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CMC—Complement Carry Flag
| Opcode | Instruction | Op/En | 64-bit Mode | Compat/Leg Mode | Description |
|---|---|---|---|---|---|
| F5 | CMC | NP | Valid | Valid | Complement CF flag. |
Instruction Operand Encoding
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| NP | NA | NA | NA | NA |
Description
Complements the CF flag in the EFLAGS register. CMC operation is the same in non-64-bit modes and 64-bit mode.
Operation
EFLAGS.CF[bit 0]← NOT EFLAGS.CF[bit 0];
Flags Affected
The CF flag contains the complement of its original value. The OF, ZF, SF, AF, and PF flags are unaffected.
Exceptions (All Operating Modes)
#UD
If the LOCK prefix is used.