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IgH EtherCAT Master - Frequently Asked Questions


I'm trying to establish communication with a slave, but the configuration fails. What can I do?

There are almost definitely information missing in the "Slave Information Interface" (SII) of your slave. Unfortunately, some slave vendors aren't aware, that they have to provide their slaves' SII with nearly the same information as in the slave device description XML files (see table below). An EtherCAT Master / configuration tool can determine the slave configuration by reading out the SII or by using the XML Device Description.

For example, the "SyncManager" category is inevitable for the master to know the physical addresses of the sync managers to configure the PDO mapping and the PDO exchange. The below table is an excerpt of the EtherCAT Knowledge Base (chapter EtherCAT Technology Description / EEPROM / SII), defining which information is optional (O), and which is mandatory (M).

Device Types No Process Data, Mailbox Fixed Process Data, No Mailbox Fixed Process Data, No Object Dictionary Fixed Process Data, Object Dictionary Variable Process Data, Object Dictionary
Info Structure
(128 Byte)
ESC Info MMMMM
Identity MMMMM
Bootstrap Mbx Info OOOO
Standard Mbx Info MMMM
Categories Strings (10) OOOOO
General (30) MMMMM
SyncManager (41) OMMMM
FMMU (40) OOOOM
PDO (50, 51) MMO (same as OD)

A quick solution for the missing information is to generate the SII contents from the slave description XML file using Beckhoff's TwinCAT, and write them to the slave. This is actually the task of the vendor, an you should tell him to do so in the future! Add the slave to a new project, then select "EtherCAT", "Advanced settings", "ESC Access", "EĀ²PROM", "Hex Editor", "Save to file...". There is an issue, when the EEPROM size in the XML file is wrongly specified too small, TwinCAT won't export the category data. Try increasing the value in the slave configuration XML and repeating the export in that case.

You can the write the SII contents file to the slave using the EtherCAT master (from version 1.4):

ethercat sii_write -pslave-position file

Before version 1.4:

cp file /sys/ethercat/masterX/slaveslave-position/sii

Please let the master scan the bus again after doing so.


Revision 6fdeefb550fa, last changed by fp, 2018/04/03 13:37:52