Modbus 协议是应用于电子控制器上的一种通用语言。通过此协议，控制器相互之间、控制器经由网络（例如以太网）和其它设备之间可以通信。它已经成为一通用工业标准。有了它，不同厂商生产的控制设备可以连成工业网络，进行集中监控。此协议定义了一个控制器能认识使用的消息结构,而不管它们是经过何种网络进行通信的。它描述了一控制器请求访问其它设备的过程，如果回应来自其它设备的请求，以及怎样侦测错误并记录。它制定了消息域格局和内容的公共格式。当在一Modbus网络上通信时，此协议决定了每个控制器须要知道它们的设备地址，识别按地址发来的消息，决定要产生何种行动。如果需要回应，控制器将生成反馈信息并用Modbus 协议发出。在其它网络上，包含了 Modbus 协议的消息转换为在此网络上使用的帧或包结构。这种转换也扩展了根据具体的网络解决节地址、路由路径及错误检测的方法。-Modbus protocol is a universal language applied on electronic controller. Through this agreement, between the controller, the controller can communicate via the network (such as Ethernet) and other devices. It has become a common industry standard. With it, different manufacturers of industrial control devices can be connected into a network, centralized monitoring. This protocol defines a message structure that controllers use to recognize, regardless of what network they are communicating. It describes the process a controller requests access to other equipment, if the response to the request　other devices, as well as how errors are detected and recorded. It developed a message domain structure and content of a common format. When the communication on a Modbus network, the protocol determines how each controller will know its device address, recognize a message addressed to it, decide what action to produce. If you need to respond, the controller will generate and send feedback info