17.3.N 'N' Instructions
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17.3.N 'N' Instructions
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
NOP -- No Operation
Opcode Instruction Clocks Description
90 NOP 3 No operation
Description
NOP performs no operation. NOP is a one-byte instruction that takes
up space but affects none of the machine context except (E)IP.
NOP is an alias mnemonic for the XCHG (E)AX, (E)AX instruction.
Flags Affected
None
Protected Mode Exceptions
None
Real Address Mode Exceptions
None
Virtual 8086 Mode Exceptions
None
NOT -- One's Complement Negation
Opcode Instruction Clocks Description
F6 /2 NOT r/m8 2/6 Reverse each bit of r/m byte
F7 /2 NOT r/m16 2/6 Reverse each bit of r/m word
F7 /2 NOT r/m32 2/6 Reverse each bit of r/m dword
Operation
r/m <- NOT r/m;
Description
NOT inverts the operand; every 1 becomes a 0, and vice versa.
Flags Affected
None
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
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