Memory Management Unit
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
6-8
ID073015
Non-Confidential
6.5
External aborts
External memory errors are defined as those that occur in the memory system rather than those
that are detected by the MMU. External memory errors are expected to be extremely rare.
External aborts are caused by errors flagged by the AXI interfaces when the request goes
external to the processor. External aborts can be configured to trap to Monitor mode by setting
the EA bit in the Secure Configuration Register.
6.5.1
External aborts on data read or write
Externally generated errors during a data read or write can be asynchronous. This means that
the r14_abt on entry into the abort handler on such an abort might not hold the address of the
instruction that caused the exception.
The DFAR is
UNPREDICTABLE
when an asynchronous abort occurs.
In the case of a load multiple or store multiple operation, the address captured in the DFAR is
that of the address that generated the synchronous external abort.
6.5.2
Synchronous and asynchronous aborts
To determine a fault type, read the DFSR for a data abort or the IFSR for an instruction abort.
The processor supports an Auxiliary Fault Status Register for software compatibility reasons
only. The processor does not modify this register because of any generated abort.