x86 Instruction Set Reference

CMC

Complement Carry Flag

Opcode Mnemonic Description
F5 CMC Complement CF flag.
Description

Complements the CF flag in the EFLAGS register.
Operation 
CF = ~CF;
Flags affected

The CF flag contains the complement of its original value. The OF, ZF, SF, AF, and PF flags are unaffected.

Exceptions
None.