Abstract: The present invention relates to a method for measuring characteristics of a tunnel magnetoresistance effect element having a tunnel multilayered film comprising a tunnel barrier layer and a first and a second ferromagnetic layer formed to sandwich the tunnel barrier layer therebetween. This method comprises the steps of setting an initial current value I0 which does not destroy the element to be measured, measuring, using the current value I0, a first resistance value R1 as an approximate resistance value of the element, defining, based on the first resistance value R1 and a voltage value Vs which is a measurement standard for the element, an inspection current value Is (Is=Vs/R1), and measuring characteristics of the element using the inspection current value Is. Therefore, “without damaging or destroying elements” and “in an effective way”, the characteristics of the element can be measured.

Abstract: A system for recording the history associated with writing data onto rewritable media includes an access head for writing data onto the media and reading data from the media. A drive motor moves the media past the access head. A write formatter formats data into a device block to be written onto the media. A read formatter detects errors in data read from the media. A control unit determines an error recovery procedure based on an error detected in reading the media and enables the write formatter to insert an indication of the error recovery procedure into the device block. The error recovery procedure is then attempted. The process is repeated until either a successful write occurs or the media is determined to be bad.

Abstract: Apparatus and method for writing data to a magnetic recording medium in the form of magnetization vectors having alternating magnetic orientations and lengths ranging from a minimum symbol length to a maximum symbol length. A write element adjacent the medium includes a leading edge and a trailing edge to form a write gap which generates a write gap recording field having a length substantially greater than the minimum symbol length. A write driver applies a write current signal to the write element as a series of current pulses, each pulse magnetizing an area of the disc corresponding to the length of the write gap recording field. A subsequent current pulse is applied while a portion of a first area magnetized by a previous pulse remains disposed between the leading edge and the trailing edge of the write element, so that the remaining portion of the first area beyond the trailing edge of the write element forms a magnetization vector of selected symbol length.

Abstract: A magnetic recording system which can suppress an influence by a thermal fluctuation and is suitable for the high density magnetic recording in which excellent S/N ratio and resolution are obtained is provided.

Abstract: A method of operating a disk drive to efficiently recover from an event which interrupts a safe-to-write condition that occurs during a write operation includes receiving a string of data blocks for writing on respective addressable locations on a track of a disk in the disk drive. During a pass of the addressable locations under the read/write head, the head is positioned to follow the track within a tolerance limit and a first write operation is started to write the string of data blocks on the track. During the first write operation, if it is detected that a safe-to-write condition no longer exists, as may be triggered by a shock event, the first write operation is aborted. When it is later determined that the safe-to-write condition is asserted, a second write operation is defined to write a set of addressable locations within the string of data blocks which have yet to pass under the read/write head and the second write operation is performed.

Abstract: A drive unit which recovers from write instability by heating the magnetic head prior to performing a dummy write operation is described. In the preferred embodiments, once write instability has been detected the head may be heated by friction with the rotating disk or by an external heater. In the friction method the head is moved to a safe area of the disk such as a textured landing zone while the disk rotation is continued. In drives using unload ramps, a heater is preferably placed at the the ramp so that the head can be heated while parked on the ramp. In each of these embodiments dummy write operations are performed while the head is in a thermally excited state due to the heating. The combination of heating and the dummy write operation aids in restoring write stability.

Abstract: A method and apparatus of detecting variations in a clearance distance between a magnetic read/write transducer and a magnetic recording disk having a clearance detection burst recorded thereon. The clearance detection burst has at least two groups of bit patterns each having different transition densities. The method may have the steps of obtaining a readback signal from the at least two groups of bit patterns, the readback signal being sensitive to variations in the clearance; detecting the amplitude of the readback signal of a first group. The amplitudes of the readback signals are detected and then compared to provide an indication of a variation in the clearance.

Abstract: A timing recovery system encodes data while impressing recognizable patterns thereon, enabling precise timing during subsequent readback operations. An uncoded binary sequence is encoded using an m/n rate block coded sequence, incorporating a unique predetermined binary bit pattern that occurs with a selected level of frequency. The encoded sequence is stored on the recording medium as a series of flux transitions. To read back the stored data, a read head measures the flux transitions stored on the medium and generates a representative analog waveform. A sampler samples the waveform in accordance with a timing scheme provided by a timing circuit. The timing circuit adjusts the timing of the samples to ensure that the analog waveform is sampled at appropriate times to yield the most accurate results. The timing circuit evaluates two consecutive samples to identify samples associated with features of the analog readback waveform that corresponds to the predetermined bit patterns.

Abstract: An improvement in a magnetic tape playback apparatus for determining the location of any portion of the magnetic tape as it passes the tape reading head including optically readable indicia means printed on the magnetic tape representing encoded information and means for optically reading the indicia including a light source and detector both mounted on one side of the tape. The improvement is compatible with existing magnetic tape playback devices and magnetic tape cassettes.

Abstract: A magnetic recording/reproduction apparatus comprises a magnetic tape running apparatus to rotate a rotary drum and run a magnetic tape with the magnetic tape being in contact with, at least, part of the circumferential surface of the rotary drum, a plurality of erasing magnetic heads installed on the rotary drum so that the magnetic tape are in contact with the heads and used to erase recording signal, a plurality of recording magnetic heads used for recording, a plurality of erasing circuits installed on the rotary drum to output erasing signal to each of the erasing magnetic heads, a plurality of recording circuits connected to the recording magnetic heads respectively and installed on the rotary drum so that the recording circuits are selectively be gone to active state and non-active state, one or more rotary transformers connected to erasing circuits in common, and a driving circuit to record information signal in the magnetic tape through recording magnetic heads, recording circuits, and rotary transfo

Abstract: A disk drive array system includes a plurality of disk drives. Each disk drive includes a period detector for monitoring the period of a common external synchronizing signal. When the period detector determines the existence of an irregularity in the external synchronizing signal, an internal synchronizing signal, generated by an internal generator, is used for controlling the rotation of each of the disks so as to continue the operation of the disks.

Abstract: A motor drive circuit for driving an electromotor having a permanent magnet rotor and a stator comprising one or more stator windings. When the supply voltage of the motor drive circuit fails, an emergency signal is generated by a signal generator. This emergency control signal activates an auxiliary power supply circuit for extracting electric energy from the motor and supplying the extracted energy to an auxiliary circuit. The auxiliary power supply circuit comprises a rectifier circuit formed by the fly back diodes bridging the switches of an electronic commutation circuit. The drive circuit comprises short-circuit switches bridging the stator windings. In response to the emergency control signal a short-circuit apparatus causes the stator windings to be temporarily intermittently short-circuited. As a result, a capacitor is charged. The energy stored in the capacitor is used for temporarily energizing the auxiliary circuit once the power supply to the drive circuit has failed.

Abstract: A magnetic recording and reproducing device and a magnetic tape library device are provided for properly recovering a function and issuing a warning when a failure of a magnetic head of the device takes place because of wear and dirt of the magnetic head. Further, a method for maintaining the magnetic head is provided. A wear sensor and a dirt sensor are prepared for sensing a wear amount of a state of dirt of the magnetic head. A head check controller operates to determine the wear amount of the magnetic head and the state of dirt based on the sensed result. In accordance with the determined result, the warning device is started for taking a precaution of preventing a head failure. As one aspect, the tape library device instructs to load the cleaning tape using a robot.

Abstract: In a method of recording digital information signals to form tracks on a magnetic tape, the samples of the signals to be recorded are divided into a plurality of odd sample groups and a plurality of even samples groups. The groups containing adjacent samples are disposed on differently-numbered regions of different tracks. Error correcting codeword may be recorded in a plurality of tracks. Errors in one region can be corrected or compensated by samples in different tracks or samples in differently-numbered regions.

Abstract: A data storage disk drive array is synchronized using drives wherein each has an onboard oscillator assembly which is connected either for independent operation of each drive or synchronization of all or any selected drives of the array using a common or slave sync line that can supply an index signal to all or any portion of the drives of the array and is capable of using the oscillator assembly of any drive in the synchronized array as the source of the common precision index signal. The system can also be partitioned in subarrays with synchronization of the entire system, of individual subarrays or any mix of subarray combinations while retaining the capability for any drive of the system to function independent of the synchronization of any group of drives within the system.

Abstract: Recording areas for tracking on which specific servo patterns are recorded are provided preceding data tracks on which data is to be recorded on a recording tape scanned by a helical scan system. The data tracks and recording areas for tracking are recorded at different azimuths. At the time of a playback operation, etc., the specific patterns in the recording areas for tracking are played back by the helical scan system and tracking is performed by using the playback timing.

Abstract: A magnetic recording disk drive has a rectifier circuit made up of bipolar transistors. Upon removal of power to the spindle motor, the rectifier circuit converts AC spindle motor output to DC actuator coil current to drive the actuator to a parking ramp where the read/write heads are "unloaded" from their respective disk surfaces. The transistor emitter-base junctions are connected to a switch, such as a pair of field-effect transistors, that is responsive to removal of power to the spindle motor. The total current flowing in these emitter-base junctions is small due to the use of series resistors and because the current in the emitter-base circuit does not flow through the actuator coil. The emitter-collector paths of the bipolar transistors are connected as a three-phase, full-wave rectifier to the actuator coil.

Abstract: A digital signal processing circuit for processing and recording data at various selectable rates, having an input/output circuit for receiving and outputting a digital signal; a recording circuit for generating a recording signal based on a digital signal received by the data signal processing circuit; a playback circuit for retrieving recorded data; and a demodulation circuit for demodulating retrieved data. The processing and recording rates are determined by control data supplied to the circuit either via an operator or from a recorded signal.

Abstract: A head positioning control device for a magnetic disk apparatus has a head selection circuit for selecting one of a plurality of magnetic heads based on an external head address, a servo control circuit for controlling a movement of a selected magnetic head to a prescribed position through a head positioning motor. A head positioning control unit sets prescribed control information in the servo control circuit based on an external instruction. A head address switching device is connected to the head selection circuit for receiving a head switching signal set by an external instruction, the head address and a burst-area information, and sending a prescribed head address to the head selection circuit. A sector pulse generator sends a sector pulse corresponding to a zone in which the magnetic head is positioned to the head address switching means.

Abstract: A magnetic disc apparatus controls the output timing of control current data by use of a servo estimation type observer. Servo information is read from a servo sector of a magnetic disc, decoded, and used to calculate control current data. Before the servo information of the following servo sector is fully decoded, the calculated control current data from the previously read servo sector is output, converted to a current, and sent to the actuator of a magnetic head.