User's Manual

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.
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