几种现场总线的介质访问控制方式

工业生产对控制网络的实时性和可靠性具有很高的要求,而介质访问控制方式直接决定了网络的实时性和可靠性,现场总线的MAC层在很大程度上决定了网络的实时性与可靠性,可以说是现场总线系统的关键。阐述了几种现场总线标准的介质访问控制方式,分析了它们在网络轻载、重载时的性能。介绍了MAC层的两大体系:令牌环／令牌总线和CSMA／CD,并深入分析了PROFIBUS和LONWORKS的MAC层的实现方式,探讨了它们的优缺点。

Media Access Control Mode of Several Fieldbuses

Industrial production has very high requirement for the real - time behavior and reliability. The media access control protocol directly determines the real- time behavior and reliability of a fieldbus. The MAC layer largely determines the real - time behavior and reliability of a fieldbus, so it is said to be the key to the fieldbus. The MAC mode of four main fieldbus was discussed, then their function under light and heavy load were analyzed. There are two mam systems of MAC layer: token ring/token bus and CSMA/CD. Moreover, the methods of realizing MAC layer, which are used by PROFIBUS and LONWORKS were analyzed, their advantages and disadvantages were also discussed.