Abstract: The present invention provides an ECL EPROM circuit which uses a MOS memory cell. The invention includes a technique for programming the memory cell using MOS voltage levels, and also includes circuitry for reading the memory cell at ECL voltage levels. Thus, the programming and reading paths are split to give the ease of programming and the reprogrammability of MOS EPROM devices combined with the reading speed of PROM devices using ECL voltage levels. In one embodiment, two parallel paths are provided to a memory cell to enable it to separately receive reading and writing (programming) signals. The reading path employs ECL components for reading the cell, while the writing path contains MOS components for programming and verifying the cell. The memory cell itself contains a MOS memory element, an ECL pass element, and a sense element coupling the MOS memory element to the ECL pass element.

Abstract: A process which stores a representation of a polygon forming a portion of a three-dimensional object and compares the polygon to pixels from a scan line as they are passed by. The processor stores a representation of a polygon and compares each pixel passed by the processor to the polygon to determine whether the pixel is within the polygon. If the pixel is within the polygon, its Z position (depth) is compared to the Z position of a corresponding position in the polygon. If the Z position of the polygon position is in front of the Z position of the pixel so that the polygon would obscure the previous pixel description, the Z position and an associates material value (e.g., color) of the polygon is substituted for the Z position of the pixel. The three-dimensional object is preferably represented with triangles and each polygon processor is preferably a triangle processor, with a series of triangle processors arranged in a pipeline. Two pipelines may be provided in parallel.

Abstract: A custom bus for a visual signal (image) processing system which can interface with a standard high speed industrial standard computer bus and requires minimal interface circuitry. Eight lines are dedicated to eight data/address bits which are supplied to a bidirectional I/O buffer on each VSP circuit card. A separate board select signal is supplied to each circuit card to enable the I/O buffer. Six bits on six lines provided to each VSP circuit card provide a signal selecting a particular device on each circuit card. Each circuit card contains a decoding circuit for decoding the device select signal and enabling an individual device on the card in response to the device select signal.

Abstract: A circuit for providing a voltage reference level using a master circuit and a plurality of slave circuits. The master circuit includes a V.sub.bb reference circuit, a temperature compensation and V.sub.cse reference circuit, and a voltage step-up and buffering circuit. Each of the slave circuits has a pair of transistors in an emitter-follower configuration to step down the voltage and drive the circuitry requiring the voltage reference.

Abstract: An improved method and apparatus for classifying triangles. A description of a triangle in the form of the coordinates of its vertices is supplied to calculation logic. The calculation logic calculates a plurality or parameters of the triangle from these coordinates. These parameters are then provided to a look-up table. The look-up table has previously been programmed to include at each address the proper triangle classification for that address, with each address being a different combination of the parameters. The addresses for the look-up table cover all possible combinations of the parameters, and thus all possible triangles.

Abstract: A BiCMOS write-recovery method and circuit for recovering bit lines in a digital memory system provides approximately 1 nS recovery time and allows a 256K BiCMOS SRAM to achieve 10 nS access time. All bit lines in the memory system connected to a column not being read are held at a high potential, approximately equal to the upper power supply. During a write, one bit line is pulled low and its complementary bit line is clamped with a bipolar transistor to an intermediate potential, thereby preloading the complementary bit line. Following a write, the bit line that was pulled low is pulled up with a bipolar transistor to the intermediate voltage. Simultaneously, the bit line and the complementary bit line are shunted together, then returned to the high potential. Undesired bootstrap capacitance effects in the bipolar transistors are minimized by connecting a plurality of pull-up transistors in parallel, and by feeding the clamping transistors with low impedance drivers.

Abstract: A system is provided for application of a lighting model to a rasterized stream of pixels. The system typically includes a series of circuits, each for applying a lighting model to a single pixel. Each chip typically includes some memory sources for storing the lighting model, an input section connected to receive data indicative of the normal vector, Z depth, and material characteristics of the object represented by the pixel to be colored. A special purpose processor connected to the input then applies the lighting model to the pixel and supplies color value of the pixel as an output signal.

Abstract: A system for clipping polygons representing three-dimensional objects to produce a representation of the portion of the objects in a desired viewing space is disclosed. A guardband space at least partially enclosing the viewing space is defined. The polygons are compared to the guardband space to determine which polygons intersect at least one of the guardband planes defining the guardband space. The intersecting polygons are also compared to the viewing space to determine if they intersect at least one of the viewing planes defining the viewing space. Only polygons intersecting both a viewing plane and a guardband plane are clipped.

Abstract: A graphic processing system for representing three-dimensional objects on a monitor which uses a pipeline of polygon processors coupled in series. The three-dimensional objects are converted into a group of two-dimensional polygons. These polygons are then sorted to put them in scan line order, with each polygon having its position determined by the first scan line on which it appears. Before each scan line is processed, the descriptions of the polygons beginning on that scan line are sent into a pipeline of polygon processors. Each polygon processor accepts one of the polygon descriptions and stores it for comparison to the pixels of that scan line which are subsequently sent along the polygon processor pipeline. For each new scan line, polygons which are no longer covered are eliminated and new polygons are entered into the pipe. After each scan line is processed, the pixels can be sent directly to the CRT or can be stored in a frame buffer for later accessing.

Abstract: A method and apparatus for controlling a parallel combination of correlation circuits which compare image pixels. A number of correlation circuits are provided, each having its own memory. The memories are loaded with image data with each memory being assigned a different block (region) of the image. Each memory is also loaded with an overlapping portion of an adjacent block so that a pattern can be stepped across the entire block, including a match of the first column of the pattern with the last column of the block. The loading is done by generating addresses corresponding to addresses for the source image with one or more of the most significant bits modified so that the address sequence received by the second and subsequent memories are identical to the address sequence received by the first memory. This allows the various blocks of the image in the different memories to be later simulataneously accessed in parallel using a single address sequence.

Abstract: A timing subsystem 10 including several test period generators for supplying a variety of timing signals to a device under test. Major, minor, and free-run period generators each supply various timing signals to a multiplexer 18, which selectively connects the timing signals to timing generators 20. A central processing unit 28 supplies data to the period generators and timing generators to define their respective timing signals. Timing signals generated by the major period generator 12 define the overall testing rate. The minor period generator 14 generates multiple timing signals within the periods of the major clock signals to permit higher clock rates. Timing signals that are independent of the major clock periods are generated by the free-run period generator 16. An external synchronizer circuit 26 provides a feedback loop from the device under test 22 to the major period generator. A reference driver trigger delay circuit 27 provides means for calibrating the timing generators.

Abstract: A video stream processing system comprising a novel modular family of image processing and pattern recognition submodules, the submodules utilize a unique system signalling and interface protocol, and thus can be cascaded and paralleled to produce complex special purpose image processing systems which can operate at video or near video data rates. A stream of digitized pixel data is pipelined through a variety of submodules to support a wide variety of image processing applications. A common video interface provides for handling pixel data in the video signal path and a processor interface allows communication to any modern microprocessor for overall system control, for optional addition image processing and for defining options within each submodule.

Abstract: A printer/plotter incorporates four individual microprocessor-based print stations, each for printing on a print media a separate color image for superimposition with one another, forming a final full-color image. The four print stations are located along a transport path for single-pass operation, and each print station includes a transport system that allows the media to traverse a print station with controlled forces exerted on the media by that station. The invention further includes a precise registration system wherein each print station monitors registration marks to detect variations of the media (i.e., stretching or shrinkage) during the printing process and to correct for such variations on obtaining accurate registration of the individual images for a full-color result.

Abstract: A video stream processing system frame buffer controller for controlling external dynamic random access memory (DRAM) of a frame buffer and interfacing to the video stream processing signal bus. The frame buffer controller has four interfaces, video input interface, video output interface, memory interface and processor interface. The circuit can input image data from a camera and store the frames in external DRAM. The circuit provides for external processor access to pixels in the frame buffer and for output of the frame or portions of the frame, as well as output of frames in a format of CRT display and external DRAM refresh.

Abstract: A temperature compensated sense amplifier is connected to the sense node of a memory array which is OR tied to the bit lines of the array. A PNP current mirror supplies voltage independent controlled current to the sense node. A level shifting stage is connected to the sense node to establish a threshold sensing level, and to switch on to steer the current into the amplifier stage. A compensation stage is connected to the level shifting stage and the amplifier stage to compensate for the .beta. factors of the transistors and the resistive changes with temperature. A temperature compensated current sink is connected to the PNP current mirror to track over temperature in opposition therewith and maintain a constant current into the sense node. The level shifting stage and the amplifier stage also include temperature compensating features to provide a sensing threshold which tracks constantly over the operating temperature range.

Abstract: The present invention is an improved subscriber line interface circuit which allows fast detection of an off-hook signal in the presence of a ringing signal during an answer mode while also permitting fast detection of dialing pulses during a calling mode. A programmable filter is used in the supervision circuit of the SLIC to allow the cutoff frequency of the filter to be varied so that the 20 Hz ringing signal will be attenuated during a ringing sequence and dialing pulse rates up to 20 Hz will be passed by the filter during the calling mode. A clamping amplifier is used to clamp the received signal to a maximum of 1.5 times the loop threshold current. This eliminates the large variations in the rise and fall times of the pulse dialing signal due to variations in the loop current caused by varying impedances of the telephone line. The filter is programmed by using an analog switch to bypass certain filter elements.

Abstract: The present invention is an improved active load which eliminates the current imbalance between the collectors of the emitter-coupled input transistors. The circuit includes a pair of first and second emitter-coupled transistors with their collectors coupled to a current source which supplies substantially equal currents to the collectors of the two transistors. The collector of one of the emitter-coupled transistors is coupled to the base of a third output transistor. A fourth transistor is coupled between the collector of the output transistor and the supply voltage. Finally, the circuit includes means for supplying the base current to the fourth transistor such that the base current of the fourth transistor and the third output transistor are substantially equal and the collector currents of the first and second emitter-coupled transistors remain substantially equal, resulting in negligible offset current and high open loop gain.