A memory repeater hub comprising a main memory channel interface circuit, an expansion control channel interface circuit, and an expansion memory channel interface circuit. The main memory channel interface circuit receives a memory control packet and a memory data packet from a main memory channel. The expansion control channel interface circuit receives a first expansion control packet and a second expansion control packet from an expansion control channel. The expansion memory channel interface circuit selectively transmits the memory control packet to an expansion memory channel responsive to the first expansion control packet, and selectively transmits the memory data packet to the expansion memory channel responsive to the second expansion control packet.

An image display system forms an output video signal which is composed of successive frames, the output video signal including a plurality of windows, each of which contains image information from an own input video signal in each frame. The image information from the input video signals is written into a memory wherefrom subsequently successive frames of an output video signal are read, each time from a respective series of locations of the memory. Upon reading, a concatenation of the respective series of the successive frames is formed. The locations are periodically repeated in this concatenation with a period of recurrence which is longer than a single series, the locations of the respective series of each frame at an end being coincident in an overlapping fashion with the locations at the beginning of the series of a directly preceding frame. Despite the overlap, no image information of the windows will be overwritten before it has been read, provided that the overlap is smaller than the minimum number of locations used in a series between the beginning and the end of a window. In the case of rectangular windows, the minimum height of the windows thus defines the overlap.

An image processing system combines a multitude of image signals to create a compound image, The system has a plurality of memory modules operative to store the image signals as pixels for the compound image as respective segments of consecutive pixels. A specific row of consecutive pixels of the compound image is formed by consecutive arrangement of the respective segments. This permits the use of a simple addressing protocol, and of simple page-mode access DRAMs.

A video multiplexing system for superimposition of scalable video data streams upon a background data stream and having a video decoder to extract a first luminance signal, an A/D converter to convert the first luminance signal to digital form, a three-port video memory for storing digitized luminance signal, a D/A converter for receiving the stored digitized luminance signal and converting it to analog form, a mixing or multiplexing means, having one input coupled to the D/A converter output, at least one other luminance signal source as an input and controlling inputs for directing the selection of one of the input luminance signals as an output, and a control means such as a microprocessor for controlling the various components. The write operations to the video memory are synchronized to the incoming luminance signal, and the read operations from the video memory are synchronized to the display device. This video multiplexing architecture provides the ability to open a viewport of arbitrary size at any position within a larger display. Scaling of the digitized luminance signal to fit in a viewport of arbitrary size is achieved by varying the frequency of the A/D converter clocks so as to expand or shrink the resulting image.

A graticule display processor that can produce an adaptive graticule for a raster-scan output waveform monitor. The graticule may be displayed in front of the waveform, behind the waveform or mixed with the waveform. The graticule can change the waveform's color or intensity in specific regions, thereby enhancing the appearance of over range conditions. A specific use is to allow the vector functions of phase and gain to be monitored in the waveform mode.