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Introduction to Vehicle Network Technology (1)

Introduction to Vehicle Network Technology (1)

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  • Time of issue:2021-11-29 17:48
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(Summary description)Development stage of automotive electronic technology

Introduction to Vehicle Network Technology (1)

(Summary description)Development stage of automotive electronic technology

  • Categories:News  center
  • Author:
  • Origin:
  • Time of issue:2021-11-29 17:48
  • Views:
01 Development stage of automotive electronic technology
The Tube Era: The 1950s. Typical application: 1959 transistor radio.
The transistor era: the 1960s. Typical applications: In the mid-1960s, transistor voltage regulators and transistor ignition devices began to be used using the principle of amplification and opening of transistors.
The integrated circuit era: the 1990s. Typical applications: The use of integrated circuit technology to control vehicles, aircraft, and typical applications are automotive anti-lock braking devices.
The era of networked comprehensive technology: the current period. It mainly includes advanced automotive electronic technology such as electronic technology, computer technology, comprehensive control technology, and intelligent sensor technology. It is mainly developed and designed with microcontrollers as the core. The communication between microcontrollers is mainly based on network management. accomplish.
02 Basic composition of automotive electronic system


03 Computer Network Architecture
For two computers to communicate, they must be made to use the same principle of exchanging information—a protocol.
Network protocol: An agreement between the two parties on how to communicate, including the agreement on the rules of information format and data exchange (sending and receiving).
The three elements of a network protocol:
Grammar: refers to the structure or format of data and information control, and determines the "how to talk" between the two communicating parties, that is, it is composed of logical descriptions. It is necessary to format each field in the information or message, and describe the header (or header) fields, commands and The structure of the response.
Semantics: It refers to what kind of control information needs to be sent, what kind of action to complete and what kind of response to make. Semantics determines what to say between the two parties in communication, and explains the request and execution function, including the processing of the recognition result, which is equivalent to A description of the meaning of a statement.
Synchronization: Detailed description of event implementation sequence, speed matching, etc.
04 Network Hierarchical Structure
In order to reduce the complexity of network design, most networks form a stack of layers or levels on top of each other.
Protocol: An agreement between two parties on how to communicate.
Peers: Entities that contain corresponding layers on different machines. Peers communicate using protocols.
Interface: Define the lower layer to provide primitive operations and services to the upper layer.
Network Architecture: A collection of layers and their protocols.
Protocol stack: A set of protocols used by a particular system (one protocol per layer).
05 The difference between service and agreement
Service: A set of operations provided by a layer to the next layer. Defines what operations the layer intends to perform on behalf of its users, but does not address how these operations are implemented. Service involves the interface between two layers, the lower layer is the provider of the service, and the upper layer is the user of the service.
Protocol: A set of rules that define the format and meaning of frames and data packets that are exchanged between peer entities at the same layer. Entities implement their service definitions using protocols; peer entities are free to change protocols, but not services.
A protocol is "horizontal", i.e. a protocol is the rules governing the communication between two peer entities.
The service is "vertical", that is, the service is provided by the lower layer to the upper layer through the inter-layer interface.
ISO reference model

  Physical layer: The bit stream (bit stream) is transmitted on the communication channel, and the definition and connection method of the connecting cable plug are determined. The physical layer is concerned with what signals are used to represent data "1" and "0"; the duration of each bit; whether data transmission is bidirectional; connection establishment and termination.

Note: The physical medium that transmits information, such as twisted pair, coaxial cable, optical cable, etc., is below the physical layer and is regarded as layer 0.
Data link layer: Its main task is to transmit data in frame units without error on the line between two adjacent nodes. Each frame includes data and necessary control information.
The data link layer provides reliable data transmission over physical network links.
It defines network and protocol characteristics, including physical addressing, network topology, error checking, frame sequence, and flow control. The data link layer actually consists of two independent parts: the media access control (Media Access Control, MAC) logical link control layer (Logical Link Control, LLC). The MAC describes how to schedule, generate and receive data for stations in a shared medium environment. The MAC ensures reliable transmission of information across links, synchronizes data transmission, identifies errors and controls the flow of data. The Logical Link Control sublayer manages communications between devices on a single network link, and the IEEE 802.2 standard defines LLC. LLC supports both connectionless and connection-oriented services.
Network layer: The task of the network layer is to select an appropriate route, so that the packets from the transmission layer of the sending station can find the destination station according to the address correctly and deliver it to the transmission layer of the destination station. Note: It generally includes network routing, and may also include flow control, error checking, etc. Data transmission between different network segments of the same MAC standard generally only involves the data link layer, while data transmission between different MAC standards involves the network layer. For example, IP routers work at the network layer, and thus can realize interconnection between various networks.
Transport layer: The transport layer provides reliable end-to-end network data streaming services to the upper layers, making them invisible to the details of data communication below the transport layer. The functions of the transport layer generally include flow control, multiplexing, error checking and recovery. Flow control: manages data transmission between devices to ensure that the transmitting device does not send more data than the receiving device can handle; multiplexing allows data from multiple applications to be transmitted over a physical link; error checking is included for detection Various structures established for transmission errors; error recovery includes actions taken (such as requesting data retransmission) to resolve any errors that occur. Transmission Control Protocol (TCP) is a transport layer protocol in the TCP/IP protocol suite that provides reliable data transmission.
Session layer: Establishes, manages and terminates the communication session between the presentation layer and the entity. Session: Usually refers to various services, including dialog control, token management, synchronization management. Conversation control: record who should transmit data; token management: prohibit both parties from performing the same key operation at the same time; synchronization management: create checkpoints in a long transmission, so that when communication is interrupted, it can return to a previous state .
Presentation layer: Pay attention to the syntax and semantics of the transmitted information; the presentation layer provides a variety of functions for application layer data encoding and transformation to ensure that information sent by one system application layer can be recognized by another system application layer. The encoding and transformation modes of the presentation layer include common data representation format, performance transformation representation format, common data compression mode and common data encryption mode.
It interprets the commands and data from the application layer, assigns corresponding meanings to various grammars, and transmits them to the session layer according to a certain format. Its main function is to "deal with the representation of user information, such as encoding, data format conversion and encryption and decryption". The specific functions of the presentation layer are as follows: Data format processing: Negotiate and establish the format of data exchange, and resolve the differences in data format representation between applications. Encoding of data: handles character set and number conversion. For example, since the data type (integer or real type, signed or unsigned, etc.), user ID, etc. in the user program can have different representations, it is necessary to have different character sets or formats between devices. conversion function. Compression and decompression: In order to reduce the amount of data transmission, this layer is also responsible for data compression and recovery. Encryption and decryption of data: It can improve the security of the network.

Application layer: It is the interface between computer users, various applications and the network. Its function is to provide services directly to users and complete various tasks that users want to complete on the network. On the basis of other 6-layer work, it is responsible for completing the connection between the application program and the network operating system in the network, establishing and ending the connection between users, and completing various network services and applications required by network users. Various agreements for supervision, management and service. In addition, this layer is also responsible for coordinating work among the various applications.

bus topology

Advantages: 1. The cable length is short and easy to wire. 2. High reliability. 3. Easy to expand. Disadvantages: 1. Difficulty in fault diagnosis. 2. Fault isolation is difficult. 3. Repeater configuration. 4. The site must be smart.
star topology
Advantages: 1. Easy to configure. 2. Only one device is connected to each connection point. 3. Centralized control and easy fault diagnosis. 4. Simple Media Access Protocol.
Disadvantages: 1. The cable length is long and the installation is complicated. 2. Difficulty expanding. 3. Depends on the central node.
Ring topology
Advantages: 1. The cable length is short. 2. No junction box required. 3. Optical fiber available.
Disadvantages: 1. Node failures cause network-wide failures. 2. Difficulty in diagnosing faults. 3. Not easy to reconfigure the network. 4. Topology affects the medium access protocol.
tree topology
Advantages: 1. Easy to expand. 2. The fault is easy to isolate. 3. High reliability.
Disadvantages: 1. High cost of cables. 2. The dependency on the root node is large. Once the root node fails, the entire network will not work.
network topology
Advantages: 1. High reliability. 2. Because there are multiple paths, the best path can be selected to reduce delay, improve traffic distribution, and improve network performance.
Disadvantages: 1. Not easy to manage and maintain. 2. High line cost; suitable for large WAN.


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