B1.78
Instruction Set Attribute Register 4
The ID_ISAR4 characteristics are:
Purpose
Provides information about the instruction sets implemented by the processor in AArch32.
Usage constraints
This register is accessible as follows:
EL0
(NS)
EL0
(S)
EL1
(NS)
EL1
(S)
EL2 EL3
(SCR.NS = 1)
EL3
(SCR.NS = 0)
-
-
RO
RO
RO
RO
RO
Must be interpreted with ID_ISAR0, ID_ISAR1, ID_ISAR2, ID_ISAR3, and ID_ISAR5. See:
•
B1.74 Instruction Set Attribute Register 0
•
B1.75 Instruction Set Attribute Register 1
•
B1.76 Instruction Set Attribute Register 2
•
B1.77 Instruction Set Attribute Register 3
•
B1.79 Instruction Set Attribute Register 5
Configurations
ID_ISAR4 is architecturally mapped to AArch64 register ID_ISAR4_EL1. See
Instruction Set Attribute Register 4, EL1
.
There is one copy of this register that is used in both Secure and Non-secure states.
Attributes
ID_ISAR4 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 B1-33 ID_ISAR4 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]
B1 AArch32 system registers
B1.78 Instruction Set Attribute Register 4
100236_0100_00_en
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