60 lines
2.0 KiB
HTML
60 lines
2.0 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 DAS</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="DAA.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DAA.HTM"> DAA Decimal Adjust AL after Addition</a><br>
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<b>next:</b><a href="DEC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DEC.HTM"> DEC Decrement by 1</a>
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<p>
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<hr>
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<p>
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<h1>DAS -- Decimal Adjust AL after Subtraction</h1>
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<pre>
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Opcode Instruction Clocks Description
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2F DAS 4 Decimal adjust AL after subtraction
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</pre>
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<h2>Operation</h2>
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<pre>
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IF (AL AND 0FH) > 9 OR AF = 1
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THEN
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AL := AL - 6;
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AF := 1;
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ELSE
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AF := 0;
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FI;
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IF (AL > 9FH) OR (CF = 1)
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THEN
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AL := AL - 60H;
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CF := 1;
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ELSE CF := 0;
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FI;
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</pre>
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<h2>Description</h2>
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Execute DAS only after a subtraction instruction that leaves a two-BCD-digit byte result in the AL register. The operands should consist of two packed BCD digits. DAS adjusts AL to contain the correct packed two-digit decimal result.
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<h2>Flags Affected</h2>
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AF and CF as described above; SF, ZF, and PF as described in <a href="APPC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/APPC.HTM">Appendix C</a>.
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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="DAA.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DAA.HTM"> DAA Decimal Adjust AL after Addition</a><br>
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<b>next:</b><a href="DEC.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DEC.HTM"> DEC Decrement by 1</a>
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</body>
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