B2.69
ID_ISAR4_EL1, AArch32 Instruction Set Attribute Register 4, EL1
The ID_ISAR4_EL1 provides information about the instruction sets implemented by the core in
AArch32.
Bit field descriptions
ID_ISAR4_EL1 is a 32-bit register, and is part of the Identification registers functional group.
This register is Read Only.
31
24 23
20 19
16 15
12 11
8 7
4 3
0
SynchPrim_frac
SWP_frac
28 27
PSR_M
Barrier
SMC
WriteBack
WithShifts
Unpriv
Figure B2-53 ID_ISAR4_EL1 bit assignments
SWP_frac, [31:28]
Indicates support for the memory system locking the bus for
SWP
or
SWPB
instructions:
0x0
SWP
and
SWPB
instructions not implemented.
PSR_M, [27:24]
Indicates the implemented M profile instructions to modify the PSRs:
0x0
None implemented.
SynchPrim_frac, [23:20]
This field is used with the ID_ISAR3.SynchPrim field to indicate the implemented
Synchronization Primitive instructions:
0x0
• The
LDREX
and
STREX
instructions.
• The
CLREX
,
LDREXB
,
LDREXH
,
STREXB
, and
STREXH
instructions.
• The
LDREXD
and
STREXD
instructions.
Barrier, [19:16]
Indicates the supported Barrier instructions in the A32 and T32 instruction sets:
0x1
The
DMB
,
DSB
, and
ISB
barrier instructions.
SMC, [15:12]
Indicates the implemented
SMC
instructions:
0x0
None implemented.
WriteBack, [11:8]
Indicates the support for Write-Back addressing modes:
0x1
Core supports all the Write-Back addressing modes as defined in Armv8-A.
WithShifts, [7:4]
Indicates the support for instructions with shifts.
B2 AArch64 system registers
B2.69 ID_ISAR4_EL1, AArch32 Instruction Set Attribute Register 4, EL1
100798_0300_00_en
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B2-241
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Summary of Contents for Cortex-A76 Core
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