Abstract: A magnetic recording/playback apparatus for recording information to a magnetic tape and playing back the information from the magnetic tape, includes first and second recording heads which are provided on a rotary cylinder and alternately record information to the magnetic tape. First and second playback heads are provided on the rotary cylinder at predetermined positions relative to the first and second recording heads, and alternately play back the information from the magnetic tape. A crosstalk canceling switch device cancels crosstalk at outputs of the first and second playback heads when the apparatus is run in a read-after-write mode, the crosstalk canceling switch device being set in a closed position during the read-and-write mode and interconnecting the output of the first playback head and the output of the second playback head.

Abstract: A system, and a method of operation thereof, for analyzing the performance f a tape recorder having a playback head is disclosed. The system allows for the recorded data of the tape recorder to be routed to a analog-to-digital converter whose output is delivered to a digital signal processor preferably having a routine to convert the digital data to an FFT data stream which, in turn, is routed to a microprocessor. The computer analyzes the FFT data and provides digital signals to external display devices that indicate the proper recording of the tape recorder, the need for the recorder's heads to be cleaned, the occurrence of excessive dropout data recording rate, or the need to manually or automatically adjust the bias and equalization levels of the tape recorder.

Abstract: A performance evaluation method of an MR head whereby resolution performance of an MR head can be estimated, an isolated repreoduction wave form V(t) of the MR head is approximated by an equation V(t)=1/(1+(2t/PW50).sup.P), t denoting time difference from a timing which gives a peak value of the isolated reproduction wave form V(t), and PW50 denoting a half-peak-width where the isolated reproduction wave form V(t) shows more than 50% of the peak value. The resolution performance of the MR head is evaluated according to the order value P of the above equation which gives the most likelihood approximation of the isolated wave form, together with the half-peak-width PW50 relative to a minimum bit-interval to be reproduced by the MR head.

Abstract: An amplification circuit for an MR head which can realize a reduction of the power consumption, simplification of the circuit configuration by providing capacitors inside the circuit, and reduction of the number of externally provided parts, wherein a current is supplied to an MR head resistor from a bias current source and the amount of change of the head resistance is converted to a voltage change when reproducing magnetically recorded data. A direct current component of the voltage dropped in the head resistor is cut by capacitors, and only the alternating current component is input to a differential amplification circuit configured by transistors. Recorded data can be distinguished in accordance with an amplified output voltage, so capacitances of direct current cut-off capacitors can be set small and thus the direct current cut-off capacitors can be provided in the IC chip and the number of external parts can be reduced.

Abstract: In a data recording apparatus and its method, data is compressed in units of a stated data block, it is detected in units of the data block whether or not data extension has occurred in consequence of the compression processing. Then, the compressed data is recorded on a recording medium in the case where the data extension has not detected, and on the other hand, in the case where the data extension has detected, the original data is recorded on a recording medium with respect to a stated number of data blocks subsequent to the data block in which the data extension has occurred. Thereby, a data recording apparatus and its method can be realized with a simple construction, which can record non-compressed original data on the recording medium with respect to a string of data in which the data extension is apt to occur, and thus can alleviate bad influence of data extension which occur in consequence of the compression processing.

Abstract: A method and apparatus for determining a number of defects detected on a disk in a hard disk drive. The hard disk drive comprises an actuator arm mounted to a housing and a head mounted to the actuator arm. A spin motor is mounted to the housing and a disk is attached to the spin motor. The disk has a plurality of tracks, each of which has a plurality of sectors. Each of the sectors has a data field. The hard disk drive further comprises a defect detection circuit coupled to the head that detects a number of defects located in the data field. In one embodiment, the hard disk drive comprises a defect size detection circuit coupled to the head, that detects a corresponding size of each defect detected.

Abstract: An apparatus for correcting read errors in a disk drive is disclosed. In one embodiment, the apparatus includes circuitry for determining that an undesired distortion exists in a data signal read from a surface of a data storage disk; circuitry for finding an approximate starting location of said distortion within said data signal; and, circuitry for correcting errors in said data signal caused by said undesired distortion using said approximate starting location of said distortion. A method for correcting read errors in a disk drive is also disclosed.

Abstract: A hard disk drive system (10) includes a read/write head (21) for reading and writing data to and from a rotating magnetic disk (12). The read/write head includes a portion which is a magneto-resistive read head (36), the output of which is supplied through a preamplifier (26) to a read channel circuit (27). The read head has a nonlinear transfer function. The read channel circuit includes an asymmetry compensation circuit (62), which generates an analog compensation signal by squaring an output signal from the read head and scaling by an asymmetry factor (.alpha.'). The analog compensation signal is combined with the analog output signal in order to obtain a corrected analog signal, which is substantially free of the distortion introduced by the read head.

Abstract: A temperature-compensated high-speed timing circuit, which is particularly advantageous in read-interface circuits for disk-drive interface. The voltage on the integrating capacitor is compared against a voltage defined by the drop, on a resistor, induced by a current which is the combination of a reference current from a reference current generator with a temperature-dependent current from another current generator.

Abstract: A disk sequencer in a headerless disk drive system includes a format calculator that performs arithmetic processing on a frame number to generate frame parameters that indicate the format of a data frame associated with the frame number. The disk sequencer then uses the frame parameters to identify boundaries of data segments during a read or write. Arguments of the arithmetic processing include the frame number, static parameters that indicate fixed field sizes, and zone parameters that depend on the track. The static and zone parameters can be transferred to the disk sequencer during initialization and a seek respectively. The arithmetic processing is completed during processing of a servo sector to permit zero latency accesses. In one embodiment, the zone parameters are less than two words per zone and include a byte count for an ending partial data sector and a number of full data sectors in a first frame.

Abstract: A discrete time servo demodulation technique incorporated within a sampled amplitude read channel to demodulate embedded servo field information stored on a magnetic medium. The servo field information is transduced by a read head into an analog signal, and converted to a sequence of sample values in the read channel. The demodulation technique is responsive to the sample values and includes a discrete time peak detector for detecting servo data, and a discrete time servo burst amplitude detector for measuring the amplitude of servo bursts. Peaks are detected in the analog read signal by sensing a change of slope from the sequence of sample values. The peaks are qualified by polarity in that a peak is detected only if its polarity is opposite in sign from the previous peak. The servo burst amplitudes are measured by interpolating, rectifying, and accumulating the sequence of sample values corresponding to the servo bursts.

Abstract: In a head displacement measuring method, prior to actual data recording or data reproduction, either one of the recording head and the reproducing head is wobbled, and the test data is recorded in the disk-shaped recording medium by the recording head. Then, the test data is reproduced from the test data by the reproducing head, and displacement between the recording head and the reproducing head is detected on the basis of the reproduced test data. Thus, the displacement may be detected more easily with higher precision than with the conventional optical detecting method.

Abstract: A magnetic recording device incorporating both a 2-channel recording mode and a multichannel recording mode in one piece of equipment and using recording heads in multiples of two. This magnetic recording device is provided with a head drum, a pair of magnetic recording heads W1+ and W2- of a head width Hw and arranged in mutual proximity and along the rotation direction of the head drum, and a pair of magnetic recording heads W1- and W2+ of a head width Hw/2 and arranged in proximity to the magnetic recording head W2-. These magnetic recording heads W1+, W2-, W1-, W2+ are positioned so that the upper edge of the magnetic recording head W1+, the lower edge of the magnetic recording head W2-, the upper edge of the magnetic recording head W1- and the lower edge of the magnetic recording head W2+ are on the imaginary common line along the rotation direction of the head drum.

Abstract: A phase-locked loop circuit and recording/reproducing apparatus of this invention include a distributor (11) for receiving reproduction data to distribute and output it as n reproduction data, a phase comparator group (6) having n phase comparators for sequentially receiving the distributed reproduction data to compare the phases of the reproduction data with that of a reproduction clock, a frequency comparator (5) for receiving a reference clock and the reproduction clock to compare their frequencies, a selector (7) for receiving a switching control signal, the phase comparison result, and the frequency comparison result, and selecting either one of the phase comparison result and the frequency comparison result to output the selected one as a voltage signal, a charge pump (8) for receiving the voltage signal and converting it into a current signal to output the current signal, a loop filter (9) for receiving the current signal to output a low-frequency voltage signal, and a VCO (10) for receiving the low-fr

Abstract: A system and method for an amplifier control circuit is provided which does not require the use of a large off-chip or on-chip capacitor for achieving a low frequency coupling corner, while still effectively allowing AC coupling the data detection circuit. In addition, the input offset voltage to the amplifier may be compensated and the inherent random low frequency input voltages provided to the amplifier may be controlled or canceled. Further, the amplifier control circuitry includes a freeze capability which allows the control circuitry to halt all updates to the input offset/low frequency control circuit when the voltage input signal is interrupted. In addition low frequency control and offset compensation updates may be performed without causing large output signal glitches so that the integrity of the received signal will not be compromised. In a preferred embodiment the system and method may be utilized for data detection circuits utilized in conjunction with optical disks.

Abstract: An apparatus and method are disclosed for minimizing damage to a disc drive during head switching operations. The disc drive comprises a plurality of magnetic recording surfaces to and from which data are transferred using read/write heads, each head utilizing the application of a bias current during operation. To switch from a presently selected head to a target head, the disc drive determines a first value indicative of the magnitude of a bias current for the presently selected head and a target bias current to be applied to the target head. When the second value is greater than the first value, the disc drive switches from the presently selected head to the target head and then applies the target bias current; conversely, when the first value is greater than the second value, the target bias current is applied to the presently selected head and then the disc drive switches from the presently selected head to the target head.

Abstract: An automatic gain control circuit, for amplifying an input signal so that it has a specific correspondence with a reference value (V.sub.ref), includes an input terminal (2) for receiving the input signal, a variable gain amplifier (4) for amplifying the input signal in response to a gain control signal, a peak detector (14) for detecting peaks in the amplified input signal, the peak detector (14) having an attack time constant (T.sub.a) and a decay time constant (T.sub.d), and supplying a peak detector output signal (V.sub.p) representative of the amplitude of the peaks in the amplified input signal, a comparator (20) for comparing the peak detector output signal (V.sub.p) with the reference value (V.sub.ref) to form an error signal (e), and an integrator (30) for integrating the error signal (e) to form the gain control signal.

Abstract: A method and apparatus are provided for thermal asperity detection in a direct access storage device. A data signal is received from a data channel in the direct access storage device. A level threshold comparator compares data samples of the data signal with a selected level threshold. Consecutive zero level data samples are detected. Responsive to each identified data sample above the selected level threshold and not an identified consecutive zero level data sample, a counter value is incremented. The counter value is compared with a predefined count threshold. A thermal asperity event is identified responsive to the counter value above the predefined count threshold.

Abstract: A recording and reproducing apparatus using a cassette, which is capable of being set to a write-protect mode for a stored recording medium, includes a head for recording data inputted from an outside of the apparatus in the recording medium and reproducing data recorded in the recording medium; a detector for detecting whether the cassette is set to a record-possible mode or the write-protect mode; and a controller for controlling the apparatus so as to record input data from the outside of the apparatus and attribute information of the recording medium in the recording medium when the cassette is set to the record-possible mode and record the attribute information but not the input data in the recording medium when the cassette is set to the write-protect mode.

Abstract: Reading data from a data channel. The data channel is received by an input, and at least one data path processes the data channel to read data from the data channel. The data path is characterized by a plurality of data path parameters, and the data read may be successful or unsuccessful. A processor updates a log entry for the data if the data read was successful, wherein the log entry stores information related to the data path parameters that have produced successful data reads.