User's Manual

THE 80286 INSTRUCTION SET
SGDT /SIDT -Store Global/Interrupt Descriptor Table
Register
Opcode
OF 01 /0
OF 01 /1
FLAGS MODIFIED
None
Instruction
SGDT m
SIDT m
FLAGS UNDEFINED
None
OPERATION
Clocks
11
12
Description
Store Global Descriptor Table register to m
Store Interrupt Descriptor Table register
to m
The contents of the descriptor table register are copied to six bytes of memory indicated by the operand.
The
LIMIT field of the register goes to the first word at the effective address; the next three bytes get
the
BASE field of the register; and the last byte is undefined.
SGDT and SIDT appear only in operating systems software; they are not used in applications programs.
PROTECTED MODE EXCEPTIONS
#UD if the destination operand is a register. #GP(O) if the destination is in a non-writable segment.
#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
These instructions are valid in Real Address mode to facilitate power-up or to reset initialization prior
to entering Protected mode.
#UD if the destination operand is a register. Interrupt 13 for a word operand at offset OFFFFH.
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