Detection of saved sectors on an optical disk

In an optical disk drive system having an optical disk comprised of a plurality of sectors for storing data, an apparatus for detecting the occurrence of a particular code when a particular field of one of said sectors of said optical disk is read, said code indicating that said sector contains data which a user desires to remain unaltered, said apparatus comprising:

• a means for reading data from said field;
• a clock for generating a clock signal;
• a first read channel comprising:
• a) a first front-end detector for determining the occurrence of input pulses read from said field in reference to said clock signal, wherein a signal representing said data read from said field is generated;
• b) a first comparator for comparing said signal generated by said first front-end detector with said code which is fixed and indicating whether said signal generated by said first front-end detector is equivalent to said fixed code;
• a second read channel having an offset clock cycle as compared to said first read channel comprising:
• a) a second front-end for determining the occurrence of input pulses read from said field in reference to said clock signal, wherein a signal representing said data read from said field is generated;
• b) a second comparator for comparing said signal generated by said second front-end with said code which is fixed and indicating whether said signal generated by said second front-end is equivalent to said fixed code;
• a means for generating a signal indicating that said sector contains data which should not be altered, said signal being based on indications of said first and said second comparators.

In an optical disk drive system including an optical disk having a sector for storing data, a method for determining whether said sector contains data which is not to be erased, comprising the steps of:

• writing a code to a field corresponding to said sector, said code specifying that said sector is not to be erased;
• generating a synthesized clock signal;
• reading said field before said sector is to be erased;
• generating a signal synchronized with said synthesized clock signal which represents data read from said field comprising the steps of:
• detecting a leading edge of a first input pulse of said read data;
• referencing said first input pulse to said synthesized clock signal;
• generating a "high" output corresponding to said input pulse;
• detecting a leading edge of a second input pulse of said read data;
• referencing said second input pulse to said synthesized clock signal;
• and
• generating a "low" output for each of said synthesized clock signals which had occurred in between said first and said second input pulses;
• shifting said signal synchronized with said synthesized clock signal to produce a shifted synchronized signal;
• comparing said shifted synchronized signal with said code;
• generating an indication that said sector contains data which is not to be erased if said synchronized signal matches said code.