Beckhoff EL6751 Documentation page 63

Colour Explanation
green This EtherCAT slave matches the entry on the other side. Both type and revision match.
blue This EtherCAT slave is present on the other side, but in a different revision. This other
revision can have other default values for the process data as well as other/additional
functions.
If the found revision is higher than the configured revision, the slave may be used provided
compatibility issues are taken into account.
If the found revision is lower than the configured revision, it is likely that the slave cannot be
used. The found device may not support all functions that the master expects based on the
higher revision number.
light blue This EtherCAT slave is ignored ("Ignore" button)
red • This EtherCAT slave is not present on the other side.
• It is present, but in a different revision, which also differs in its properties from the one
specified.
The compatibility principle then also applies here: if the found revision is higher than the
configured revision, use is possible provided compatibility issues are taken into account,
since the successor devices should support the functions of the predecessor devices.
If the found revision is lower than the configured revision, it is likely that the slave cannot
be used. The found device may not support all functions that the master expects based on
the higher revision number.
Device selection based on revision, compatibility
The ESI description also defines the process image, the communication type between master and
slave/device and the device functions, if applicable. The physical device (firmware, if available) has
to support the communication queries/settings of the master. This is backward compatible, i.e.
newer devices (higher revision) should be supported if the EtherCAT master addresses them as an
older revision. The following compatibility rule of thumb is to be assumed for Beckhoff EtherCAT
Terminals/ Boxes/ EJ-modules:
device revision in the system >= device revision in the configuration
This also enables subsequent replacement of devices without changing the configuration (different
specifications are possible for drives).
Example:
If an EL2521-0025-1018 is specified in the configuration, an EL2521-0025-1018 or higher (-1019, -1020) can
be used in practice.
Fig. 75: Name/revision of the terminal
If current ESI descriptions are available in the TwinCAT system, the last revision offered in the selection
dialog matches the Beckhoff state of production. It is recommended to use the last device revision when
creating a new configuration, if current Beckhoff devices are used in the real application. Older revisions
should only be used if older devices from stock are to be used in the application.
In this case the process image of the device is shown in the configuration tree and can be parameterised as
follows: linking with the task, CoE/DC settings, plug-in definition, startup settings, ...
EL6751
Parameterization and commissioning
Version: 3.5 63