Each exception is in one of the
following states:
- Inactive: The exception is not active and not pending.
- Pending: The exception is waiting to be serviced by the processor. An
interrupt request from a peripheral or from software can change the state of
the corresponding interrupt to pending.
- Active: An exception is being serviced by the processor but has not
completed. An exception handler can interrupt the execution of another
exception handler. In this case, both exceptions are in the active
state.
- Active and Pending: The exception is being serviced by the processor,
and there is a pending exception from the same source