US 7,605,992 B2 · Robust LPOS detection with predictor and bit verifier

Abstract

A tape drive system which includes the ability to reliably reproduce LPOS information even if both of the servo channels of the tape drive system could not detect the LPOS information due to defects. The system recognizes that an LPOS sequence is sequentially incremented by one if a tape is moving in a forward direction and decremented by one if the tape is moving in a backward direction. This sequential property of the LPOS information lends itself to LPOS prediction, where the LPOS prediction is the previous LPOS value plus one if the tape is moving forward and the previous LPOS value minus one if the tape is moving backward. Even if the LPOS words from the two servo channels are both bad, but not all of the bits in the LPOS word are bad. The system uses the remaining good bits from the two servo channels to verify all of the bits of the LPOS prediction word.

Claims18

Dependent claims

A method for providing linear position (LPOS) predictions for a tape within a tape drive system comprising:

generating a first LPOS verifier, the first LPOS verifier comprising a plurality of first LPOS verifier bits;
generating a second LPOS verifier the second LPOS verifier comprising a plurality of second LPOS verifier bits;
and
determining whether bits of the plurality of first LPOS verifier bits are bad bits;
determining whether any bits within the plurality of second LPOS verifier bits are bad bits;
and,
determining whether bad bits of the plurality of first LPOS verifier bits are coincident with bad bits of the plurality of second LPOS verifier bits.

4 more elements

A tape drive system comprising:

a tape head;
a linear position (LPOS) detection module coupled to the tape head, the LPOS detection module providing predictions for a tape within the tape drive system, the LPOS detection system comprising
a first LPOS verifier module, the first LPOS verifier module generating the first LPOS verifier comprising a plurality of first LPOS verifier bits;
a second LPOS verifier module, the second LPOS verifier module generating a second LPOS verifier the second LPOS verifier comprising a plurality of second LPOS verifier bits;
and
a first determining module, the first determining module determining whether bits of the plurality of first LPOS verifier bits are bad bits;
a second determining module, the second determining module determining whether any bits within the plurality of second LPOS verifier bits are bad bits;
and,
a coincident module, the coincident determining whether bad bits of the plurality of first LPOS verifier bits are coincident with bad bits of the plurality of second LPOS verifier bits.

6 more elements

Dependencies are inferred from the claim text.

Robust LPOS detection with predictor and bit verifier

Life of this patent

Robust LPOS detection with predictor and bit verifier

Life of this patent

Abstract

Claims18