OS_EnterOS (changes)

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Programmer's OS Reference SWI Manuals Calls

» OS_EnterOSPart 15 – SWI Calls

OS_EnterOS

(SWI &16)

Use

The purpose of this call is to set the processor to Supervisor mode.

Notes

Interrupt and Fast Interrupt status is unaltered. Note that SWI calls while in SVC mode will alter R14, and will use R13 as stack.

To return to User mode on an ARM6 or later:

MSR   CPSR_c,#%10000  ; USR32

alternatively to return to either USR32 or USR26

MRS   R14,CPSR
BIC   R14,R14,#%1111  ; Only sets usermode
MSR   CPSR_c,R14

To return to User mode pre ARM6 (deprecated):

TEQP  PC,#0
MOV   R0,R0  ; Anything that doesn't use banked R8-R14

alternatively to return to user mode leaving the other PSR bits constant

BIC   R14,PC,#%11  ; Only sets usermode
TEQP  R14,#0
MOV   R0,R0  ; Anything that doesn't use banked R8-R14

See also

• OS_LeaveOS