Datasheet

75
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
the return stack and processor mode. Table 12-10 shows the EXC_RETURN values with a description of the exception
return behavior.
All EXC_RETURN values have bits[31:5] set to one. When this value is loaded into the PC, it indicates to the processor
that the exception is complete, and the processor initiates the appropriate exception return sequence.
12.4.3.8 Fault Handling
Faults are a subset of the exceptions, see “Exception Model” . The following generate a fault:
 A bus error on:
 An instruction fetch or vector table load
 A data access
 An internally-detected error such as an undefined instruction
 An attempt to execute an instruction from a memory region marked as Non-Executable (XN).
 A privilege violation or an attempt to access an unmanaged region causing an MPU fault.
Fault Types
Table 12-11 shows the types of fault, the handler used for the fault, the corresponding fault status register, and the
register bit that indicates that the fault has occurred. See “Configurable Fault Status Register” for more information about
the fault status registers.
Table 12-10. Exception Return Behavior
EXC_RETURN[31:0] Description
0xFFFFFFF1
Return to Handler mode, exception return uses non-floating-point state
from the MSP and execution uses MSP after return.
0xFFFFFFF9
Return to Thread mode, exception return uses non-floating-point state from
MSP and execution uses MSP after return.
0xFFFFFFFD
Return to Thread mode, exception return uses non-floating-point state from
the PSP and execution uses PSP after return.
Table 12-11. Faults
Fault Handler Bit Name Fault Status Register
Bus error on a vector read
Hard fault
VECTTBL
“Hard Fault Status Register”
Fault escalated to a hard fault FORCED
MPU or default memory map mismatch:
Memory
management
fault
--
on instruction access IACCVIOL
“MMFSR: Memory Management Fault
Status Subregister”
on data access DACCVIOL
(2)
during exception stacking MSTKERR
during exception unstacking MUNSKERR
during lazy floating-point state preservation MLSPERR
Bus error:
Bus fault
--
during exception stacking STKERR
“BFSR: Bus Fault Status Subregister”
during exception unstacking UNSTKERR
during instruction prefetch IBUSERR
during lazy floating-point state preservation LSPERR
Precise data bus error PRECISERR
Imprecise data bus error IMPRECISERR