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. |