MODBUS协议简述及通讯应用格式详解。MODBUS协议只允许在主机（PC，PLC等）和终端设备之间通讯，而不允许独立的终端设备之间的数据交换，这样各终端设备不会在它们初始化时占据通讯线路，而仅限于响应到达本机的查询信号。-MODBUS protocol format Detailed Descr iption and communications applications. MODBUS protocol allows only the host (PC, PLC, etc.) and communication between terminal equipment, and does not allow independent data exchange between terminals, so that the terminal does not occupy the communication line when they are initialized, but only limited response to a query signal to reach the machine.