2.4.2. Fault escalation and hard faults

All fault exceptions except for HardFault have configurable exception priority, see System Handler Priority Registers. Software can disable execution of the handlers for these faults, see System Handler Control and State Register.

Usually, the exception priority, together with the values of the exception mask registers, determines whether the processor enters the fault handler, and whether a fault handler can preempt another fault handler. as described in Exception model.

In some situations, a fault with configurable priority is treated as a HardFault. This is called priority escalation, and the fault is described as escalated to HardFault. Escalation to HardFault occurs when:

If a BusFault occurs during a stack push when entering a BusFault handler, the BusFault does not escalate to a HardFault. This means that if a corrupted stack causes a fault, the fault handler executes even though the stack push for the handler failed. The fault handler operates but the stack contents are corrupted.


Only Reset and NMI can preempt the fixed priority HardFault. A HardFault can preempt any exception other than Reset, NMI, or another HardFault.

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