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DIV -- Unsigned Divide

Opcode    Instruction        Clocks   Description

F6 /6     DIV AL,r/m8        14/17    Unsigned divide AX by r/m byte
                                      (AL=Quo, AH=Rem)
F7 /6     DIV AX,r/m16       22/25    Unsigned divide DX:AX by r/m
                                      word (AX=Quo, DX=Rem)
F7 /6     DIV EAX,r/m32      38/41    Unsigned divide EDX:EAX by r/m
                                      dword (EAX=Quo, EDX=Rem)

Operation

temp := dividend / divisor;
IF temp does not fit in quotient
THEN Interrupt 0;
ELSE
   quotient := temp;
   remainder := dividend MOD (r/m);
FI;

Note

Divisions are unsigned. The divisor is given by the r/m operand. The dividend, quotient, and remainder use implicit registers. Refer to the table under "Description"

Description

DIV performs an unsigned division. The dividend is implicit; only the divisor is given as an operand. The remainder is always less than the divisor. The type of the divisor determines which registers to use as follows:

    Size    Dividend     Divisor   Quotient   Remainder
    byte    AX           r/m8       AL          AH
    word    DX:AX        r/m16      AX          DX
    dword   EDX:EAX      r/m32      EAX         EDX

Flags Affected

OF, SF, ZF, AR, PF, CF are undefined.

Protected Mode Exceptions

Interrupt 0 if the quotient is too large to fit in the designated register (AL, AX, or EAX), or if the divisor is 0; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Interrupt 0 if the quotient is too big to fit in the designated register (AL, AX, or EAX), or if the divisor is 0; Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH

Virtual 8086 Mode Exceptions

Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault


up: Chapter 17 -- 80386 Instruction Set
prev: DEC Decrement by 1
next: ENTER Make Stack Frame for Procedure Parameters