i386/i386.reference/STD.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode STD</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
   9 <B>prev:</B><A HREF="STC.htm"> STC Set Carry Flag</A><BR>
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  11 <P>
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  13 <P>
  14 <H1>STD -- Set Direction Flag</H1>
  15
  16 <PRE>
  17 Opcode  Instruction   Clocks    Description
  18
  19 FD      STD           2         Set direction flag so (E)SI and/or (E)DI
  20                                 decrement
  21 </PRE>
  22
  23
  24 <H2>Operation</H2>
  25
  26 <PRE>
  27 DF := 1;
  28 </PRE>
  29
  30 <H2>Description</H2>
  31
  32 STD sets the direction flag to 1, causing all subsequent string operations
  33 to decrement the index registers, (E)SI and/or (E)DI, on which they
  34 operate.
  35
  36 <H2>Flags Affected</H2>
  37
  38 DF := 1
  39
  40 <H2>Protected Mode Exceptions</H2>
  41
  42 None
  43
  44 <H2>Real Address Mode Exceptions</H2>
  45
  46 None
  47
  48 <H2>Virtual 8086 Mode Exceptions</H2>
  49
  50 None
  51
  52
  53 <P>
  54 <HR>
  55 <P>
  56 <B>up:</B> <A HREF="c17.htm">
  57 Chapter 17 -- 80386 Instruction Set</A><BR>
  58 <B>prev:</B><A HREF="STC.htm"> STC Set Carry Flag</A><BR>
  59 <B>next:</B><A HREF="STI.htm"> STI Set Interrupt Flag</A>
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