Hitachi, Ltd.

Hitachi Maxell, Limited

Hitachi Computer Peripherals Co., Ltd.

Hitachi Instrument Engineering Co., Ltd.

Nobumasa Nishiyama

Hajime Aoi

Toshiaki Tsuyoshi

Makoto Koizumi

Yasuhide Ouchi

Kazuhisa Shiraishi

Yoshibumi Matsuda

Takuji Ogawa

Reijiro Tsuchiya

Takashi Tamura

Makoto Saito

Yasuhiro Katoh

Naoki Sato

Yoshihisa Kamo

Yasuhiro Kato

Hiroaki Koyanagi

Makoto Saitou

Makoto Saitoh

Sayaka Shinomoto

Tetsuji Kameoka

Kouichi Hoashi

Masaya Tanaka

Ryuichiroh Tamochi

Kouji Takai

Yoshihasa Kamo

In a magnetic recording drive having a plurality of magnetic heads each employing a magnetoresistive sensor for the purpose of averaging the time required for sense currents to be caused to flow through the respective magnetoresistive sensors to shorten the longest reproducing time and to suppress the degradation of the characteristics due to the electromigration, thereby improving the reliability of the magnetic recording drive, the magnetic recording drive includes circuits for averaging the useful life depending on the currents caused to flow through the respective magnetoresistive sensors among the plurality of magnetic heads, whereby the time required for the sense current to be caused to flow through one MR reproducing head is greatly shortened. Therefore, the levels of outputs of the MR reproducing heads can be increased without reduction of the reliability and thus the reliability of the magnetic recording drive can be improved.

Magnetic recording drive having arrangement for averaging useful life of

Magnetic recording drive

A fast data transfer system capable of eliminating the need to extremely increase the necessary transmission frequency band for the high-density recording and fast revolution rate of data recording and reproducing system has a recording and reproduced signal processor including an encoder/decoder, a disk enclosure including a parallel-to-serial converter, a record head, and a serial-to-parallel converter, and a transmission cable, and makes recording parallel data transfer from the encoder/decoder to a recording amplifier by shifting the phases of a plurality of recording signals and reproduced parallel data from the serial-to-parallel converter to the encoder/decoder by shifting the phases of a plurality of reproduced signals. The necessary transmission frequency on the transmission cable can be reduced by this parallel data transfer on the transmission cable. In addition, a record timing correction circuit can be provided on a parallel data transfer path.

Method and apparatus for fast transfer of data in recording and

A personal information display system is provided with a portable information display device for reading information to be used from a storage medium, a communication network for transmission of information, input/output apparatus for input/output of information, an input/output control apparatus connected between the communication network and the input/output apparatus, an information control apparatus having a hierarchical memory connected to the communication network, and an information output apparatus connected to the information control apparatus to transfer information to the storage medium of the portable information display device.

Personal information display system for serving large capacities of

In a magnetic disk apparatus of high-speed data transfer, in order to cover an uncompensable section of the thermal asperity by error code correction to shorten the uncompensable section, upper and lower envelopes of a reproduced waveform are detected to obtain a level variation waveform due to the thermal asperity and subtract it from the reproduced signal. A thermal asperity processing circuit shown in FIG. 1 for compensating for the thermal asperity is used. In an envelope detection circuit in the thermal asperity processing circuit, a forced charge and discharge current control circuit is used in the thermal asperity portion to thereby be able to improve the follow-up characteristic to level variation of the thermal asperity and shorten the uncompensable section.

Magnetic recording and reproducing apparatus with thermal asperity

Magnetic recording drive having arrangements for average useful life of

A magnetic recording and reproducing apparatus, comprising a magnetic recording medium, a head arrangement for reading data from or writing data on the magnetic recording medium including an inductive recording head and a magnetoresistive reproducing head, and a phase discriminating circuit for discriminating data `1` from peaks of a waveform reproduced by the head. The phase discriminating circuit has a differential circuit for differentiating the waveform, a pulse circuit for producing a zero cross pulse from a zero-level crossing point of the differentiated waveform, a discriminating circuit for discriminating `1` and `0` of the data with use of pulses output from the pulse circuit and a discriminating window needed for judgment of `1` and `0` of the data, and a decoding circuit for decoding and feeding out the data output of the discriminating circuit. The head comprises a recording head of inductive type, and a reproducing head of magnetoresistive type. The phase discriminating circuit comprises a circuit for controlling a magnetic bias level for the magnetoresistive reproducing head so that a change of resistance of the magnetoresistive reproducing head due to magnetic field is made virtually equal both at positive and negative polarity waveform peaks.

Magnetic recording and reproducing apparatus with reproducing head of

A waveform equalizer for processing a signal read by a magnetic head from a magnetic written medium includes a slimming circuit which, in turn, has a first delay unit for delaying the read signal, a first attenuator connected in parallel with the first delay unit, a first differentiating circuit for receiving the output from the first delay unit and the output from the first attenuator, and a resistor connected to a first delay unit side input of the first differential circuit; and a pseudo-peak elimination circuit connected in series with the slimming circuit and including a circuit for separating the from the read signal the read signal or a signal reverse in phase to the read signal, a second delay unit for delaying the separated signal, a second attenuator for attenuating the amplitude of the separated signal, and a second differential circuit for receiving the read signal and the separated, delayed and attenuated signal.

Digital magnetic writing and reading apparatus

A system which records and reproduces a digital signal in the form of a magnetic reversal on and from a recording medium includes a magnetic head for reproducing data recorded on the recording medium; an automatic gain control unit for controlling the reproduced signal so as to have a constant amplitude; an equalizer for processing the output waveform from the automatic gain control unit; a differentiator for changing the output from the equalizer to a differentiated waveform; a low pass filter for limiting the signal band of the differentiated waveform; a low pass filter for limiting the signal band of the equalizer output; a pulser for receiving the equalizer output, the band of which is limited by the low pass filter and the differentiated waveform, the band of which is limited; a differentiator for receiving the output from the automatic gain control unit and producing a differentiated signal from the output signal; an attenuator for attenuating the differentiator output; and a waveform processor for adding the attenuated differentiated signal to the band-limited differentiated waveform and inputting the resulting signal to the pulser.

Data reproducing apparatus for eliminating undershoots in the vicinity

A readout circuit in magnetic recording device is disclosed, in which a test data signal for detecting an error in the characteristics of an automatic equalizer is recorded in a predetermined position of each track of a magnetic recording medium. In readout mode, a test data signal for a selected track is read out first, and this signal is compared with a reference signal dependent on the system conditions to determine an error from the reference signal. The optimum equalization coefficient is determined to eliminate this error from the reference signal and set in the equalizer. The data is readout under the optimum equalization characteristics thus set.

Readout circuit in magnetic recording device

A readout circuit in magnetic recording device is disclosed, in which a test data signal for detecting an error in the characteristics of an automatic equalizer is recorded in a predetermined position of each track of a magnetic recording medium. In readout mode, a test data signal for a selected track is read out first, and this signal is compared with a reference signal dependent on the system conditions to determine an error from the reference signal. The optimum equalization coefficient is determined to eliminate this error from the reference signal and is set in the equalizer. The data is readout under the optimum equalization characteristics thus set.

A signal read out circuit included in a magnetic recording device is disclosed in which plural kinds of slice levels are used simultaneously for a reproduced analog waveform to produce a plurality of gate signals corresponding to the slice levels, and it is judged on the basis of the gate signals whether each portion of the reproduced waveform is correct or not in producing a digital output.

Multi slice level signal circuit

In a read channel for magnetic recording used to reproduce information recorded on a magnetic recording medium, a signal reproduced from a magnetic head and a differentiated signal of the reproduction signal are ORed together to produce a gate signal. By using the gate signal, the information can be reproduced correctly.

Read channel for magnetic recording

An equalizer equalizes a reproduced waveform reproduced by a thin film magnetic head by reproducing information recorded magnetically on a medium. In the equalizer, the reproduced waveform is delayed to a position of an undershot portion, and is attenuated to an amplitude corresponding to a magnitude of the undershot portion, and the resultant waveform is superposed on the reproduced waveform, to thereby eliminate the undershot portion. Furthermore, by superposing a waveform obtained by inverting the reproduced waveform and amplifying or attenuating the inverted waveform, on the reproduced waveform at a half power position thereof, the width is narrowed.

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Odawara, Japan

Nobumasa Nishiyama