2.6.10.7.1 Syntax
MSR{cond} spec_reg, Rn
where:
cond is an optional condition code, see Conditional Execution.
Rn is the source register.
spec_reg can be any of: APSR, IPSR, EPSR, IEPSR, IAPSR, EAPSR, PSR, MSP, PSP, PRIMASK, BASEPRI, BASEPRI_MAX, FAULTMASK, or CONTROL.
Note: The processor ignores MSR writes to the EPSR and IPSR fields.