FlexRay通信系统协议规范V2.1修订本A-第五章 媒体访问控制.pdf

FlexRay Protocol Specification Chapter 5: Media Access Control Chapter 5 Media Access Control This chapter defines how the node shall perform media access control. 5.1 Principles In the FlexRay protocol, media access control is based on a recurring communication cycle. Within one communication cycle FlexRay offers the choice of two media access schemes. These are a static time division multiple access (TDMA) scheme, and a dynamic mini-slotting based scheme. 5.1.1 Communication cycle The communication cycle is the fundamental element of the media access scheme within FlexRay. It is defined by means of a timing hierarchy. The timing hierarchy consists of four timing hierarchy levels as depicted in Figure 5-1. t communication cycle level static segment dynamic segment symbol window network idle time arbitration grid level static slot static slot minislot minislot action point action point action point macrotick level macrotick microtick level microtick Figure 5-1: Timing hierarchy within the communication cycle. The highest level, the communication cycle level, defines the