ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

ARMv6 Differences
G.4.2 Thumb instruction set support
ARMv6 includes all the Thumb instructions present in ARMv5TE, see Thumb instruction set support on
page AppxH-15. the 16-bit Thumb instructions added in the ARMv6 base architecture are:
CPS
CPY
REV, REV16, REVSH
SETEND
SXTB, SXTH
UXTB, UXTH.
Thumb instruction set and ARMv6T2
From the ARMv6T2 version of the Thumb instruction set:
The Thumb instruction set provides 16-bit and 32-bit instructions that are executed in Thumb state.
Most forms of ARM instructions have an equivalent Thumb encoding. Instructions that are only in
the ARM instruction set in ARMv6T2 on page AppxG-13 lists the exceptions to this in ARMv6T2.
The CBZ, CBNZ, and IT instructions are only in the Thumb instruction set and are introduced in ARMv6T2.
Before ARMv6T2, a BL or BLX (immediate) Thumb instruction can be executed as a pair of 16-bit
instructions, rather than as a single 32-bit instruction. For more information, see BL and BLX (immediate)
instructions, before ARMv6T2 on page AppxG-4. From ARMv6T2 these instructions are always executed
as a single 32-bit instruction.
From ARMv6T2, the branch range of the BL and BLX (immediate) instructions is increased from
approximately ±4MB to approximately ±16MB.
Thumb instructions introduced in ARMv7
The CLREX, LDREXB, LDREXD, LDREXH, STREXB, STREXD, and STREXH instructions are added to the Thumb instruction
set in ARMv7. They are Thumb equivalents to the ARM instructions added in ARMv6K. These instructions
are UNDEFINED in ARMv6T2.
The DBG, SEV, WFE, WFI, and YIELD hint instructions are added in ARMv7. They execute as NOP instructions in
ARMv6T2. The 16-bit encodings of the SEV, WFE, WFI, and YIELD instructions are UNDEFINED in the ARMv6
base architecture and in ARMv6K.
G.4.3 System level instruction set support
The system instructions supported in ARMv6 are the same as those listed for ARMv7 in Alphabetical list
of instructions on page B6-2:
the SMC instruction only applies to the Security Extensions
the VMRS and VMSR instructions only apply to VFP.
AppxG-14 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B