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Assembler User Guide

Current Program Status Register

Current Program Status Register

The Current Program Status Register (CPSR) holds:

  • the APSR flags

  • the current processor mode

  • interrupt disable flags

  • current processor state (ARM, Thumb, ThumbEE, or Jazelle®)

  • endianness state (on ARMv4T and later)

  • execution state bits for the IT block (on ARMv6T2 and later).

The execution state bits control conditional execution in the IT block.

Only the APSR flags are accessible in all modes. The endianness bit (E) of the CPSR is accessible only in privileged software execution. It can be read by MRS and written by MSR, but SETEND is the preferred instruction to write to the E bit.

The execution state bits for the IT block (IT[1:0]), Jazelle bit (J), and Thumb bit (T) can be accessed by MRS only in Debug state.

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