"To De-assert" and Deassertion Hysteresis
After the PXE asserts a worse state for a sensor, it may de-assert that
state later on if the readings improve.
To de-assert a state:
To de-assert a state is to announce the end of the previously-asserted
worse state.
Below are good state changes that cause the PXE to de-assert the
previous state.
Deassertion Hysteresis:
Appendix H: Additional PXE Information
1. above upper critical --> above upper warning
2. above upper warning --> normal
3. below lower warning --> normal
4. below lower critical --> below lower warning
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