Brief Analysis of the Similarities and Differences between Single-Chip Microcomputer and Embedded System

　　What is a single-chip microcomputer? Generally, we refer to a single-chip microcomputer as a single-chip microcomputer. It is not a chip that completes a certain logical function, but a computer system integrated into one chip. It is equivalent to a microcomputer. Compared with a computer, a single-chip microcomputer only lacks I/O devices. It is a typical embedded microcontroller. So, what is an embedded system? An embedded system refers to a special computer system that is application-centric, based on computer technology, with software and hardware that can be tailored to meet the strict requirements of the application system on functions, volume, cost, reliability, and power consumption. What are the differences and connections between single-chip microcomputers and embedded systems (embedded operating system functions)? Let's discuss and learn about it together.

　　Comparison of the structure of single-chip microcomputer and embedded system

　　(1) Basic structure of single chip microcomputer

　　The single-chip microcomputer is composed of an arithmetic unit, a controller, a memory, and input and output devices.

　　(2) Embedded system components:

　　Embedded systems generally consist of the following groups of embedded microprocessors, peripheral hardware devices, embedded operating systems, and specific applications.

　　The first step in embedded system design is to combine specific applications, comprehensively consider the system's requirements for cost, performance, scalability, development cycle, etc., determine the system's main control device, and build the system hardware platform with it as the core.

　　The connection between single chip microcomputer and embedded system

　　A single-chip microcomputer is an integrated circuit chip that uses ultra-large-scale integrated circuit technology to integrate a central processing unit (CPU) with data processing capabilities, random access memory (RAM), read-only memory (ROM), multiple I/O ports and interrupt systems, timers/counters and other functions (may also include display driver circuits, pulse width modulation circuits, analog multiplexers, A/D converters and other circuits) on a silicon chip to form a small and complete microcomputer system. It is widely used in the field of industrial control. Since the 1980s, the 4-bit and 8-bit single-chip microcomputers at that time have developed into the current 32-bit 300M high-speed single-chip microcomputers.

　　The earliest single-chip microcomputer was Intel's 8048, which appeared in 1976. Motorola also launched the 68HC05, and Zilog launched the Z80 series. These early single-chip microcomputers all contained 256 bytes of RAM, 4K of ROM, 4 8-bit parallel ports, 1 full-duplex serial port, and two 16-bit timers. Later in the early 1980s, Intel further improved the 8048 and successfully developed the 8051 based on it. This is a memorable page in the history of single-chip microcomputers. To date, the 51 series of single-chip microcomputers are still the most successful single-chip microcomputer chips, and are widely used in various products.

　　The emergence of embedded systems was initially based on single-chip microcomputers. From the emergence of single-chip microcomputers in the 1970s to the large-scale application of various embedded microprocessors and microcontrollers today, cars, home appliances, industrial machines, communication devices and thousands of products can achieve better performance through embedded electronic devices: easier to use, faster and cheaper. These devices have initially possessed the application characteristics of embedded systems, but the applications at that time only used 8-bit chips and executed some single-threaded programs, and there was no concept of "system".

　　Since the early 1980s, embedded system programmers have begun to use commercial-grade "operating systems" to write embedded application software, which has enabled shorter development cycles, lower development costs and higher development efficiency, and "embedded systems" have truly emerged. To be more precise, the operating system at this time is a real-time kernel, which contains many features of traditional operating systems, including task management, inter-task communication, synchronization and mutual exclusion, interrupt support, memory management and other functions.

　　Among them, the more famous ones are VRTX from Ready System, PSOS from Integrated System Incorporation (ISI), VxWorks from IMG, QNX from QNX, etc. These embedded operating systems all have typical characteristics of embedded systems: they all use preemptive scheduling, the response time is very short, and the task execution time can be determined; the system kernel is very small, and it is cuttable, expandable and portable, and can be ported to various processors; it has strong real-time and reliability, and is suitable for embedded applications. The emergence of these embedded real-time multi-tasking operating systems has liberated application developers from small-scale development, and has also prompted embedded systems to have a broader application space.

　　After the 1990s, with the increasing requirements for real-time performance, the software scale continued to rise, and the real-time kernel gradually developed into a real-time multitasking operating system (RTOS), and as a software platform, it gradually became the mainstream of the current international embedded system. At this time, more companies saw the broad development prospects of embedded systems and began to vigorously develop their own embedded operating systems. In addition to the above-mentioned old companies, there are also Palm OS, WinCE, embedded Linux, Lynx, Nucleux, and domestic Hopen, Delta Os and other embedded operating systems. With the increasingly broad development prospects of embedded technology, I believe that more embedded operating system software will appear. [page]

　　Several embedded real-time operating systems suitable for PIC18F series microcontrollers

      As shown in the following figure:

　　◆Embedded systems are user-oriented, product-oriented, and application-oriented. They must be combined with specific applications to be viable and have more advantages. Therefore, the meaning of the above three aspects can be understood in this way, that is, embedded systems are closely integrated with applications, they are highly specialized, and must be reasonably tailored and utilized in combination with actual system requirements.

　　◆Embedded systems are the product of combining advanced computer technology, semiconductor technology, electronic technology and specific applications in various industries. This determines that it must be a technology-intensive, capital-intensive, highly decentralized, and constantly innovative knowledge integration system. Therefore, when entering the embedded system industry, you must have a correct positioning. For example, the reason why Palm occupies more than 70% of the market in the PDA field is because it is based on personal electronic consumer products and focuses on the development of graphical interfaces and multi-task management; and the reason why Wind River's Vxworks is used on the Mars rover is because of its high real-time performance and high reliability.

　　◆Embedded systems must tailor their hardware and software according to application requirements to meet the application system's requirements for functionality, reliability, cost, volume, etc. Therefore, if a relatively universal hardware and software foundation can be established, and then systems that meet various needs can be developed on it, this is a better development model. The core of current embedded systems is often a microkernel of only a few K to tens of K, which needs to be expanded or reduced in function according to actual use, but due to the existence of the microkernel, this expansion can be carried out very smoothly.

　　Summarize

　　With the development of electronic information science and technology, the application of single-chip microcomputer and embedded system has been broadened. This paper briefly analyzes the relationship between single-chip microcomputer and embedded system, the basic knowledge of composition structure comparison, and lists several embedded real-time operating systems suitable for PIC18F series single-chip microcomputer.