Beckhoff EL6751 Documentation page 49

Online description
If the EtherCAT configuration is created online through scanning of real devices (see section Online setup)
and no ESI descriptions are available for a slave (specified by name and revision) that was found, the
System Manager asks whether the description stored in the device should be used. In any case, the System
Manager needs this information for setting up the cyclic and acyclic communication with the slave correctly.
Fig. 43: OnlineDescription information window (TwinCAT 2)
In TwinCAT 3 a similar window appears, which also offers the Web update:
Fig. 44: Information window OnlineDescription (TwinCAT 3)
If possible, the Yes is to be rejected and the required ESI is to be requested from the device manufacturer.
After installation of the XML/XSD file the configuration process should be repeated.
Changing the 'usual' configuration through a scan
ü If a scan discovers a device that is not yet known to TwinCAT, distinction has to be made between two
cases. Taking the example here of the EL2521-0000 in the revision 1019
a) no ESI is present for the EL2521-0000 device at all, either for the revision 1019 or for an older revision.
The ESI must then be requested from the manufacturer (in this case Beckhoff).
b) an ESI is present for the EL2521-0000 device, but only in an older revision, e.g. 1018 or 1017.
In this case an in-house check should first be performed to determine whether the spare parts stock al-
lows the integration of the increased revision into the configuration at all. A new/higher revision usually
also brings along new features. If these are not to be used, work can continue without reservations with
the previous revision 1018 in the configuration. This is also stated by the Beckhoff compatibility rule.
Refer in particular to the chapter 'General notes on the use of Beckhoff EtherCAT IO components' and for
manual configuration to the chapter 'Offline configuration creation' [} 52].
If the OnlineDescription is used regardless, the System Manager reads a copy of the device description from
the EEPROM in the EtherCAT slave. In complex slaves the size of the EEPROM may not be sufficient for the
complete ESI, in which case the ESI would be incomplete in the configurator. Therefore it's recommended
using an offline ESI file with priority in such a case.
The System Manager creates for online recorded device descriptions a new file
"OnlineDescription0000...xml" in its ESI directory, which contains all ESI descriptions that were read online.
EL6751
Parameterization and commissioning
NOTE
Version: 3.5 49