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Chapter 17 -- 80386 Instruction Set
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NEG -- Two's Complement Negation
Opcode Instruction Clocks Description
F6 /3 NEG r/m8 2/6 Two's complement negate r/m byte
F7 /3 NEG r/m16 2/6 Two's complement negate r/m word
F7 /3 NEG r/m32 2/6 Two's complement negate r/m dword
Operation
IF r/m = 0 THEN CF := 0 ELSE CF := 1; FI;
r/m := - r/m;
Description
NEG replaces the value of a register or memory operand with its two's
complement. The operand is subtracted from zero, and the result is placed
in the operand.
The carry flag is set to 1, unless the operand is zero, in which case the
carry flag is cleared to 0.
Flags Affected
CF as described above; OF, SF, ZF, and PF as described in Appendix C
Protected Mode Exceptions
#GP(0) if the result is in a nonwritable segment; #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 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: MUL Unsigned Multiplication of AL or AX
next: NOP No Operation