Abstract: A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

Abstract: A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a magnetic disk drive. In the method, track following is performed along a reference track, defined by previously written servo burst patterns, using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to the two-dimensional state model of the servo loop. Servo patterns are written at a target radial location on the magnetic disk medium during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the servo burst patterns at the target radial location.

Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks to the disk by actuating in a closed loop system a head positioning pin inserted into the disk drive. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The high frequency signal and sync marks in the spiral tracks are demodulated to maintain synchronization of a servo write clock as well as maintain the head along a circular target path while writing product servo sectors to the disk.

Abstract: A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo burst patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives position error signals, a first output that generates control signals for positioning a transducer head, a second output that generates track-following state variables, and a second input that receives processed and stored track-following state variables. The first target track is followed using the servo control loop while servo burst patterns are written, and while the processed and stored track-following state variables corresponding to the servo burst patterns defining the first target track are applied to the second input.

Abstract: A method of writing product servo bursts to a disk in a disk drive is disclosed. An external spiral servo writer comprising a head positioning pin and head positioning mechanics periodically writes a plurality of reference servo bursts in a plurality of spiral reference patterns to the disk. The reference servo bursts in the spiral reference patterns are processed to write product servo bursts to the disk. In one embodiment control circuitry within the disk drive processes the reference servo bursts to self-servo write the disk drive, and in another embodiment an external product servo writer processes the reference servo bursts to write the product servo bursts to the disk. In one embodiment, a slope of each spiral reference pattern is selected so that each spiral reference pattern is written over at least twenty revolutions of the disk to increase the accuracy of the head position error generated from the reference servo bursts.

Abstract: A method is disclosed for reducing disk expansion effects while writing spiral reference patterns on a disk. The disk drive comprises control circuitry and a head disk assembly (HDA). In the method, an external spiral servo writer is used to control a radial location of the head for writing a plurality of the spiral reference patterns in an order such that at least two of the spiral reference patterns are not written temporally sequential to an adjacent spiral reference pattern. The head internal to the disk drive is used to read the spiral reference patterns in order to write product servo bursts to the disk, thereby defining a plurality of radially spaced, concentric data tracks.

Abstract: A method of manufacturing a disk drive by demodulating product servo sectors and spiral tracks written on a disk of the disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The spiral tracks are used to write product servo sectors to the disk during a fill operation. Common circuitry, such as burst demodulation circuitry, is used to demodulate the high frequency signal in the spiral tracks during the fill operation as well as demodulate the product servo sectors.

Abstract: A disk drive is disclosed comprising a disk and a head actuated radially over the disk. An external servo writer is used to write reference servo bursts to the disk at a coarser radial resolution than product servo bursts. During a self servo writing operation, the reference servo bursts are processed to servo circularly to write a first set of product servo bursts to the disk. The reference servo bursts are also processed to servo spirally to write a second set of product servo bursts to the disk.

Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. An external spiral servo writer writes a plurality of reference servo sectors at an outer diameter of the disk and a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. At the beginning of the product servo writing process, the reference servo sectors are demodulated to initially synchronize a servo write clock. The spiral tracks are then demodulated to maintain synchronization of the servo write clock as well as maintain the head along a target circumferential path while writing product servo sectors to the disk.

Abstract: A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives timing error signals, a first output that generates control signals for a controlled oscillator, a second output that generates timing state variables, and a second input that receives stored timing state variables. The first target track is followed using the servo control loop while servo patterns are written, and while the stored timing state variables corresponding to the servo patterns defining the first target track are applied to the second input.

Abstract: A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a disk drive. Servo patterns are written on a reference track of the disk medium. Track following of the written servo patterns on the reference track is performed using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to a two-dimensional state model of the servo loop. Servo patterns are written on a target track during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the target track.

Abstract: A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo burst patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives position error signals, a first output that generates control signals for positioning a transducer head, a second output that generates track-following state variables, and a second input that receives stored track-following state variables. The first target track is followed using the servo control loop while servo burst patterns are written, and while the stored track-following state variables corresponding to the servo burst patterns defining the first target track are applied to the second input.

Abstract: A phase locked loop (PLL) circuit is disclosed comprising a phase detector for generating a phase error between an input oscillating signal and an output oscillating signal. A fractional frequency synthesizer (FFS) generates the output oscillating signal in response to the phase error, wherein the FFS comprises an input for receiving a reference oscillating signal, and a fractional divider responsive to variables I and Fr. The variable I is an integer value, and the variable Fr is a fractional value, both of which are generated in response to the phase error.

Abstract: A computer system is disclosed comprising a host connected to a disk drive, the disk drive comprising a disk having a disk surface. The disk drive further includes a controller and a channel integrated circuit chip. The controller includes a controller port. The channel integrated circuit chip includes an input for receiving a time-multiplexed analog read signal. The time-multiplexed analog read signal is processed to generate data symbols representing recovered servo data and recovered user data. The channel integrated circuit chip includes a channel port for transferring both the recovered servo data and the recovered user data. The disk drive further includes a communication bus connected between the channel port and the controller port. The channel port transfers both the recovered servo data and the recovered user data to the communication bus. The communication bus transfers both the recovered servo data and the recovered user data to the controller port.

Abstract: A computer system is disclosed comprising a host connected to a disk drive, the disk drive comprising a disk surface having a plurality of tracks arranged in an embedded servo format including servo track segments for storing servo data and data track segments for storing user data. The disk drive includes a read element operative during a user-data read operation for reading data from the disk surface to produce a time-multiplexed analog read signal that during a revolution of the disk represents analog read servo data during each of a first set of time intervals and represents analog read user data during each of a second set of time intervals. The disk drive includes a sampled signal processing circuit that generates a servo state variable while processing the time-multiplexed read signal during the first servo time interval and a user data state variable while processing the time-multiplexed read signal during the first user data time interval.

Abstract: A disk drive includes a disk having a disk surface. The disk surface has a plurality of tracks arranged in an embedded servo format including servo track segments for storing servo data and data track segments for storing user data. Data from the disk surface is read to produce a time-multiplexed analog read signal that during a revolution of the disk represents analog read servo data during each of a first set of time intervals and represents analog read user data during each of a second set of time intervals. The disk drive further includes a controller and a channel integrated circuit chip. The controller includes a controller port. The channel integrated circuit chip includes an input for receiving the time-multiplexed analog read signal. The time-multiplexed analog read signal is processed to generate data symbols representing recovered servo data and recovered user data.

Abstract: A system for polling a preamplifier unit to remotely determine pre-established parametric values in a disk drive is disclosed. The disk drive comprises a controller, a preamplifier, and a plurality of transducers. The system for polling the preamplifier comprises means in the controller for generating a succession of serial bit characters each representative of a different pattern. A means is provided for successively transferring said serial bit characters from the controller to the preamplifier unit. A plurality of individual bit lines are provided in the preamplifier unit representative of at least one parametric value. A means is included in the preamplifier unit for comparing each serial bit pattern character received with said plurality of individual bit lines, and for generating a match signal when a serial bit pattern character received matches the plurality of individual bit lines. A means is provided for transferring the match signal from the preamplifier unit to the controller.

Abstract: A disk drive comprising a plurality of read/write transducers, a programmable preamplifier, and a controller for furnishing control and data signals to the programmable preamplifier and for receiving data signals therefrom, is disclosed. The programmable preamplifier comprising a write data input circuit for receiving data signals to be supplied to a transducer, a read data output circuit for manifesting data signals supplied to said preamplifier unit by a transducer, and a transducer interface circuit for providing write data signals to a transducer and receiving read data signals from a transducer.

Abstract: A disk drive preamplifier unit includes a serial interface circuit for receiving serially formatted control signals from an associated disk drive controller. The control signals contain several types of information, including head select, write current magnitude, bias for MR transducers, gain magnitude for a variable gain amplifier, and test and mode information. The preamplifier unit incorporates several test circuits in addition to the usual write unsafe detector circuit, and a multiplexer controlled by the mode control signals from the serial interface unit is used to select which test circuit or detector is coupled to a common test output terminal whose signals are coupled back to the controller for further processing.

Abstract: A gate generator useful for validating readout signals incorporates three channels, including differentiators and threshold comparators, and a logic circuit coupled to the output circuits of the channels for passing valid readout signals. The output signals of the comparators and of detected zero crossings derived from a differentiated signal are fed to the logic circuit for processing.