链路层

[中文适用范围]： 本 SAE 推荐实践详细介绍了智能交通系统 (ITS) 数据总线的链路层，该总线通常供车载使用。 ITS 数据总线 (IDB) 是一种非专有令牌传递总线，旨在允许不同的消费者、车辆和商业电子组件通过标准的开放数据总线进行通信和共享信息。 IDB 的第一个版本称为 IDB-C。本推荐实践描述了 IDB-C 的链路层，如第 1 节所示。IDB-C 链路层下方是 CAN 2.0B 链路层。 IDB-C 的物理层合并了 SAE J2366-1 和 J2590 指定的物理层。 IDB-C链路层在逻辑上分为两个功能子层，即逻辑链路控制（LLC）和媒体访问控制（MAC）。然而，这些逻辑分组会重复使用 CAN 2.0B 帧中的一些相同位以提高效率。 [外文原描述]： This SAE Recommended Practice details the Link Layer of the Intelligent Transportation Systems (ITS) Data Bus, which is generally intended for in-vehicle use.The ITS Data Bus (IDB) is a non-proprietary token passing bus, designed to allow disparate consumer, vehicle, and commercial electronic components to communicate and share information across a standard, open data bus. This first version of the IDB is called IDB-C.This Recommended Practice describes the Link Layer of the IDB-C, as shown in Section 1 . Below the Link Layer of the IDB-C is the CAN 2.0B Link Layer. The Physical Layer of the IDB-C incorporates the Physical Layer as specified by SAE J2366-1 and J2590.The IDB-C Link Layer is logically divided into two functional sub-layers, viz., Logical Link Control (LLC) and Media Access Control (MAC). However, these are logical groupings that re-use some of the same bits within the CAN 2.0B frame for efficiency.The MAC sub-layer handles all media access functions, such as virtual token handling, addressing, and notifications of IDB-C configuration changes to other MAC layers on the IDB-C.The LLC sub-layer provides the mechanisms to send and receive point-to-point or broadcast frames to other LLC sub-layers on the IDB-C. In addition, the LLC provides an Alternate Transport Identifier (ATID) allowing more than one set of higher layer protocols to be used on a single Node.Cross Reference: CAN Specification, Version 2.0B,CANSpecificatio,ISO7498:1990,J2355,J2366-1,J2366-4,J2366-7,J2366/1,J2366/4,J2366/7,J2590