Technical Articles
2025-01-11

Common Embedded Processors

Common Embedded Processors

Introduction to Embedded Processors
Embedded processors are the core of embedded systems, serving as the hardware unit that controls and assists system operations. Their range is extremely vast, from the initial 4-bit processors to the 8-bit microcontrollers that are still widely used today, to the latest 32-bit and 64-bit embedded CPUs that are increasingly favored.
Since the advent of microprocessors, embedded systems have developed rapidly, and embedded processors are undoubtedly the core part of embedded systems, directly affecting the performance of the entire embedded system. Generally, embedded processors are considered a collective term for the computational and control core devices within embedded systems.
There are over 1000 types of processors with embedded functionality worldwide, with popular architectures including MCU, MPU, and more than 30 series. Given the broad development prospects of embedded systems, many semiconductor manufacturers are mass-producing embedded processors, and independently designed processors by companies have become a major trend in the future of the embedded field, with various types ranging from microcontrollers, DSPs to FPGAs, becoming faster, more powerful, and cheaper. The addressing space of embedded processors can range from 64kB to 16MB, with processing speeds reaching up to 2000 MIPS, and packages ranging from 8 pins to 144 pins.
The design of embedded microprocessors is fundamentally similar to that of ordinary desktop computer microprocessors, but they have higher stability, lower power consumption, and stronger adaptability to environmental factors (such as temperature, humidity, electromagnetic fields, vibrations, etc.), smaller size, and more integrated functions. In the desktop computer field, the main metric for comparing processors is computational speed, from the 33MHz main frequency of the 386 computer to the 3GHz main frequency of the Pentium 4 processor, with speed improvements being the main concern for users. However, in the embedded field, the situation is completely different. The selection of embedded processors must be based on design requirements, making trade-offs among performance, power consumption, functionality, size and packaging, SoC level, cost, and commercial considerations, among many other factors.
As the core of embedded systems, embedded processors undertake important tasks of control and system operation, making host devices intelligent, flexibly designed, and easy to operate. To efficiently complete these tasks, embedded processors generally have the following characteristics: strong support for real-time multitasking, memory protection capabilities, scalable microprocessor architecture, strong interrupt handling capabilities, and low power consumption.
The core of embedded systems is the embedded microprocessor. Embedded microprocessors generally have the following four characteristics:

  • Strong support for real-time multitasking, capable of completing multiple tasks with a short interrupt response time, thereby minimizing the execution time of internal code and real-time core.

  • Strong memory protection capabilities. This is due to the modular software structure of embedded systems, and to avoid erroneous interactions between software modules, a robust memory protection feature must be designed, which also facilitates software diagnostics.

  • Scalable processor architecture to quickly develop embedded microprocessors that meet the highest performance requirements of applications.

  • Embedded microprocessors must have very low power consumption, especially in portable, wireless, and mobile computing and communication devices powered by batteries, requiring power consumption at the mW or even μW level.

Embedded ARM Microprocessors
Origin and Development of ARM Microprocessors
ARM (Advanced RISC Machines) can be considered a company name, a term for a class of microprocessors, or a name for a technology. Currently, microprocessors that adopt ARM technology intellectual property (IP) cores are what we commonly refer to as ARM microprocessors. They are high-performance, low-power 32-bit microprocessors widely used in embedded systems. Microprocessors based on ARM technology account for over 75% of the market share of 32-bit RISC microprocessors, and ARM technology is gradually penetrating various aspects of our lives. ARM9 represents the mainstream processors from ARM and has been widely applied in handheld phones, set-top boxes, digital cameras, GPS, personal digital assistants, and Internet devices.
Application Fields of ARM Microprocessors

  • ARM microprocessors are currently among the most widely used processors, with applications covering industrial control, consumer electronics, communication systems, network systems, wireless systems, and various product markets.

  • Industrial Control: As a 32-bit RISC architecture, microcontroller chips based on ARM cores not only occupy a large portion of the high-end microcontroller market but are also gradually expanding into low-end microcontroller applications, challenging traditional 8-bit/16-bit microcontrollers with their low power consumption and high cost-performance ratio.

  • Wireless Communication: Currently, over 85% of wireless communication devices use ARM technology, and ARM’s high performance and low cost are solidifying its position in this field.

  • Network Applications: With the promotion of broadband technology, ARM-based ADSL chips are gradually gaining competitive advantages. In addition, ARM has optimized voice and video processing, gaining widespread support and challenging the application fields of DSP.

  • Consumer Electronics: ARM technology is widely adopted in popular digital audio players, digital set-top boxes, and game consoles.

  • Imaging and Security Products: Most of the currently popular digital cameras and printers use ARM technology. The 32-bit SIM smart cards in mobile phones also utilize ARM technology.

Characteristics of ARM Microprocessors Based on RISC Architecture

  • Small size, low power consumption, low cost, high performance;

  • Supports Thumb (16-bit)/ARM (32-bit) dual instruction sets, allowing compatibility with 8-bit/16-bit devices;

  • Extensive use of registers, resulting in faster instruction execution;

  • Most data operations are performed in registers;

  • Flexible and simple addressing modes, high execution efficiency;

  • Fixed instruction length;

Embedded MIPS Processors
Overview of MIPS Processor Development
MIPS is a very popular RISC processor worldwide. MIPS stands for “Microprocessor withouT Interlocked piped stages”, and its mechanism aims to avoid data-related issues in the pipeline using software methods. MIPS Technology Company is a well-known chip design company in the U.S. that designs chips using a RISC architecture to manufacture high-performance, high-end embedded 32-bit and 64-bit processors, holding an important position in RISC processors.
The system architecture and design concepts of MIPS are quite advanced, with its instruction systems evolving from general-purpose processor instruction sets MIPSI, MIPSII, MIPSIII, MIPSIV to MIPSV, and the embedded instruction sets MIPS16, MIPS32 to MIPS64 having matured significantly.
In terms of design philosophy, MIPS emphasizes the collaboration of hardware and software to enhance performance while simplifying hardware design. Compared to the complex instruction set computing architecture (CISC) used by Intel, RISC has advantages such as simpler design and shorter design cycles, allowing for the application of more advanced technologies to develop faster next-generation processors. MIPS is one of the earliest commercial RISC architecture chips, and the new architecture integrates all the previous MIPS instruction sets while adding many more powerful features.
Applications of MIPS Processors
In general, MIPSR series microprocessors are used to build SGI’s high-performance workstations, servers, and supercomputing systems. In embedded applications, MIPSK series microprocessors are currently the second most used processors after ARM (before 1999, MIPS was the most widely used processor in the world), covering various applications such as gaming consoles, routers, laser printers, and handheld computers.
PowerPC
The PowerPC architecture specification was developed in the 1990s by IBM, Apple, and Motorola to create multiprocessor computers based on PowerPC.
The characteristics of the PowerPC architecture include good scalability and flexibility. It is a 64-bit specification (which also includes a 32-bit subset). Almost all commonly available PowerPCs (except for the new IBM RS/6000 models and all IBM pSeries high-end servers) are 32-bit.
The market share of PowerPC is not very high, but it is widely used in the control and management of communication systems.
Embedded X86 Processors
x86 is a standard abbreviation for Intel’s general computer series, also signifying a set of general computer instruction sets. The X does not relate to the processor; it is a simple wildcard definition for all *86 systems. Since early Intel CPU numbers were designated as 8086, 80286, and so on, and since all CPUs in this series are instruction-compatible, they are all denoted by x86.
x86 has become the standard computing platform due to its unparalleled performance-to-price ratio. However, x86 is still based on 32-bit technology—ineffective for high-end enterprise servers and workstation applications. Compared to ARM architecture products, embedded x86 processors generally have much higher performance but also much higher power consumption, although they can still maintain fanless operation, they are fundamentally unsuitable for handheld computing products that rely entirely on battery power, such as PDAs and smartphones.
The application range of x86 embedded processors is narrower compared to ARM and MIPS. They are mainly used in desktop and low-end server processors.
Embedded DSP Processors
DSPs are specialized processors that perform high-speed real-time processing after converting analog signals into digital signals, with processing speeds 10 to 50 times faster than the fastest CPUs. In today’s digital age, DSPs have become fundamental components in fields such as communication, computing, and consumer electronics. Industry insiders predict that DSPs will be the fastest-growing electronic products in future integrated circuits and will become decisive factors in the renewal of electronic products.
DSPs belong to the Modified Harvard architecture, which has two internal buses: data bus and program bus. The program and data storage spaces are separate, each with independent address and data buses, allowing simultaneous addressing and reading. It employs pipelining, with each instruction execution divided into fetching, decoding, fetching data, and executing steps, completed by multiple functional units within the chip. This is equivalent to parallel execution of multiple instructions, greatly increasing computational speed. Multiplication instructions are completed in a single cycle, optimizing algorithms such as convolution, digital filtering, FFT, correlation, and matrix operations that involve numerous repetitive multiplications. Special instructions such as circular addressing and bit-reversed addressing greatly enhance the addressing, sorting, and computation speed in operations like FFT and convolution. DSPs have independent DMA buses and controllers, with one or more independent DMA buses working in parallel with the CPU’s program and data buses. Multi-processor interfaces allow multiple processors to work conveniently in parallel or serially to improve processing speed.

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