EtherCAT
EtherCAT is an open, high performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times (also called cycle times) with low communication jitter (for synchronization purposes) and low hardware costs. The EtherCAT protocol is optimised for process data and is transported directly within the standard IEEE 802.3 Ethernet frame using Ethertype 0x88a4. It may consist of several sub-datagrams, each serving a particular memory area of the logical process images that can be up to 4 gigabytes in size. The data sequence is independent of the physical order of the nodes in the network; addressing can be in any order. Broadcast, multicast and communication between slaves are possible. If IP routing is required, the EtherCAT protocol can be inserted into UDP/IP or TCP/IP datagrams. This also enables any control with Ethernet protocol stack to address EtherCAT systems.
History
Protocol dependencies
Example traffic
Frame 1 (128 bytes on wire, 128 bytes captured)
Ethernet II, Src: MS-NLB-PhysServer-14_a6:c9:01:8e (02:0e:a6:c9:01:8e), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
EtherCAT frame header
.... .000 0111 0000 = Length: 0x0070
.... 0... .... .... = Reserved: Valid (0x0000)
0001 .... .... .... = Type: EtherCAT command (0x0001)
EtherCAT datagram(s): 'LRW': Len: 100, Adp 0x0, Ado 0x1, Wc 2
EtherCAT datagram: Cmd: 'LRW' (12), Len: 100, Addr 0x10000, Cnt 2
Header
Command : Logical memory read write (0x0c)
Index : 0x39
Log Addr : 0x00010000
Length : 100 (0x64) - No Roundtrip - Last Sub Command
.... .000 0110 0100 = Length: 100
..00 0... .... .... = Reserved: Valid (0)
.0.. .... .... .... = Round trip: Frame is not circulating (0)
0... .... .... .... = Last indicator: Last EtherCAT datagram (0)
Interrupt : 0x0000
Data : 000000000000000000000000000000000000000000000000...
Working Cnt: 2
Wireshark
Preference Settings
There are no EtherCAT specific preference settings. Allowing sub dissectors to handle data based on heuristic analysis is always enabled and cannot be turned off.
Sub dissectors
Dissectors that are interested in dissecting the EtherCAT datagram portion of the EtherCAT frame (there may be multiple EtherCAT datagrams in each frame), may do so using heuristic analysis by registering themselves using the function heur_dissector_add("ecat.data", ...).
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Example capture file
Capture of startup sequence for some Beckhoff devices.
Display Filter
A complete list of IP display filter fields can be found in the display filter reference
- Show only the EtherCAT based traffic:
ecat
Filter on a specific address offset (ado):ecat.ado == 0x130
Filter on a specific slave by its position or fixed EtherCAT address (adp):ecat.adp == 0x3e9
Filter on a specific cmd (here APRD):ecat.cmd == 0x1
Filter on a specific field of a sub command :ecat.sub1.idx < 0x80
Show only the EtherCAT mailbox traffic:ecat_mailbox
Capture Filter
- Capture Ethercat-over-Ethernet traffic only:
ether proto 0x88a4
Capture Ethercat-over-UDP traffic only:udp port 0x88a4
External links
More information about EtherCAT can be found on the website of the EtherCAT Technology Group:http://www.ethercat.org/
Open-source EtherCAT driver can be found at http://ethercatmaster.berlios.de/ (no longer available - April 2010)
IgH EtherCAT Master for Linux can be found at http://www.etherlab.org/en/ethercat/index.php
Discussion
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General
- HowToEdit: Information about how to edit the Wireshark wiki
- SampleCaptures: Sample capture files for your edification and amusement
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Prepare Wireshark / TShark
- BuildingAndInstalling: Building and Installing Wireshark
- CaptureSetup: How to setup your network to successfully capture packets
- CaptureSetup/Ethernet: Discusses capturing on switched Ethernet networks
- CaptureSetup/WLAN: Frequently asked WLAN capture setup info
Use Wireshark / TShark
Things not (yet) part of the Wireshark User's Guide.
- CaptureFilters: A collection of capture filter examples
- DisplayFilters: A collection of display filter examples
- ColoringRules: A collection of coloring rules examples
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- Timestamps: Accuracy, precision, and resolution
- Tools: tools and scripts that relate to the use of Wireshark and TShark
References
- ProtocolReference: Reference for network protocols
- Display Filter Reference: comprehensive list of all valid display filter fields
- FileFormatReference: Wireshark's read/write support of (foreign) capture file formats
- SwitchReference: Notes on using particular switch models for capture
- HubReference: Notes on using particular hub models for capture
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Interesting starting points
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Q and A
Q1)I installed Wireshark v1.4.3
When I tried to capture EtherCAT packet from my Realtek NIC, I can not see the EtherCAT packet.
I only can capture DHCP protocol packet.
Should I have to config other option to capture EtherCAT packet?
Q2)Hello i have a similiar problem. I cant capture ethercat messages. I am connecting to a beckhoff i/o module(EK1100) using a cross network cable. I use Twincat program for ethercat master protocol. There is no problem with the operation of the device. On same pc i use wireshark to monitor messages.
The program has two modes: run and config mode. I can capture an ethercat message which shows the switching between modes but when input and output values change i can not get a message. In twincat program i can see what has changed. I did not change anythin in wireshark and i have all the plugins, i use version 1.4.3. I could notunderstand what is going on any help will be helpful.
2 Answers:
According to http://www.ethercat.org/en/technology.html#3.1, EtherCAT uses either Ethertype 0x88A4 or UDP port 0x88A4. And at the link layer, it's just ethernet.So you don't have to do anything special to be able to capture EtherCAT packets. Take a look at http://wiki.wireshark.org/CaptureSetup/Ethernet for information on how to capture in different setups.
Regarding dissecting of the EtherCAT frame, it's done in a separate plugin, have you installed all the plugins that came with Wireshark?
I am sure I already installed ethercat plugin for wireshark.
I can see ethercat.dll in Wiresharkplugins1.4.3 directory.
I don`t know why this problem happened to me.
Does anyboy has another idea?
(16 Feb '11, 23:00)Younghyun Jo
(I converted your "answer" to a "comment" to adhere to the Q&A nature of this site)
Is the PC you are capturing on communicating over EtherCAT itself? If not, did you enable "promiscuous mode"? How is your capturing PC connected to the network that transfers EtherCAT messages? Did you check the CaptureSetup link I mentioned earlier?
(17 Feb '11, 00:35)SYN-bit ♦♦
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Hello, i have come across the same problem. I have found the solution in the Slave Implementation Guide. The steps below are the solution.
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