Abstract: A dual function cyclic code error correcting method and system are disclosed for correcting from a single syndrome byte a random single-bit error which occurs in a multi-byte data word or, alternatively, correcting a multi-bit error in one byte of the data word by providing an indication of the location of the byte in error, and employing the same syndrome byte to determine the error pattern of the multi-bit error so the multi-bit error can be corrected.The method involves non-zero syndrome processing steps which comprise a first series of steps which function to determine if the non-zero syndrome correlates to a 1-bit error in one of the byte positions of the data word being protected, and if so, to automatically correct the single-bit error by processing the entire byte containing the single-bit error.

Abstract: An improved ECC method and system are disclosed for correcting either a random single-bit error, or alternately, a multi-bit error in one byte of a data word from a single syndrome byte. The improvement involves determining the location of the multi-bit error in successive data words which result because of a failure in one of a plurality of failure independent storage units employed for storing a block of multi-byte words.The location of the defective byte position is determined by summing each non-zero syndrome byte that is developed for each multi-byte word that is processed to produce a summed syndrome byte .SIGMA.S.noteq.0. This summed syndrome byte is then employed to generate a set of vectors which are positionally related in an m-sequence to the summed syndrome byte. A block syndrome byte, developed during the processing of a number of words and representing the sum modulo-2 of the error pattern in each word of the block, is compared to each of the set of vectors.

Abstract: A reel for web material such as magnetic recording tape is disclosed. The reel may be advantageously employed in a reel-to-reel magnetic tape transport where magnetic tape is wound under tension that is converted to radial forces which subject layers of the tape disposed over discontinuities associated with the reel hub to adversely affect the transducing relationship between the flux gap and the transducer of the recording surface of the tape.The section of the cylindrical tape receiving surface which is associated with a discontinuity is formed to function as a cantilever beam with the distal end of the beam being aligned with the discontinuity. The outer portion of the hub is made of relatively compressible material, while the inner portion is relatively solid. Compressibility of the outer portion is enhanced by providing a plurality of circumferentially disposed cylindrically shaped openings which also function to relieve radially induced forces on the tape layers.

Abstract: An improved arrangement is disclosed for storing link address data which is generated by a microcontroller during the execution of a program which involves a series of nested link type instructions and for returning the stored link address data under program control so that the program may be returned to a selected one of a plurality of branch points. The improved arrangement involves memory addressing circuitry for addressing a memory which stores instructions, a storage device for storing link addresses which are transferred from the memory address circuitry to the storage device when link type instructions are executed, storage addressing circuitry which controls the location in the storage device where the link address data is stored, control circuitry which is responsive to one instruction having a predefined field, the value of which is determined by the microprogrammer and which determines which of the nested link address data is to be returned to the memory addressing circuitry.

Abstract: A system for reading information stored on a flexible magnetic disk is disclosed. The system involves an amplitude detector for detecting at predetermined times whether the amplitude of the read signal is positive, zero or negative. This system includes an amplifier for the differential raw data signal whose gain is variable in response to changes in the amplitude of the raw data signal which occur over a relatively long period. The output of the automatic gain control amplifier is an equalized differential signal applied to the detector and to a threshold generator which provides an output reference signal which is a predetermined percentage of the input signal, and which is capable of following relatively rapid changes in the amplitude of the input signal. A positive and negative comparator circuit continually compares the differential equalized data signal against the generated threshold reference signal.

Abstract: An apparatus for driving a replaceable reel of magnetic tape is disclosed. The apparatus comprises a magnetic clamp for holding the reel to a cup-shaped driving member. The cup-shaped driving member carries a doughnut-shaped magnet and is provided with an integral center shunt member which extends into the center of the reel when the reel is positioned in driving engagement. The reel is provided with a central opening, and a circular metal plate is attached to the bottom surface of the reel hub to be attracted by the doughnut-shaped magnet. By extending the center pole piece a predetermined distance above the plane of the doughtnut-shaped magnet, the extended center pole piece provides an easy path for the flux as the members are being separated, since a relatively small air gap is maintained between the extended center pole and the central opening of the disk.

Abstract: A system is disclosed for a microcontroller which permits the interruption of a sequence of instructions, each of which are executable in a fixed machine cycle in response to one of a plurality of interrupt/trap signals. The microcontroller is interrupted for one fixed period machine cycle, during which period one of a plurality of instructions are read out from an instruction storage location of a memory determined by the active interrupt/trap signal concurrently as data stored in separate registers, which define the condition of the microcontroller at the point of interruption, are transferred to one group of locations in a storage device which is different than the memory which stores the instruction. After the transfer, another group of storage locations also determined by the active trap request signal is available to instructions which executed in subsequent machine cycles.

Abstract: A microcontroller is disclosed which executes all instructions in a fixed period machine cycle. A storage device is provided for storing data which is involved in the execution of instructions that are stored in a different memory device, such as a read only memory device. Specific locations in the data storage device are selected during execution of instructions by combining one partial storage address from two separate groups of partial storage address generators. One location "00" in the storage device is addressed automatically when no partial storage address generators are selected. An auxiliary register having a load control input terminal and the write input to the storage device are connected to a common source of data so that in response to certain instructions, the same data is entered into location "00" of the storage device and the auxiliary register from the data source during one fixed period machine cycle.

Abstract: A microcontroller is disclosed for controlling the bidirectional transfer of data between two external units. The external units supply data to the microcontroller selectively on a plurality of input byte busses and receive data from the microcontroller on a plurality of output byte busses. The microcontroller includes an input port including a plurality of instruction addressable input funnels, each adapted to be connected to one of the input busses, and an output port including a plurality of instruction addressable output registers, each adapted to be connected to one of the output busses. Also included are an ALU unit, an ALU register, a memory for storing instructions, an instruction register, an instruction register decoder, and control circuitry which causes the transfer of a byte of data from an addressed funnel through the ALU to the ALU register during a first portion of a fixed machine cycle, and from the ALU register to the external address register during the second portion of the machine cycle.

Abstract: An automatic threading apparatus for a magnetic tape transport is disclosed in which a flexible sprocketed guide tape loop is disposed in a continuous guide channel which is shaped to conform to the shape of the complex tape path extending from the supply reel to the take-up reel of the magnetic tape transport. The guide tape is driven by a sprocketed gear to move in sliding engagement with the continuous channel in either direction to move a leader block coupling device attached to the sprocket tape from a first position adjacent the supply reel where the leader block is coupled and decoupled from the device to a second position associated with the take-up reel where the leader block is maintained coupled to the device and caused to rotate relative thereto by and with the take-up reel during a winding operation.

Abstract: A method and apparatus for automatically threading web material, e.g., magnetic tape, from a replaceable supply reel to a non-replaceable take-up reel of a web transport device, in which the web path is nonlinear and relatively complex as a result of various components, e.g., magnetic transducer tape guides, which act on the web while it is being transported.The apparatus comprises a coupling device and a mechanism for moving and guiding the coupling device between the supply reel and the take-up reel. The coupling device couples to a leader block attached to the tape at the supply reel. The mechanism moves and guides the coupling device to thread the tape over the predefined tape path and positions the leader block wholly within a radially disposed slot in the hub of the take-up reel. The coupling device remains attached to the moving mechanism and coupled to the leader block when the leader block is rotated with the take-up reel.

Abstract: A disk file for storing data is disclosed which comprises two major separable assemblies, an HDA assembly and a disk drive assembly. The HDA assembly is characterized by two separate carriage units each of which function to position a plurality of magnetic transducers in transducing relationship with a different group of magnetic disks which are mounted on a common horizontally disposed disk spindle.The disk drive assembly is characterized by an integral baseplate whose front section is generally U-shaped in cross-sections permitting the lower portion of the HDA assembly which surrounds the magnetic disks to be positioned within the opening defined by the opposed surfaces of the U-shaped front portion. The front portion is open to accommodate the positioning of the HDA assembly on the drive assembly by a horizontal loading motion.The drive portion of the baseplate is provided with a horizontally disposed shelf portion to which the magnetic structure of a voice coil motor is mounted.

Abstract: This invention is directed to a system for generating clock signals from a source signal having two harmonically related and phase coherent frequencies such as shown in U.S. Pat. No. 3,534,344 (Santana) and U.S. Pat. No. 3,879,753 (Dunn). The clock system employs a pair of synchronous demodulators for generating a phase error signal to control a voltage controlled oscillator (VCO). The source signal is applied to a pair of synchronous demodulators, each of which is supplied with a different carrier frequency. The output of each demodulator represents the area of the signal being demodulated. The output of each demodulator is zero and a null condition exists when the system is in a phase locked condition. At a non-locked condition, the output of one demodulator has multiple null points. The function of the second demodulator is to resolve the ambiguity between the desired and undesired null points.

Abstract: A drive belt loading system for automatically loading and unloading a drive belt onto a pulley of a removable device employs a conical transfer means for automatically transferring the drive belt to the pulley upon tensioning of the belt. The transfer means is located below the device pulley so that upon slackening of the belt, the belt is automatically unloaded by dropping back onto the transfer means to allow removal of the device. The system is applied to drive belt loading in a magnetic disk file employing a disk module with an external pulley.

Abstract: Data track positioning information for data tracks on a stack of recording disks is provided by servo information pre-recorded on one surface of the stack. In addition, each data track on the remaining surfaces of the stack has servo information relative to that track pre-recorded in sectors around the track. Track following operations are controlled in a closed loop servo system using on-track position information derived from the sectored servo tracks associated with the track being followed. The bandwidth of the position error signal derived from the sectored servo information is increased by adding high frequency components obtained from the continuous servo information on the servo surface. Track access operations are controlled using track crossing information derived from the pre-recorded servo information on the servo surface.

Abstract: A positioning system for data storage apparatus in which a magnetic transducer is positioned relative to data tracks on a moving record member by means of a closed loop servo system. Improved velocity control information is provided to the servo system by pre-recorded servo tracks read by a single servo head forming part of the closed loop system. Each servo track consists of a plurality of servo cells, alternate ones of which are laterally displaced by half a track width. A position reference signal is prerecorded in each cell at a point which is predetermined to permit the signal to be sensed by the single servo head independently of any other detectable signal. Accordingly, a position error signal derived from displaced cells is always 90.degree. out of phase with the position error signal derived from undisplaced cells.

Abstract: A gas filtering arrangement is described for a magnetic disk file consisting of a closed housing surrounding the magnetic disks. A bearing mounted in a wall of the housing carries a drive shaft upon which the disk (or disks) and a gas impeller are mounted. The impeller pumps gas through a main filter, located within the housing, to clean the gas. The air flow due to the impeller and the disk is arranged to maintain a positive air pressure adjacent the bearing to prevent gas entering the housing through the bearing. A breather filter within the housing connected to the exterior of the housing by a breather aperture is arranged so that during operation a negative pressure is applied to the breather filter to prevent gas leaving the housing through the breather filter.

Abstract: A magnetic disk information storage apparatus comprises a head/disk assembly removably mounted in a housing assembly. The head/disk assembly encloses rotatably mounted disks, and accessing heads mounted for linear movement on a carriage. Fixed to the carriage and therefore part of the subassembly is a linear actuator coil. The linear actuator magnet structure which cooperates with the coil to produce motion of the carriage is located in the housing assembly. Loadings of the subassembly into the housing assembly locates the actuator coil in a magnetic flux gap of the magnet structure.