EL6731 by Beckhoff

The EL6731 is a PROFIBUS master terminal produced by Beckhoff within the EL EtherCAT Terminals series. Acting as a protocol gateway, it lets an EtherCAT controller address PROFIBUS-DP field devices directly from the I/O station, eliminating stand-alone gateways and reducing cabinet wiring. In automated lines, the terminal occupies one slot on the DIN rail and provides deterministic exchange of cyclic and acyclic data between the real-time EtherCAT network and subordinate PROFIBUS slaves.

The terminal connects to the bus through one 9-pin D-Sub socket, and the embedded PROFIBUS transceiver can transmit telegrams at up to 12 Mbit/s. Each slave on the segment can contribute a process data block of 244 bytes, and the EtherCAT side maps these blocks into a local image with a maximum capacity of 1.4 kB input and 1.4 kB output. The shortest allowed PROFIBUS cycle is 200 µs, which supports fast actuators and sensors without overloading the E-bus bandwidth. Status LEDs on the front panel provide visual diagnostics for the master state, telegram errors, and voltage supply, allowing faults to be isolated without external analyzers.

Galvanic separation between the field and logic domains is rated at 500 V, protecting the control electronics from ground loops on mixed-voltage machinery. The housing meets IP20 requirements and withstands ambient humidity of up to 95% without condensation. A PROFIBUS segment can include up to 125 slaves, and the EL6731 maintains address tables for the entire list while executing token passing internally. Because the module is supplied through the E-bus, no additional power wiring is needed. It snaps onto a 35 mm DIN rail, and its variable installation position allows the LEDs to remain visible inside compact enclosures. One fieldbus channel handles all traffic, and the terminal accepts any mounting orientation permitted by the cabinet airflow profile.