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US 7,330,320 B1Granted
Method and apparatus to limit DC-level in coded data
AssigneeMarvell International Ltd.
InventorsMats Oberg, Pantas Sutardja
Life of this patent
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Abstract
In a perpendicular magnetic recording system, the data that is being written by the write channel is fed back into the read channel. The read channel processes the data and decides if the written sequence is likely to have very poor DC characteristics. If that is the case, the write channel changes a scrambler seed and rewrites the data using the new scrambler seed. The data may also be inspected for patterns that might cause large baseline wander before being written to disk, i.e., in the write channel. A data sequence may be repeatedly scrambled and encoded until an acceptable level of estimated DC-wander has been achieved. The data sequence may then be written to disk.
Claims64
A method comprising:
- encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander, including determining an estimate of DC wander;
- and
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence;
- and
- encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence.
4 more elements
A method comprising:
- encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- and
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence with a scrambler;
- encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence;
- storing the first encoded data sequence in an output buffer;
- and
- in response to determining that the first encoded sequence does not include one or more of said patterns, outputting the first encoded data sequence to a write channel for writing to a magnetic medium.
6 more elements
A method comprising:
- encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- and
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence with a scrambler;
- encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence;
- and
- prior to encoding the data sequence to form the first encoded data sequence,
- scrambling the data sequence with another scrambler seed.
6 more elements
An apparatus comprising:
- a scrambler module;
- a modulation encoder to encode a data sequence to form a first encoded data sequence;
- and
- an estimation module to determine if the first encoded sequence includes one or more patterns associated with large baseline wander and produce an estimate of the DC wander, and in response to determining that the first encoded sequence includes one or more of said patterns, control the scrambler module to scramble the data sequence with a scrambler seed.
1 more element
An apparatus comprising:
- a scrambler module;
- a modulation encoder to encode a data sequence to form a first encoded data sequence;
- an estimation module to determine if the first encoded sequence includes one or more patterns associated with large baseline wander, and in response to determining that the first encoded sequence includes one or more of said patterns, control the scrambler module to scramble the data sequence with a scrambler seed;
- and
- an output buffer to store the first encoded data sequence,
- wherein the estimation module is operative to control the output buffer to output the first encoded data sequence to a write channel for writing to the magnetic medium in response to determining that the first encoded sequence does not include one or more of said patterns.
3 more elements
An apparatus comprising:
- a scrambler module;
- a modulation encoder to encode a data sequence to form a first encoded data sequence;
- and
- an estimation module to determine if the first encoded sequence includes one or more patterns associated with large baseline wander, and in response to determining that the first encoded sequence includes one or more of said patterns, control the scrambler module to scramble the data sequence with a scrambler seed, wherein the scrambler module is operative to scramble the data sequence with another scrambler seed prior to being encoded to form the first encoded data sequence.
1 more element
An apparatus comprising:
- means for encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- means for determining if the first encoded sequence includes one or more patterns associated with large baseline wander including means for determining an estimate of DC wander;
- and
- means for scrambling the data sequence with a scrambler seed in response to determining that the first encoded sequence includes one or more of said patterns;
- and
- means for encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence.
3 more elements
An apparatus comprising:
- means for encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- means for determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- means for scrambling the data sequence with a scrambler seed in response to determining that the first encoded sequence includes one or more of said patterns;
- and
- means for encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence;
- and
- means for buffering the first encoded data sequence, said means operative to output the first encoded data sequence to a write channel for writing to the magnetic medium in response to determining that the first encoded sequence does not include one or more of said patterns.
4 more elements
An apparatus comprising:
- means for encoding a data sequence with a modulation encoder to form a first encoded data sequence;
- means for determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- means for scrambling the data sequence with a scrambler seed in response to determining that the first encoded sequence includes one or more of said patterns;
- and
- means for encoding said scrambled data sequence with the modulation encoder to form a second encoded data sequence;
- and
- means for scrambling the data sequence with another scrambler seed prior to encoding the data sequence to form the first encoded data sequence.
4 more elements
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- encoding a data sequence to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander including determining an estimate of DC wander;
- and
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence with a scrambler seed;
- and
- encoding said scrambled data sequence to form a second encoded data sequence.
4 more elements
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- encoding a data sequence to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- and
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence with a scrambler seed;
- encoding said scrambled data sequence to form a second encoded data sequence storing the first encoded data sequence in an output buffer;
- and
- in response to determining that the first encoded sequence does not include one or more of said patterns, outputting the first encoded data sequence to a write channel for writing to the magnetic medium.
5 more elements
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- encoding a data sequence to form a first encoded data sequence;
- determining if the first encoded sequence includes one or more patterns associated with large baseline wander;
- in response to determining that the first encoded sequence includes one or more of said patterns,
- scrambling the data sequence with a scrambler seed;
- encoding said scrambled data sequence to form a second encoded data sequence;
- and
- prior to encoding the data sequence to form the first encoded data sequence, scrambling the data sequence with another scrambler seed.
4 more elements
Dependencies are inferred from the claim text.