Beckhoff BK1120/BK1250 EtherCAT Coupling Debugging and KL Terminal Parameterization Complete Guide

If you need to write protection registers (R32-R47), you need to first write register 31 as 0x1235 (code word). Set through 0x4280:20 (sub index=register number+1).

Write to other registers as needed (such as R33 offset, R34 gain, etc.), with each register corresponding to a sub index (register number+1), for example, register 33 → sub index 22 (hexadecimal).

The final reset code word is 0x4280:20=0.

Finally, clear the terminal selection: 0x427F:00=0.

These entries will be executed in order to ensure parameter distribution.

Example: Modify the user offset (register 33) of the third terminal (KL3314) to 0x04D2 (1234 decimal). Add: 0 to the startup list x427F:00 = 3，0x4280:20 = 0x1235，0x4280:22 = 0x04D2，0x4280:20 = 0，0x427F:00 = 0。

4.2 Approach 2: Online CoE Access

During operation, the KL terminal register can be directly read and written through the CoE directory of the BK coupler. Operation Method:

Select the "CoE Online" tab of the BK coupler.

Firstly, write 0x427F:00 as the target terminal number (2-byte value).

Then access different channels/pages of the register through indexes 0x4280~0x4287. Each channel has a maximum of 64 registers (0-63), with sub index=register number+1. For example, register 33 of channel 1 corresponds to 0x4280:22.

After modification, view the values online. Note: If the terminal number does not exist or does not support register communication, "SDO Abort" will be displayed.

4.3 Approach Three: AoE (ADS over EtherCAT) - Suitable for dynamic access of PLC programs

AoE allows access to KL terminal registers from PLC or remote TwinCAT stations via ADS protocol. A unique AmsNetId (such as 172.16.8.29.3.10) needs to be generated in the "Advanced Settings" → "Mailbox" → "AoE" of the BK coupler. Then, the ADS access parameters are:

AmsNetId: Generated AoE NetId

Port: 100 (fixed)

IndexGroup: 0 represents the coupler itself,>0 represents the terminal number (e.g. 3 represents the third KL terminal)

IndexOffset: The high word represents the channel number (0-3), and the low word represents the register number (16 bits)

For example, accessing register 31 (code word) of channel 2 on the third terminal, IndexGroup=3，IndexOffset=0x0001001F。 This method facilitates dynamic parameter adjustment in PLC programs without the need to intervene in the startup list.

Process data mapping and PDO configuration

The BK coupler automatically generates process images, but users can adjust PDO allocation (via 0x1C12/0x1C13). By default, analog (non digital) terminals are arranged in Word Alignment, while digital terminals are arranged compactly in bits. The status word (CouplerState) and control word (CouplerCtrl) occupy the first 16 bits of the process image with a fixed offset of 0. Non digital terminals (such as KL3062) occupy three parts (three 16 bit words) of "status/virtual word/data" for each channel, while digital terminals are arranged by bit or byte.

In TwinCAT, PDO allocation can be modified through the "Process Data" tab, such as disabling certain channels or changing data length. However, it should be noted that the modifications must be consistent with the actual configuration of the KL terminal, otherwise it will result in an "Invalid SM IN cfg" error (AL Status Code 0x001E).

Detailed explanation and troubleshooting of LED diagnosis

6.1 Power and Status LEDs

Us (green): The power supply of the coupler is normal.

Up (green): The power contacts are supplying power normally.

RUN (green): EtherCAT state machine indication: off=Initiat, flashing=PREOP, single flash=SAFEOP, constant light=OP.

ERROR (red): off=no error, flashing=error or lost frame.

LINK/ACT (green): X1/X2 port link/activity indicator.

6.2 K-bus error flashing code (I/O ERR LED flashing red)

When the I/O ERR LED flashes continuously or regularly, it indicates a K-bus fault. The error code consists of "fast flashing (start)"+"slow sequence (error code)"+"slow sequence (parameter)".

Error code (number of pulses) parameter description and solution measures

1 0 EEPROM checksum error using KS2000 to restore factory settings

1 n>0 Configuration table overflow reduces the number of terminals

2 n>0 configuration table item error check whether the configuration matches the terminal

30 K-bus command error: No terminal or damaged terminal, use the split method to locate

Check the n+1 terminal connection after disconnecting the 40 coupler

Check for broken wires at terminal n+1 and terminal KL9010 after terminal n of 4 n

5 n register communication error, replace the nth terminal

14 n terminal format error. Restart the coupler. If it still persists, replace the terminal

The number of 15n terminals is incorrect. Restart or restore to factory settings

16 n K-bus data length error, restart or restore to factory settings

Important: Continuous rapid flashing indicates EMC interference, and power, grounding, and shielding need to be checked.

6.3 EtherCAT Master Station Error Messages

AL Status Code 0x0003: K-bus error causing inability to enter SAFEOP, K-bus fault needs to be investigated.

AL Status Code 0x001E (Invalid SM IN cfg): Process data length mismatch, usually due to the configuration reported by the KL terminal not matching the TwinCAT ESI preset. Solution: Check if the terminal is in special mode (such as enabling other PDOs), or use KS2000 to verify the register configuration.