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Ethernet/IP Protocol

Ethernet/IP Protocol

okt 20, 2020

Supported device types and versions 
Communication line configuration
Communication line protocol parameters
Communication station configuration
Station protocol parameters
I/O tag configuration 
Literature
Changes and modifications
Document revisions

Supported device types and versions

 

Ethernet/IP protocol is one of the most widespread communications protocols in the US designed for communication with PLCs, motors, and other process-level devices. The protocol is managed and developed by ODVA, which includes companies such as Rockwell, Honeywell, or Schneider Electric.

Ethernet/IP protocol is an adaptation of the Common Industrial Protocol (CIP) for the Ethernet bus.

Implementation in D2000 supports:

  • communication via TCP

  • explicit messages (request/response type of communication)

  • standard addressing of objects (Class/Instance/Attribute)

  • symbol addressing of objects (proprietary Rockwell implementation)

  • optimization of symbol objects addressing - so-called Symbol Instance Addressing

Implementation in D2000 does not support:

  • communication via UDP

  • implicit messages (I/O messaging)

The communication was tested with:

  • Allen-Bradley Micro820 

  • 1769 CompactLogix 5370 Controller (1769-L18ER/A)

  • ControlLogix EtherNet/IP bridge Module (1756-EN2TR/C) connected to 1756-L85E ControlLogix 5580 Controller (1756-L85E/B)

Note: The Micro820 firmware version 6 only partially supported work with symbol addresses. Reading and writing worked, but browsing didn't - there was no class Symbol Object [0x6b]. Firmware version 10.0.12 supported browsing.
Note: CompactLogix 5370 supported work with symbol addresses, browsing as well as optimization of work in symbolic mode using Symbol Instance ID.

 

Communication line configuration

Category of communication line: TCP/IP-TCP

  • TCP parameters - server parameters are mandatory:

    • Host: server name in form of INET (name or numerical address a.b.c.d). In the case of redundant systems, multiple names/addresses separated by commas can be entered.

    • Port: TCP port number (0..65535). The standard port of Ethernet/IP protocol is 44818

    • Line number: unused, set to 0

Note: if all of the stations are in StOFF mode on a TCP/IP-TCP line, the TCP connection will be closed. Thus it is possible to control TCP communication from the event using a STSTAT tell command.

Communication line protocol parameters

 

Configuration line dialog box - tab Protocol parameters.
They influence some of the optional protocol parameters. The following line parameters can be set:

 

Table 1

Keyword

Full title

Description

Unit

Replacement value

RT

Read Wait Timeout

Waiting between individual reads of data from the communication if no data has been received..

sec.mss

0.010

SD

Send Delay

Waiting after sending one message. The purpose is not to overload the device with too many messages.
Note: while testing the Micro820 device, problems were encountered when sending approximately 200 messages  (browsing instances of the class File Object [0x37] with zero delay. Waiting for 1 ms solved the problem.

sec.mss

0.001

SE

Write Symbolic: Array Elements

Methods of writing array using symbolic addressing (Rockwell). There are three supported modes:

  • 0 .. Array Index + Item Count: all the elements defined for a particular point are written (Array Index+1 or Item Count, whichever is greater)

  • 0 .. Array Index: minimalistic variant - elements from 0 to Array Index are written

  • 0 .. Max Array Index: maximalist variant - entries from 0 to Max Array Index are written, where Max Array Index is the largest number of elements of all I/O tags with the same symbolic address (within the station)

-

0 .. Array Index

OW

Optimized write of array element

Optimized write is used when only one array element is written. Optimization consists of writing only one specific element and specifying its index (in the protocol specified as Member ID).
Note: the tested Micro820 device supported the optimization, the test software server did not.

-

False

MP

Max Packet Size

The maximum size of Ethernet/IP messages (Unconnected Explicit message) - according to the standard 504 bytes.
Note: in symbolic mode (Rockwell) it is also possible to work with larger arrays using proprietary services Read Tag Fragmented Service and Write Tag Fragmented Service.

Bytes

504

RS

Response Timeout

Timeout to receive an answer for a request. If the response for a request is not received within this time, this is considered an error, and the TCP connection will be closed.

sec.mss

10.000

SO

Optimized Work with Symbolic Names

Optimization of work in a symbolic mode (Rockwell) - so-called Symbol Instance Addressing. Instead of using symbolic names, a Symbol Instance ID is used for reading. The Symbolic name is converted to the Instance identifier by the same service which is used for browsing.
Note: Not every device or Rockwell firmware version supports this optimization (tested Micro820 with firmware 10.0.12 or 11.0.11 did not support this optimization). In this case, if the device returns the Service not supported [0x08] error code, the optimization will be disabled until the KOM process is restarted or the configuration of the respective line is re-saved.

-

False