测量和控制用数字数据通信.工业控制系统用现场总线.弟2部分:物理层规范和服务定义

[中文适用范围]： 现场总线是一种数字串行、多点数据总线，用于与低级工业控制和仪表设备（例如传感器、执行器和本地控制器）进行通信。物理层提供数据链路的透明传输 [外文原描述]： Fieldbus is a digital serial, multidrop, data bus for communication with low-level industrial control and instrumentation devices such as transducers, actuators and local controllers. The Physical Layer provides for transparent transmission of Data Link Layer entities across physical connections. Specifies the requirements for Fieldbus component parts. Also specifies the media and network configuration requirements necessary to ensure agreed levels of: a) data integrity before Data Link error checking; b) interoperability between devices at the Physical Layer. The contents of the corrigendum of July 2004 have been included in this copy.