Abstract: Method and apparatus for removing residual magnetization in a data transducer, such as a recording head used to write data to a recording medium in a data storage device. A residual magnetization sense circuit senses a residual magnetization of a pole of the data transducer as a result of the application of a data transmission current to the transducer. A demagnetization current generator removes the residual magnetization by supplying the transducer with a demagnetizing current that decreases to a final magnitude in accordance with a selected profile. The demagnetization current preferably comprises a bi-directional, time varying current of selected frequency to the transducer that tapers linearly, exponentially or in a step-wise fashion to the final magnitude. The demagnetization profile is preferably continuously adapted during operation.

Abstract: Embodiments of the present invention illustrate various configurations of a channel-to-controller interface. In one embodiment, width of symbols crossing the interface is fixed, as is the clock rate. In other embodiments, the symbol width is variable, and the clock rate is also varied based upon the size of the interface symbol width and the operation of the channel.

Abstract: Embodiments of the present invention illustrate various configurations of a channel-to-controller interface. In one embodiment, width of symbols crossing the interface is fixed, as is the clock rate. In other embodiments, the symbol width is variable, and the clock rate is also varied based upon the size of the interface symbol width and the operation of the channel.

Abstract: An apparatus and method are disclosed for reducing the effects of thermal asperities and other anomalous conditions on disc drive read operations. An improved data block format is provided having first and second sync fields in which sync patterns are stored, the first and second sync fields being separated by a selected distance within the data block. The sync pattern of the second sync field enables synchronization of a disc drive read channel to the user data in the data block when the read channel fails to be synchronized by the sync pattern of the first sync field. In one embodiment, control information used by the read channel to prepare for receipt of the user data is stored in a field between the first and second sync fields; in an alternative embodiment, a portion of the user data is stored between the first and second sync fields.

Abstract: A pulse qualification apparatus and method provides for qualifying signal pulses from a raw data signal by comparison to a variable qualification level. Pulse qualification is done on a read signal developed by moving a magnetic transducer relative to addressable portions of a magnetic disk. A qualification level generator circuit generates a qualification level signal which varies in value depending upon the addressed portion of the magnetic disk. A threshold detector is used in qualifying pulses from a transducer read signal by comparison to the qualification level signal to generate an encoded pulse signal representing occurrences of qualifying pulses.

Abstract: A circuit for slimming signals read signals from a read/write head of a rotating disk data storage device. A low-pass filter and a high-pass filter are connected in parallel to the read signal from the read/write head. These filters each have a variable gain amplifier connected to their respective output ports. The gain of each of the variable gain amplifiers is programmably adjusted in accordance with preselected criteria. A summing circuit is connected to the outputs of the variable gain amplifiers to generate a slimmed read signal. A multi-pole low pass filter has an input port coupled to the output port of the summing circuit.

Abstract: A circuit for slimming signals read signals from a read/write head of a rotating disk data storage device. A low-pass filter and a high-pass filter are connected in parallel to the read signal from the read/write head. These filters each have a variable gain amplifier connected to their respective output ports. The gain of each of the variable gain amplifiers is programmably adjusted in accordance with preselected criteria. A summing circuit is connected to the outputs of the variable gain amplifiers to generate a slimmed read signal. A multi-pole low pass filter has an input port coupled to the output port of the summing circuit.

Abstract: A method and related system for use with a disk drive are disclosed for adjusting the current level emanating from a read/write head during recording of data onto a disk to compensate for differences in read/write head and disk relationships. Also, a method and related system are disclosed for determining the optimum slimming constant to be utilized to minimize data pulse peak shifts to compensate for differences in read/write head and disk relationships.

Abstract: A raw data signal, of the type generated from magnetic storage systems, is qualified by detecting the highest peak after the raw data signal passes qualification thresholds. This peak is used to indicate the true data pulse location. The location of the highest peak after the raw data signal has passed a minimum qualification threshold may be detected using a transistor circuit for charging a capacitor connected to a comparator or through a tri-level qualification scheme. Using tri-level qualification, a set of comparators and flip flops are used to locate raw data signal peaks.

Abstract: A circuit for phase locking a clock signal to a series of data pulses includes a wide band signal generator, a power supply, a flip-flop, a loop filter and a voltage controlled oscillator ("VCO"). The circuit adds current or subtracts current from the loop filter which controls the voltage across the VCO. The voltage across the VCO determines the frequency of the clock signal which it outputs. During the PLO sync zone, the circuit adds or subtracts increased amounts of current from the loop filter during every other pulse to cause greater amounts of correction in the frequency of the clock signal during every other pulse. The wide band signal generator, which includes a component which decays over time, operates only during the PLO sync zone. The circuit uses a flip-flop triggered by each data pulse to either send the current from the wide band signal generator to ground or add it to the constant current level produced by the power supply.