Abstract: A monitor for selectively detecting and recording conditions at selected points within a system during operation includes trigger logic connected from first selected points and responsive to selected conditions occurring at each of the first points for generating corresponding trigger outputs representing the occurrence of the selected conditions and a silo bank memory having a sub-silo for each second point. Each sub-silo has a first sub-silo segment with data inputs connected from the corresponding second point for recording data from the second point and a second sub-silo segment with data inputs connected from a time stamp generator.

Abstract: A monitor device for selectively detecting and recording conditions at selected points within a system during operation, including a trigger enable memory for storing selectable trigger enabling codes wherein each code corresponds to a trigger signal representing the occurrence of a corresponding condition to be detected, a trigger generation device connected from first selected points and responsive to selected conditions thereupon for generating the trigger signals representing the occurrence of selected conditions, a trigger output device responsive to the enabling codes and the trigger signals for providing trigger outputs upon the occurrence of a trigger signal corresponding to a selected trigger enabling code, and a silo bank memory connected from second selected points and responsive to the trigger outputs for recording conditions present at the second points.

Abstract: A monitoring means for selectively detecting and recording signals representing at selected points within a system, includes trigger generation logic responsive to selected bus signals for generating trigger signals representing the occurrence of selected conditions, and a recording memory for recording the conditions thereupon, a trigger selection logic for selecting trigger outputs corresponding to the trigger signals. The trigger selection logic includes a trigger enabling memory for storing selectable trigger enabling codes, wherein each enabling code corresponds to a trigger signal, and trigger output logic responsive to the trigger enabling codes and to the trigger signals for providing trigger outputs. The trigger enabling codes include bus enabling codes representing selected conditions on a bus of the system, trigger sequence enabling codes corresponding to sequential combinations of trigger signals and external trigger enabling codes corresponding to triggers external to the system.

Abstract: An adapter is connected between a peripheral controller and an intelligent peripheral device. The adapter allows the peripheral device to communicate with the controller. The adapter has control logic rather than a microprocessor for transmitting and receiving data. The control logic is comprised of combinatorial logic circuitry and a command register. The command register allows the controller to configure the cominatorial logic circuitry in order to control adapter operation.

Abstract: A monitor for selectively detecting and recording conditions at selected points within a system includes a trigger memory for storing patterns of trigger signals, wherein each pattern of trigger signals corresponds to a selected condition to be detected on first points of the system. The trigger memory includes a first port having a read address input connected from the first points and a data output connected to trigger output logic for providing patterns of trigger signals corresponding to the conditions to be detected. Each pattern of trigger signals is stored in the trigger memory location whose address corresponds to a pattern of signals from the first points representing the corresponding condition to be detected. The trigger memory is a dual port memory having a second port with a write address input and a data input for receiving trigger patterns to be stored therein.

Abstract: A disk drive of a mass storage subsystem includes areas on a disk surface wherein a vendor-generated defective sector log, a software-generated defective sector log and an alternate sector log are stored. A random access memory (RAM) stores a copy of the defective sector logs. During a seek operation, firmware tests the defective sector logs in RAM to generate the alternate sector log for that cylinder number. During the read or write operation, the alternate sector log is checked before processing the sector to determine if it is a defective sector. If the sector is defective, the head is positioned to another cylinder at a head and sector address read from the alternate sector log.

Abstract: A track on a disk surface of a disk drive is formatted in sectors, each sector having an address portion and a data portion. The disk drive generates a byte clock signal which increments a counter. The counter output signals address a read only memory which generates signals to control the address comparison in the address portion and the reading or writing of data bytes in the data portion of the sector.

Abstract: A track of a disk device is formatted on a single revolution of the disk by using a read only memory (ROM) to store control codes and a random access memory (RAM) to store address field and data field bytes. A DMA controller simultaneously addresses ROM and RAM. Control codes are read into a control first in-first out memory and data codes are read into a data first in-first out memory. The control codes are applied to a decoder whose output signals control cyclic redundancy check and error detection and correction logic as well as the data first in-first out memory. The serial output from both the data first in-first out memory and the cyclic redundancy check logic are written on disk track.

Abstract: A diskette read data recovery system generates a clock which is locked to an incoming data stream. In a phase locked loop, a signal generated by an oscillator and frequency dividers is compared in phase to the incoming data stream to provide first or second signals depending on whether the incoming data signal leads or lags the clock signal. In order that the system may handle different types of incoming signals, different frequency divider circuits in the phase locked loop are selected for different incoming signals.

Abstract: Digital data is recorded on the surface of a magnetic media such as a disk or diskette in the form of magnetic flux transitions identifying clock and data information in either a frequency modulation (FM) mode or a modified frequency modulation (MFM) mode. A read head senses the flux transitions which are in turn converted to digital signals. Apparatus converts the time between successive digital signals into PROM addresses. The PROM address locations store coded signals identifying the data as binary ONE or binary ZERO signals.

Abstract: Digital data is recorded on the surface of a magnetic media such as a disk or diskette in the form of magnetic flux transitions identifying clock and data information in a modified frequency modulation (MFM) mode. A read head senses the flux transitions which are in turn converted to digital signals. A counter in the adapter starts to count when the adapter receives a digital signal. The count is transferred to a register and the counter presets when the adapter receives the next digital signal. The count is indicative of the time between the successive digital signals and should be representative of multiples of an integer. The count signals stored in the register address a read only memory whose output signals preset the counter to a value to compensate for the difference between the expected time and the actual time between the successive digital signals thereby reducing the read error rate.

Abstract: Information to be written in the form of magnetic flux reversals on the surface of a disk or diskette is applied in serial fashion to a first shift registor. The parallel outputs of the shift register address a PROM. The PROM output is applied to a second shift register in the form of clock and data bits to be written on the disk or diskette magnetic surface. Control signals applied to the PROM address terminals select the mode, FM or MFM, the address mark or if precompensation is required.

Abstract: A logic system requiring no tuning adjustments is provided for converting an MFM encoded information stream read from a mass storage medium to a non-return-to-zero (NRZ) information stream. The MFM encoded information stream is routed through an input shift register to provide plural information bit cells in parallel. Outputs of the shift register are sampled with a multiplexer to generate timing strobes for detecting an address mark, and for identifying clock bits, data bits and logic zero data appearing in the MFM encoded data field following the address mark. Clock bits are separated from the data, and both data bits and logic zero data are applied serially to an output shift register to form a serial NRZ data stream. Each time a data bit or logic zero data is loaded into the output shift register, a synchronization strobe is generated to transfer the NRZ data to succeeding systems.

Abstract: In a peripheral controller of a data processing system having a plurality of system units electrically coupled to a common communication bus for asynchronous intercommunication, an array of counters responsive to both hardware and firmware are connected in a manner to form a serial control data path. Prior to a data transfer, a serial data stream including an offset range count, a range count and a main memory address is shifted through the counters under firmware control. During a data transfer, the firmware enables the hardware control to increment the memory address and decrement the range count to accommodate the higher data transfer rates characteristic of hardware control.

Abstract: A logic system is provided for precompensating data and clock bits of a formatted binary information stream during a modified frequency modulation (MFM) encoding for recording on a magnetic medium. The binary information stream is formatted into a gap field, an address preamble field, an address mark field and a data field. Clock bit generation is inhibited during the gap and address preamble fields. Further, a second of three clock bits occurring during the high order half-byte of the address mark field is suppressed to provide a modified MFM (M.sup.2 FM) field. An address mark is provided thereby for indicating the near proximity of a data field. Beginning with the low order half-byte of the address mark field, both MFM clock precompensation and MFM data precompensation is applied as required. The amount of peak shift occurring in the MFM encoded information stream after precompensation is substantially reduced.

Abstract: In a data processing system wherein a plurality of functional units are interconnected by way of a common communication bus in an environment of high data transfer rates, a logic control system is provided for interjecting firmware control during a data transfer between a disk device and main memory to accommodate unsolicited bus requests without incurring data errors or compromising the data transfer rate. Data transferred between the disk device and a disk controller interfacing directly with the common bus is routed through a FIFO (first-in-first-out) buffer under hardware control. The buffer signals the absence of data in its input register and the presence of data in its output register. The signals are logically combined and ANDed with a firmware controlled logic gate to indicate the occurrence of data transfer states. During such transfer states, data is transferred under hardware control between the FIFO buffer and main memory.

Abstract: A logic data control system including a first-in-first-out (FIFO) buffer predictor is provided for the transfer of data between a main memory unit and a peripheral control unit of a data processing system. Data from main memory is stored into the input registers of the peripheral unit, and thereafter loaded into an array of data FIFOs for transfer to a peripheral storage device. A predictor FIFO operates in parallel with the data FIFOs, and is loaded with a dummy or flag byte each time a data request is made to main memory. When a data word is loaded into the data FIFOs, the input register of the predictor FIFO is sensed. If the flag byte in the predictor FIFO has dropped from the input register into the FIFO stack, a request is issued to main memory for an additional data word. When the data FIFOs are filled, the predictor FIFO also is filled and cannot generate an additional data request until a data byte has been unloaded from the data FIFOs to a peripheral storage device.

Abstract: Data and clock bits are sampled by use of two delay means such as shift registers which are enabled at a clock rate which is set so that a first such delay means coupled to receive the bits includes no more than one bit therein at any time. The receipt of a bit substantially at the midway point of the second delay means, which is coupled serially to receive bits from the first delay means, causes a sampling signal to be generated in response to which a determination is made as to whether another bit has been received by the first delay means. Further logic is provided to recover the data bits.