Change management by Beckhoff

Beckhoff reserves the right to change all three elements for itself and unannounced during the product lifetime in order

to introduce functional improvements and
to implement new functions

Such a change by Beckhoff

is then usually marked by a changed HW/FW/revision version.
takes place in such a way that the Beckhoff EtherCAT IO compatibility rule can be adhered to in existing applications:
device revision in the system >= device revision in the configuration
Background: 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 (including firmware, if available) has to support the communication queries/settings of the master. This is the case downwardly compatible, i.e. newer devices (higher revision, higher firmware version, higher hardware version) should also support it if the EtherCAT master addresses them as an older revision due to an existing configuration. This permits the later swapping/replacement of devices if necessary without changing the configuration, i.e. without access to the application files.
Sample: If the configuration provides for an EL2521-0025-1018 EtherCAT terminal (i.e. revision -1018), then a terminal that is programmed as an EL2521-0025-1018 or higher (- 1019, -1020) can be used as a real IO device. Higher revision also means in many cases a newer firmware version, but at least the same firmware version on the part of Beckhoff production.
For Beckhoff and the user this means that the further developed or changed edition of an EtherCAT IO product with incremented hardware, firmware or revision version should support all of the properties and features of the predecessor products with a lower FW or revision version.

	ESI device descriptions with revision history The ESI-XML files (zipped) offered for downloading on the Beckhoff website contain almost all EtherCAT devices ever published together with their complete revision history. The user thus has the possibility to deliberately integrate predecessor revisions in his configuration.

	Beckhoff ESI device descriptions, compatibility From the IO compatibility rule it follows that, even if the default process data have been changed with regard to the predecessor model in a newer firmware/revision, this device can nevertheless still be converted via the PDO setting (e.g. PredefinedPDOsettings) to the "old" process data or should at least "understand" them, because the new firmware/revision ought to support them without fail. The respective device documentation provides assistance with this on the process data page.