System Control
ARM DDI 0500D
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4-30
ID021414
Non-Confidential
Table 4-35
shows the ID_ISAR1_EL1 bit assignments.
To access the ID_ISAR1_EL1:
MRS <Xt>, ID_ISAR1_EL1 ; Read ID_ISAR1_EL1 into Xt
Register access is encoded as follows:
4.3.14
AArch32 Instruction Set Attribute Register 2
The ID_ISAR2_EL1 characteristics are:
Purpose
Provides information about the instruction sets implemented by the
processor in AArch32.
Table 4-35 ID_ISAR1_EL1 bit assignments
Bits
Name
Function
[31:28]
Jazelle
Indicates the implemented Jazelle state instructions:
0x1
Adds the
BXJ
instruction, and the J bit in the PSR. This setting might indicate a trivial
implementation of the Jazelle extension.
[27:24]
Interwork
Indicates the implemented Interworking instructions:
0x3
•
The
BX
instruction, and the T bit in the PSR.
•
The
BLX
instruction. The PC loads have
BX
-like behavior.
•
Data-processing instructions in the A32 instruction set with the PC as the destination
and the S bit clear, have
BX
-like behavior.
[23:20]
Immediate
Indicates the implemented data-processing instructions with long immediates:
0x1
•
The
MOVT
instruction.
•
The
MOV
instruction encodings with zero-extended 16-bit immediates.
•
The T32
ADD
and
SUB
instruction encodings with zero-extended 12-bit immediates, and
other
ADD
,
ADR
, and
SUB
encodings cross-referenced by the pseudocode for those
encodings.
[19:16]
IfThen
Indicates the implemented
If-Then
instructions in the T32 instruction set:
0x1
The
IT
instructions, and the IT bits in the PSRs.
[15:12]
Extend
Indicates the implemented Extend instructions:
0x2
•
The
SXTB
,
SXTH
,
UXTB
, and
UXTH
instructions.
•
The
SXTB16
,
SXTAB
,
SXTAB16
,
SXTAH
,
UXTB16
,
UXTAB
,
UXTAB16
, and
UXTAH
instructions.
[11:8]
Except_AR
Indicates the implemented A profile exception-handling instructions:
0x1
The
SRS
and
RFE
instructions, and the A profile forms of the
CPS
instruction.
[7:4]
Except
Indicates the implemented exception-handling instructions in the A32 instruction set:
0x1
The
LDM
(exception return),
LDM
(user registers), and
STM
(user registers) instruction versions.
[3:0]
Endian
Indicates the implemented Endian instructions:
0x1
The
SETEND
instruction, and the E bit in the PSRs.
Table 4-36 ID_ISAR1_EL1 access encoding
op0
op1
CRn
CRm
op2
11
000
0000
0010
001