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2.8. Processor operating states

The processor has the following operating states controlled by the T bit and J bit in the CPSR.

ARM state

32-bit, word-aligned ARM instructions are executed in this state.

T bit is 0 and J bit is 0.

Thumb state

16-bit and 32-bit, halfword-aligned Thumb-2 instructions.

T bit is 1 and J bit is 0.

ThumbEE state

16-bit and 32-bit, halfword-aligned variant of the Thumb-2 instruction set designed as a target for dynamically generated code. This is code compiled on the device either shortly before or during execution from a portable bytecode or other intermediate or native representation.

T bit is 1 and J bit is 1.

Note

  • The processor does not support Jazelle state, that is, when the T bit is 0 and J bit is 1.

  • Transition between ARM and Thumb states does not affect the processor mode or the register contents. See ARM Architecture Reference Manual, Thumb-2 Execution Environment supplement for details on entering and exiting ThumbEE state.

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