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

The Instruction Sets
A4.5 Status register access instructions
The MRS and MSR instructions move the contents of the Application Program Status Register (APSR) to or
from a general-purpose register.
The APSR is described in The Application Program Status Register (APSR) on page A2-14.
The condition flags in the APSR are normally set by executing data-processing instructions, and are
normally used to control the execution of conditional instructions. However, you can set the flags explicitly
using the MSR instruction, and you can read the current state of the flags explicitly using the MRS instruction.
For details of the system level use of status register access instructions CPS, MRS, and MSR, see Chapter B6
System Instructions.
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