Behavior in case of missing supply voltage (EP281x only)

The digital outputs are supplied from the supply voltage U_P. If the supply voltage U_P is not present, the digital outputs cannot output a high level.

If an output is set and does not output a high level, this is detected as a fault. On expiry of the fault reaction time, the fault is reported in the process data:

• The "Diag Input x" bit of the output is set to "1".
• The "Error Channel y" bit of the channel to which the output belongs is set to "1".

In the factory setting, all outputs of a channel in which a fault has occurred are disabled. The outputs also remain disabled when U_P is switched on again.

Re-enabling outputs

There are two ways to re-enable disabled outputs:

• Manual: Apply a positive edge to the variable "Reset outputs".
  
• Automatic: Set the parameter F800:01 to TRUE. All outputs will then be re-enabled as soon as U_P is switched on.
  Note: F800:01 also influences the behavior in case of short circuit.