B2.61
AArch32 Instruction Set Attribute Register 4, EL1
The ID_ISAR4_EL1 characteristics are:
Purpose
Provides information about the instruction sets implemented by the processor in AArch32.
Usage constraints
This register is accessible as follows:
EL0 EL1
(NS)
EL1
(S)
EL2 EL3
(SCR.NS = 1)
EL3
(SCR.NS = 0)
-
RO
RO
RO
RO
RO
Configurations
ID_ISAR4_EL1 is architecturally mapped to AArch32 register ID_ISAR4. See
B1.78 Instruction Set Attribute Register 4
.
Attributes
ID_ISAR4_EL1 is a 32-bit register.
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 B2-34 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:
0x1
The
SMC
instruction.
B2 AArch64 system registers
B2.61 AArch32 Instruction Set Attribute Register 4, EL1
100236_0100_00_en
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B2-463
Non-Confidential
Summary of Contents for Cortex-A35
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