Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD データシート

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SAM4S Series [DATASHEET]

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

The processor pops the stack and restores the processor state to the state it had before the interrupt occurred. 

See 

 for more information.

This mechanism speeds up exception servicing. On completion of an exception handler, if there is a pending 

exception that meets the requirements for exception entry, the stack pop is skipped and control transfers to the 

new exception handler.

This mechanism speeds up preemption. If a higher priority exception occurs during state saving for a previous 

exception, the processor switches to handle the higher priority exception and initiates the vector fetch for that 

exception. State saving is not affected by late arrival because the state saved is the same for both exceptions. 

Therefore the state saving continues uninterrupted. The processor can accept a late arriving exception until the 

first instruction of the exception handler of the original exception enters the execute stage of the processor. On 

return from the exception handler of the late-arriving exception, the normal tail-chaining rules apply.

An Exception entry occurs when there is a pending exception with sufficient priority and either the processor is in 

Thread mode, or the new exception is of a higher priority than the exception being handled, in which case the new 

exception preempts the original exception.
When one exception preempts another, the exceptions are nested.
Sufficient priority means that the exception has more priority than any limits set by the mask registers, see 

. An exception with less priority than this is pending but is not handled by the 

processor.
When the processor takes an exception, unless the exception is a tail-chained or a late-arriving exception, the 

processor pushes information onto the current stack. This operation is referred as stacking and the structure of 

eight data words is referred to as stack frame.