EtherNet/IP

EtherNet/IP (Ethernet Industrial Protocol) is an Ethernet-based communications protocol for interfacing with Programmable Logic Controllers (PLCs) and Programmable Automation Controllers (PACs). This protocol permits devices to exchange digital I/O signal states as well as more complex, general numeric and string data values. EtherNet/IP was developed by Rockwell Automation and is now managed and maintained by ODVA (www.odva.org) as an open communications standard. This protocol is fully software and hardware compatible with common Ethernet-based local area networks.

When the EtherNet/IP software option is enabled, a Guidance Controller acts as a server that handles “explicit” and “implicit” communication requests from client or scanner devices (PLC's and PACs). “Explicit” requests are read and write operations that are triggered by specific commands in a remote PLC or PAC. Explicit requests bi-directionally transfer arrays of integer or floating point numeric data as well as string data. “Implicit” messages exchange the values of groups of digital input and output signals. Unlike explicit messages that are executed a single time, implicit messages are setup by the PLC or PAC to automatically transfer a fixed set of digital signal values at a regular interval. After initialization, the Guidance Controller will automatically send output DIO values to the PLC or PAC at a fixed repetition rate and expects to receive input DIO values from the PLC or PAC at (possibly a different) fixed repetition rate.

Using this protocol, remote clients (either PLCs or PACs) can perform the following operations:

Setup automatic, periodic bi-directional exchange of digital I/O values via implicit messages
Read or write numeric or string data on a Guidance Controller on demand via explicit messages

Activation and Status Information

Assuming the proper software licenses are installed on a Guidance Controller, EtherNet/IP can be enabled by setting the Database Parameter ID value defined in the following table. The table also describes values that can be accessed to obtain status information on the operation of this protocol.

Parameter Database ID	Parameter Name	Description
590	EtherNet/IP Enable	Set to 1 to enable operation of the EtherNet/IP server. Set to 0 to disable the server. If set to 1 in the configuration file stored on the flash, the server starts whenever the Guidance Controller is booted.
591	EtherNet/IP State, Open, Close, Timeout, Errors, DIO read, DIO write, Data read, Data write	An array of read-only values that show the current state of the EtherNet/IP server. The array elements are interpreted as follows: 1. Server enable state: 1 if enabled, 0 if disabled. 2. Number of implicit or explicit connections that have been opened. 3. Number of implicit or explicit client connections that have been closed. Subtract element 3 from element 2 to determine the number of connections currently open. 4. Number of connection timeouts that have occurred. 5. Number of connection errors that have occurred. 6. Number of implicit DIO messages that have been received. These are O2T (PLC to GPL) transfers. 7. Number of implicit DIO messages that have been sent. These are T2O (GPL to PLC) transfers. 8. Number of data read requests that have been received from the remote client (PLC). 9. Number of data write requests that have been received from the remote client (PLC).

In the following sections, the configuration and use of both implicit and explicit messages to exchange digital IO, numeric and string values are described.