Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

2-20

ARM DDI0198D

Table 2-16 shows the encodings used for the status field in the FSR, and if the Domain 
field contains valid information. See Fault address and fault status registers on 
page 3-21 for details of MMU aborts. 

Register c6 accesses the Fault Address Register (FAR). The FAR contains the Modified 
Virtual Address of the access being attempted when a Data Abort occurred. The FAR is 
only updated for Data Aborts, not for Prefetch Aborts. The FAR is updated for 
alignment faults, and external aborts that occur while the MMU is disabled.

You can use the following instructions to access the FAR:

MRC p15, 0, <Rd>, c6, c0, 0 ; read FAR 
MCR p15, 0, <Rd>, c6, c0, 0 ; write FAR

Writing c6 sets the FAR to the value of the data written. This is useful for a debugger to 
restore the value of the FAR to a previous state.

The CRm and Opcode_2 fields Should Be Zero when reading or writing CP15 c6.

Register c7 controls the caches and the write buffer. The function of each cache 
operation is selected by the Opcode_2 and CRm fields in the MCR instruction used to 
write to CP15 c7. Writing other Opcode_2 or CRm values is Unpredictable.

Highest

Alignment

-

b00x1

Invalid

External abort on translation

First level 
Second level

b1100 
b1110

Invalid 
Valid

Translation

Section
Page

b0101 
b0111

Invalid 
Valid

Domain

Section 
Page

b1001 
b1011

Valid 
Valid

Permission

Section 
Page

b1101 
b1111

Valid 
Valid

Lowest

External abort

Section or page

b10x0

Invalid