Data General Corporation

Honeywell Information Systems Inc.

William A Braun

Stephen A Caldara

Louis A Lemone

Edward Gershenson

Mark C Lippitt

Salvatore Faletra

A digital data bus system for connecting a controller and a disk drive. Data on the disk is stored in track sectors containing a header and data. The controller includes a high-speed processor which performs a header compare operation comparing the values received from a header with the expected contents of the header and operations which determine when all of the data in a track sector has been transferred. The digital data bus system includes a bus for transferring data between the controller and the disk drive and a header-data mode bus for providing a header mode signal and a data mode signal from the controller to the disk drive. During an operation transferring data between the controller and the disk, the disk drive responds to the header mode signal by transferring a header to the controller. If the header compare operation indicates that the header is valid, the controller provides the data mode signal and the disk drive respond by transferring data to or from the track sector as required for the operation. When the controller determines that all of the data has been transferred, it again provides the header mode signal to the disk drive and the disk drive responds as just described.

Digital data bus system for connecting a controller and disk drives

There is disclosed a circuit for providing a comparison signal representing phase relationship between a clock pulse train and a variable rate input pulse train. The comparison signal can be used to synchronize clock and input pulse trains. The circuit includes a phase difference measuring circuit providing a first signal proportional to phase difference between input pulse train and clock pulse train, the signal having related discontinuities at the points of minimum and maximum phase difference between input and clock pulse trains. A second signal is generated representing a selected value of phase difference, the selected value being greater than the minimum phase difference and less than the maximum phase difference. First and second signals are then compared to provide a signal representing difference between the measured and selected values of phase difference. The comparison signal thereby avoids the discontinuities at minimum and maximum values of phase difference by representing phase relationship between input and clock pulse trains relative to the selected value of phase difference rather than to the maximum or minimum values. In a preferred embodiment, decoding circuitry decodes an input pulse train in self-clocking code to provide data output in binary code.

Circuit indicating phase relationship

A system for generating a write clock signal for use with a rotating magnetic memory apparatus, such as a disk memory, in a data processing system which includes a slotted disk transducer which produces an intermediate pulse signal having a repetition rate related to the disk speed, a freqency-locked loop which produces a write clock pulse output signal having a repeptition rate related to the intermediate repetition rate independently of variations in the disk speed. The time response of the loop can be relatively low to lock the write clock output signal frequency to relatively slow variations in the intermediate frequency and to avoid locking to any extraneous high frequency variations therein. A coded slot region provides a coded pulse sequence, having selected pulses missing therefrom which can be decoded for providing an index pulse, the missing pulses being supplied to the pulses from the transducer to form the intermediate pulse signal. A sector identifying pulse signal can also be obtained from the intermediate pulse signal.

Write clock signal generator for use with rotating magnetic memory

A system is provided for positioning a transducer over a magnetic media by the sensing of previously recorded information. The previously recorded information is in the form of a plurality of tracks containing position information. A servo transducer traverses a path over the tracks of position information and produces a signal in response to sensing the position information. A position detection circuit analyzes the signal thus produced and defines two separate data tracks for each and every individual track of position information thus traversed.

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Acton, MA, United States of America

William A Braun