B2.66 ID_ISAR1_EL1, AArch32 Instruction Set Attribute Register 1, EL1
The ID_ISAR1_EL1 provides information about the instruction sets implemented by the core in
AArch32.
Bit field descriptions
ID_ISAR1_EL1 is a 32-bit register, and is part of the Identification registers functional group.
This register is Read Only.
31 28 27 24 23 20 19 16 15 12 11 8 7 4 3 0
Jazelle Interwork Immediate IfThen Extend Except_AR Except Endian
Figure B2-50 ID_ISAR1_EL1 bit assignments
Jazelle, [31:28]
Indicates the implemented Jazelle state instructions:
0x1 Adds the BXJ instruction, and the J bit in the PSR.
Interwork, [27:24]
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.
Immediate, [23:20]
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.
IfThen, [19:16]
Indicates the implemented If-Then instructions in the T32 instruction set:
0x1 The IT instructions, and the IT bits in the PSRs.
Extend, [15:12]
Indicates the implemented Extend instructions:
0x2 • The SXTB, SXTH, UXTB, and UXTH instructions.
• The SXTB16, SXTAB, SXTAB16, SXTAH, UXTB16, UXTAB, UXTAB16, and UXTAH
instructions.
Except_AR, [11:8]
Indicates the implemented A profile exception-handling instructions:
0x1 The SRS and RFE instructions, and the A profile forms of the CPS instruction.
Except, [7:4]
Indicates the implemented exception-handling instructions in the A32 instruction set:
B2 AArch64 system registers
B2.66 ID_ISAR1_EL1, AArch32 Instruction Set Attribute Register 1, EL1
100798_0300_00_en Copyright © 2016–2018 Arm Limited or its affiliates. All rights
reserved.
B2-235
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