Providing OEM PLC libraries with license protection

Always query OEM license with FB_CheckLicense! The method described below can be used as a supplement to the query with FB_CheckLicense (not as an alternative method).

The license status must always be queried with FB_CheckLicense, as this is the only way to determine a secure current license status.

This license check with FB_CheckLicense is completely sufficient; it is not necessary (and therefore not recommended) to additionally enter the License GUID in the properties of the self-created library.

With the entry of the License GUID additionally in the properties of the self-created library, the TwinCAT 3 Runtime knows that this license is required for the project, and a first check of this license is performed when the runtime is started.

This first check takes place very early in the start-up phase of the TwinCAT Runtime. The EtherCAT bus is not started until later in the startup process, for example; the presence of an EL6070 License Key Terminal can therefore only be verified afterwards.

It is therefore very important to perform a license check with FB_CheckLicense in every case, after the complete system has been started (and thus the EtherCAT bus is in operation).

The status of all licenses is checked by the TwinCAT Runtime (after startup) during operation approx. every two minutes. This should be taken into account accordingly in the PLC program (e.g. no call of FB_CheckLicense in each PLC cycle).