Abstract: A writeable control store for storing a plurality of instructions used to control the operation of a processor in a data processing system. The control store may be utilized in a first mode wherein the instructions are accessed for controlling the operation of the processor and in a second mode wherein data is transferred to or retrieved from the control store. In the second mode of operation, a secondary control means is utilized to control the operation of the data transfers to and from the writeable control store.

Abstract: A linear servo circuit for A.C. motors is disclosed. The servo circuitry is used in a magnetic tape transport to control the motor which operates a tape reel on which the magnetic tape is stored. The servo circuitry develops two complimentary saw-tooth voltage waveforms synchronized to the sinusoidal A.C. line voltage. One saw-tooth waveform is used to control the motor in the forward direction and the other saw-tooth waveform is used to control the motor in the reverse direction. Comparator circuitry compares the saw-tooth waveforms to a D.C. control voltage which is proportional to the angular position of an arm that controls the tension of the magnetic tape. The comparator circuitry provides a control pulse to a photodiode when the saw-tooth waveform exceeds the D.C. control voltage. Light pulses from the photodiode impinge on a light sensitive SCR which in turn triggers a triac to apply power in the forward or reverse direction to the A.C. tape reel motor.

Abstract: Apparatus for performing high-speed, parallel multiplication in a data processing system wherein each multiplication requires only one step to reduce a plurality of summands to two numbers whose summation equals the product. The fractional portion of two floating point numbers, the multiplier and the multiplicand, are coupled to registers. Thereafter, the multiplicand is multiplied by segments of the multiplier and the resultant products are summed together using a conventional shift and add means. The multiplicand and a segment of the multiplier are each coupled to a plurality of multiplier circuits which produce a plurality of summands. These summands are coupled to a plurality of counter circuits in a manner such that the digits of all of the summands representing the same power of the number 2 may be counted.

Abstract: A method and apparatus for recording data on a rotating magnetic disk at plural density rates on different areas of the disk is disclosed. The method is particularly useful in magnetic disk recording systems in which the header or control fields of the recorded information are recorded in "single" density FM recording and the data fields of the recorded information are in "double" density modified frequency modulation (MFM) code. The technique involves changing the conventional MFM coding rules to prevent certain data patterns from appearing to the data recording system read circuitry as part of the control fields. In particular, the data pattern 011110 is encoded according to the invention as a data pattern which consists of 000000 with synchronization bits between the first and second, third and fourth, and fifth and sixth data bits. This encoding modification prevents any misinterpretation of the data field as part of a control field.

Abstract: A dynamic filter circuit used to process analog position error information in a disk drive head-positioning servo system is disclosed. The filter circuit monitors the velocity of the disk drive carriage and dynamically increases the gain and bandwidth of the filter as the carriage velocity increases. Specifically, an operational amplifier in feedback configuration is used in which the feedback networks are switched in response to the velocity signal. At low carriage velocity the filter has low gain and reduced bandwidth and therefore helps to decrease sensitivity of the system to noise. At high carriage velocities the gain and bandwidth of the filter are increased to minimize the effects of missing servo data.

Abstract: A data processing system is described herein having a central processor unit which responds to a plurality of diverse instructions including a diagnostic instruction. The diagnostic instruction is comprised of a first and second portion preferably in the form of distinct words which are separately transmitted to the processor from a peripheral storage location or manually transmitted from a control panel for the data processing system. The first word of the instruction, when decoded by the processor, identifies the diagnostic instruction and the second word specifies the particular function to be performed. The processor is arranged such that, in the response to the first word of instruction, the second word is coupled to a specialized decoding circuit which will generate a starting address in the microprogrammable control store of the processor for a routine to execute the function specified by the second word.

Abstract: An analog measuring system is disclosed which simultaneously stores in a first memory element a voltage generated by a physical phenomenon including the errors introduced by the measuring system and in a second memory element a voltage corresponding to the errors introduced by the measuring system. Subsequently, the voltages are combined so that true electrical representation of the physical phenomenon is provided. Additional means are disclosed which establish a reference for the physical phenomenon. The electrical representation of the reference is combined with the electrical representation of the sensed physical phenomenon to provide an absolute reading. Thus, the measuring system provides an electrical representation of the physical phenomenon which is independent of time, temperature and frequency.

Abstract: A circuit for filtering electrical waveforms in which the useful information is contained in patterns and spacing of zero-voltage crossings is disclosed. Illustratively, a disk memory system is disclosed in which the voltage peaks developed by the disk memory read-transducers are converted into zero-voltage crossing waveforms by differentiation. To eliminate false zero-voltage crossings caused by noise, the digital filter generates a linear ramp waveform whose magnitude is proportional to the time duration between successive zero-voltage crossings. False zero crossings typically have a short time duration between successive crossings. They are eliminated from the integrated ramp waveform by a comparator which only responds when the integrated waveform reaches a predetermined threshold level indicating the time between successive zero-voltage crossing exceeds a minimum time duration.

Abstract: A memory control apparatus for use in a digital computer system. The computer system comprises a central processing unit and a main memory which has a plurality of memory units. The processor has control circuitry for simultaneously addressing a plurality of words stored in the memory locations in the memory units. The processor addresses the plurality of words by the combination of a memory address signal and word request control signal which are equal to the number of words to be transferred. While addressing of the memory units occurs in parallel, the transfer of words occurs serially. The initial word as defined by the memory address signal is transferred first with the remaining words transferred in ascending modulo four order. If one or more of the four words has not been requested, it is automatically skipped by the control apparatus with no loss in time or continuity.

Abstract: A modular electrolytic recorder comprises four mechanical subassemblies and one electrical module for easy construction and replacement. Upon the chassis subassembly is mounted the anode subassembly including a flexible anode, a helix drum subassembly and a gear box transmission subassembly to which is attached the printed circuit board electrical module.

Abstract: A video terminal system having a plurality of distinct output devices providing humanly perceivable, alphanumeric information is disclosed. The video terminal processes and transfers the binary representations of each alphanumeric character to a character generator. A dot matrix corresponding to the character is provided by the character generator and is time-multiplexed so as to be time-shared by each of the output devices without the requirement for specialized circuitry and with minimal time degradation. The distinct output devices may be video displays and hard copy printers which display alphanumeric characters for a complete line, the video display devices receiving each complete line of characters in a predetermined time period and the printer devices receiving a slice of each character for a line upon request.

Abstract: A high speed display processing unit (DPU) for displaying vectors on a cathode ray tube is disclosed. Each vector to be displayed is classified as to whether it is virtual, visible or both. If the displayed vector is partially visible, a digital section of the DPU calculates the length of the visible portion of the vector. Prior to drawing the vector, the digital section determines the major axis of the vector and its tangent. Each of the above values is provided to an analog section of the DPU which then draws at a constant velocity the visible vector. The DPU also includes circuitry for scaling, offset calculations and light pen hits.

Abstract: When two asynchronous signals may occur at approximately the same time, only one of the signals being able to control consequent events, a circuit accounts for the conflict situation by selectively adding a delay until the conflict situation has settled. While the circuit does not determine which asynchronous event may control, the selective delay extends the time for the decision to be made. This circuit provides high reliability while minimizing delays and eliminates the need for indiscriminately adding a delay to each asynchronous event so as to resolve conflict situations. The circuit has particular applicability to volatile memory systems wherein conflict between processor requests and refresh requests to memory occur and allows processor requests to proceed with minimum delay in nearly all situations.

Abstract: In a video terminal system wherein a number of characters are to be displayed on each forward horizontal scan, a scan control circuit is utilized to synchronize the displaying of characters with the scanning of the cathode ray tube. Both the scan control circuit and the displaying characters are tied to a timing chain. Since the displaying of characters occurs at a fixed predetermined time in the timing chain, the scan control circuit is required to control the movement of the scan such that the phase of the scan is regulated in time. The scan control circuit accomplishes synchronization by a self-regulating feedback circuit which controls the magnitude of the base drive to a power transistor. Since the storage time of a power transistor is proportional to the magnitude of the base drive current to the power transistor, a simplified circuit results which accurately places the characters at a fixed position.

Abstract: A self-zeroing, drift-free analog-to-digital conversion system is disclosed in which a single amplifier is shared between an analog-to-digital converter circuit and a sample-and-hold circuit. The offset errors generated by the sample-and-hold circuit cancel with the offset errors generated by the analog-to-digital converter circuit since the circuitry introducing the offset errors is shared. As a result, system offset errors are negated and the system enables changing from a unipolar to bipolar input range without inclusion of any additional circuitry. Usage of a gain preamplifier is provided with no corresponding system offset errors being introduced. moreover, usage of a differential-input gain preamplifier is also provided, with the self-zeroing feature resulting in greatly improved common-mode rejection.

Abstract: A transducer assembly for a disc drive having an array of magnetic heads contained in a transducer device which, during operation of the disc drive, is maintained at the appropriate distance from a disc by an air bearing. The transducer device is secured to a flexible gimbal connected to a bracket. A pivot is located between the gimbal and bracket about which the transducer device may pivot to properly position itself in response to the air flow at the surface of the disc.

Abstract: Apparatus for a matrix printer by which the distance between the printhead and the paper being printed upon may be adjusted. The printhead is secured to a carriage whose position may be adjusted with respect to the paper by rotating a pair of bearings that are rotatably mounted in the carriage and centrally located around a stationary shaft.