Abstract: A novel method is disclosed for performing a high speed search for a selected data block or data file utilizing any one of several presently existing helical scan tape formats which utilize, in addition to the helically scanned tracks, one or more longitudinal tracks for recording indexing information indicative of the location of data blocks and file marks stored on the associated helical tracks. Data file location information is written to a header area on a series of helical tracks and to one (or more) of the longitudinal tracks when a data block or a file mark is written to a tape. A high speed search for a desired data block or data file can then be performed using this track location information.

Abstract: The control software and hardware in the tape drive control unit creates and manages a header segment at the beginning of the magnetic tape. This header is interposed between a leader portion of the magnetic tape on the 3480-type cartridge and the remainder of the magnetic tape contained therein. This header segment contains two sections, a first of which is a data record directory that is used by the control unit to denote the location of each data record written on to the magnetic tape as well as administrative information associated with the data record. The second section of the header is an administrative information section that contains data relating to the magnetic tape itself. The stream of data records is divided into data segments, a plurality of which comprise a single helical scan track. The helical scan tracks are formed into scan groups and written on the magnetic tape.

Abstract: The system of the present invention makes use of a data synthesizer to produce a synthesized analog data signal representative of a special encoded binary waveform to perform a test on both the magneto resistive element as well as the associated read path electronics independent of operator intervention. The special encoded binary waveform is coupled to the magneto resistive element to produce an approximation of the typical read back signal that is read by the magneto resistive element from a test magnetic tape. The analog signal output by the magneto resistive element is applied to the read back electronics, where it is converted in well known fashion to a digital data signal indicative of the synthesizer block of data that is applied to the magneto resistive element. The output of the read path electronics is applied to a special pattern detector, a sync pattern detector and a test pattern detector which function to detect anomalies in the digital data that is output by the read path electronics.

Abstract: The data write pulse compensator circuit functions to produce an erase frequency that is greater than twice the data frequency using a single clock source to thereby improve the signal to noise ratio in the read back signal. This apparatus uses a precision delay line to produce a series of clock signals with each successively replicated clock signal being delayed a predetermined amount of time with respect to the last previously replicated clock signal. The plurality of generated and delayed clock signals is then combined by a programmable pulse synthesizer to produce a data pulse of a predetermined frequency and width. The same apparatus is also used to produce a pair of erase pulses using a different combination of the delayed replicated clock signals to produce a pulse identical in size and shape to that produced for the data frequency. However, the erase pulses are time shifted such that their apparent frequency is greater than twice the data frequency.

Abstract: An improved phase-locked loop control having DEAD TRACK acquisition wherein a separate oscillator generates a fixed frequency of digital pulses corresponding to the frequency of the data board in the storage media and, in the event of a DEAD TRACK in the storage media, the phase-locked loop control locks onto the fixed frequency output of the oscillator to insure lock during DEAD TRACK integral.

Abstract: An improved phase-locked loop control having a phase detector receptive of a data preamble of all "ones" from a storage sub-system for producing early and late signals to a voltage controlled oscillator in order for the frequency of the oscillator to be synchronized with the frequency of the data. A pattern detector senses the incoming preamble pulses and prevents the generation of the early and late signals when a preamble pulse is not present within a predetermined window of time.