Overview of EtherNet/IP

EtherNet/IP is an industrial communication protocol based on TCP/IP and UDP/IP. It is used as a high level network for industrial automation applications. EtherNet/IP shares a common data structure with DeviceNet® and ControlNet®, but built on Ethernet as a physical medium. The protocol uses two communication channels:

Explicit
Messages

The AKD2G supports parameter access using Explicit Messaging.

Explicit Messages are used for reading or writing values on-demand, for drive configuration, and occasional reads or writes of parameter values. Communication rates depend on the particular parameter or command, and can range from approximately 5ms to 5s.

Explicit Messages allow access to a single parameter value at a time independent of cyclic messaging and the I/O Assemblies. The desired parameter is selected by specifying the class object number, instance number, and attribute number in an explicit message.

I/O Assembly Messages

I/O Assembly Messages are data structures usually sent on a timed cyclic basis for drive control and status.

I/O Assembly Messaging is used for most motion control. There are three possible I/O Assembly data structures: Standard, Free Mapping, and CIP Sync. The I/O Assembly data structure is predefined for the Standard and CIP Sync assemblies and undefined (user-configurable) for the Free Mapping Assemblies. Only one assembly connection can be made to a specific AKD2G-SPI node (i.e., Standard and Free Mapping or CIP Sync and Free Mapping cannot be used simultaneously with the same drive).


  • I/O Assembly Messages and Explicit Messages may be used simultaneously.

Typically, Explicit Messaging is used to configure the amplifier and I/O Assemblies are used to control movement. Most programmable logic controllers (PLCs) will support both types of messaging simultaneously. Check the documentation for your controller to determine which messaging types are supported.

I/O Assembly Messages combine many control and status bits into command and Response Messages. They are less versatile than Explicit Messages (only certain parameters are accessible), but several control values may be changed within one message. For this reason, Explicit Messaging is better for configuration and I/O Assembly Messaging is better for motion control.

  • Standard Assembly only: 
    • The Position Controller Object is used to set the operational mode (torque, velocity, or position), home, and configure motion.
    • Motion sequences may be pre-programmed into the amplifier using the AKD2G motion tasking feature. Once the Motion Task sequence has been configured, it may be executed with the Command Assembly Message Block Number field and Start Block bit.
  • Additional configurations over EtherNet/IP can be made using the Parameter Object which provides access to drive parameters, including parameters accessible through WorkBench.