Datasheet

191
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
12.6.11.6MRS
Move the contents of a special register to a general-purpose register.
Syntax
MRS{cond} Rd, spec_reg
where:
condis an optional condition code, see “Conditional Execution” .
Rdis the destination register.
spec_regcan be any of: APSR, IPSR, EPSR, IEPSR, IAPSR, EAPSR, PSR, MSP, PSP,
PRIMASK, BASEPRI, BASEPRI_MAX, FAULTMASK, or CONTROL.
Operation
Use MRS in combination with MSR as part of a read-modify-write sequence for updating a PSR, for example to
clear the Q flag.
In process swap code, the programmers model state of the process being swapped out must be saved, including
relevant PSR contents. Similarly, the state of the process being swapped in must also be restored. These
operations use MRS in the state-saving instruction sequence and MSR in the state-restoring instruction sequence.
Note: BASEPRI_MAX is an alias of BASEPRI when used with the MRS instruction.
See “MSR” .
Restrictions
Rd must not be SP and must not be PC.
Condition Flags
This instruction does not change the flags.
Examples
MRS R0, PRIMASK ; Read PRIMASK value and write it to R0
12.6.11.7MSR
Move the contents of a general-purpose register into the specified special register.
Syntax
MSR{cond} spec_reg, Rn
where:
condis an optional condition code, see “Conditional Execution” .
Rnis the source register.
spec_regcan be any of: APSR, IPSR, EPSR, IEPSR, IAPSR, EAPSR, PSR, MSP, PSP,
PRIMASK, BASEPRI, BASEPRI_MAX, FAULTMASK, or CONTROL.