Beckhoff · EL6900 Operating Instructions
This diagnostic flashing code (Diag 3 off, Diag 4: 3 flash pulses with longer pause) signifies both a function block error and a communication error within one of the TwinSAFE groups. This combined fault suggests issues with both the internal logic processing and the external data exchange within the safety system, indicating a complex problem requiring thorough investigation of both aspects.
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Address potential communication errors first by verifying EtherCAT cabling and slave statuses in the TwinCAT System Manager.
Subsequently, investigate TwinSAFE function block parameters and logic within TwinCAT, checking for invalid states or unexpected outputs, similar to a 'Function Block Error' scenario.
Review recent changes to the safety project or hardware configuration that could simultaneously affect both communication and safety logic execution.