Distinction between Online and Offline

The distinction between online and offline refers to the presence of the actual I/O environment (drives, terminals, EJ-modules). If the configuration is to be prepared in advance of the system configuration as a programming system, e.g. on a laptop, this is only possible in “Offline configuration” mode. In this case all components have to be entered manually in the configuration, e.g. based on the electrical design.

If the designed control system is already connected to the EtherCAT system and all components are energised and the infrastructure is ready for operation, the TwinCAT configuration can simply be generated through “scanning” from the runtime system. This is referred to as online configuration.

In any case, during each startup the EtherCAT master checks whether the slaves it finds match the configuration. This test can be parameterised in the extended slave settings. Refer to note “Installation of the latest ESI-XML device description”.

For preparation of a configuration:

• the real EtherCAT hardware (devices, couplers, drives) must be present and installed
• the devices/modules must be connected via EtherCAT cables or in the terminal/ module strand in the same way as they are intended to be used later
• the devices/modules be connected to the power supply and ready for communication
• TwinCAT must be in CONFIG mode on the target system.

The online scan process consists of:

• detecting the EtherCAT device (Ethernet port at the IPC)
• detecting the connected EtherCAT devices. This step can be carried out independent of the preceding step
• troubleshooting

The scan with existing configuration can also be carried out for comparison.