49 lines
1.6 KiB
HTML
49 lines
1.6 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 STD</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="STC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STC.HTM"> STC Set Carry Flag</a><br>
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<b>next:</b><a href="STI.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STI.HTM"> STI Set Interrupt Flag</a>
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<p>
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<hr>
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<p>
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<h1>STD -- Set Direction Flag</h1>
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<pre>
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Opcode Instruction Clocks Description
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FD STD 2 Set direction flag so (E)SI and/or (E)DI
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decrement
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</pre>
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<h2>Operation</h2>
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<pre>
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DF := 1;
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</pre>
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<h2>Description</h2>
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STD sets the direction flag to 1, causing all subsequent string operations to decrement the index registers, (E)SI and/or (E)DI, on which they operate.
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<h2>Flags Affected</h2>
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DF := 1
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<h2>Protected Mode Exceptions</h2>
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None
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<h2>Real Address Mode Exceptions</h2>
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None
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<h2>Virtual 8086 Mode Exceptions</h2>
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None
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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="STC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STC.HTM"> STC Set Carry Flag</a><br>
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<b>next:</b><a href="STI.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/STI.HTM"> STI Set Interrupt Flag</a>
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</body>
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