西门子S7-300 /400 等具有Profibus 接口的PLC 在工业控制系统的应用越来越广泛，而老的智能仪表和传感 器多数只有Modbus 接口，要实现数据通信，需要进行协议转换。设计了一种Modbus-RTU 与Profibus-DP 协议转换网关，并 对电源管理模块、处理器模块、Profibus-DP 从站模块、RS485 通信模块和软件设计流程图进行了重点阐述。

Siemens S7-300/400 PLC has Profibus interface and applies in industrial control field widely. Normal intelligent instruments and sensors only have Modbus interface and must convert the protocol for data communication. The paper designs a Modbus- RTU to Profibus-DP gateway and introduces design schemes of power module, processor module, Profibus-DP substation module, RS485 communication module and software.