Beckhoff EK110x/EK15xx Coupling Guide

Passive terminals do not participate in active data exchange and do not consume E-bus current (such as EL9195). To ensure the integrity of the E-bus signal, it is not allowed to connect more than two passive terminals in series, and the passive terminals cannot be directly attached to the coupler for installation (at least one active terminal should be placed after the coupler). Incorrect placement can lead to unstable E-bus communication and even frame loss.

EtherCAT Communication Fundamentals and Port Allocation

4.1 Data Flow (Taking EK1100 as an Example)

EK1100 integrates EtherCAT Slave Controller (ESC) internally, with a total of 3 valid ports:

Port 0 (A): Physical input (X1 IN)

Port 1 (B): Internal E-bus output (connected to the right terminal chain)

Port 2 (C): Physical output (X2 OUT)

Processing sequence: frames enter from X1 IN → port 0 is sent to ESC for processing → data updates enter the terminal chain from port 1 → frames returned by the terminal chain return from port 1 to ESC → then leave from port 2 to the next device → finally return to the main station from X1 IN. Port 3 (D) is not in use and is considered closed.

4.2 EtherCAT State Machine (ESM)

Status abbreviation function

Init - No communication, initialize synchronization manager

Pre Operational Pre OP email communication available, no process data available

Safe Operational Safe OP: The input data is valid, and the output remains in a safe state

Operational OP normal input/output

Boot - Only used for FoE firmware updates

The corresponding states of the RUN LED of the coupler are: off=Init, flashing=Pre OP, single flash=Safe OP, constant light=OP, fast flashing=Bootstrap.

4.3 Distributed Clock (DC) Support

Partial couplers (EK1100 from firmware 06, EK1101 from firmware 01, EK1501 from firmware 01, etc.) support as DC reference clocks. It is necessary to manually select "Cyclic Mode Enable" and "Use as potential Reference Clock" in TwinCAT. If it is forcibly enabled without support, it will cause communication abnormalities.

Hot Connect and Fast Hot Connect (FHC)

5.1 Standard Hot Connect (EK1101, EK1501, EK1541)

Assign unique IDs to couplers and their subordinate terminal groups through a three digit hexadecimal dip switch (0-4095). EtherCAT master stations (such as TwinCAT) can dynamically add or remove this group during operation, achieving flexible production lines or interchangeable workstations. When configuring, the Group ID needs to be specified in System Manager.

5.2 Fast Hot Connect（EK1101‑0080）

Specially designed for tool quick change or modular robot workstations, with a connection recovery time of less than 1 second (standard Hot Connect takes several seconds). Mandatory requirement:

FHC ports can only connect to FHC ports (marked with special icons) and cannot connect to standard EtherCAT devices.

If misconnected, TwinCAT ADS Logger will report the error "invalid hot connect group" and require a power outage and restart.

Distributed clock (DC) cannot be used, otherwise it will prolong the synchronization time and lose the FHC advantage. Confirm that 'DC in use' is not selected in the Master settings.

The FHC group configuration method is the same as the standard Hot Connect, but the system will automatically recognize the FHC port (marked in red in TwinCAT).

Diagnostic LED Quick Check Table

All EK couplers have the following LEDs (see manual figures 60-62 for specific locations):

Meaning of LED color

Us green light: 24V power supply is normal

Up green light: Power contact 24V is normal

RUN green refers to the ESM status mentioned earlier

Link/ACT (X1 IN) green off: no connection; Always on: Connected; Flashing: Data transmission and reception

Link/ACT (X2 OUT) green as above, pointing to downstream devices

Link/ACT E-bus green out: no terminal or E-bus disconnection; Always on: Connected terminals; Flashing: in communication

Troubleshooting ideas for abnormal RUN or E-bus LED:

Us does not light up → Check the 24V input and fuse.

RUN keeps flashing (Pre OP) → The main station has not configured process data correctly or has not sent OP instructions.

E-bus LINK off → poor terminal contact or end not connected to EL9011 terminal cover plate.

Fiber coupler LINK/ACT does not light up → Check if the fiber is reversed (Tx → Rx), use a mobile phone camera to observe infrared light (EK1501 is 1300   nm invisible and requires an infrared detector; EK1541 is visible red light at 650nm.

Deep application of fiber optic and POF couplers

7.1 Optical Power Budget and Attenuation Calculation (Example EK1501/EK1521)

Taking EK1501 (multimode) and EK1521 with a distance of 2.1 km and using 50/125 μ m fiber as an example:

Minimum transmission power: -23.5 dBm

Receiver sensitivity: -31 dBm

Power budget=(-23.5) - (-31)=7.5 dB

Source of attenuation:

Fiber loss: 0.8 dB/km × 2.1 km=1.68 dB

SC connectors (2 pieces): 0.25   dB × 2=0.5   dB

Fusion point (3 pieces): 0.3   dB × 3=0.9   dB

Total attenuation=3.08 dB

Power margin=7.5-3.08=4.42 dB (>3 dB, safe)

Attention: EK1501-0010 (single-mode) will have an increased transmission power of -5 dBm, sensitivity of -35 dBm, and a power budget of 30 dB starting from 2023. It can cover a distance of 20 km.