Modbus RTU

The Modbus protocol is an open communication protocol that was developed in 1979 by the American company Gould-Modicon to allow programmable logical controllers to communicate with one another. Using Modbus, a master can exchange data with multiple slaves. In principle, each node can send messages via the bus but communication is usually initiated by the master.

In general, there are three Modbus variants:

• Modbus RTU
• Modbus ASCII
• Modbus TCP

Modbus RTU and ASCII use a serial interface (RS485 or RS232) as physical transmission layer; Modbus TCP uses Ethernet (TCP/IP).

Nanotec controllers with serial interface use Modbus RTU (Remote Terminal Unit) as protocol. Here, data are transferred in binary form. Data can thereby be transferred more quickly than with Modbus ASCII, though the data cannot be evaluated directly by people and must instead first be converted to a readable format. 

Using the standard function codes, Modbus controllers can access the preconfigured process data objects (PDO), the NanoJ objects and the “Plug & Drive interface.” In addition, it is possible to use the 2Bh function code (CAN encapsulation) to access the entire object dictionary of the controller. The Nanotec-specific “Plug & Drive interface” allows for direct and simple access to the most important parameters of the motor controller.

Nanotec offers motor controllers as well as brushless DC motors and stepper motors with integrated controller and Modbus RTU interface.