i386/i386.reference/XCHG.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode XCHG</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  13 <P>
  14 <H1>XCHG -- Exchange Register/Memory with Register</H1>
  15
  16 <PRE>
  17 Opcode    Instruction      Clocks     Description
  18
  19 90 + r    XCHG AX,r16      3          Exchange word register with AX
  20 90 + r    XCHG r16,AX      3          Exchange word register with AX
  21 90 + r    XCHG EAX,r32     3          Exchange dword register with EAX
  22 90 + r    XCHG r32,EAX     3          Exchange dword register with EAX
  23 86  /r    XCHG r/m8,r8     3          Exchange byte register with EA byte
  24 86  /r    XCHG r8,r/m8     3/5        Exchange byte register with EA byte
  25 87  /r    XCHG r/m16,r16   3          Exchange word register with EA word
  26 87  /r    XCHG r16,r/m16   3/5        Exchange word register with EA word
  27 87  /r    XCHG r/m32,r32   3          Exchange dword register with EA dword
  28 87  /r    XCHG r32,r/m32   3/5        Exchange dword register with EA dword
  29 </PRE>
  30
  31
  32 <H2>Operation</H2>
  33
  34 <PRE>
  35 temp := DEST
  36 DEST := SRC
  37 SRC := temp
  38 </PRE>
  39
  40 <H2>Description</H2>
  41
  42 XCHG exchanges two operands. The operands can be in either order. If a
  43 memory operand is involved, BUS LOCK is asserted for the duration of the
  44 exchange, regardless of the presence or absence of the
  45 <A HREF="LOCK.htm">LOCK</A> prefix or of the
  46 value of the IOPL.
  47
  48 <H2>Flags Affected</H2>
  49
  50 None
  51
  52 <H2>Protected Mode Exceptions</H2>
  53
  54 #GP(0) if either operand is in a nonwritable segment; #GP(0) for an
  55 illegal memory operand effective address in the CS, DS, ES, FS, or GS
  56 segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)
  57 for a page fault
  58
  59 <H2>Real Address Mode Exceptions</H2>
  60
  61 Interrupt 13 if any part of the operand would lie outside of the effective
  62 address space from 0 to 0FFFFH
  63
  64 <H2>Virtual 8086 Mode Exceptions</H2>
  65
  66 Same exceptions as in Real Address Mode; #PF(fault-code) for a page
  67 fault
  68
  69
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  72 <P>
  73 <B>up:</B> <A HREF="c17.htm">
  74 Chapter 17 -- 80386 Instruction Set</A><BR>
  75 <B>prev:</B><A HREF="WAIT.htm"> WAIT Wait until BUSY# Pin is Inactive (HIGH)</A><BR>
  76 <B>next:</B><A HREF="XLAT.htm"> XLAT/XLATB Table Look-up Translation</A>
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