i386/i386.reference/LTR.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode LTR</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  13 <P>
  14 <H1>LTR -- Load Task Register</H1>
  15
  16 <PRE>
  17 Opcode       Instruction    Clocks    Description
  18
  19 0F  00 /3    LTR r/m16      pm=23/27  Load EA word into task register
  20 </PRE>
  21
  22 <H2>Description</H2>
  23
  24 LTR loads the task register from the source register or memory location
  25 specified by the operand. The loaded task state segment is marked busy.
  26 A task switch does not occur.
  27 <P>
  28 LTR is used only in operating system software; it is not used in
  29 application programs.
  30
  31 <H2>Flags Affected</H2>
  32
  33 None
  34
  35 <H2>Protected Mode Exceptions</H2>
  36
  37 #GP(0) for an illegal memory operand effective address in the CS, DS,
  38 ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment;
  39 #GP(0) if the current privilege level is not 0; #GP(selector) if the object
  40 named by the source selector is not a TSS or is already busy;
  41 #NP(selector) if the TSS is marked "not present"; #PF(fault-code) for
  42 a page fault
  43
  44 <H2>Real Address Mode Exceptions</H2>
  45
  46 Interrupt 6; LTR is not recognized in Real Address Mode
  47
  48 <H2>Virtual 8086 Mode Exceptions</H2>
  49
  50 Same exceptions as in Real Address Mode
  51
  52 <H2>Notes</H2>
  53
  54 The operand-size attribute has no effect on this instruction.
  55
  56
  57 <P>
  58 <HR>
  59 <P>
  60 <B>up:</B> <A HREF="c17.htm">
  61 Chapter 17 -- 80386 Instruction Set</A><BR>
  62 <B>prev:</B><A HREF="LSL.htm"> LSL Load Segment Limit</A><BR>
  63 <B>next:</B><A HREF="MOV.htm"> MOV Move Data</A>
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