ARM Technical Support Knowledge Articles

Which ARMv7-M Special Registers may be accessed by MSR/MRS instructions?

Applies to: Cortex-M3

Answer

APSR can always be read or written
EPSR always reads as zero, no write
IPSR privileged read, no write

Combined 'PSR's act as the sum of the parts. For example, IEPSR would allow privileged read of the IPSR bits but the EPSR bits would return zeros.

MSP privileged read and write
PSP

privileged read and write
 
PRIMASK privileged read and write
BASEPRI privileged read and write
BASEPRI_MAX

privileged read and write
 
FAULTMASK privileged read and write
CONTROL always readable, privileged write

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