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4.2.2 Fault Escalation and Hard Faults
All fault exceptions except for hard fault have configurable exception priority. Software can disable
execution of the handlers for these faults.
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 Section 4.1, Exception Model.
In some situations, a fault with configurable priority is treated as a hard fault. This process is called priority
escalation, and the fault is described as escalated to hard fault. Escalation to hard fault occurs when:
• A fault handler causes the same kind of fault as the one it is servicing. This escalation to hard fault
occurs because a fault handler cannot preempt itself because it must have the same priority as the
current priority level.
• A fault handler causes a fault with the same or lower priority as the fault it is servicing. This situation
happens because the handler for the new fault cannot preempt the fault handler that is currently
executing.
• An exception handler causes a fault for which the priority is the same as or lower than the exception
that is currently executing.
• A fault occurs and the handler for that fault is not enabled.
NOTE: If a bus fault occurs during a stack push when entering a bus fault handler, the bus fault
does not escalate to a hard fault. Thus, 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.
4.2.3 Fault Status Registers and Fault Address Registers
The fault status registers indicate the cause of a fault. For bus faults, the fault address register indicates
the address accessed by the operation that caused the fault, as shown in Table 4-6.
Table 4-6. Fault Status and Fault Address Registers
Handler Status Register Name Address Register Name Register Description
Hard fault Hard Fault Status (HFSR) – HFAULTSTAT
FAULTSTAT
Bus fault Bus Fault Status (BFSR) Bus Fault Address (BFAR)
FAULTADDR
Usage fault Usage Fault Status (UFSR) – FAULTSTAT
4.2.4 Lockup
The processor enters a lockup state if a hard fault occurs when executing the hard fault handlers. In a
CC26xx device, a lockup state resets the system.
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Interrupts and Events SWCU117A–February 2015–Revised March 2015
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