i386/i386.reference/DIV.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode DIV</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  13 <P>
  14 <H1>DIV -- Unsigned Divide</H1>
  15
  16 <PRE>
  17 Opcode    Instruction        Clocks   Description
  18
  19 F6 /6     DIV AL,r/m8        14/17    Unsigned divide AX by r/m byte
  20                                       (AL=Quo, AH=Rem)
  21 F7 /6     DIV AX,r/m16       22/25    Unsigned divide DX:AX by r/m
  22                                       word (AX=Quo, DX=Rem)
  23 F7 /6     DIV EAX,r/m32      38/41    Unsigned divide EDX:EAX by r/m
  24                                       dword (EAX=Quo, EDX=Rem)
  25 </PRE>
  26
  27 <H2>Operation</H2>
  28
  29 <PRE>
  30 temp := dividend / divisor;
  31 IF temp does not fit in quotient
  32 THEN Interrupt 0;
  33 ELSE
  34    quotient := temp;
  35    remainder := dividend MOD (r/m);
  36 FI;
  37 </PRE>
  38
  39 <EM>
  40 <H3>Note</H3>
  41   Divisions are unsigned. The divisor is given by the r/m operand.
  42   The dividend, quotient, and remainder use implicit registers. Refer to
  43   the table under "Description"
  44 </EM>
  45
  46 <H2>Description</H2>
  47
  48 DIV performs an unsigned division. The dividend is implicit; only the
  49 divisor is given as an operand. The remainder is always less than the
  50 divisor. The type of the divisor determines which registers to use as
  51 follows:
  52 <PRE>
  53
  54     Size    Dividend     Divisor   Quotient   Remainder
  55     byte    AX           r/m8       AL          AH
  56     word    DX:AX        r/m16      AX          DX
  57     dword   EDX:EAX      r/m32      EAX         EDX
  58 </PRE>
  59
  60 <H2>Flags Affected</H2>
  61
  62 OF, SF, ZF, AR, PF, CF are undefined.
  63
  64 <H2>Protected Mode Exceptions</H2>
  65
  66 Interrupt 0 if the quotient is too large to fit in the designated register
  67 (AL, AX, or EAX), or if the divisor is 0; #GP(0) for an illegal memory
  68 operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0)
  69 for an illegal address in the SS segment; #PF(fault-code) for a page fault
  70
  71 <H2>Real Address Mode Exceptions</H2>
  72
  73 Interrupt 0 if the quotient is too big to fit in the designated register
  74 (AL, AX, or EAX), or if the divisor is 0; Interrupt 13 if any part of the
  75 operand would lie outside of the effective address space from 0 to 0FFFFH
  76
  77 <H2>Virtual 8086 Mode Exceptions</H2>
  78
  79 Same exceptions as in Real Address Mode; #PF(fault-code) for a page
  80 fault
  81
  82
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  86 <B>up:</B> <A HREF="c17.htm">
  87 Chapter 17 -- 80386 Instruction Set</A><BR>
  88 <B>prev:</B><A HREF="DEC.htm"> DEC Decrement by 1</A><BR>
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