i386/i386.reference/DAA.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode DAA</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  14 <H1>DAA -- Decimal Adjust AL after Addition</H1>
  15
  16 <PRE>
  17 Opcode    Instruction        Clocks   Description
  18
  19 27        DAA                4        Decimal adjust AL after addition
  20 </PRE>
  21
  22 <H2>Operation</H2>
  23
  24 <PRE>
  25 IF ((AL AND 0FH) > 9) OR (AF = 1)
  26 THEN
  27    AL := AL + 6;
  28    AF := 1;
  29 ELSE
  30    AF := 0;
  31 FI;
  32 IF (AL > 9FH) OR (CF = 1)
  33 THEN
  34    AL := AL + 60H;
  35    CF := 1;
  36 ELSE CF := 0;
  37 FI;
  38 </PRE>
  39
  40 <H2>Description</H2>
  41
  42 Execute DAA only after executing an
  43 <A HREF="ADD.htm">ADD</A> instruction that leaves a
  44 two-BCD-digit byte result in the AL register. The
  45 <A HREF="ADD.htm">ADD</A> operands should
  46 consist of two packed BCD digits. The DAA instruction adjusts AL to
  47 contain the correct two-digit packed decimal result.
  48
  49 <H2>Flags Affected</H2>
  50
  51 AF and CF as described above; SF, ZF, PF, and CF as described in
  52 <A HREF="appc.htm">Appendix C</A>.
  53
  54 <H2>Protected Mode Exceptions</H2>
  55
  56 None
  57
  58 <H2>Real Address Mode Exceptions</H2>
  59
  60 None
  61
  62 <H2>Virtual 8086 Mode Exceptions</H2>
  63
  64 None
  65
  66
  67 <P>
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  69 <P>
  70 <B>up:</B> <A HREF="c17.htm">
  71 Chapter 17 -- 80386 Instruction Set</A><BR>
  72 <B>prev:</B><A HREF="CWD.htm"> CWD/CDQ  Convert Word to Doubleword/Convert Doubleword to Quadword</A><BR>
  73 <B>next:</B><A HREF="DAS.htm"> DAS Decimal Adjust AL after Subtraction</A>
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