60 lines
2.2 KiB
HTML
60 lines
2.2 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 DAA</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="CWD.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/CWD.HTM"> CWD/CDQ Convert Word to Doubleword/Convert Doubleword to Quadword</a><br>
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<b>next:</b><a href="DAS.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DAS.HTM"> DAS Decimal Adjust AL after Subtraction</a>
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<p>
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<hr>
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<p>
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<h1>DAA -- Decimal Adjust AL after Addition</h1>
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<pre>
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Opcode Instruction Clocks Description
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27 DAA 4 Decimal adjust AL after addition
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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 DAA only after executing an <a href="ADD.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/ADD.HTM">ADD</a> instruction that leaves a two-BCD-digit byte result in the AL register. The <a href="ADD.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/ADD.HTM">ADD</a> operands should consist of two packed BCD digits. The DAA instruction adjusts AL to contain the correct two-digit packed decimal result.
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<h2>Flags Affected</h2>
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AF and CF as described above; SF, ZF, PF, and CF 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="CWD.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/CWD.HTM"> CWD/CDQ Convert Word to Doubleword/Convert Doubleword to Quadword</a><br>
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<b>next:</b><a href="DAS.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/DAS.HTM"> DAS Decimal Adjust AL after Subtraction</a>
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</body>
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