Atmel SAM4S Series, Preliminary Data Sheet

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
• A fault occurs and the handler for that fault is not enabled.
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. 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.
Note: Only Reset and NMI can preempt the fixed priority hard fault. A hard fault can preempt any excep-
tion other than Reset, NMI, or another hard fault.
Fault Status Registers and Fault Address Registers
The fault status registers indicate the cause of a fault. For bus faults and memory management
faults, the fault address register indicates the address accessed by the operation that caused
the fault, as shown in
Table 11-12 .
Lockup
The processor enters a lockup state if a hard fault occurs when executing the NMI or hard fault
handlers. When the processor is in lockup state, it does not execute any instructions. The pro-
cessor remains in lockup state until either:
• it is reset
• an NMI occurs
• it is halted by a debugger.
Note: If the lockup state occurs from the NMI handler, a subsequent NMI does not cause the processor
to leave the lockup state.
Table 11-12. Fault Status and Fault Address Registers
Handler
Status Register
Name Address
Register Name
Register Description
Hard fault SCB_HFSR - “Hard Fault Status Register”
Memory
management fault
MMFSR SCB_MMFAR
“MMFSR: Memory Management Fault
Status Subregister”
“MemManage Fault Address Register”
Bus fault BFSR SCB_BFAR
“BFSR: Bus Fault Status Subregister”
“Bus Fault Address Register”
Usage fault UFSR -
“UFSR: Usage Fault Status
Subregister”