ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Common Memory System Architecture Features
AlignmentFault(address, FALSE);
else // if legacy non alignment-checking configuration
VA = Align(address, size);
// MMU or MPU
memaddrdesc = TranslateAddress(VA, privileged, FALSE);
// Memory array access, and sort out endianness
value = _Mem[memaddrdesc, size];
if CPSR.E == ‘1’ then
value = BigEndianReverse(value, size);
return value;
// Assignment form
MemA_with_priv[bits(32) address, integer size, boolean privileged] = bits(8*size) value
// Sort out alignment
if address == Align(address, size) then
VA = address;
elsif SCTLR.A == ‘1’ || SCTLR.U == ‘1’ then
AlignmentFault(address, FALSE);
else // if legacy non alignment-checking configuration
VA = Align(address, size);
// MMU or MPU
memaddrdesc = TranslateAddress(VA, privileged, TRUE);
// Effect on exclusives
if memaddrdesc.memattrs.shareable then
ClearExclusiveByAddress(memaddrdesc.physicaladdress, ProcessorID(), size);
// Sort out endianness, then memory array access
if CPSR.E == ‘1’ then
value = BigEndianReverse(value, size);
_Mem[memaddrdesc,size] = value;
return;
B2.4.5 Unaligned memory accesses
The MemU[] function performs a memory access at the current privilege level, and the MemU_unpriv[] function
performs an access that is always unprivileged.
In both cases:
if the SCTLR.A bit is 0, unaligned accesses are supported
if the SCTLR.A bit is 1, unaligned accesses produce Alignment faults.
B2-32 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B