什么是现场总线？
现场总线（Fieldbus）是20世纪80年代末、90年代初国际上发展形成的，用于现场总线技术过程自动化、制造自动化、楼宇自动化等领域的现场智能设备互连通讯网络。它作为工厂数字通信网络的基础，沟通了生产过程现场及控制设备之间及其与更高控制管理层次之间的联系。它不仅是一个基层网络，而且还是一种开放式、新型全分布控制系统。这项以智能传感、控制、计算机、数字通讯等技术为主要内容的综合技术，已经受到世界范围的关注，成为自动化技术发展的热点，并将导致自动化系统结构与设备的深刻变革。现场总线设备的工作环境处于过程设备的底层，作为工厂设备级基础通讯网络，要求具有协议简单、容错能力强、安全性好、成本低的特点：具有一定的时间确定性和较高的实时性要求，还具有网络负载稳定，多数为短帧传送、信息交换频繁等特点。由于上述特点，现场总线系统从网络结构到通讯技术，都具有不同上层高速数据通信网的特色。
目前国际上有40多种现场总线，但没有任何一种现场总线能覆盖所有的应用面，按其传输数据的大小可分为3类：传感器总线（sensorbus），属于位传输；设备总线（devicebus），属于字节传输；现场总线，属于数据流传输。下面让我一起去认识主要的几种总线。
PPC322BE
What is a fieldbus?
Fieldbus (Fieldbus) is the international development in the late 1980s and early 1990s, which is used for field intelligent equipment interconnection communication network in the field of fieldbus technology process automation, manufacturing automation, building automation and other fields. It is the basis of the digital communication network of the factory, which communicates the connection between the production process site and the control equipment and the higher control management level. It is not only a basic network, but also an open and new fully distributed control system. This integrated technology with intelligent sensing, control, computer, digital communication and other technologies as the main content has received worldwide attention, become a hot spot in the development of automation technology, and will lead to profound changes in the structure and equipment of automation systems. The working environment of fieldbus equipment is at the bottom of the process equipment. As a basic communication network at the factory equipment level, it requires simple protocol, strong fault tolerance, good security and low cost. It has certain time certainty and high real-time requirements, and it also has the characteristics of stable network load, mostly short frame transmission and frequent information exchange. Because of the above characteristics, the fieldbus system has the characteristics of different high speed data communication networks from the network structure to the communication technology.
At present, there are more than 40 kinds of fieldbuses in the world, but no fieldbus can cover all applications, according to the size of its transmission data can be divided into three categories: sensorbus (sensorbus), which belongs to bit transmission; Device bus (devicebus), which belongs to byte transmission; Fieldbus, which belongs to data stream transmission. Let me go to know the main bus.