Operation of ELM3xxx on EKxxxx/CX7xxxx as EtherCAT-to-X gateway

EtherCAT Terminals (slaves, SubDevice) such as ELM3xxx require an EtherCAT master (MainDevice) in order to be operated in a system.

In order to operate ELM3xxx terminals on fieldbuses other than EtherCAT (e.g. Profibus, ProfiNET, Ethernet/IP etc.), Beckhoff offers two options for such an EtherCAT-to-X gateway

1. Use of a programmable IPC that includes an EtherCAT master
   Advantage: the IPC must/can be programmed individually via TwinCAT, can manipulate the data as required and exchange it with the respective fieldbus in an application-specific manner.
• IPC devices: Cxxxx require EtherCAT Terminals on the EtherCAT Coupler and fieldbus interface as EL6xxx fieldbus terminal or built into the IPC
• Embedded PC of the CX series: with corresponding fieldbus interface on the left or right as EL6xxx fieldbus terminal
2. Using non-programmable bus couplers with EtherCAT master for EtherCAT Terminals
   The EKxxxx (non-programmable, e.g. EK9000, EK3100, etc.) and CX7xxx (small controller, programmable, e.g. CX7031, CX7051, etc.) series bus couplers enable EtherCAT Terminals to be operated on various fieldbus systems. The EKxxxx Bus Couplers are fieldbus slaves and contain an independently operating EtherCAT master for the EtherCAT Terminals. They convert the telegrams from the higher-level fieldbus systems into the E-bus signal representation. A station then consists of an EKxxxx / CX7xxx and a number of EtherCAT Terminals attached to it. The EKxxxx for EtherCAT Terminals are integrated in the same way as the BKxxxx series bus couplers for KL terminals via the corresponding fieldbus system configuration tools and the associated configuration files, such as GSD, ESD or GSDML.

Devices in the second group generally offer reduced support for EtherCAT functions compared to a "normal" TwinCAT 3, as used in devices in the first group. In particular, the DistributedClocks (DC) function is generally not supported (see respective documentation), but attached terminals are operated in SM-synchronous mode "frame-triggered" or FreeRun.

ELM3xxx devices can offer up to 3 operation modes, see also chapter Time operation modes, basics:

• due to the high time accuracy usually required in measurement technology, they prefer to work in DC mode, with or without oversampling
• alternatively, the SM-synchronous mode is available for cases where the EtherCAT master does not support DC, but this requires EtherCAT frames with low jitter for permanently successful synchronization, especially if oversampling is used
• in order to be able to use the high measurement quality of the ELM3xxx devices even for non-time-critical measurement tasks with low-cost EtherCAT masters, FreeRun support (without oversampling, i.e. oversampling = 1) is continuously retrofitted to the ELM3xxx Terminals in firmware updates.