Abstract: Embedded servo sectors within a data track of a hard disk drive including a rotating data storage disk and a closed loop rotary actuator structure for positioning a data transducer head relative to the data track are written by a method including the steps of positioning the rotary actuator structure relative to the data track with a laser-interferometer-based servo writer and writing a pattern of circumferentially sequential, radially offset fine position bursts within each servo sector with the data transducer head, this step including writing-in undetermined position errors within each pattern being written, moving the disk drive to a self scan environment away from the servo writer, operating the rotary actuator structure in closed loop for following the data track by reference to the servo burst pattern, extracting the undetermined position error from each pattern thereby to iteratively determine written-in position errors, generating burst correction values from the determined written-in position errors

Abstract: A magnetic tape head actuator assembly has a stepper motor having a threaded output shaft and a bracket for supporting a tape head assembly. The bracket includes a pair of outwardly extending flanges. The flanges each have a bore, whereby the bores are axially aligned and dimensioned to accept the output shaft therethrough. The bracket further has an integral platform portion oriented normal to the threaded output shaft for mounting a tape head assembly. A threaded split nut positioned intermediate the bores is rigidly attached to the bracket and engages the threaded output shaft for movement of the bracket back and forth along the shaft. The nut further has an annular groove encircling its outer perimeter, wherein a circular spring positioned therein provides an inwardly directed compressive force on the nut.

Abstract: A deflection mirror tower (DMT) of a multiple-disk array, optical storage system includes a plurality of prism members, each having an angular mirror surface, arranged along a vertical axis of the DMT and configured at a predetermined angular orientation to deflect a laser beam to a respective disk surface. The DMT is generally fabricated using a two-level partitioning process. Several prepared glass substrates, i.e., one for each mirror type, are initially sliced into bars having predetermined geometries. A bar from each substrate is sequentially aligned to a master reference and bonded to adjacent bars to form an intermediate bar stack. The stack is then segmented into a plurality of DMT components, each having a plurality of prism members.

Abstract: A single reel tape cartridge includes a type of magnetic recording tape having characteristics which are identified to a cartridge tape handling system in accordance with size variation of a tape type hole following a beginning of tape (BOT) hole by a predetermined, qualifying distance. A cartridge tape handling system for identifying the particular tape type, and for formatting the tape in accordance with determined tape type is also described.

Abstract: A method of performing spectral analysis of signals recorded by a magnetic recording or storage system is provided using a modified channel chip of the system. The modified channel chip enables measurement of harmonic components of the recorded signal. The recorded signal is a periodic analog signal having a period N. The method is performed by reading the recorded periodic analog signal and converting the signal into a discrete time periodic signal. The discrete time periodic signal is digitally sampled at predetermined intervals, and the digital samples are selectively accumulated in a register or registers of the channel chip. Incoming digital samples are accumulated by selectively being added to contents of the registers, or alternately being added and substracted to contents of a single register. The accumulated results represent summations used to determine harmonic coefficients of the recorded signal.

Abstract: A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g.

Abstract: A system architecture for implementing a 10-bit Reed-Solomon code for detecting and correcting data errors in a single code word to protect a data block containing up to 1023 10-bit data symbols, i.e., the equivalent of up to 1278 8-bit symbols, including error check redundancy, maximizes the use of all allocated error correction overhead for an entire block of data, regardless of the particular error pattern characteristics encountered in a given system application. The architecture is particularly well suited for digital data processing and/or storage systems encountering non-bursty, (i.e., substantially random), error patterns, such is characteristic of data storage and retrieval systems employing semiconductor based memory stores. 5-bit extension field operations, (i.e., over a Galois field GF(2.sup.5)), generated by using the irreducible polynomial, P.sub.32 (X)=X.sup.5 +X.sup.2 +1, over GF(2), are utilized to perform certain, requisite arithmetic functions over the Galois field GF(2.sup.

Abstract: A multiple-solid-burst error correcting system determines the number and locations of "solid burst" errors in a high-rate Reed Solomon or BCH code by determining the greatest common divisor of the error locator polynomial .sigma.(x), which has roots .alpha..sup.-i.sbsp.k that correspond to error locations i.sub.k, and a mapping error locator polynomial .sigma.(.alpha.*x) that maps the error locations , i.sub.k, to locations i.sub.k+1. The roots that are common to both polynomials, that is, the roots that are included in the greatest common divisor, d(x), correspond to adjacent error locations that are contained in the solid bursts. The roots of the non-common factors, p.sub.1 (x), of the error locator polynomial correspond to the first locations of the respective solid bursts and the roots of the non-common factors p.sub.2 (x) of the mapping error locator polynomial correspond to one location beyond the end locations of the solid bursts.

Abstract: A method of responding to a request for data over a bus structure, such as a SCSI bus. Upon receiving a request, a data storage device releases control of the bus and accumulates the requested data in a buffer. Before the data has been completely accumulated, the device acquires control of the bus and begins transmitting the data over the bus. The beginning of transmission occurs late enough that the transmission can occur in a single burst. If the data can be transmitted over the bus in a time period t.sub.burst, then the beginning of transmitting should begin substantially a t.sub.burst period before the time at which the buffer completes accumulating the requested data.

Abstract: A buckling mechanism for improving buckling reliability between a take-up leader and a cartridge leader. The mechanism includes a buckling link, buckling arm and a link driver. The buckling link is biased about one end and includes a protruding portion having a T-shape face at the other end. The combination of the dimensions of the protruding portion and the constant biasing force ensures that the leaders are positioned and remain in position for successful buckling as the tape cartridge is inserted into the tape drive. The buckling link is mounted such that it functions independently of the link driver and buckling arm, enabling the buckling link to maintain the biasing force against the take-up leader even after the buckling arm releases the take-up leader.

Abstract: An asymmetric quadrature-providing servo burst format for a tracking servo within a hard disk drive is particularly well suited for MR heads. The four-burst format may be written onto the disk with only two servo-writer passes per track by using an alternating one-third, two-thirds track pitch regimen. During operation of a drive incorporating the servo format of the present invention, the servo system uses an appropriate combination of bursts and burst sums, based on burst amplitude profiles, in order to achieve optimized position error signal (PES) continuity and linearity as the head moves off of nominal track centerline of each concentric data track.

Abstract: A Reed-Solomon error-correction coding (ECC) scheme selectively supports two different-length codes to optimize the trade-off between error performance and the amount of disk space required to store protection symbols. The encoder contains two sets of alpha multipliers; part of one set is multiplexed with the other depending on which code is being used. Also, a shift register within the encoder is selectively lengthened or shortened depending on the code. The code pair is selected so that the generator polynomial of the shorter code is a complete divisor of the generator polynomial of the longer code. Thus, one code is a sub-code of the other. Accordingly, the ECC system is able to use the same syndrome calculator for each code. The error-correction decoder uses those syndromes that correspond to the roots of the generator polynomial of the code being used.

Abstract: A pulse width modulated, digital-to-analog converter (PWM DAC) that includes a pulse generator for generating width modulated pulses in accordance with a digital control value is set forth. The generator includes a clock for generating a clocking signal, a counter responsive to the clocking signal for generating repeating sequences of N-bit counts, each sequence representing a count interval. The PWM DAC further includes a bit rotator for receiving the sequences of N-bit counts and for rotating the bit position of at least a most significant one of N-bits. A latch holds a digital control value, whereby a comparator compares the digital control value with each one of the rotated bit counts to put out the width modulated pulses during the count interval. The rotated bit counts increases the frequency of the comparator, in a substantially linear manner, such that subsequent filtering can be accomplished with minimum time requirements.

Abstract: A multi-drive, multi-magazine mass storage and retrieval unit for tape cartridges which automatically retrieves a selected one of a plurality of tape cartridges from one of a plurality of tape cartridge magazines for transfer to a selected one of a plurality of tape drives. The unit further retrieves a selected one of a plurality of tape cartridges from one of the plurality of tape drives for storage in one of the plurality of tape cartridge magazines. A tape cartridge elevator retrieves and transports the tape cartridges between the plurality of tape cartridge magazines and the plurality of tape drives. An interunit cartridge transport unit enables multiple tape storage and retrieval units to be coupled together and cartridges to be passed automatically between the coupled units.

Abstract: A modulation method generates a rate 16/17 (d=0, G=7/I=11) modulation code for transferring user digital data bytes having a three-way ECC interleave through a data transfer channel in accordance with the steps of:shuffling the user data bytes in order to rearrange an order of the bytes in a predetermined manner and putting out A.sub.i B.sub.i byte pairs,encoding eight bits of the Ai bytes of the AiBi byte pairs in accordance with a predetermined rate 8/9 modulation code to produce nine code bits a0-a8, andinterleaving the nine code bits a0-a8 of each Ai byte with eight unencoded bits of each Bi byte in accordance with a predetermined bitwise interleave pattern to generate the rate 16/17 modulation code. A preferred code and circuitry for the modulation method are also described.

Abstract: A synchronous DMA burst transfer method is provided for transferring data between a host device and a peripheral drive device connected by an ATA bus. The method provides synchronous data transfer capability in an asynchronous system by having one device in charge of both a strobe signal and a data signal. When a host read or write command is delivered to the peripheral drive device, the peripheral device decides when to start the synchronous DMA burst. For a read command, the peripheral device requests the synchronous DMA burst then drives a data word onto the ATA bus after the host acknowledges that it is ready to begin the burst. After allowing time for the data signal to settle, the peripheral device toggles a strobe signal from a high state to a low state. The host sees the edge of the strobe signal at which time the host latches the data word on the bus. Additional data words can be driven on the bus and the strobe signal can be retoggled to latch the additional data words into the host.

Abstract: A word-wise encoder circuit that processes word formatted data blocks in response to a word clock signal and generates redundancy in accordance with an 8 bit symbol code. The encoder is provided with two parallel data paths, each receiving one of the respective bytes halves of the received data words during one word clock period to implement an 8 bit symbol code in response to a word clock signal. The word-wise encoder replicates, in one word clock period, the state of the registers in a standard sequential encoder after two consecutive bytes have been processed in response to a byte clock. In a preferred embodiment, a word-wise encoder is used to implement a Reed-Solomon data integrity code. In this example, the word-wise encoder generates redundancy that is appended to associated data blocks temporarily stored in a block buffer memory within a data channel to provide a mechanism for detecting data errors caused by the buffer.

Abstract: A method and arrangement for mounting a rotary actuator bearing cartridge between a disk drive base and cover, are disclosed. The mounting arrangement minimizes any possible deformations to bearing sleeve as well as any effects to bearing preload and friction while enabling a top down assembly.

Abstract: A method and apparatus for processing a magnetic transducer which uses gallium ion beam milling to precisely define pole tip widths of the magnetic transducer. The gallium ion beam may be defocused to improve definition of the region which is damaged by gallium ion implantation. The precision pole tip widths provide a transducer that may record correspondingly precise track widths on a magnetic storage medium, such as a rotating disk. Subsequent to the ion milling process, the invention restores the magnetically conductive properties of the pole tip region, which may be degraded as a result of the ion milling process, by means of a lapping process.