Power ISA™ Version 2.03 - Power.org

Version 2.03
Write MSR External Enable X-form Write MSR External Enable Immediate
X-form
wrtee RS
wrteei RS
31 RS /// /// 131 /
0 6 11 16 21 31 31 RS /// E /// 163 /
0 6 11 16 17 21 31
MSR EE ← (RS) 48
The content of (RS) 48 is placed into MSR EE .
Alteration of the MSR EE bit is effective as soon as the
instruction completes. Thus if MSR EE =0 and an External
interrupt is pending, executing a wrtee instruction
that sets MSR EE to 1 will cause the External interrupt to
occur before the next instruction is executed, if no
higher priority exception exists (Section 5.9, “Exception
Priorities” on page 569).
Execution of this instruction is privileged.
Special Registers Altered:
MSR
MSR EE ← E
The value specified in the E field is placed into MSR EE .
Alteration of the MSR EE bit is effective as soon as the
instruction completes. Thus if MSR EE =0 and an External
interrupt is pending, executing a wrtee instruction
that sets MSR EE to 1 will cause the External interrupt to
occur before the next instruction is executed, if no
higher priority exception exists (Section 5.9, “Exception
Priorities” on page 569).
Execution of this instruction is privileged.
Special Registers Altered:
MSR
Programming Note
wrtee and wrteei are used to provide atomic
update of MSR EE . Typical usage is:
mfmsr Rn #save EE in (Rn) 48
wrteei 0 #turn off EE
mfmsr Rn #save EE in (Rn) 48
wrteei 0 #turn off EE
: : :
: #code with EE disabled
wrtee Rn #restore EE without altering
#other MSR bits that might
#have changed
506
Power ISA -- Book III-E