The safety function of safety modules (DX581-S) with safety output channels is to correctly write their output channel signals. If this function cannot be correctly executed, the safety module or its output channel group, depending on the fault scope, has to go to a safe state. In case of a channel fault, the safe value (de-energized = ‘0’) is set for the given safety output channels. In case of module fault, no valid telegrams are generated by the safety output module to the safety CPU. The values of all safety output channels will be assigned to safe values (de-energized = ‘0’).

Faults in the cyclic communication between the safety CPU and the safety output modules are detected by the safety output module DX581-S. If a communication fault occurs, all outputs of the affected safety output module are de-energized = ‘0’. The switch-over (reintegration) from safety values ‘0’ to process data takes place only after user acknowledgment, when the communication is re-established.