LTR -- Load Task Register

Opcode       Instruction    Clocks    Description

0F  00 /3    LTR r/m16      pm=23/27  Load EA word into task register

Description

LTR loads the task register from the source register or memory location specified by the operand. The loaded task state segment is marked busy. A task switch does not occur.

LTR is used only in operating system software; it is not used in application programs.

Flags Affected

None

Protected Mode Exceptions

#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #GP(0) if the current privilege level is not 0; #GP(selector) if the object named by the source selector is not a TSS or is already busy; #NP(selector) if the TSS is marked "not present"; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Interrupt 6; LTR is not recognized in Real Address Mode

Virtual 8086 Mode Exceptions

Same exceptions as in Real Address Mode

Notes

The operand-size attribute has no effect on this instruction.

up: Chapter 17 -- 80386 Instruction Set
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