1.1.1. ARM assembly language

The RVCT v2.2 assembler implements a substantially enhanced version of the assembly language, while continuing to support the old version to enable the assembly of old code. The new version can be assembled to either ARM® or Thumb® instructions.

The new version is necessary to support Thumb-2, an upgraded version of the Thumb instruction set available on the latest processors from ARM. Thumb-2 has most of the functionality of the ARM instruction set. The old Thumb assembly language is insufficiently versatile to describe all the new instructions.

You can write source code that can be assembled for either ARM or Thumb-2.

You can also use the new ARM assembly language for writing Thumb code for earlier, pre-Thumb-2 processors. In this case, you must only use instructions that are available on the processor you are writing for. This manual provides the information necessary for you to do this. The assembler faults the use of unavailable instructions.

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