THE
80286
INSTRUCTION SET
LMSW
-Load
Machine
Status
Word
Opcode
Instruction
Clocks Description
OF
01
/6
LMSWew
3,mem=6
Load
EA
word into Machine Status Word
FLAGS MODIFIED
None
FLAGS UNDEFINED
None
OPERATION
The Machine Status Word
is
loaded from the source operand. This instruction may be used to switch
to protected mode.
If
so,
then it must be followed
byan
intra-segment jump to flush the instruction
queue.
LMSW
will
not switch back to Real Address Mode.
LMSW appears only
in
operating systems software.
It
does not appear
in
applications programs.
PROTECTED MODE EXCEPTIONS
#GP(O) if the current privilege level
is
not
O.
#GP(O) for an illegal memory operand effective address
in
the CS, DS, or ES segments;
#SS(O)
for an illegal address
in
the SS segment.
REAL ADDRESS MODE EXCEPTIONS
Interrupt
13
for a word operand
at
offset OFFFFH.
8-67
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