Method and apparatus to limit DC-level in coded data
AssigneeMarvell International Ltd.
InventorsMats Oberg, Pantas Sutardja
Life of this patent
Estimating the term…
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.
Claims19
A method comprising:
- receiving a first data stream, the first data stream including one or more patterns associated with a predetermined level of DC wander;
- scrambling the first data stream with at least one of a plurality of scrambler seeds;
- determining if the predetermined level meets a minimum baseline;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if it is determined that the predetermined level does not meet the minimum baseline, and
- determining whether there is at least one scrambler seed remaining in the plurality of scrambler seeds that has not been used previously for scrambling the first data stream,
- if there are no scrambler seeds that have not been used previously for scrambling a data stream, scrambling the first data stream with at least one of a plurality of scrambler seeds includes:
- selecting a scrambler seed among the plurality of scrambler seeds that yields a minimal baseline;
- and
- scrambling the first data stream using the selected scrambler seed.
A method comprising:
- scrambling a first data stream with at least one of a plurality of scrambler seeds, the first data stream including one or more patterns associated with a baseline wander;
- measuring the baseline wander in the first data stream;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if the baseline wander exceeds a predetermined baseline;
- and
- determining whether there is at least one scrambler seed that has not been used previously for scrambling a data stream,
- wherein if there are no scrambler seeds that have not been used previously for scrambling a data stream, scrambling the first data stream with a second scrambler seed includes:
- selecting a scrambler seed among the scrambler seeds that yields a minimal baseline wander;
- and
- scrambling the first data stream using the selected scrambler seed.
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- receiving a first data stream, the first data stream including one or more patterns associated with a predetermined level of DC wander;
- scrambling the first data stream with at least one of a plurality of scrambler seeds;
- determining if the predetermined level meets a minimum baseline;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if it is determined that the predetermined level does not meet the minimum baseline, and
- determining whether there is at least one scrambler seed that has not been used previously for scrambling a data stream,
- wherein if there are no scrambler seeds that have not been used previously for scrambling a data stream, scrambling the first data stream with a second scrambler seed includes:
- selecting a scrambler seed among the scrambler seeds that yields a minimal baseline wander;
- and
- scrambling the first data stream using the selected scrambler seed.
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- scrambling a first data stream with at least one of a plurality of scrambler seeds, the first data stream including one or more patterns associated with a baseline wander;
- measuring the baseline wander in the first data stream;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if the baseline wander exceeds a predetermined baseline, and
- determining whether there is at least one scrambler seed that has not been used previously for scrambling a data stream,
- wherein if there are no scrambler seeds that have not been used previously for scrambling a data stream, scrambling the first data stream with a second scrambler seed includes:
- selecting a scrambler seed among the scrambler seeds that yields a minimal baseline wander;
- and
- scrambling the first data stream using the selected scrambler seed.
A method comprising:
- scrambling a first data stream with at least one of a plurality of scrambler seeds, the first data stream including one or more patterns associated with a baseline wander;
- measuring the baseline wander in the first data stream;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if the baseline wander exceeds a predetermined baseline;
- and
- monitoring a mean of an absolute value of a running digital sum over at least one of the first data stream or the second data stream to determine if the mean of the absolute value exceeds a given threshold.
A computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform operations comprising:
- scrambling a first data stream with at least one of a plurality of scrambler seeds, the first data stream including one or more patterns associated with a baseline wander;
- measuring the baseline wander in the first data stream;
- scrambling the first data stream with another one of the scrambler seeds to form a second data stream if the baseline wander exceeds a predetermined baseline;
- and
- monitoring a mean of an absolute value of a running digital sum over at least one of the first data stream or the second data stream to determine if the mean of the absolute value exceeds a given threshold.
Dependencies are inferred from the claim text.