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Debugging Intermittent EtherCAT Communication Issues

The following fault, error, and alarm are each indicative of possible cable or connection problems.

  • F125 on the AKD, "Fieldbus Sync frames lost."
  • E30 in KAS, "EtherCAT communication failure during operational mode."
  • A38 in KAS, "EtherCAT missed a receive frame during operational mode."

The command ECAT.DIAG can be executed in the workbench terminal to help identify the location of the problem after it occurs.

The following is an example of the output from this command.

Port errors
Port A
Invalid frame: 0
Rx error counter: 255
Forwarded error counter: 0
Link lost counter: 0
Port B
Invalid frame: 0
Rx error counter: 0
Forwarded error counter: 0
Link lost counter: 0

In the example, "Port A" has lost the connection due to the EtherCAT cable being unplugged. This is indicated by "Rx error counter: 255". In normal operating mode the counter values should be zero (0).


ECAT.DIAG is supported by firmware version and later. It is a hidden command, and the output may be different than shown here.

Older firmware can access the Rx error counter with the following commands:

DRV.MEMADDR 0x20200300.u32

The Rx counter value for Port A is coded as 0xFF00, which is the decimal value for 255.