CL3-E CANopen/USB/Modbus RTU Online Manual

Modbus RTU

The controller can be addressed by means of Modbus RTU and can function in an RS-485 network as a slave. In this chapter, the function codes of the Modbus communication structure are described.

Modbus references: www.modbus.org.

  • MODBUS APPLICATION PROTOCOL SPECIFICATION V1.1b3, Date: 26.04.2014, Version: 1.1b3
  • MODBUS over Serial Line Specification and Implementation Guide V1.02, Date: 20.12.2006, Version: 1.02

The I/O data with any preconfigured drive values (see Process data objects (PDO)) can be sent with the standard Modbus function codes. To configure your own I/O data, however, function code 2Bh (CAN Encapsulation) must be supported by the Modbus master in order for the parameters to be read and written independent of the process image.

If the master does not support this function code, the I/O image can be configured and stored using Plug & Drive Studio. The master can then access the data using the standard Modbus function codes.

Configuration via the configuration file is not otherwise possible (see chapter Configuration via USB).

RS-232 and RS-485

The "Two-Wire Modbus Interface" electrical interface is supported by the controller in accordance with standard EIA/TIA-485 (RS-485).

For a connection via RS-485, make certain that jumpers J1 and J2 are plugged in correctly (see chapter Jumper J1/J2 for further information). When using the RS-232 interface, the corresponding connector is to be used; no further configuration is necessary.

In principle, Modbus RTU can be operated with RS-232 and RS-485. An unused bus can be deactivated with object 2102h. Object 2103h indicates the active fieldbuses.

Modbus Modicon notation with PLCs

Many PLC devices use the Modicon addressing model. This notation is not used in the Modbus standard.

The following address notation is relevant for Nanotec controllers:

  • Input register 30001 - 39999 is mapped to Modbus telegram address 0 (0h) - 9998 (270Eh).
  • Holding register 40001 - 49999 is mapped to Modbus telegram address 0 (0h) - 9998 (270Eh).
Note: Where Modbus addresses are mentioned in the manual, it may be necessary to implement the register addresses in the PLC in accordance with Modicon notation.
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