Abstract: In an optical disk drive system, an apparatus and method for determining whether data read from a particular field within a particular sector of an optical disk corresponds to a code which specifies that the sector should not be erased. A crystal clock generates a synthesized clock signal. A front-end detector generates a signal synchronized to the synthesized clock signal which represents data read from the field. The signal is then serially shifted by a serial shift register. A comparator compares the shifted signal with the code specifying that the sector should not be erased. If there is a match, a counter is incremented. When the counter reaches or exceeds a pre-determined number, a signal is sent to the optical disk drive system indicating that the sector contains data which should not be erased.