44 lines
2.1 KiB
HTML
44 lines
2.1 KiB
HTML
<html><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<html>
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<head>
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<title>80386 Programmer's Reference Manual -- Opcode LTR</title>
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</head>
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<body>
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<b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="LSL.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LSL.HTM"> LSL Load Segment Limit</a><br>
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<b>next:</b><a href="MOV.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/MOV.HTM"> MOV Move Data</a>
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<p>
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<hr>
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<p>
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<h1>LTR -- Load Task Register</h1>
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<pre>
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Opcode Instruction Clocks Description
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0F 00 /3 LTR r/m16 pm=23/27 Load EA word into task register
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</pre>
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<h2>Description</h2>
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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.
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<p>LTR is used only in operating system software; it is not used in application programs.
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<h2>Flags Affected</h2>
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None
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<h2>Protected Mode Exceptions</h2>
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#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
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<h2>Real Address Mode Exceptions</h2>
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Interrupt 6; LTR is not recognized in Real Address Mode
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<h2>Virtual 8086 Mode Exceptions</h2>
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Same exceptions as in Real Address Mode
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<h2>Notes</h2>
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The operand-size attribute has no effect on this instruction.
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<p>
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<hr>
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<p><b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="LSL.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LSL.HTM"> LSL Load Segment Limit</a><br>
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<b>next:</b><a href="MOV.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/MOV.HTM"> MOV Move Data</a>
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</body>
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