Systems and methods are disclosed for timing servo operations within a channel based on a counter for a disc locked clock. In certain embodiments, an apparatus may comprise a servo channel configured to lock a frequency of a servo channel clock to a rotational velocity of a disc data storage medium, and maintain a counter of clock cycles for the servo channel clock. The servo channel may perform operations to read servo data from a servo sector on the disc data storage medium at a first counter value selected relative to a target counter value corresponding to an expected location of a servo timing mark (STM).

A data storage device is disclosed wherein a first plurality of codewords are generated each comprising a plurality of symbols, and a first parity sector is generated over the first plurality of codewords. A second plurality of codewords are generated each comprising a plurality of symbols, and a second parity sector is generated over the second plurality of codewords. A third parity sector is generated over a first subset of the first plurality of codewords and a first subset of the second plurality of codewords, and a fourth parity sector is generated over a second subset of the first plurality of codewords and a second subset of the second plurality of codewords. When processing of a first codeword fails, the first codeword and the first parity sector are processed using a LDPC type decoder, and the first codeword and the third parity sector are processed using the LDPC type decoder.

According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

A data storage device is disclosed comprising a storage medium. Input data is encoded according to at least one channel code constraint to generate first data and second data. The first data is encoded into a first codeword, and the second data is encoded into a second codeword, wherein a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.

A data storage device is disclosed comprising a storage medium. First data is encoded into a first codeword comprising a plurality of i-bit symbols, and second data is encoded into a second codeword comprising a plurality of j-bit symbols, wherein i is different than j and a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are symbol interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.

A data storage device is disclosed comprising a disk comprising servo data, and an actuator configured to actuate a head over the disk. A servo controller is configured to generate digital control values at a first sample rate based on the servo data and transmit the digital control values over a serial interface to a driver circuit. The driver circuit is configured to generate predictive oversampled control values at a second sample rate higher than the first sample rate based on at least two of the digital control values received from the servo controller, apply the predictive oversampled control values to a digital-to-analog converter (DAC) to generate an analog control signal, and apply the analog control signal to the actuator.

According to one embodiment, a storage device includes a detector, a demodulator, a controller, and a recorder. When a user data item is split data including first data being at least part of a first code word and second data being at least part of a second code word, the controller sets a start position of the second data for forced search of the second code word on the basis of the position of a sync mark recorded in the recorder when the forced search of the first code word has succeeded.

In some implementations, a system includes a magnetic media disk and a read/write unit. The read/write unit includes a plurality of phase-locked loops (PLLs), an interpolator unit, a delay-locked loop, and a precompensation unit. The PLLs are configured to generate, using a reference clock signal, a first plurality of clock signals having different frequencies phases. The interpolator unit is configured to interpolate the first plurality of clock signals in accordance with a frequency offset signal to generate a single-phase clock signal. The delay-locked loop is configured to delay the single-phase clock signal in accordance with a PLL data clock signal to generate a second plurality of clock signals having different phases. The precompensation unit is configured to apply precompensation to the second plurality of clock signals to generate a timing signal for writing data to the magnetic media disk.

A data storage device is disclosed comprising a storage medium. First data is encoded into a first codeword comprising a plurality of i-bit symbols, and second data is encoded into a second codeword comprising a plurality of j-bit symbols, wherein i is different than j and a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are symbol interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.

A data storage device is disclosed comprising a storage medium. Input data is encoded according to at least one channel code constraint to generate first data and second data. The first data is encoded into a first codeword, and the second data is encoded into a second codeword, wherein a first code rate of the first codeword is less than a second code rate of the second codeword. The first codeword and the second codeword are interleaved to generate an interleaved codeword, and the interleaved codeword is written to the storage medium.