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AAA.htm
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML>
<HEAD>
<TITLE>80386 Programmer's Reference Manual -- Opcode AAA</TITLE>
</HEAD>
<BODY>
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B> <A HREF="s17_02.htm">
17.2 Instruction Format</A><BR>
<B>next:</B><A HREF="AAD.htm"> AAD ASCII Adjust AX before Division</A>
<P>
<HR>
<P>
<H1>AAA -- ASCII Adjust after Addition</H1>
<PRE>
Opcode Instruction Clocks Description
37 AAA 4 ASCII adjust AL after addition
</PRE>
<H2>Operation</H2>
<PRE>
IF ((AL AND 0FH) > 9) OR (AF = 1)
THEN
AL := (AL + 6) AND 0FH;
AH := AH + 1;
AF := 1;
CF := 1;
ELSE
CF := 0;
AF := 0;
FI;
</PRE>
<H2>Description</H2>
Execute AAA only following an
<A HREF="ADD.htm">ADD</A> instruction that leaves a byte result
in the AL register. The lower nibbles of the operands of the
<A HREF="ADD.htm">ADD</A> instruction
should be in the range 0 through 9 (BCD digits). In this case, AAA adjusts
AL to contain the correct decimal digit result. If the addition produced a
decimal carry, the AH register is incremented, and the carry and auxiliary
carry flags are set to 1. If there was no decimal carry, the carry and
auxiliary flags are set to 0 and AH is unchanged. In either case, AL is left
with its top nibble set to 0. To convert AL to an ASCII result, follow the
AAA instruction with <A HREF="OR.htm">OR</A> AL, 30H.
<H2>Flags Affected</H2>
AF and CF as described above; OF, SF, ZF, and PF are undefined
<H2>Protected Mode Exceptions</H2>
None
<H2>Real Address 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="s17_02.htm">
17.2 Instruction Format</A><BR>
<B>next:</B><A HREF="AAD.htm"> AAD ASCII Adjust AX before Division</A>
</BODY>