DMB

Data memory barrier

This instruction is a memory barrier that ensures the ordering of observations of memory accesses, see Data Memory Barrier.

313029282726252423222120191817161514131211109876543210
11010101000000110011CRm10111111
opcRt

Encoding

DMB (<option>|#<imm>)

Decode for this encoding

var types : MBReqTypes; case CRm[1:0] of when '00' => types = MBReqTypes_All; when '01' => types = MBReqTypes_Reads; when '10' => types = MBReqTypes_Writes; when '11' => types = MBReqTypes_All; end;

Assembler Symbols

<option>

Specifies the limitation on the Memory Effects ordered by the barrier operation, and is encoded in "CRm".

For more information on whether a Memory Effect is before or after a barrier instruction, see Data Memory Barrier (DMB).

CRm <option> Description
xx00 RESERVED
0001 OSHLD

This option has the same behavior as LD and is deprecated.

0010 OSHST

This option has the same behavior as ST and is deprecated.

0011 OSH

This option has the same behavior as SY and is deprecated.

0101 NSHLD

This option has the same behavior as LD and is deprecated.

0110 NSHST

This option has the same behavior as ST and is deprecated.

0111 NSH

This option has the same behavior as SY and is deprecated.

1001 ISHLD

This option has the same behavior as LD and is deprecated.

1010 ISHST

This option has the same behavior as ST and is deprecated.

1011 ISH

This option has the same behavior as SY and is deprecated.

1101 LD

Reads are the required access type before the barrier instruction. Reads and writes are the required access types after the barrier instruction.

1110 ST

Writes are the required access type, both before and after the barrier instruction.

1111 SY

Reads and writes are the required access types, both before and after the barrier instruction.

All encodings of "CRm" that are listed as reserved can be encoded using the #<imm> syntax. All reserved options have the same behavior as SY, but software must not rely on this behavior.
<imm>

Is a 4-bit unsigned immediate, in the range 0 to 15, encoded in the "CRm" field.


2026-03_rel 2026-03-26 20:48:11

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