Unified Assembler Language (UAL) is a common syntax for ARM and Thumb instructions. It supersedes earlier versions of both the ARM and Thumb assembler languages.
Code written using UAL can be assembled for ARM or Thumb for any ARM processor. The assembler faults the use of unavailable instructions.
RealView® Compilation Tools (RVCT) v2.1 and earlier can only assemble the pre-UAL syntax. Later versions of RVCT and ARM Compiler toolchain can assemble code written in pre-UAL and UAL syntax.
By default, the assembler expects source code to be written
in UAL. The assembler accepts UAL syntax if any of the directives
THUMBX is used or if you assemble with any of the
thumbx command line options. The assembler
also accepts source code written in pre-UAL ARM assembly language
when you assemble with
The assembler accepts source code written in pre-UAL Thumb
assembly language when you assemble using the
line option, or the
CODE16 directive in the source
The pre-UAL Thumb assembly language does not support 32-bit Thumb instructions.