Ethernet/IP Communications | 3 Overview
3 Overview
EtherNet/IP is an industrial communication protocol based on TCP/IP and UDP/IP. It is used as 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:
l Explicit Messages are used for reading or writing values on-demand. Typically they are used 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. The AKD can be fully
configured using Explicit Messages.
l I/O Assembly Messages are data structures usually sent on a timed cyclic basis. These are normally
use for drive control and status. The data structure is predetermined and only certain values can be
read and written.
Typically, Explicit Messaging is used to configure the amplifier and I/O Assemblies are used to control move-
ment. Most PLC’s will support both types of messaging simultaneously.
Explicit Messages allow you to access a single parameter value at a time. The desired parameter is selected
by specifying the class object number, instance number and attribute number in an explicit message.
I/OAssembly 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.
The Position Controller Object and Position Controller Supervisor Objects are used to set the operational
mode (torque, velocity, or position), home, and configure motion.
Additional configuration may be done through the Parameter Object, which exposes vendor configuration para-
meters such as those accessible through Workbench.
Motion sequences may be pre-programmed into the amplifier using the AKD 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.
I/O Assembly Messaging is used for most motion control. Control bits in a command message are used to
enable the amplifier, do a controlled stop of the motor, initiate motion, and initiate stored motion block pro-
grams. Command messages can also set the target position, target velocity, acceleration, deceleration, and
torque set points. Status bits in a response message display error states and the general state of the amp-
lifier. Response messages can also display the actual position, commanded position, actual velocity and
torque.
6 Kollmorgen | December 2014
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