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DAA.htm
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML>
<HEAD>
<TITLE>80386 Programmer's Reference Manual -- Opcode DAA</TITLE>
</HEAD>
<BODY STYLE="width:80ch">
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="CWD.htm"> CWD/CDQ Convert Word to Doubleword/Convert Doubleword to Quadword</A><BR>
<B>next:</B><A HREF="DAS.htm"> DAS Decimal Adjust AL after Subtraction</A>
<P>
<HR>
<P>
<H1>DAA -- Decimal Adjust AL after Addition</H1>
<PRE>
Opcode Instruction Clocks Description
27 DAA 4 Decimal adjust AL after addition
</PRE>
<H2>Operation</H2>
<PRE>
IF ((AL AND 0FH) > 9) OR (AF = 1)
THEN
AL := AL + 6;
AF := 1;
ELSE
AF := 0;
FI;
IF (AL > 9FH) OR (CF = 1)
THEN
AL := AL + 60H;
CF := 1;
ELSE CF := 0;
FI;
</PRE>
<H2>Description</H2>
Execute DAA only after executing an
<A HREF="ADD.htm">ADD</A> instruction that leaves a
two-BCD-digit byte result in the AL register. The
<A HREF="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.
<H2>Flags Affected</H2>
AF and CF as described above; SF, ZF, PF, and CF as described in
<A HREF="appc.htm">Appendix C</A>.
<H2>Protected Mode Exceptions</H2>
None
<H2>Real Address Mode Exceptions</H2>
None
<H2>Virtual 8086 Mode Exceptions</H2>
None
<P>
<HR>
<P>
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="CWD.htm"> CWD/CDQ Convert Word to Doubleword/Convert Doubleword to Quadword</A><BR>
<B>next:</B><A HREF="DAS.htm"> DAS Decimal Adjust AL after Subtraction</A>
</BODY>