The embedded processor is the core of the embedded system and is the hardware unit that controls and assists the system operation. The range is extremely wide, from the original 4-bit processor, 8-bit microcontrollers still in large-scale applications, to the latest 32-bit, 64-bit embedded CPUs that are widely favored.
Since the advent of microprocessors, embedded systems have developed rapidly. Embedded processors are undoubtedly the core of embedded systems. Embedded processors are directly related to the performance of the entire embedded system. Embedded processors are often considered the general term for computing and controlling core devices in embedded systems.
There are more than 1000 processors with embedded features in the world, and the popular architecture includes more than 30 series such as MCU and MPU. In view of the broad development prospects of embedded systems, many semiconductor manufacturers have mass-produced embedded processors, and the company's self-designed processors have become a major trend in the embedded field in the future, from microcontrollers to DSPs to FPGAs. With all kinds of varieties, the speed is getting faster and faster, the performance is getting stronger and stronger, and the price is getting lower and lower. The embedded processor's addressing space can range from 64kB to 16MB, processing speeds up to 2000 MIPS, and packages ranging from 8 pins to 144 pins.
Characteristics
The microprocessor design of the embedded microprocessor and the ordinary desktop computer is similar in basic principle, but the work stability is higher, the power consumption is smaller, and the adaptability to the environment (such as temperature, humidity, electromagnetic field, vibration, etc.) is strong. It is smaller in size and has more integrated functions. In the field of desktop computers, the main indicator when comparing processors is the calculation speed. From the 386 computer with 33MHz frequency to the PenTIum 4 processor with 3GHz frequency, the speed increase is the most important change for users, but it is embedded. In the field, the situation is completely different. The choice of embedded processor must be compromised in terms of performance, power consumption, functionality, size and package form, SoC level, cost, business considerations, etc., depending on the design requirements.
The embedded processor is the core of the embedded system. The embedded processor is responsible for the important tasks of control and system work, making the host device intelligent, flexible and easy to operate. In order to accomplish these tasks reasonably and efficiently, the embedded processor generally has the following features: strong real-time multi-tasking support, storage area protection, scalable microprocessor structure, strong interrupt handling capability, low power Consumption.
The core of the embedded system is the embedded microprocessor. Embedded microprocessors generally have the following four features:
1) Strong support for real-time multitasking, multitasking and short interrupt response time, minimizing internal code and real-time core execution time.
2) Has a very powerful storage area protection function. This is because the software structure of the embedded system has been modularized, and in order to avoid the wrong crossover between the software modules, it is necessary to design a powerful memory area protection function, and also facilitate software diagnosis.
3) Scalable processor architecture to enable the fastest implementation of embedded microprocessors that meet the highest performance requirements of the application.
4) Embedded microprocessors must have low power consumption, especially for battery-powered embedded systems in portable wireless and mobile computing and communication devices, such as power consumption of only mW or even μW.
classification
1, the microprocessor
The Micro Processor Unit (MPU) evolved from a CPU in a general-purpose computer. It is characterized by a processor with more than 32 bits, which has high performance, and of course its price is correspondingly higher. However, unlike computer processors, in practical embedded applications, only the functional hardware closely related to the embedded application is retained, and other redundant functional parts are removed, so that the embedded application can be realized with the lowest power consumption and resources. special requirements. Compared with industrial control computers, embedded microprocessors have the advantages of small size, light weight, low cost and high reliability. The main embedded processor types are Am186/88, 386EX, SC-400, Power PC, 68000, MIPS, ARM/StrongARM series.
Among them, Arm/StrongArm is an embedded microprocessor developed for handheld devices, which is a mid-range price.
2, the microcontroller
A typical representative of an embedded microcontroller (Microcontroller Unit, MCU) is a single-chip microcomputer. Since the emergence of single-chip microcomputers in the late 1970s, today, although it has been more than 20 years old, such 8-bit electronic devices still have extreme A wide range of applications. The integrated chip/EPROM, RAM, bus, bus logic, timer/counter, watchdog, I/O, serial port, pulse width modulation output, A/D, D/A, Flash RAM, EEPROM, etc. A necessary function and peripherals. Compared with embedded microprocessors, the biggest feature of microcontrollers is that they are singular and greatly reduced in size, resulting in lower power consumption and cost, and improved reliability. Microcontrollers are the mainstream of the embedded system industry. The on-chip peripheral resources of the microcontroller are generally rich and suitable for control, so it is called a microcontroller.
Due to the low price and excellent function of the MCU, it has the most varieties and quantities, including 8051, MCS-251, MCS-96/196/296, P51XA, C166/167, 68K series and MCU 8XC930/. 931, C540, C541, and support I2C, CAN-Bus, LCD and many dedicated MCUs and compatible series. MCUs account for about 70% of the market share of embedded systems. Atmel's Avr MCU has a high cost performance due to its integration of FPGAs and other devices, which is bound to promote the development of MCUs.
3, DSP processor
The Embedded Digital Signal Processor (EDSP) is a processor specially designed for signal processing. It is specially designed in terms of system structure and instruction algorithm, and has high compilation efficiency and instruction execution speed. DSP has achieved large-scale applications in various instruments such as digital filtering, FFT, and spectral analysis.
The theoretical algorithm of DSP has appeared in the 1970s, but since the special DSP processor has not appeared yet, this theoretical algorithm can only be realized by discrete components such as MPU. The lower processing speed of the MPU cannot meet the algorithm requirements of the DSP, and its application field is limited to some cutting-edge high-tech fields. With the development of large-scale integrated circuit technology, the first DSP chip was born in the world in 1982. Its operation speed is several times faster than that of MPU, and it has been widely used in speech synthesis and codecs. By the mid-1980s, with the advancement and development of CMOS technology, the second generation of DSP chips based on CMOS technology came into being, and its storage capacity and operation speed were doubled, which became the basis of speech processing and image hardware processing technology. By the late 1980s, the computing speed of DSPs was further improved, and the application field was expanded from the above scope to communication and computer. After the 1990s, DSP developed into the fifth generation of products, with higher integration and wider use.
The most widely used is TI's TMS320C2000/C5000 series. In addition, Intel's MCS-296 and Siemens' TriCore also have their own applications.
4, system on chip
Embedded System On Chip: SoC is one of the hot topics in embedded applications in pursuit of the most inclusive integrated device for product systems. The biggest feature of SOC is the successful integration of software and hardware, and the code module of the operating system is embedded directly in the processor chip. Moreover, the SOC has a very high level of integration, and a hardware description language such as VHDL is used inside a silicon chip to realize a complicated system. Users don't need to draw huge and complex boards like traditional system design. A little bit of soldering requires only precise language. The integrated timing design directly calls the standards of various general-purpose processors in the device library. After the simulation, the chip manufacturer can be directly delivered for production. Since most of the system components are inside the system, the whole system is particularly simple, which not only reduces the size and power consumption of the system, but also improves the reliability of the system and improves the design and production efficiency.
Since SOC is often dedicated, most of it is not known to the user. The typical SOC product is Philips' Smart XA. A few general-purpose series such as TriCore from Siemens, M-Core from Motorola, some ARM series devices, and the Neuron chip jointly developed by Echelon and Motorola.
It is expected that in the near future, some large chip companies will repel competitors by launching mature SOC chips that can occupy most markets. The SOC chip will also play an important role in applications such as sound, imaging, video, networking and system logic.
(1) Embedded ARM microprocessor (embedded microprocessor structure)
The origin and development of ARM microprocessor
ARM (Advanced RISC Machines) can be considered as the name of a company, or as a generic term for a type of microprocessor. It can also be considered as a technical name. Currently, microprocessors that use ARM technology intellectual property (IP) cores are what we usually call ARM microprocessors. It is a high performance, low power 32-bit micro-processor that is widely used in embedded systems. Microprocessor applications based on ARM technology account for more than 75% of the market share of 32-bit RISC microprocessors, and ARM technology is gradually infiltrating into all aspects of our lives. ARM9 represents the mainstream processor of ARM, and has been widely used in handheld phones, set-top boxes, digital cameras, GPS, personal digital assistants and Internet devices.
ARM microprocessor application areas
ARM microprocessor is a very widely used processor in the current application. So far, the application of ARM microprocessor and technology has almost spread to various product markets such as industrial control, consumer electronics, communication systems, network systems, and wireless systems. , deep into various fields.
1. Industrial control field: As the 32 RISC architecture, the ARM core-based microcontroller chip not only occupies most of the market share of the high-end microcontroller market, but also gradually expands to the low-end microcontroller application field, ARM micro-control The low power consumption and high cost performance of the device pose challenges to traditional 8-bit/16-bit microcontrollers.
2. Wireless communication field: At present, more than 85% of wireless communication devices adopt ARM technology, and ARM has become increasingly solid in this field with its high performance and low cost.
3, network applications: With the promotion of broadband technology, ADSL chips using ARM technology are gradually gaining competitive advantage. In addition, ARM has been optimized for voice and video processing and has received wide support, and it has also challenged the application of DSP.
4. Consumer Electronics: ARM technology is widely used in popular digital audio players, digital set-top boxes and game consoles.
5, imaging and security products: Most of the popular digital cameras and printers now use ARM technology. The 32-bit SIM smart card in the mobile phone also uses ARM technology.
Features of ARM microprocessor based on RISC architecture
1. Small size, low power consumption, low cost and high performance;
2, support Thumb (16-bit) / ARM (32-bit) dual instruction set, can be well compatible with 8-bit / 16-bit devices;
3, the use of a large number of registers, the instruction execution speed is faster;
4. Most data operations are done in registers;
5. The addressing mode is flexible and simple, and the execution efficiency is high;
6, the instruction length is fixed;
(2) Embedded MIPS processor
Overview of the development of MIPS processors
MIPS is a popular RISC processor in the world. MIPS means "MicroprocessorwithouTInterlockedpipedstages", the mechanism is to use software as much as possible to avoid data related problems in the pipeline. MIPS Technologies is a well-known chip design company in the United States that designs chips using the Reduced Instruction System Computing Architecture (RISC), which designs and manufactures high-performance, high-end and embedded 32-bit and 64-bit processors in RISC processors. The aspect occupies an important position.
MIPS's system structure and design concept are relatively advanced. Its instruction system has passed the general processor instruction system MIPSI, MIPSII, MIPSIII, MIPSIV to MIPSV. The development of embedded instruction system MIPS16, MIPS32 to MIPS64 is very mature.
In terms of design concept, MIPS emphasizes hardware and software synergy to improve performance while simplifying hardware design. Compared with the complex instruction system computing architecture (CISC) adopted by Intel, RISC has the advantages of simpler design and shorter design cycle, and can apply more advanced technologies to develop faster next-generation processors.
MIPS is one of the earliest commercial RISC architecture chips. The new architecture integrates all of the original MIPS instruction sets and adds many more powerful features.
MIPS processor application
MIPS In general terms, the MIPSR family of microprocessors is used to build SGI's high-performance workstations, servers and supercomputer systems. In terms of embedded, MIPSK series microprocessor is one of the most used processors next to ARM (MIPS is the most used processor in the world before 1999), and its application covers game consoles, routers, Laser printers, handheld computers and other aspects.
(3) PowerPC
The PowerPC Architecture Specification (PowerPC Architecture Specification) is a chip developed by IBM (International Business Machines), Apple (Apple) and Motorola (Motorola) in the 1990s, and a PowerPC-based multiprocessor computer. .
The PowerPC architecture is characterized by scalability, convenience and flexibility. It is a 64-bit specification (also contains a 32-bit subset). Almost all of the regular PowerPCs available (except for the new IBMRS/6000 and all IBMpSeries high-end servers) are 32-bit.
The PowerPC market share is not very high, but it is used a lot in the control and management of communication systems.
(4) Embedded X86 processor
X86 is a standard number abbreviation for the Intel general-purpose computer family. It also identifies a common set of computer instructions. X has nothing to do with the processor. It is a simple wildcard definition for all *86 systems, for example: i386, 586, Pentium. Since the CPU numbers of early Intel are numbered as 8086 and 80286, since the entire series of CPUs are instruction-compatible, X86 is used to identify the set of instructions used. Today's Pentium, P2, P4, Celeron series are all It is supported by the X86 command system, so it belongs to the X86 family.
The x86 is the standard for computing platforms with unparalleled performance and price advantages. But x86 is still based on 32-bit technology - no power for high-end enterprise server and workstation applications. Compared with ARM architecture products, embedded X86 processors generally have much higher performance, but the power consumption is much higher. Although they can still maintain fanless operation, they cannot be used completely for PDAs, smartphones, etc. * Battery-operated handheld computing products. What really needs to be embedded in the X86 processor is the network terminal, thin client, low-cost/low-power PC, home consumer electronics, POS terminal, etc., which require PC software continuity. The corresponding device is relatively large and does not depend on it. * Battery operation, but requires high performance, low power consumption, low noise and high reliability. In 2006, X86 introduced the first dual-core processor.
Compared with ARM and MIPS, X86 architecture has a narrower range of embedded processor applications. It is mainly used on desktop and low-end server processors.
(5) Embedded DSP processor
DSP is a dedicated processor that performs high-speed real-time processing after analog signals are converted into digital signals. The processing speed is 10 to 50 times faster than the fastest CPU. In the context of today's digital age, DSP has become the basic device in the fields of communications, computers, consumer electronics and other fields. Industry insiders predict that DSP will be the fastest growing electronic product in the future of integrated circuits, and become the decisive factor in the replacement of electronic products.
The DSP is a ModifiedHarvard architecture, which has two internal buses: a data bus and a program bus. The program is separated from the data storage space. Each has its own address bus and data bus. The address and reading can be performed simultaneously. It has reached 9 billion floating point operations per second (9000 MFLOPS). It adopts pipeline operation, and the execution of each instruction is divided into several steps of instruction fetching, decoding, fetching, and execution, which are respectively performed by multiple functional units in the chip. Equivalent to multiple instructions executed in parallel, which greatly increases the speed of the operation. Multiplication instructions are completed in a single cycle, optimizing a large number of repeated multiplications in algorithms such as convolution, digital filtering, FFT, correlation, and matrix operations. The use of special addressing such as circular addressing (bit-reversed) makes the addressing, sorting and calculation speeds in FFT and convolution operations greatly improved. The time of the 1024-point FFT is less than 1μs. It has independent DMA bus and controller, and has one or more independent DMA buses. It works in parallel with the program and data bus of the CPU. The DMA speed has reached 800Mbyte/s or more without affecting the CPU operation. Multiprocessor interface. Enable multiple processors to work in parallel or serially to increase processing speed.
The DSP processor has been developed into an embedded DSP processor (EDSP) to promote the development of embedded DSP processors through singularization, EMC modification, adding on-chip peripherals, or adding DSP coprocessors to general-purpose microcontrollers or SOCs. The main factor is the intelligence of embedded systems. At present, semiconductor manufacturers such as TI, ADI, Freescale, and CEVA have strong capabilities in this field.
The main market for DSP general purpose DSPs is communication applications, while embedded DSPs are mainly used in consumer electronics such as DVD players and recorders, set-top boxes, audio and video receiving devices, MP3 players and digital cameras. However, communication chips such as WLAN, DSL, and cable broadband networks also have embedded DSPs.
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