprocessors. It is estimated that the average American household has about 60 embedded processors. Some embedded processors are things handed down from the desktop market. Even though they are obsolete for today's PCs, they are more than enough chips for tasks with lower functional requirements. The Z80 and 6502 processors that used to drive early PCs such as TRS-80, Apple II and Commodore 64 are still very popular products. Even the lowest-level 4-bit processors are sold far more than 32-bit processors like PenTIum. Old-fashioned processors have not faded out: they have just become embedded. Therefore, the embedded microprocessor market is unusually broad. At any moment in the PC market, the performance gap between microprocessors is only about 3 to 1. The fastest chip currently runs at 1GHz, while the slowest and most commonly used chip is 333MHz. In contrast, the performance range of only 32-bit embedded microprocessors is 500 to 1. If you compare between 4-bit and 8-bit embedded processors, the performance range is a few thousand to one. As such processors become smaller and smaller, cheaper and more powerful, they will enter more devices and products. They already exist in greeting cards that can sing and sneakers that measure travel. Eventually, due to the emergence of nanometer technology, they will become as ordinary as atoms, and almost as small as atoms. The widespread application of embedded systems is precisely that embedded microprocessors have the following four characteristics: ①It has strong support for real-time multi-tasking, can complete multi-tasking and has a short interrupt response time, thereby reducing the execution time of internal code and real-time core to a minimum. ②It has a powerful storage area protection function. This is because the software structure of the embedded system has been modularized, and in order to avoid false cross-effects between software modules, it is necessary to design a powerful storage area protection function, which is also conducive to software diagnosis. ③Extensible processor structure to develop embedded microprocessors with the highest performance to meet the application most quickly. ④ Embedded microprocessors must have very low power consumption, especially for battery-powered embedded systems used in portable wireless and mobile computing and communication devices. The power consumption is only mW or even μW. 1.1 Types of embedded processors At present, according to incomplete statistics, the total number of varieties of embedded processors in the world has exceeded 1,000, and there are more than 30 series of popular architectures, of which 8051 systems account for most. There are more than 20 semiconductor manufacturers producing 8051 single-chip microcomputers, with a total of more than 350 derivative products, and Philips alone has nearly 100. Now almost every semiconductor manufacturer produces embedded processors, and more and more companies have their own processor design departments. The addressing space of embedded processors generally ranges from 64KB to 16-32MB, the processing speed ranges from 0.1 MIPS to 2000 MIPS, and the commonly used packages range from 8 pins to 144 pins. According to its current situation, embedded computers can be divided into the following categories: ①Embedded Microprocessor (Embedded Microprocessor Unit, EMPU) The basis of an embedded microprocessor is the CPU in a general-purpose computer. In the application, the microprocessor is assembled on a specially designed circuit board, and only the motherboard functions related to embedded applications are retained, which can greatly reduce the system volume and power consumption. In order to meet the special requirements of embedded applications, although embedded microprocessors are basically the same in function as standard microprocessors, they generally have various enhancements in terms of operating temperature, anti-electromagnetic interference, and reliability. Compared with industrial control computers, embedded microprocessors have the advantages of small size, light weight, low cost, and high reliability, but the circuit board must include ROM, RAM, bus interface, various peripherals and other devices, thereby reducing To improve the reliability of the system, the technical confidentiality is also poor. The embedded microprocessor and its memory, bus, peripherals, etc. are installed on a circuit board, which is called a single board computer. Such as STD-BUS, PC104, etc. In recent years, some companies in Germany and Japan have developed embedded computer series OEM products similar to the size of a "matchbox" business card. Embedded microprocessors currently mainly include Am186/88, 386EX, SC-400, Power PC, 68000, MIPS, ARM series, etc. ② Embedded Microcontroller (Microcontroller Unit, MCU) Embedded microcontrollers are also called single-chip microcomputers. As the name suggests, they integrate the entire computer system into a chip. Embedded microcontrollers generally take a certain kind of microprocessor core as the core. The chip integrates ROM/EPROM, RAM, bus, bus logic, timer/counter, WatchDog, I/O, serial port, pulse width modulation output, A /D, D/A, FlashRAM, EEPROM and other necessary functions and peripherals. In order to adapt to different application requirements, generally a series of single-chip microcomputers have a variety of derivative products, the processor core of each derivative product is the same, the difference is the configuration and packaging of the memory and peripherals. In this way, the single-chip microcomputer can be matched to the application requirements to the greatest extent, with no more and no functions, thereby reducing power consumption and cost. Compared with embedded microprocessors, the biggest feature of microcontrollers is monolithic and greatly reduced in size, which reduces power consumption and cost, and improves reliability. Microcontrollers are currently the mainstream of the embedded system industry. The on-chip peripheral resources of the microcontroller are generally abundant and suitable for control, so it is called a microcontroller. Embedded microcontrollers currently have the largest variety and quantity. The more representative general-purpose series include 8051, P51XA, MCS-251, MCS-96/196/296, C166/167, MC68HC05/11/12/16, 68300, etc. In addition, there are many semi-universal series such as: MCU8XC930/931, C540, C541 that support USB interface; support I2C, CAN-Bus, LCD and many dedicated MCU and compatible series. MCU currently accounts for about 70% of the market share of embedded systems. It is particularly noteworthy that AMD, a well-known manufacturer of X86 microprocessors in recent years, has called embedded processors such as Am186CC/CH/CU as Microcontroller, and MOTOROLA has included Power PC-based PPC505 and PPC555 as microcontrollers. Ranks. TI Company also promotes its TMS320C2XXX series DSP as MCU. ③ Embedded DSP processor (Embedded Digital Signal Processor, EDSP) The DSP processor has specially designed the system structure and instructions to make it suitable for executing DSP algorithms, with higher compilation efficiency and higher instruction execution speed. In terms of digital filtering, FFT, spectrum analysis, etc., DSP algorithms are entering the embedded field in large numbers. DSP applications are moving from general-purpose single-chip microcomputers to realize DSP functions with ordinary instructions to the use of embedded DSP processors. Embedded DSP processors have two development sources. One is that DSP processors have undergone monolithic, EMC transformation, and added on-chip peripherals to become embedded DSP processors. TI’s TMS320C2000/C5000, etc. belong to this category; the other is in general-purpose microcontrollers. Or add DSP coprocessor to SOC, such as Intel MCS-296 and Siemens TriCore. Another factor that promotes the development of embedded DSP processors is the intelligence of embedded systems, such as various consumer products with intelligent logic, biometric information recognition terminals, keyboards with encryption and decryption algorithms, ADSL access, and real-time voice Compression system, virtual reality display, etc. This kind of intelligent algorithm generally has a large amount of calculation, especially vector operations, pointer linear addressing, etc., and these are the strengths of DSP processors. The more representative products of embedded DSP processor are TMS320 series of Texas Instruments and DSP56000 series of Motorola. The TMS320 series processors include the C2000 series for control, the C5000 series for mobile communications, and the C6000 and C8000 series with higher performance. DSP56000 has now developed into several different series of processors such as DSP56000, DSP56100, DSP56200 and DSP56300. In addition, PHILIPS company this year also launched the REAL DSP processor based on the low-cost and low-power technology of the resettable SP structure. It features a dual Harvard structure and a dual multiply/accumulate unit. The application target is high-volume Consumer products. ④ Embedded System On Chip (System On Chip) With the popularization of EDI and the popularization of VLSI design, and the rapid development of semiconductor technology, the era of implementing a more complex system on a silicon chip has come, which is System On Chip (SOC). Various general-purpose processor cores will serve as the standard library of the SOC design company. Like many other embedded system peripherals, they will become a standard device in VLSI design, described in standard VHDL and other languages, and stored in the device library. Users only need to define their entire application system, and after the simulation passes, the design drawings can be handed over to the semiconductor factory to make samples. In this way, with the exception of individual devices that cannot be integrated, most of the entire embedded system can be integrated into one or several chips, and the application system circuit board will become very simple, which is very beneficial for reducing volume and power consumption and improving reliability. . SOC can be divided into general and special two categories. General-purpose series include Siemens' TriCore, Motorola's M-Core, certain ARM series devices, and Neuron chips jointly developed by Echelon and Motorola. A dedicated SOC is generally dedicated to a certain system or type of system and is not known to ordinary users. A representative product is Philips SmartXA, which manufactures the XA microcontroller core and the CCU unit supporting more than 2048-bit complex RSA algorithms on a silicon chip to form a dedicated SOC that can load JAVA or C language, which can be used by the public Internet such as Internet security. 1.2 Changes in the classification of embedded processors There are three types of universal embedded processors recognized internationally: MCU, DSP and MPU (Micro-Processor Unit). TI once compared the processor to a car. There is a vivid analogy: DSP is a sports car, which pursues speed; MPU is a car, which pursues a compromise between economy and speed; MCU is a car for special purposes. Now, as the requirements for processing speed are getting higher and higher, and the data processed at the same time is more complex, dual-core and multi-core processors have appeared, usually DSP+RISC cores, such as Infineon's TriCore (CISC+RISC+DSP), Philips The company's Trimedia. With the rise of a large number of application markets, some new terms have emerged, such as communication processors used in networks and communication equipment (emerged around 2000), digital cameras, digital video recorders, and other video and audio streaming media processing required Device (rise in 2003), application processor on smart phone (rise in 2004). Because some processors not only need speed, but also control functions, a combination of DSP and MCU has appeared, focusing on the motor control market. For example, Freescale's DSP utilizes its technology in MCU control; Microchip also launched this product in February 2004, called DSC (Digital Signal Controller). Processor IP (Intellectual Property): In order to meet the needs of multi-core and SoC design, there are also IP vendors that specialize in supplying processor cores. The cores are mainly 16-bit, 32-bit, and 64-bit, with soft and hard cores. It is worth mentioning that the most successful IP manufacturer in the world is the processor core company-ARM, and the shipment volume has reached 2 billion by June this year, which shows the vastness of the processor industry. The multi-core market has great potential for development. At the Electronic Summit 2004 in the United States in February 2004, Dr. Chris Rowen, President of Tensilica, a 64-bit RISC IP company, said that in the next ten years, a chip will require thousands of processor cores. 1012 operations are completed every second. 2 Development of embedded processor chip 2.1 The general development process of embedded processor chips Although there are thousands of off-the-shelf chips to choose from, the designers of many products require some distinctive features. Therefore, they develop their own embedded chips, so-called application specific integrated circuits. A designer needs to obtain an authorization for the core of an embedded microprocessor from a company, and then add features specific to his own application. For example, for a digital camera processor, he might add a controller to the chip of this charge-coupled device. For another example, for a home appliance processor with Internet functionality, an Ethernet interface can be added. The designer then delivers his design to a "foundry", a company that owns a "factory" (chip manufacturing plant), and sells part of the manufacturing volume to other companies. The main manufacturing plants are United Microelectronics, TSMC of Taiwan and IBM Microelectronics of the United States. For some designers, even this flexibility is not enough. They can find certain companies that have licenses for highly customizable embedded microprocessor cores. Using this type of kernel, new machine-level instructions for special purposes can be developed. For digital camera processors, an instruction to improve JPEG image compression is of high value. For MP3 music players, an instruction to accelerate audio decompression has the same usefulness. Then, the customized design is handed over to the "foundry" for production. Unlike general-purpose computers, the hardware and software of the embedded system must be designed efficiently, tailored, and redundant, and strive to achieve higher on the same silicon chip area. In this way, it can be more competitive in the selection of processors for specific applications. Embedded processors must tailor and add chip configurations to meet the specific needs of users in order to achieve the desired performance; but at the same time, they are also restricted by user orders. Therefore, the users of different processors are different, and they may be general users, industry users or single users. The development of embedded processors also reflects stability, and a system generally needs to exist for 8-10 years. An architecture and its related on-chip peripherals, development tools, library functions, and embedded application products are a complex knowledge system. Users and semiconductor manufacturers will not easily give up a processor. 2.2 Development tools for embedded systems based on embedded processors Embedded processor is a complex high-tech system. It is not easy to master and develop all functions in a short period of time. Market competition requires products to be launched quickly. This contradiction requires embedded processors to be easy The development tool platform to master and use. Improve user and programmer time-return on investment. Faced with hundreds of thousands of processors, choice is a problem. It takes more time to learn to master the processor structure and its applications. Therefore, an overall solution based on development tools and technical consultation is urgently needed. Besides being able to develop all the functions of the processor, a good development tool should also be user-friendly. The current embedded system development tool platforms mainly include the following categories: ①Real-time online simulation system ICE (In-CircuitEmulator) Today, when computer-aided design is very developed, real-time online simulation system (ICE) is still the most effective development tool for debugging embedded application systems. First of all, ICE can carry out the principle test of the application program through actual implementation, and eliminate the design logic errors that are difficult to find in human thinking. Another main function of ICE is to simulate the real-time execution of the microcontroller in the application system, discover and eliminate abnormal execution behaviors caused by hardware interference. In addition, the advanced ICE has a complete tracking function, which can integrate the actual state changes of the application system, the microcontroller's response to the state changes, and the application system The response to the control is continuously recorded in a video mode for analysis, and the control process is optimized in the analysis. It is difficult for many electromechanical systems to establish an accurate and effective digital model, or the establishment of a model requires a lot of manpower. At this time, it is a fast and effective method to use the tracking function of ICE to record and analyze the system. The characteristics of embedded applications are related to the hardware system in the real world. There are various abnormal changes and unknown changes in advance. This brings various uncertainties to the instruction execution of the microcontroller. This uncertainty is only It can be found only through the real-time online simulator of ICE, especially when analyzing reliability, it is necessary to simulate multiple times under the same conditions to find accidental errors. ICE is not only a software and hardware troubleshooting tool, but also a tool to improve and optimize system performance indicators. High-end ICE tools (such as the products of NOHAU in the United States) are systems that can be tailored according to user investment, and can also be configured with various grades of real-time logic tracer (Trace), real-time image memory (Shadow RAM) and program efficiency according to needs Real-time analysis function (PPA). ② High-level language compiler (Compiler Tools) As a general high-level language, C language greatly improves the work efficiency of embedded system engineering, gives full play to the increasing performance of embedded processors, and shortens the time for products to enter the market. In addition, the C language is easy to transplant and modify, making product upgrades and inheritance more rapid. More importantly, programs written in C language are easy to communicate among different developers, which promotes the industrialization of embedded system development. Different from the C language compiler in general computers, the C language compiler in embedded systems must be optimized specifically to improve compilation efficiency. The code length and execution time of an excellent embedded system C compiler is only 5-20% longer than the same function level written in assembly language. The difference in compilation efficiency is one of the important basis for distinguishing the performance difference between C compilers in embedded systems. The remaining 5-10% efficiency difference of the C compiler can be fully compensated by the high speed, large memory space of modern microcontrollers and the early entry of products into the market. The instruction speed of the new type of microcontrollers continues to increase, and the memory space is correspondingly increased, which has reached or even exceeded the current microprocessors in general-purpose computers, creating conditions for the embedded system engineering to adopt the C + + language that has not been dared to care in the past. . The powerful classes and inheritance functions of C++ language make it easier to realize complex program functions. However, in order to support complex grammar, C++ language inevitably decreases in code generation efficiency. For this reason, the Embedded C++ Technical Committee established in Japan at the beginning of 1995, after several years of research, formulated the EC++ standard to reduce the code size for embedded applications. EC++ retains the main advantages of C++, provides upward compatibility with C++, and meets some special requirements of embedded system design. Tasking, a leader in embedded high-level language compilers, is a member of the EC++ technical committee and the first company to launch EC++ products. The introduction of C/C++/EC++ into embedded systems makes the development differences between embedded development and personal computers and minicomputers gradually eliminated. Many experiences, methods and library functions in software engineering can be transplanted to embedded systems. The use of high-level languages ​​in embedded development also enables the division of labor between hardware development and software development. It is no longer necessary to be proficient in system hardware and corresponding instruction set assembly to engage in embedded software development. The development of another high-level language JAVA is dramatic. JAVA was originally a language designed for device-independent embedded systems to improve program inheritance. However, the code generation length of embedded development tools based on JAVA is currently more than 10 times worse than that of embedded C compiler tools. Therefore, EC++ is likely to remain the mainstream of embedded systems for some time to come. ③ Source program simulator (Simulator) The source program simulator is a test tool for the source program written by a certain embedded processor core to simulate and execute a source program written by an embedded processor core through software means on a widely used working platform with a complete human-machine interface, such as a minicomputer and a PC. Simple simulators can execute source programs one by one through instruction interpretation, and allocate virtual storage space and peripherals for programmers to check; advanced simulators can use the computer's external interface to simulate the processor's I/O electrical signals. There is a huge price gap between different grades and functional simulator tools. The simulator software is independent of the processor hardware, and is generally integrated with the compiler in the same environment. It is an effective source program verification and testing tool. However, it is worth noting that the simulator is after all a processor to simulate the operation of another processor, and it is likely to be quite different from the actual processor in terms of instruction execution time, interrupt response, and timer. In addition, it cannot simulate the actual execution of embedded systems in application systems like ICE. 3 Conclusion Embedded system is to embed the computer directly into the application system, which is the final product of information technology. The core of an embedded system is an embedded processor. Embedded system is one of the most important economic growth points for the information industry to move towards the era of knowledge economy in the 21st century. It is an industry that cannot be monopolized and is full of opportunities and challenges for China's information industry. The world is so vast and full of diversification, especially we have entered the post-PC era-ubiquitous computing (nomadic computing) will make embedded processors everywhere we can imagine, therefore, every processor has The reason for existence has a stretchable direction. This point should particularly arouse the attention of China's information industry. With the advent of my country's Godson, Beijing Volkswagen, Ark, Xingguang, Hanxin and other processor chips, the era of China's coreless has passed. "Software is the brain, and the chip is the heart." The significance of China Chip is not only that China has its own core chip, but more importantly, China has also begun to participate in the world semiconductor arena. This is more conducive to my country in the 21st century. Actively, profitably, and effectively share the big cake of embedded applications.
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