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2-8
User manual IC220SDL953 - September 2011
GFK-2731
2.8
Safe state
The safe state for the module is the low state at the output terminals (see "Safe digital
outputs" on page 2-3).
The safe state can be entered in the following cases:
1. Operating state
2. Error detection in I/O devices
3. Device errors
4. Parameterization errors
2.8.1
Operating state
In the operating state, the outputs can enter states "1" or "0". In general, state "0" is the
safe state.
2.8.2
Error detection in I/O devices
Outputs
If an error is detected at an output, the affected output is disabled ("0" = OFF = safe state).
Depending on the parameterization, the following errors can be detected at outputs:
– Short circuit
– Cross circuit
– Overload
The relevant diagnostic message is transmitted to the controller (see "Safe digital output
errors" on page 8-4). For information about which errors are detected and when, please
refer to "Connection examples for safe outputs" on page 6-1.
WARNING: Loss of the safety function possible due to undetected accumulation
of errors
Also evaluate the diagnostics of modules that are not used, but are connected to the
power supply, at regular intervals or disconnect these modules from the supply voltage.
If an error occurs on a channel of an output parameterized as "two-channel", the other
corresponding channel also enters the safe state.