Archive Corporation

Seagate Technology Incorporated

Jones V Howell

Gregory Alyn Unruh

William R Miller

Leroy J Thompson

Ashok Babubhai Nayak

William A Buchan

Kurt A Buckland

Walter Fehlmann

Donald Schilling

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.

Method for detecting data encoded as state transitions in a read signal

Method and an arrangement for detecting state transitions in a read

An arrangement and method of searching a tape at high speeds for a specific recording location with an arcuate scanner includes passing recorded tape past a scanner at a speed significantly higher than a read/write speed. Since the reading by an arcuate scanner of search information recorded at approximately a centerline of a tape is the least affected by changes in speed, compared to information recorded at the top and bottom of a tape, the search information located approximately along the centerline of the recorded tape is read. A specific recording location on the tape is then determined from the search information read.

Method and apparatus for high speed searching in arcuate scan tape drives

Apparatus for fine positioning a tape head relative to a head carriage that is coarsely positionable by a lead screw. The fine positioning apparatus includes parallel first and second resilient support beams oriented generally parallel to the direction of tape travel and having their ends fixedly secured to the head carriage so as to be deflectable in a direction transverse to the direction of tape travel. The centers of the parallel first and second support beams have their centers secured to a tape head frame which contains the tape. A linear motor drives the tape head frame against the resilience of the first and second resilient support beams in response to a drive signal which, for example, is derived from tracking error information produced pursuant to reading of servo information on tape. Pursuant to the displacement of the tape head frame against the resilience of the support beams, the magnetic tape head is moved along a linear path transverse to the tape travel direction. For operation with tapes without servo information on tape, a piezoelectric transducer detects the deflection of one of the support beams and provides an output which is utilized to provide damping of the natural resonance the spring/mass system that includes the first and second resilient support beams and the tape head and tape head frame supported thereby. Alternatively, the operation with tapes without servo tracks can be open-loop with the damping being provided by damping members disposed symmetrically on either side of the tape head frame.

Mechanisms for a closed loop head positioner for streaming tape drives

A digital audio tape (DAT) drive (100) for use with computer systems includes a circuit (130) and a corresponding method for setting the read amplitude threshold for testing written data to determine whether it has a sufficient magnitude to be successfully reproduced. The threshold is set by writing a predetermined data pattern onto a segment of tape (118) to be written with actual data. The predetermined data pattern is selected to comprise pseudo-random ones and zeros so that the reproduced data signals comprise a wide range of frequencies and corresponding amplitudes so that the average amplitude can be determined. The reproduced data signals are sampled and digitized, and the digitized samples are provided as inputs to a microprocessor (250). The microprocessor (250) discards approximately one-half the lowest magnitude data samples so that low amplitude signals caused by media flaws in the test portion of the tape (118) do not affect the method. The microprocessor (150) averages the remaining data samples and computes a threshold value corresponding to a fraction of the calculated average. The computed threshold value is applied to a comparator (256) and is compared with the magnitude of reproduced data signals when reading actual data while performing a read after write operation. The detection of a data signal of lower amplitude than the computed threshold causes a low amplitude signal to be generated and causes a controller (112) to rewrite the corresponding data on a different section of the tape (118).

Apparatus and method for automatic adjustment of read amplitude

A circuit for randomizing data or de-randomzing previously randomized data according to a randomization scheme utilizing an irreducible generator polynomial which operates on a serial bit stream of words of data which is supplied to said circuit in a format, either LSB or MSB first, different from the format according to which the data was previously randomized or will be subsequently de-randomized. The circuit includes means for generating said irreducible generator polynomial; means for triggering said generating means in a given direction in response to a clock signal; means for exclusively ORing the contents of a bit in said generating means with a bit in said bit stream; and means for periodically interrupting said triggering means and instead setting the state of said generating means a predetermined number of states in a direction effectively the opposite to which said generating means normally generates data.

Data randomizing/de-randomizing circuit for randomizing and

The following specification sets forth a digital tape erasure conditioning circuit and system in combination with a tape drive. The tape drive is such that it drives a magnetic digital tape across an erasing and recording head within a streaming cartridge tape drive. Information is written onto the tape and subsequently read and checked in a continuous streaming manner to assure the correctness thereof. The tape is driven with respect to its various channels over write and read head portions of the head and returned in the opposite direction for writing and reading on another channel. In order to provide for multiple channels, the head is moved laterally across the face of the tape and when moved, is provided with an air cushion between the tape and the head to prevent laceration and attendant damage to the tape surface. When the tape is to be erased, an AC erasure takes place as opposed to a DC erasure wherein the media is saturated at only one level as it passes the field of the erase head. The AC erasure is provided by a rapidly alternating field as the tape moves across the head. Thus, the media is subjected to a slowly diminishing cyclic field as it moves away from the erasure gap. This causes the magnetic intensity to diminish and leave a minimal amount of magnetization, due to the AC erasure. The erasing circuitry of this invention provides a 3.58 MHz square wave to two erase drive transistors. The inductance of the erase head in parallel with stray capacitance and a resonating capacitor, allows for a resonant circuit to pump the erase head until self limiting occurs, thereby provided an AC erasure to the previously magnetized tape.

Digital tape erasure conditioning system

The following specification discloses a streaming cartridge tape drive, wherein magnetic tape in a cartridge is driven over a magnetic head for purposes of recording and reading information magnetically on the tape. The information is written onto the tape and subsequently read and checked in a continuous streaming manner to assure the correctness thereof. The tape is driven over the first channel of the head in one direction wherein a write and read head on one portion of the tape effectively writes and reads the information imparted thereto. The tape is returned in the other direction over a second channel of the write and read head which respectively writes and reads the information on the tape as it passes thereover in its return direction. Subsequent thereto, the head is moved laterally across the face of the tape to provide for a third and fourth channel, or track, being respectively written and read in the same manner as the previous first and second channels, thereby providing four serpentine tracks. The head, when moving across the face of the tape, is provided with an air cushion so as to avoid tearing, laceration, or attendant damage to the tape surface. This is accomplished when the tape has reached its terminal or stopping point by oscillating the tape over the head by the drive system and logic of the drive control circuit. In the alternative, when the tape is moving, at the beginning or the end of the tape, the head is moved laterally only at the time when the tape is still moving but is no longer being written upon and having information read therefrom in a usual manner. Accordingly, the entire device provides for longer tape life, less damage, as well as substantially precluding tearing and degradation of the magnetic properties thereof.

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Newport Beach, CA, United States of America

Jones V Howell