工业物联网OSI参考模型

软件接口	            OPC
应用层	              ModBus
数据链路层	          CAN，ProfiBus
物理层	              RS232，RS485

OPC服务器

OPC SERVER = OPC驱动器

OPC

简单来说，OPC是一套标准，其目的是把PLC特定的协议（如Modbus，Profibus等）抽象成为标准化的接口，作为“中间人”的角色把通用的OPC“读写”请求转换成具体的设备协议来与HMI/SCADA系统直接对接

When the standard was first released in 1996, its purpose was to abstract PLC specific protocols (such as Modbus, Profibus, etc.) into a standardized interface allowing HMI/SCADA systems to interface with a “middle-man” who would convert generic-OPC read/write requests into device-specific requests and vice-versa.