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

Operation
Instruction Details
OSH Outer Shareable is the required shareability domain, reads and writes are the
required access types. Encoded as option == '0011'.
OSHST Outer Shareable is the required shareability domain, writes are the required
access type. Encoded as option == '0010'.
All other encodings of option are reserved. It is IMPLEMENTATION DEFINED whether options
other than SY are implemented. All unsupported and reserved options must execute as a full
system DSB operation, but software must not must rely on this operation.
Note
The following alternative values are supported, but ARM recommends that you do not
use these alternative values:
SH as an alias for ISH
SHST as an alias for ISHST
UN as an alias for NSH
UNST is an alias for NSHST.
if ConditionPassed() then
EncodingSpecificOperations();
case option of
when ‘0010’ domain = MBReqDomain_OuterShareable; types = MBReqTypes_Writes;
when ‘0010’ domain = MBReqDomain_OuterShareable; types = MBReqTypes_All;
when ‘0110’ domain = MBReqDomain_Nonshareable; types = MBReqTypes_Writes;
when ‘0111’ domain = MBReqDomain_Nonshareable; types = MBReqTypes_All;
when ‘1010’ domain = MBReqDomain_InnerShareable; types = MBReqTypes_Writes;
when ‘1011’ domain = MBReqDomain_InnerShareable; types = MBReqTypes_All;
when ‘1110’ domain = MBReqDomain_FullSystem; types = MBReqTypes_Writes;
otherwise domain = MBReqDomain_FullSystem; types = MBReqTypes_All;
DataSynchronizationBarrier(domain, types);
Exceptions
None.
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. A8-93