Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

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SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

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.

The exception is being serviced by the processor and there is a pending exception from the same source.

The exception types are:

Reset is invoked on power up or a warm reset. The exception model treats reset as a special form of exception. 

When reset is asserted, the operation of the processor stops, potentially at any point in an instruction. When reset 

is deasserted, execution restarts from the address provided by the reset entry in the vector table. Execution 

restarts as privileged execution in Thread mode.

A non maskable interrupt (NMI) can be signalled by a peripheral or triggered by software. This is the highest 

priority exception other than reset. It is permanently enabled and has a fixed priority of -2.
NMIs cannot be:



Masked or prevented from activation by any other exception. 



Preempted by any exception other than Reset.

A hard fault is an exception that occurs because of an error during exception processing, or because an exception 

cannot be managed by any other exception mechanism. Hard Faults have a fixed priority of -1, meaning they have 

higher priority than any exception with configurable priority.

A Memory Management Fault is an exception that occurs because of a memory protection related fault. The MPU 

or the fixed memory protection constraints determines this fault, for both instruction and data memory transactions. 

This fault is used to abort instruction accesses to Execute Never (XN) memory regions, even if the MPU is 

disabled.

A Bus Fault is an exception that occurs because of a memory related fault for an instruction or data memory 

transaction. This might be from an error detected on a bus in the memory system.

A Usage Fault is an exception that occurs because of a fault related to an instruction execution. This includes:



An undefined instruction



An illegal unaligned access



An invalid state on instruction execution



An error on exception return.

The following can cause a Usage Fault when the core is configured to report them:



An unaligned address on word and halfword memory access



A division by zero.

A supervisor call (SVC) is an exception that is triggered by the SVC instruction. In an OS environment, applications 

can use SVC instructions to access OS kernel functions and device drivers.