ARM VERSION 1.2 - Manual (Page 183)

ARM Instruction Reference
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All rights reserved. 4-73
4.8.2 MRS
Move the contents of the CPSR or SPSR to a general-purpose register.
Syntax
MRS{cond} Rd, psr
where:
cond is an optional condition code (see Conditional execution on page 4-4).
Rd is the destination register. Rd must not be r15.
psr is either CPSR or SPSR.
Usage
Use MRS in combination with MSR as part of a read-modify-write sequence for
updating a PSR , for example to change processor mode, or to clear the Q flag.
Caution
You must not attempt to access the SPSR when the processor is in User or System mode.
This is your responsibility. The assembler cannot warn you about this as it does not
know what processor mode code will be executed in.
Condition flags
This instruction does not affect the flags.
Architectures
This instruction is available in ARM architecture versions 3 and above.
Example
MSR r3, SPSR