PM0214 Rev 9 187/262
PM0214 The STM32 Cortex-M4 instruction set
261
3.11.7 MSR
Move the contents of a general-purpose register into the specified special register.
Syntax
MSR{cond} spec_reg, Rn
Where:
• ‘cond’ is an optional condition code, see Conditional execution on page 65.
• ‘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.
Operation
The register access operation in MSR depends on the privilege level. Unprivileged software
can only access the APSR, see Table 5: APSR bit definitions on page 21. Privileged
software can access all special registers.
In unprivileged software writes to unallocated or execution state bits in the PSR are ignored.
When you write to BASEPRI_MAX, the instruction writes to BASEPRI only if either:
• Rn is non-zero and the current BASEPRI value is 0
• Rn is non-zero and less than the current BASEPRI value.
See MRS on page 186.
Restrictions
Rn must not be SP and must not be PC.
Condition flags
This instruction updates the flags explicitly based on the value in Rn.
Examples
MSR CONTROL, R1 ; Read R1 value and write it to the CONTROL register
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