BECKHOFF ET2000 - Manual (Page 14)

Product overview
Fig. 7: From the ET2000 appended additional data in the ESL (EtherCAT Switch Link) protocol
Constitution of the16 additional bytes of data
The 16 byte additional data of the ET2000 have the following meaning (in serialization), see Fig. "From the
ET2000 appended additional data in the ESL (EtherCAT Switch Link) protocol":
6 Byte Identifier 01 01 05 10 00 00 (symbolic IP address)
1 Byte Port designation 0 ..7 of arriving frame
1 Byte Bit 0..2 reserved, bit 3: CRC error in recorded
frame
8 Byte Timestamp in ns (accuracy: 10 ns) ­
x000003EF4FDB83E0 (reading direction
backwards)
Note
ET2000 extensions
This is not a final description. Future development can cause a modification of the constitu­
tion of the additional data. In this case a corresponding version of the "ethercat.dll" will be
provided on the Beckhoff website (http://www.beckhoff.com)
Note
Compensation of the minimal Ethernet frame length
If there are only little process data in the EtherCAT protocol, e.g. in a small network with
only a few participants, the rate of the user data is correspondingly low. Therefore, the
EtherCAT frame is filled up with dummy bytes (x00) between the regular end of the frame
and the ET2000 extension (16 bytes), to reach the minimal Ethernet frame length.
Analysing EtherCAT datagrams
Fig. "Screenshot of a Wireshark recording" shows a log of EtherCAT frames from the TwinCAT EtherCAT
master. Frame 348 is highlighted, and its content is broken down in the fields underneath. In the lower
section of the central window, the EtherCAT datagrams contained in frame 348 are broken down with
explanations.
ET2000 14 Version 2.0