摘要:
Geometrically-dependent error rates are used to identify sectors for XORing data in a RAID system for parity purposes in such a way that the probability of failure of any particular group is minimized.
摘要:
Techniques are provided for identifying the servo sectors in a track on a data storage device. A data storage device identifies the servo sectors in a track by reading distributed index bits from multiple servo sectors in a track. The data storage device analyzes only one index bit from each servo sector to identify the index of a track. In some embodiments, the index of a track can be identified after examining the index bits stored in a particular number of consecutive servo sectors, even in the presence of errors. The index bits in each track can have an error tolerance with a minimum Hamming distance greater than one. In other embodiments, a data storage device compares a sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within a pattern of the index bits stored on a track.
摘要:
Servo patterns for patterned media. The servo pattern includes specification of cylinder/track ID with and without a Gray code. The servo pattern space is minimized by the optimum usage of the islands. This is achieved by island allocation rules to take advantage of non-magnetic island. The island allocation also provides for easier lift-off. Logic is used to encode and decode the Gray code. Further, the Gray code is designed to stabilize the magnetic island/non-magnetic island ratio to allow for easier manufacture.
摘要:
An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.
摘要:
Bit and byte synchronization for sampling and decoding a data string is provided a single data field u. The data string x has pre-pended to it a short string of is (ones), followed by u to yield a string y= . . . 1111, u, x. The string is pre-coded by convolution with 1/(1⊕D2). PRML-sampling of y starts at an initial phase, and vectors are obtained from that string by sampling at pre-selected phases following the initial sampling point. The vectors of y are compared with vectors corresponding to PRML samples of an initial set of bits in u obtained at predetermined phases. The pair of y, u vectors exhibiting the minimum Euclidian distance yields a sampling correction value by which the initial sampling phase is corrected and a new initial sampling point preceding x is determined. Here, bit and byte synchronization have been achieved and sampling of x proceeds at the corrected phase, from the new initial sampling point.
摘要:
A byte synchronization detection system and method in which a vector subtractor circuit determines an error vector between a current read data pattern and a synchronization bit pattern, and an offset adder circuit determines a Hamming Distance of the next read data pattern by adding the difference between the Hamming Distance from current error vector to the synchronization bit pattern and the Hamming Distance from the next error vector to the synchronization bit pattern. The Hamming Distance is determined by selected elements of the error vector which are the output from the vector subtractor circuit. The offset adder circuit determines a difference between the Hamming Distance of the current read data pattern and of the next read data pattern. The synchronization bit pattern is between 16 and 18 bits in length, inclusive. This approach reduces the probability of synchronization failure and/or mis-synchronization about 4 orders of magnitude over conventional approaches, while also reducing the length of the byte synchronization pattern to 16 bits.
摘要:
Disclosed is an error tolerant binary encoded synchronization mark concatenated with a known pattern, such as a VFO pattern, comprising an encoded pattern of a fixed plurality of bits, the encoded synchronization pattern being at maximum Hamming distance from the concatenated known pattern for the number of bits in the fixed plurality of bits. The error tolerant synchronization mark may also be concatenated with the VFO pattern seen in reverse, and the synchronization pattern additionally is at maximum Hamming distance from the concatenated known VFO pattern seen in reverse.
摘要:
Servo patterns for patterned media. The servo pattern includes specification of cylinder/track ID with and without a Gray code. The servo pattern space is minimized by the optimum usage of the islands. This is achieved by island allocation rules to take advantage of non-magnetic island. The island allocation also provides for easier lift-off. Logic is used to encode and decode the Gray code. Further, the Gray code is designed to stabilize the magnetic island/non-magnetic island ratio to allow for easier manufacture.
摘要:
Servo patterns for patterned media. The servo pattern includes specification of cylinder/track ID with and without a Gray code. The servo pattern space is minimized by the optimum usage of the islands. This is achieved by island allocation rules to take advantage of non-magnetic island. The island allocation also provides for easier lift-off. Logic is used to encode and decode the Gray code. Further, the Gray code is designed to stabilize the magnetic island/non-magnetic island ratio to allow for easier manufacture.
摘要:
Techniques are provided for reducing error propagation in encoded data using Fibonacci modulation codes. The Fibonacci modulation codes have a Fibonacci base with a variable span that limits error propagation. Some of the elements in the Fibonacci base have a larger span than limited span elements in the base. Errors occurring in bit positions of an encoded sequence that correspond to the limited span elements do not propagate to adjacent bytes in the decoded sequence. The Fibonacci modulation codes can also have a relatively high code rate.