Beckhoff EL3773 Documentation page 65

Colour Explanation
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 mas-
ter and slave/device and the device functions, if applicable. The physical device (firmware,
Note
if available) has to support the communication queries/settings of the master. This is back-
ward 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, ...
EL3773 Version: 2.5
Commissioning
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