1. Processor Technology Processor technology is related to the computing engine architecture that implements system functions. Many non-programmable digital systems can also be regarded as processors. The difference between these processors lies in their specialization for specific functions, which leads to their design specifications being different from other processors. (1) General-purpose processors This type of processor can be used for different types of applications. An important feature is that it is stored program. Since the designer does not know what kind of operation the processor will perform, it is impossible to build the program with digital circuits. Another feature is the general data path. In order to handle different types of calculations, the data path is general. Its data path generally has a large number of registers and one or more general arithmetic logic units. The designer only needs to program the processor's memory to perform the required functions, that is, design the relevant software. Using general-purpose processors in embedded systems has some advantages in terms of design specifications. The time to market and NRE costs are lower because the designer only needs to write the program and does not need to do any digital design. It is highly flexible, and changes in functions can be made by modifying the program. Compared with self-designed processors, the unit cost is lower when the number is small. Of course, this approach also has some design specification defects. The unit cost is relatively high when the number is large because when the number is large, the cost of self-designed NREs is spread out, which can reduce the unit cost. Meanwhile, for some applications, the performance may be poor. Due to the inclusion of unnecessary processor hardware, the system size and power consumption may increase. (2) Single-purpose processor A single-purpose processor is a digital circuit designed to execute a specific program, also referring to coprocessors, accelerators, peripherals, etc. For example, a JPEG codec executes a single program to compress or decompress video information. Embedded system designers can build single-purpose processors by designing specific digital circuits. Designers can also use pre-designed commercial single-purpose processors. There are some advantages and disadvantages in terms of performance when using single-purpose processors in embedded systems. These advantages and disadvantages are basically the opposite of those of general-purpose processors. The performance may be better, the size and power consumption may be smaller, the unit cost may be lower when the quantity is large, while the design time and NRE cost may be higher, the flexibility is poor, the unit cost is higher when the quantity is small, and the performance is not as good as that of general-purpose processors for some applications. (3) Dedicated processor A dedicated instruction set processor (ASIP) is a programmable processor optimized for a specific type of application. These specific applications have the same characteristics, such as embedded control, digital signal processing, etc. Using ASIPs in embedded systems can provide greater flexibility while ensuring good performance, power, and size. However, these processors still require expensive NRE costs to build the processor itself and the compiler. Microcontrollers and digital signal processors are two widely used ASIPs. A digital signal processor is a microprocessor that performs common operations on digital signals, while a microcontroller is a microprocessor optimized for embedded control applications. Common peripherals in control applications, such as serial communication peripherals, timers, counters, pulse width modulators, and digital-to-analog converters, are usually integrated on the microprocessor chip, making the product smaller and cheaper. 2. IC Technology (1) Full Custom/VLSI In full custom IC technology, designers need to optimize each layer according to the digital implementation of the specific embedded system. They start from the transistor layout size, location, and interconnection to achieve the optimal performance of high chip area utilization, high speed, and low power consumption. The actual chip is produced in the manufacturing plant using a mask. Full custom IC design is also often called large-scale integrated circuit design (VLSI). It has high NRE costs and long manufacturing time, and is suitable for large-scale or high-performance applications. (2) Semi-custom ASIC Semi-custom ASIC is a constrained design method, including gate array design and standard cell design. It is a semi-finished hardware where some general-purpose unit elements and component groups are made on the chip. The designer only needs to consider the logic function of the circuit and the reasonable connection between the functional modules. This design method is flexible, convenient, cost-effective, shortens the design cycle, and improves the yield. (3) Programmable ASIC All layers in a programmable device already exist. After the design is completed, the designed chip can be burned in the laboratory without the participation of the IC manufacturer, and the development cycle is significantly shortened. Programmable ASIC has a lower NRE cost, higher unit cost, higher power consumption, and slower speed. 3. Design/Verification Technology Embedded system design technology mainly includes two categories: hardware design technology and software design technology. Among them, the technology in the field of hardware design mainly includes chip-level design technology and circuit board-level design technology. The core of chip-level design technology is compilation/synthesis, library/IP, and testing/verification. Compilation/synthesis technology enables designers to describe the required functions in an abstract way and automatically analyze and insert implementation details. Library/IP technology uses pre-designed low-level abstraction implementations for high-level applications. Testing/verification techniques ensure the correctness of each functional level, reducing the cost of iterative design between levels. The core of software design technology is the software language. Software languages ​​have evolved from low-level languages ​​(machine language, assembly language) to high-level languages ​​(such as structured design languages, object-oriented design languages), driven by assembly technology, analysis technology, compilation/interpretation technology, and many other related technologies. The levels of software languages ​​have also gradually transitioned from implementation level, design level, and functional level to requirement-level languages. Early on, with the gradual formation of the general-purpose processor concept, software technology developed rapidly, and software complexity began to increase, leading to a complete separation of software design and hardware design technologies and domains. Design techniques and tools developed synchronously in both domains, enabling behavioral descriptions to be performed at increasingly abstract levels to adapt to the ever-increasing design complexity. This synchronous development has now resulted in both domains using the same timing model to describe behavior, making it possible for these two domains to be unified into one again.