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Cortex-A8 Technical Reference Manual - ARM Information Center

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6.5 External aborts<br />

6.5.1 External aborts on data read or write<br />

6.5.2 Precise and imprecise aborts<br />

Memory Management Unit<br />

External memory errors are defined as those that occur in the memory system but are not<br />

detected by the MMU. External memory errors are expected to be extremely rare and are likely<br />

to be fatal to the running processor. External aborts are caused by errors flagged by AXI when<br />

the request goes external to the processor. External aborts can be configured to trap to the<br />

monitor by setting the EA bit in the Secure Configuration Register to 1. See c1, Secure<br />

Configuration Register on page 3-53 for more information.<br />

Externally generated errors during a data read or write can be imprecise. This means that the<br />

r14_abt on entry into the abort handler on such an abort might not hold the address of the<br />

instruction that caused the exception.<br />

The DFAR is Unpredictable when an imprecise abort occurs.<br />

In the case of a load multiple or store multiple operation, the address captured in the DFAR is<br />

that of the address that generated the precise external abort.<br />

Chapter 3 System Control Coprocessor describes precise and imprecise aborts, their priorities,<br />

and the IFSR and DFSR. To determine a fault type, read the DFSR for a data abort or the IFSR<br />

for an instruction abort.<br />

The processor supports an Auxiliary Fault Status Register for software compatibility reasons<br />

only. The processor does not modify this register because of any generated abort.<br />

<strong>ARM</strong> DDI 0344K Copyright © 2006-2010 <strong>ARM</strong> Limited. All rights reserved. 6-6<br />

ID060510 Non-Confidential

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