CAN 2.0b协议详解:标准与扩展格式及应用兼容

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CAN总线协议V2.0是一个重要的工业通信标准,它在串行通信领域得到了广泛应用,尤其在需要高效、精确报文识别的场景中。该规范引入了两种报文格式:标准格式和扩展格式。标准格式使用11位识别位,适用于那些不需要大范围地址的应用,而扩展格式则提供更宽的29位地址范围,适应了对地址识别更为精细化的需求。 CAN规范V2.0技术文档分为两个主要部分: A部分详细描述了CAN的报文格式,遵循CAN1.2标准,包括数据帧、远程帧、错误帧、过载帧、帧间空间以及发送器和接收器的定义。这部分着重于基础概念、报文传输流程、错误检测和处理、位定时要求等。 B部分则专门讨论标准格式和扩展格式的区别与共存,强调了如何区分两者,尤其是在兼容CAN2.0的情况下,要求设备能够支持A部分或B部分的功能。同时,还提到对于未使用扩展格式的系统,A部分设计的仪器可以与B部分设计的仪器无缝交互。 值得注意的是,为了兼容性和灵活性,CAN规范允许系统设计者根据实际需求选择使用标准格式或扩展格式,或者同时使用两者。此外,规范还涉及了如何处理增加CAN振荡器容差、协议修改等内容,确保在实际应用中能够应对各种可能的故障情况。 广州周立功单片机发展有限公司提供相关的技术支持和产品服务,如联系电话和网址,对于理解和实施CAN总线协议V2.0具有实用价值。学习和掌握CAN总线协议有助于工程师们设计高效、可靠的工业控制系统,提升通信效率和系统的稳定性。
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The Controller Area Network (CAN) is a serial communications protocol which efficiently supports distributed realtime control with a very high level of security. Its domain of application ranges from high speed networks to low cost multiplex wiring. In automotive electronics, engine control units, sensors, anti-skid-systems, etc. are connected using CAN with bitrates up to 1 Mbit/s. At the same time it is cost effective to build into vehicle body electronics, e.g. lamp clusters, electric windows etc. to replace the wiring harness otherwise required. The intention of this specification is to achieve compatibility between any two CAN implementations. Compatibility, however, has different aspects regarding e.g. electrical features and the interpretation of data to be transferred. To achieve design transparency and implementation flexibility CAN has been subdivided into different layers. • the (CAN-) object layer • the (CAN-) transfer layer • the physical layer The object layer and the transfer layer comprise all services and functions of the data link layer defined by the ISO/OSI model. The scope of the object layer includes • finding which messages are to be transmitted • deciding which messages received by the transfer layer are actually to be used, • providing an interface to the application layer related hardware. There is much freedom in defining object handling. The scope of the transfer layer mainly is the transfer protocol, i.e. controlling the framing, performing arbitration, error checking, error signalling and fault confinement. Within the transfer layer it is decided whether the bus is free for starting a new transmission or whether a reception is just starting. Also some general features of the bit timing are regarded as part of the transfer layer. It is in the nature of the transfer layer that there is no freedom for modifications. The scope of the physical layer is the actual transfer of the bits between the different nodes with respect to all electrical properties. Within one network the physical layer, of course, has to be the same for all nodes. There may be, however, much freedom in selecting a physical layer. The scope of this specification is to define the transfer layer and the consequences of the CAN protocol on the surrounding layers.