What is data abort exception?
A data-abort exception is a response by a memory system to an invalid data access. These exceptions may originate in software, such as improper C-structures, or appear in code ported from a different processor architecture.
What is difference between prefetch abort and data abort?
A prefetch abort is associated with an instruction fetch as opposed to a data access. If the processor does not execute the instruction, for example because a branch occurs while it is in the pipeline, the abort does not take place.
What is Prefetch abort exception?
Prefetch Abort (PABT) Exception occurs when an instruction fetch causes an error. When a Prefetch Abort occurs, the processor marks the prefetched instruction as invalid, but does not take the exception until the instruction is to be executed.
What is external abort?
The ARM architecture defines external aborts as errors that occur in the memory system, other than those that are detected by the MMU or Debug hardware. External aborts include parity errors detected by the caches or other parts of the memory system.
What is the vector address of data abort exception in ARM processor?
the PC value is the Data Abort vector address, see Exception vectors and the exception base address.
What is synchronous external abort?
A synchronous external abort means you’re rather fortunate, in that it’s not going to be utterly hideous to debug – in the case of a prefetch abort, it means the IFAR is going to contain a valid VA for the faulting instruction, so you know exactly what caused it.
Which exception has highest priority?
NMI – A NonMaskable Interrupt (NMI) can be signalled by a peripheral or triggered by software. This is the highest priority exception other than reset.
What is an ARM exception?
Typically an external hardware activates a specific input line. On ARM processors all these interrupts (including hardware reset) are called exceptions. The architecture supports seven processor modes, six privileged modes called FIQ, IRQ, supervisor, abort, undefined and system mode, and the non-privileged user mode.
What is abort in arm?
An abort indicates that the current memory access cannot be completed. An abort is signaled by the external ABORT input. The ARM7TDMI processor checks for the abort exception at the end of memory access cycles.
What are ARM exceptions?
The Armv8-A architecture has two exception types, IRQ and FIQ, that are intended to be used to generate peripheral interrupts. In other versions of the Arm architecture, FIQ is used as a higher priority fast interrupt. This is different from Armv8-A, in which FIQ has the same priority as IRQ.
What are types of ARM exceptions?
ARM Exceptions
| Event | Exception | Mode |
|---|---|---|
| Reading from or writing to invalid address | Data Access Memory Abort (Data Abort) | Abort |
| FIQ input asserted | Fast Interrupt (FIQ) | FIQ |
| IRQ input asserted | Normal Interrupt (IRQ) | IRQ |
| Executing BKPT 3 or instruction at invalid address | Instruction Fetch Memory Abort (Prefetch Abort) | Abort |
Which of the following exception has the highest priority a data abort B SWI C reset D FIQ?
Because the Data Abort exception has a higher priority than the FIQ exception, the Data Abort is actually registered before the FIQ is handled.