Supported device types and versions
Communication line configuration
Communication line configuration
I/O tag configuration
Literature
Changes and modifications
Document revisions
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The 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.
The Ethernet/IP protocol is an adaptation of the Common Industrial Protocol (CIP) for the Ethernet bus.
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The communication was tested against Allen-Bradley Micro820 and against 1769 CompactLogix 5370 Controller.
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.
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Categeory of communication line:
- TCP/IP-TCP: standard port of Ethernet/IP procotol is 44818
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 event using a tell command STSTAT.
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Configuration line dialog box - tab Protocol parameters.
They influences some of the optional protocol parameters. The following line parameters can be set:
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| Key word | Full title | Description | Unit | Replacement value | ||||||
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| Read Wait Timeout | Waiting between individual reads of data from the communication if no data has been received.. | sec.mss | 0.010 | ||||||
| Send Delay | Waiting after sending one message. The purpose is not to overload the device with too many messages. Note: while testing Micro820 device, problems were encountered when sending approximately 200 messages (browsing instances of the class File Object [0x37] with zero delay. Waiting 1 ms solved the problem. | sec.mss | 0.001 | ||||||
| Write Symbolic: Array Elements | Methods of writing array using symbolic adressing (Rockwell). There are three supported modes:
| - | 0 .. Array Index | ||||||
| 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 protocol specified as Member ID). Note: the tested Micro820 device supported the optimization, testing software server did not. | - | False | ||||||
| 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 | ||||||
| Response Timeout | Timeout to receive 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 | ||||||
| Optimized Work with Symbolic Names | Optimization of work in a symbolic mode (Rockwell) - so-called Symbol Instance Addressing. Instead of using symbolic names, the 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 respective line is re-saved. | - | False |
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- Communication protocol: Ethernet/IP.
- Station address is not configured. Multiple stations may be configured on a single line (e.g. because of different time parameters of individual stations).
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Possible value types of I/O tag: Di, Ai, Ci, TxtI, TiR, TiA, Dout, Ao, Co, TxtO, ToR, ToA
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By clicking the Browse button, a browse dialog can be opened and a list of classes and instances within the class can be retrieved as long as the communication with the device is established. When opening, only a list of classes (rows with folder icon) are read for speed reasons. Double-click on a class retrieves a list of instances (if the number of instances was determined, i.e. it is not zero or unknown - "???"). Double-clicking on a specific instance (lines with the tag icon) copies the class and the instance to the configuration dialog of I/O tag.
Note 1: the number of actually retrieved class instances may be less than the number displayed within the list of classes.
Note 2: browsing attempts to read all instances of 1 .. Max Instance, where Max Instance is detected when reading a list of classes. However, if Max Instance > 1000, only the first 1000 instances are tested during browsing. Reading of all instances can take up to several tens of seconds. When it is finished, the folder icon is changed from closed to open.
Note 3: In versions from 20th December 2018 and newer, recycling of browser dialogue has been implemented. If the dialog is closed by the Close button or after selecting an instance, it is actually only hidden and it is available for browsing by another I/O tag within the same station so that the tree structure of the browsed objects is preserved. Clicking on the close icon at the top right corner will cause the dialog to be really closed.
The Refresh button is used to repeatedly retrieve the list from the device. The KOM process caches a list of classes and instances, so the second and subsequent opening of the browse dialog or reading of the list of instances for a specific class is significantly faster than the first one during which the data is being read from the device.
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Fragmented read - indicationthat the Read Tag Fragmented Service message should be used for reading, because the entire array does not fit into a message with the length specified by the Max Packet Size parameter.
Note: If the reading using Read Tag Service message returns an error code Partial Transfer [0x06], next reads will use the Read Tag Fragmented Service message as if the Fragmented read indication was set.
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Note: not all types of attributes from the offered list have read/write implemented. All numeric types, time types, strings (SHORT_STRING, STRING, STRING2) and numeric and time array types are supported. International string (STRINGI) type is supported for reading.
Array index - index of an element in array, if the attribute is an array. In Ethernet/IP protocol, an array is indexed from zero, so if Item count is equal to 3, indices 0, 1 and 2 are allowed.
Note: if Array index + 1> Item count, then Array index + 1 element will be read instead of Item count.
Bit (1..n) - if an attribute type is unsigned number (BOOL, USINT, UINT, UDINT, ULINT, DATE, TIME_OF_DAY, BYTE, WORD, DWORD, LWORD, ENGUNIT and arrays of these types) it is possible to enter a specific bit (1 to 64, depending on the number of bits for a specific type).
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- Active read - the I/O tag generates read requests.
- Passive read - the I/O tag does not generate read requests, but it processes values read by another I/O tag with the same Class/Instance/Attribute address or Symbolic name. This mode makes sense for reading arrays, where a single I/O tag can be active and the other I/O tags are passive, so values of all (or selected) array items are read with one request.
Note: the Ethernet/IP protocol supports the reading of arrays into the structure (Target tab), so it is possible to read the entire array into the column of a structure using a single I/O tag. - Write only - the I/O tag is intended only for writing.
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- Normal - writing to the I/O tag will cause the write request to be sent.
- Delayed - writing to the I/O tag will be deferred and executed only as part of the writing of another I/O tag with the same Class/Instance/Attribute address or Symbolic name.This mode makes sense for writing to arrays, when multiple array elements are written using deferred I/O tags, and then writing to a Normal I/O tag generates a single request to write a complete array.
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Literature
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THE CIP NETWORKS LIBRARY, Volume 1, Common Industrial Protocol (CIP™)
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RSLogix 500 Getting Results Guide, Rockwell Automation
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- Ver. 1.0 - November 28, 2018 - Creating of document.
- Ver. 1.1 - January 2, 2019 - Improved browsing, testing with 1769 CompactLogix 5370 Controller
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