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:
lExplicit 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.
lI/O Assembly Messages are data structures usually sent on a timed cyclic basis. These are nor-
mally 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
movement. 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 mes-
sage.
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 con-
trol values may be changed within one message. For this reason, Explicit Messaging is better for con-
figuration 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
parameters 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 Mes-
sage 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
amplifier. Response messages can also display the actual position, commanded position, actual velocity
and torque.
6 Kollmorgen | December 2013
