Disk drive employing read error tolerant sync mark detection

A disk drive having a pattern detector for providing fault-tolerant detection of a data sync mark represented by a substring of a concatenated string of error-prone read symbols and for providing a reduced risk of detection error, the disk drive comprising:

• a disk having a plurality of track segments;
• write means having an input for receiving bits;
• means operative during a first operation for supplying a sequence of write bits that are received at the input of the write means;
• the sequence of write bits defining a preamble write string, a data sync mark write string, and a user data write string;
• the preamble write string and the data sync mark write string corresponding to a concatenated string of expected symbols;
• the write means having means responsive to each write bit received at the input of the write means for magnetically defining a respective bit cell of a sequence of bit cells along a track segment;
• a sampled-data read channel;
• the sampled-data read channel including read means operative during a second operation for responding to the sequence of bit cells defined during the first operation to produce a sequence of error-prone symbols that are subject to error in duplicating the concatenated string of expected symbols;
• the data sync mark write string corresponding to an ordered set of m expected symbols selected to have maximum distance from all non-mark substrings of m consecutive expected symbols that exist in the concatenated string of expected symbols;
• means for enabling the pattern detector during an enabling interval within the second operation beginning after the read means has produced a portion of the sequence of error-prone read symbols;
• and
• the pattern detector including fault-tolerant means operative during the enabling interval for producing a sync mark detection signal.