Abstract: A disc drive includes a recording head preamplifier circuit having a plurality of preamplifiers. Each preamplifier includes a receiver circuit and a preamplifier enable circuit. The receiver circuit receives a serial command having command address bits. The preamplifier enable circuit is operatively coupled to the receiver circuit and generates an enable output for enabling the preamplifier when the command address bits match a first predetermined logic pattern which is unique to chat preamplifier and when the command address bits match a second predetermined logic pattern which is universal to the plurality of preamplifiers.

Abstract: A clock circuit for the reading of sequential information elements includes a phase-locked loop for the control of the controlled oscillator. In the case of a reading system with n tracks, the phase computation circuit, the digital filter and the controlled oscillator each include as many memories (delay circuits R 1.1, . . . R 2.1, . . . R 3.1, . . . ) as there are samples of information elements (or information tracks) to be processed almost simultaneously. The invention finds particular application in the reading of high-density recording media.

Abstract: A disk drive has a fall detection control system that detects when a disk drive is in a free fall, and takes precautionary protective action to minimize physical damage from any resulting shock upon impact. The disk drive includes an accelerometer device that measures acceleration of the disk drive along three mutually orthogonal axes x, y, and z and resolves the measurement into respective vectors a.sub.x, a.sub.y, and a.sub.z. In one embodiment, a processor is programmed to (1) compute a net acceleration a.sub.net of the disk drive, (2) compare the net acceleration a.sub.net with the selected acceleration threshold level, (3) measure a duration that the net acceleration a.sub.net exceeds the acceleration threshold level, (4) compare the measured duration with a selected reference time period, and (5) output the warning signal when the measured duration exceeds the reference time period. Upon receipt of the warning signal, a controller initiates protective routines in preparation for shock.

Abstract: A data detection circuit for a read channel that recovers data encoded as the presence or absence of flux transitions on a magnetic recording medium, compares a current data sample of a read signal with a previous data sample and a threshold to determine whether the previous data sample represents a flux transition. The use of two data samples in the determination of flux transitions provides a more accurate detection of the data than comparing a single data sample to a threshold value. The data detection circuit generates an output data signal having data values based on the determined flux transitions of the data samples.

Abstract: A recording and reproducing apparatus for recording and reproducing a data signal on and from a magnetic tape includes a rotary head drum, first and second magnetic heads, third and fourth magnetic heads, a data processor, a data signal decoder, and controller. The magnetic tape is wrapped around the rotary head drum slanted at a predetermined angle. The first and second magnetic heads are provided on the rotary head drum at positions apart from each other by a predetermined rotational angle and have a first azimuth angle. The third and fourth magnetic heads are provided on the rotary head drum at positions apart from each other by a predetermined rotational angle and have a second azimuth angle different from the first azimuth angle. The data processor adds address data to each recording unit of a data signal and outputs the data signal as a recording signal.

Abstract: A digital servo system is provided for controlling a cylinder motor in a video tape recorder. The servo system includes a servo loop and a digital filter inserted in the servo loop. The digital filter includes a coefficient multiplying circuit for multiplying a coefficient. A coefficient changing circuit is further provided for changing the coefficient of the coefficient multiplying circuit. The digital filter is provided to improve the servo gain at a low frequency region. This avoids lag caused by the filter in this region, and advantageously provides resistance to disturbances.

Abstract: In an encoding circuit for a digital video signal, a digital video signal is subjected to given orthogonal transform to be converted into corresponding conversion data. Components of the conversion data are scanned in a given order to generate a main data sequence from the conversion data. The main data sequence is separated into at least two sub data sequences. A first of the two sub data sequences is encoded into corresponding words of a given variable-length code. A second of the two sub data sequences is encoded into corresponding words of the variable-length code.

Abstract: A reading apparatus for reading information recorded on a first longitudinal recording medium in the form of helical scanned information tracks, according to a first format in which the tracks have been recorded on the medium at a first track pitch and have a first track width, the information being read by the apparatus at a given tape velocity, the information being read from the first medium at a first bit rate, immediately adjacent tracks exhibiting alternately a first and a second azimuth angle, pilot tones being recorded in information tracks, the frequency of the recorded tones cycling through at least two different frequencies (f1, f2); and a second longitudinal recording medium recorded in the form of helical scanned information tracks, in accordance with a second, new, format in which the information track pitch is substantially twice the first track pitch, the information track width is greater than the first track width, the information being read from the second medium at substantially half the f

Abstract: There is disclosed a magnetic disk device of the external synchronization system using a head assembly of the recording/reproducing heads separation type. This magnetic device comprises: a reproducing head for reproducing data from a magnetic disk; a clock signal generator for generating a clock signal on the basis of a reproduced signal corresponding to a clock pattern from the reproducing head; a delay circuit for delaying recording data relative to the clock signal generated at the clock signal generator; a recording head for recording the recording data delayed by the delay circuit onto the magnetic disk; a position detecting circuit for detecting head position information (e.g.

Abstract: A recording/reproducing apparatus by which recording data can be retransferred and a bit error rate can be greatly improved by a simple arrangement. Recording data REC is transferred as well as stored in a record buffer 30 in which the recording data REC of the number of blocks corresponding to a simultaneous reproducing time is sequentially stored and when the recording data REC is retransferred, the recording data REC stored in the record buffer 30 is read and retransferred. Further, during reproduction, reproducing data PB is sequentially reproduced through the record buffer 30 however, when a retransfer which occurred during recording is detected in the reproducing data PB, the reproducing data is reproduced without passing through the record buffer 30.

Abstract: A seek control system in a disk system, in which the object measured is a mechanism including a voice coil motor which positions a head, and in which the temperature of the voice coil motor is detected and seek operations are controlled based on the thus detected temperature, includes a unit for determining the amount of heat causing the temperature rise of the object under measurement as the square of a voice coil motor current command value multiplied by predetermined coefficients; a unit for integrating the result obtained by subtracting the amount of naturally radiated heat from the amount of heat including the amount of heat causing the thus determined temperature rise, to determine the amount of heat in the object; and a unit for detecting the temperature of the object in accordance with the thus determined amount of heat in the object.

Abstract: Proper operation of a recording and reproducing apparatus is verified by comparing, after a suitable delay, error detection codes calculated for compressed data prior to being recorded on a medium with error detection codes calculated for the corresponding compressed data reproduced from the medium, thereby reducing the amount of delay memory needed to temporarily store the error detection codes calculated prior to recording of the data.

Abstract: An information signal recording apparatus for recording information signals on a recording medium comprises information signals which are input to the apparatus in a predetermined quantity. The apparatus is adapted to retain the information signals thus input and allows an arbitrary portion of the predetermined quantity of information signals to be designated. The designated portion of the predetermined quantity of information signals can be edited before the information signals are recorded on the recording medium, thus making it possible to record on the recording medium the information signals with an arbitrary portion of the predetermined quantity deleted or corrected.

Abstract: Method of optimizing a write current for at least one rotatable magnetic head and arrangement for carrying out such a method.In a method of optimizing a write current for at least one rotatable magnetic head (K1, K2), in which method a write current (I) is applied to the magnetic head (K1, K2) as a test signal with a given number of graded amplitude values within a given time interval and this test signal is recorded on the magnetic tape (5) by the magnetic head (K1, K2), the total given number of graded amplitude values of the write current (I), which is applied to the magnetic head (K1, K2) as a test signal, is applied to the magnetic head (K1, K2) within a single scanning period (T) of this magnetic head.

Abstract: An apparatus for recording and reproducing a burst-like digital information signal, a method capable of predicting the time of occurrence of a header indicating the beginning of the first data of a digital information signal during its reproduction from a recording medium. The digital signal includes a plurality of data blocks, each including a first header indicative of the head of the block, and each first header including the address of the block. During recording of a digital signal on the recording medium, a plurality of second headers, which are substantially the same as the first headers of the data blocks and including addresses having given relations with the addresses of the data blocks, are inserted in a clock regenerating signal recorded before the digital signal for regenerating the clock for the signal. The second headers are inserted at a period equal to the period of each data block so as to be synchronized with the headers of the data blocks.

Abstract: A finite impulse response (FIR) filter and a Viterbi detector system for a magnetic read channel are disclosed. The FIR equalizer generates equalized sampled outputs to the Viterbi detector system. The Viterbi detector system determines the most probable value of all references, R.sub.i by accumulating a summation of data sample values, D.sub.t, for selected legal bit sequences over a significant amount of random data. The summation and count of data samples are output to a system microprocessor for calculation of an average reference for each path of the Viterbi system. The Viterbi detector system also calculates, in real time, magnitude of differences between the output data received from the FIR equalizer and transition references for each data sample to generate transition metrics, adds transition metrics to state metrics from the source node of two paths, and compares the result. The lesser of the two results yields the most likely correct state metric.

Abstract: A read channel is described for use in a storage device including a storage medium for storing data, an interactive element for reading information from and writing information on the storage medium and a processor for performing control functions in the storage device. The read channel comprises a set of electronic components for receiving and processing information read by the interactive element from the storage medium. An adjustable noise generator is included in the read channel and is coupled to the set of electronic components. The noise generator is selectively operated to introduce noise into the set of electronic components to cause the set of electronic components to operate at a marginal level of performance and thereby increase the error rate of the read channel. A calibration of the read channel is performed when the read channel is operating at the marginal level of performance to decrease the time required to accumulate error statistics used in the calibration.

Abstract: In a sampled amplitude read channel for magnetic recording, a nonlinear discrete time decimation filter in a negative feed back loop adjusts a DC offset in an analog read signal from a magnetic read head without distorting the read signal. In sampled amplitude recording, adding the samples of an isolated positive pulse to the samples of an isolated negative pulse generates the DC offset of the discrete time sample values. A decimation filter adds the sample values from a positive pulse to the sample values of a negative pulse in order to detect and pass the DC offset in the read signal. The detected discrete time DC offset from the discrete time decimation filter is converted into an analog DC offset signal and subtracted from the analog read signal in a negative feedback loop. A running average decimation filter removes the DC offset during acquisition, and a decision-directed decimation filter removes the DC offset during tracking.

Abstract: A servo system for controlling the position of a read/write head in a disk drive is provided. The servo system includes an input terminal for sequentially receiving a plurality of input signal bursts of a burst pattern, wherein the input signal bursts include positional information of the head. Demodulation circuitry, coupled to the input terminal, sequentially demodulates each input signal burst and provides a demodulated signal for each burst. An ADC, coupled to the demodulation circuitry, sequentially converts each demodulated signal. The ADC converts a first demodulated signal corresponding to the first of the plurality of input signal bursts before the demodulation circuitry completes demodulating the next of the plurality of input signal bursts. In a preferred embodiment, the ADC converts a demodulated signal corresponding to a first input signal burst while the demodulation circuitry demodulates a signal corresponding to a second, and subsequent, input signal burst.

Abstract: In a digital video tape recorder that has rotary magnetic heads for recording digital video information on a magnetic tape in the form of data blocks having a predetermined length, an ID signal is generated for each data block. The ID signal includes a number of data bits which identify the address of the data block, the information contained in the data block, and so forth. For the purpose of generating error code parity symbols, the ID signal is divided into a sequence of four-bit symbols, and at least two parity symbols are generated according to an error correction code for correcting errors in the sequence of four-bit symbols. The ID signal and parity symbols are recorded together on the magnetic tape. In this way, error correction can be performed on the ID signal during reproduction.