Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet

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SAM4E [DATASHEET]

Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14

Move the contents of a special register to a general-purpose register.

Syntax

MRS{cond} Rd, spec_reg

where:

cond

is an optional condition code, see 

.

Rd

is the destination register.

spec_reg

can 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. 

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 

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 

.

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.