The basic Modbus commands can instruct an RTU to change the value in one of its registers, control or read an I/O port, and command the device to send back one or more values contained in its registers.
基本的ModBus命令能指令一个RTU改变它的寄存器的某个值，控制或者读取一个I/O端口，以及指挥设备回送一个或者多个其寄存器中的数据。