Abstract: A configurable RAM interface connecting a bus to RAM is adapted to receiving large multiword variable length tokens at a high data arrival rate, using a swing buffer and a buffer manager. An address source provides complete addresses to the interface. The buffer manager has a state machine which transitions among a plurality of states, maintaining status information about the buffers, allocating the buffers for reference by a write address generator, clearing the buffers for occupation by subsequently arriving data, and maintaining status information concerning the buffers. The buffer manager also examines tokens of received data in order to update the status of the arrival buffer.

Abstract: The invention provides a single chip implementation of a digital receiver for multicarrier signals that are transmitted by orthogonal frequency division multiplexing. Improved channel estimation and correction circuitry are provided. The receiver has highly accurate sampling rate control and frequency control circuitry. BCH decoding of tps data carriers is achieved with minimal resources with an arrangement that includes a small Galois field multiplier. An improved FFT window synchronization circuit is coupled to the resampling circuit for locating the boundary of the guard interval transmitted with the active frame of the signal. A real-time pipelined FFT processor is operationally associated with the FFT window synchronization circuit and operates with reduced memory requirements.

Abstract: An apparatus for recording data includes a source of digital data arranged into data words having a given number of bits and a converter that converts the data words to code words having one more bit than the given number using a group code recording format. The code words include a binary signal having first and second binary values at a given clock interval determined by a bit rate of the code words. The apparatus also includes a storage disk having a recording surface, a drive member for rotatably driving the disk, a laser having a focused beam, and a control assembly for directing the laser at the recording surface so that the beam accesses one of a plurality of concentric tracks on the recording surface. A circuit assembly provides a driving signal utilized for generating energizing pulses having a duration less than the clock interval when the binary signal has the first binary value.

Abstract: A multi-standard video decompression apparatus has a plurality of stages interconnected by a two-wire interface arranged as a pipeline processing machine. Control tokens and DATA Tokens pass over the single two-wire interface for carrying both control and data in token format. A token decode circuit is positioned in certain of the stages for recognizing certain of the tokens as control tokens pertinent to that stage and for passing unrecognized control tokens along the pipeline. Reconfiguration processing circuits are positioned in selected stages and are responsive to a recognized control token for reconfiguring such stage to handle an identified DATA Token. A wide variety of unique supporting subsystem circuitry and processing techniques are disclosed for implementing the system.

Abstract: A pipeline video decoder and decompression system handles a plurality of separately encoded bit streams arranged as a single serial bit stream of digital bits and having separately encoded pairs of control codes and corresponding data carried in the serial bit stream. The pipeline system employs a plurality of interconnected stages to decode and decompress the single bit stream, including a start code detector. When in a search mode, the start code detector searches for a specific start code corresponding to one of multiple compression standards. The start code detector responding to the single serial bit stream generates control tokens and data tokens. A respective one of the tokens includes a plurality of data words. Each data word has an extension bit which indicates a presence of additional words therein. The data words are thereby unlimited in number.

Abstract: A method for converting frame data at a slower rate into field data at a faster rate in a video decoder comprises determining a basic field repetition rate such that a field is repeated an integer number of times in a frame period, calculating a ratio differential of the repetition rate by subtracting from the speed-up ratio of the faster to the slower rate, the ratio of the fields per frame period to the slower rate, comparing the ratio differential with the differential of the field repetition rate and adding or subtracting extra fields when the two are substantially at variance.

Abstract: A method for moving an optical head from an initial track to a target track on a storage medium having data arranged in tracks thereon. The method includes determining a track crossing number indicating a number of tracks between the initial track and the target track, moving the optical head from the initial track toward the target track, and measuring a reflectivity level of light from the medium. The method continues with deriving a tracking error signal responsive to the reflectivity level. A waveform of the tracking error signal has zero crossings corresponding to the optical head crossing one of the tracks. The method may further include incrementing a track count number for each the zero crossing, and passing the reflectivity level through a high pass filter to obtain a data indicator signal. In this embodiment, a waveform of the data indicator signal has indicator points corresponding to the zero crossings.

Abstract: An optical drive system includes a computer that monitors the current in an improved bias coil assembly in conjunction with a magnetomotive field generator to determine when a predetermined current threshold is exceeded. The bias coil assembly includes a wire coil wrapped around a center bar contained by a bias coil housing. The bias coil assembly is positionable above an information storage medium so that the entire medium may be within the magnetic field thereby allowing writing of information to all portions of the medium. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on the storage medium utilizing a laser. A laser pulse generator is then enabled. The device thereby achieves a substantially shortened write cycle while employing the improved bias coil assembly.

Abstract: An apparatus and method is disclosed for focus control of a beam of radiant energy, wherein a detector of the beam has first and second outputs responsive to a position of the beam. A circuit is coupled to the outputs of the detector for producing an error signal representing a displacement of the focus from a predetermined position, wherein the error signal has a periodic characteristic relative to the displacement. A servo responsive to the error signal restores the displaced beam to the predetermined position. A local feedback loop is coupled to the outputs of the detector, and includes first and second periodic function generators, each responsive to the error signal. The second periodic function generator has an output that differs from an output of the first periodic function generator by a phase angle, preferably 90 degrees. A first multiplier multiplies the first output of the detector by the output of the first periodic function generator.

Abstract: This invention discloses a method for accessing Dynamic Random Access Memory (DRAM) to store and retrieve data words associated with a two dimensional image. The DRAM includes two separate banks, a first bank and a second bank. Each bank is capable of operating in page mode to read and write the data words. The two dimensional image is organized in a two dimensional grid pattern of cells, each cell containing an M by N matrix of pixels. The words associated with each cell occupy one page or less of a bank. Each cell is assigned a particular one of the two banks so that all data words associated with that particular cell are read from and written to one particular page of that particular bank. The assignment of banks to cells is done such that each cell is associated with a different bank than any bordering cell which is also either in the same row or in the same column.

Abstract: An optical drive system includes a computer that monitors the current in the bias coil of a magnetomotive field generator to determine when a predetermined current threshold is exceeded. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on a storage medium utilizing a laser. A laser pulse generator is then enabled. The system is provided with an optics module for processing light produced by the laser light source. A laser driver for energizing the laser light source is positioned in close proximity to the optics module and the laser light source to reduce noise in signals associated with the optics module. The system thereby achieves a substantially shortened write cycle while reducing relevant signal noise.

Abstract: An analog to digital circuit assembly for use in an optical information includes a circuit for multiplexing a reference voltage input of an analog to digital converter to produce alternating normalized and referenced digital outputs of a plurality of analog signal inputs at a rate controlled by a sampling clock which includes a switch including first and second inputs, an output, and a control input for alternately connecting the first and the second inputs to the output, the output being applied to the reference voltage input.

Abstract: A plurality of processing stages interposed between an input and an output of a system including a pipeline machine interconnect for conveyance of tokens along the pipeline. Control and or data tokens in the form of universal adaptation units interface with all of the stages in the pipeline and alternatively interact with selected stages in the pipeline so that the processing stages in the pipeline are afforded enhanced flexibility in configuration and processing. In one embodiment of the system, the stages accept a data stream having portions encoded according to respectively different video formats. At least one of the stages includes circuitry for generating signals to indicate an end-of-picture data decoding. The stage includes state machine logic that is responsive to the generated signals for effecting an end of picture data decoding by clearing the pipeline.

Abstract: An optical drive system includes an optical assembly, a light source, a lens positioned to direct light between the optical assembly and an information storage medium or disc, and an actuator suspending the lens. A photodetector is disposed in a path of returning light to measure light received from the medium. A monitoring circuit is provided to monitor a Quad Sum signal associated with return light. A first servomotor is employed to move the lens in a tracking direction and to move the lens during focus capture while system circuitry searches for a maximum Quad Sum signal. A second servomotor is employed to move the lens in a focusing direction. A first electronic circuit is provided to control the first and second servomotors.

Abstract: A magneto-optical drive system having a computer that monitors the current in the bias coil of a magnetomotive field generator to determine when a predetermined current threshold is exceeded. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on a storage medium utilizing a laser. A laser pulse generator is then enabled. The device thereby achieves a substantially shortened write cycle.

Abstract: An MPEG video decompression method and apparatus utilizing a plurality of stages interconnected by a two-wire interface arranged as a pipeline processing machine. Control tokens and DATA Tokens pass over the single two-wire interface for carrying both control and data in token format. A token decode circuit is positioned in certain of the stages for recognizing certain of the tokens as control tokens pertinent to that stage and for passing unrecognized control tokens along the pipeline. Reconfiguration processing circuits are positioned in selected stages and are responsive to a recognized control token for reconfiguring such stage to handle an identified DATA Token. A wide variety of unique supporting subsystem circuitry and processing techniques are disclosed for implementing the system, including memory addressing, transforming data using a common processing block, time synchronization, asynchronous swing buffering, storing of video information, a parallel Huffman decoder, and the like.

Abstract: An interferometer includes a beamsplitter for splitting a source beam into a test beam and a reference beam, an imaging device for detecting an interference pattern, a mirror disposed in a path of the test beam for reflection of the test beam toward the imaging device, a micromirror disposed in a path of the reference beam for reflection of a portion of the reference beam toward the imaging device, and a focusing mechanism disposed for focusing the reference beam on the micromirror. The micromirror has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the reference beam focused thereon by the focusing mechanism. A spatial filter for reducing effects of aberration in a beam includes a reflector disposed upon a transparent base wherein the reflector has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the spatial intensity distribution of the beam focused upon the reflector.

Abstract: The mechanism for loading and unloading a disk cartridge uses two sliders (one on each side of a base plate), which move in opposite directions under the influence of a tiller. Each slider has a slot to receive one of the two lifting pins provided on the cartridge receiver. The movement of the sliders drives the lifting pins along the slots, thereby raising or lowering the cartridge receiver depending upon the direction of rotation of the tiller. The sliding motion of the lifting pins engaged in the S-shaped slots thus unloads a disk from or, alternatively, loads the disk onto the drive spindle. As the lifting pins travel along their respective slots, the lifting and lowering of the disk is accomplished in such a manner that the disk hub is peeled from the spindle magnet rather than being lifted vertically off the spindle. This reduces the peak force required to break the magnetic clamp force between the spindle magnet and the disk hub.

Abstract: The present invention preferably includes a shading band which is suitably electro-optically created in a grid pattern formed through a photolithographic process, so consequently, the electro optic shading band is easily eliminated or re-configured dynamically to substantially eliminate its shading effect for lower density optical disks which do not experience substantial adjacent track crosstalk (ATC). Eliminating or reconfiguring the shading effect also helps in accommodating different media types and generations and those of different manufacturers. Moreover, the electro-optic shading band suitably adjusts the amplitude, phase, frequency, polarization and/or the like of the light beam to compensate for possible material property variations, defects, misalignments or other imperfections in the reading process. The present electro-optic shading band substantially restricts or alters any portion of a light beam containing signal information read from an optical disk.

Abstract: An improved system for recording and playing back digital information in a special pulse-length modulation format on a disc-shaped record. The digital information is stored in a succession of alternating marks and spaces, both having lengths that are discretely variable in accordance with a succession of multi-bit binary code blocks.