Abstract: A method of software clamping a video signal for waveform display on a general purpose oscilloscope where the video signal is a.c. coupled to an input of the oscilloscope includes acquiring samples of the video signal in response to a trigger signal derived from the video signal, which samples are then stored. Then samples relative to the trigger signal that are at a nominally known voltage are retrieved, averaged and compared to a reference value. The reference value may be a value determined from a first acquisition of the video signal or a value corresponding to the nominally known voltage. The difference between the averaged samples and the reference value is then used to adjust the sample values when retrieved for display by the oscilloscope.

Abstract: A portable general-purpose oscilloscope employs circuitry for receiving and converting serial digital video signals to composite and component analog signals via a digital to analog converter. The converted analog signals are applied to signal inputs of the oscilloscope for monitoring and display. Preferably, the oscilloscope is a digital phosphor oscilloscope. The oscilloscope control menus are arranged to control all of the usual functions of the oscilloscope and also to control the serial digital video circuitry. Apparatus is provided for storing data and waveforms. Circuitry is disclosed for deriving a trigger signal from a specific digital word of the serial digital bit stream. The trigger signal is applied to the trigger input terminal of the oscilloscope to allow the oscilloscope capture and display television waveform information around a unique occurrence of an event, as specified by the digital word.

Abstract: A digital storage oscilloscope includes a source of two or more input signals and a display device. An alternate triggering mechanism includes a selector for selecting one of the input signals. A trigger circuit is responsive to the selected input signal, and generates a trigger signal when a trigger condition is satisfied. A raster signal generator includes a plurality of waveform memories each associated with a respective input signal and responsive to the trigger signal for storing data representing the selected input signal in the waveform memory associated with the selected input signal. The raster signal generator generates a raster image signal representing the selected input signal.

Abstract: An apparatus and method useful in a test and measurement instrument for selecting a particular television field for display, determines the television system standard from the input signal, uses the standard selection to determine the time for one field, and multiplies the field rate by an operator-supplied number of fields to calculate the required holdoff time. The subject invention relieves the operator from turning the holdoff control multiple times, and also relieves the operator from having to calculate the time delays for any of one to seven fields of holdoff (in the case of a PAL signal).

Abstract: A luminance component extractor coupled to a source of a composite video signal including a luminance component. A sampler, coupled to the video signal source, produces samples representing a frame the video signal. A memory maintains minimum and maximum values of each sample in the frame of the video signal. A non-linear low pass filter, responsive to the minimum and maximum values, generates samples representing the luminance component.

Abstract: Generation of digital cursors for serial digital television waveform monitors includes inputting hexadecimal values for the cursors by an operator via a front panel. The hexadecimal values are received by a microprocessor which loads them into appropriate registers of a co-processor. The outputs of the cursor registers in the co-processor are input to respective inputs of a multiplexer together with a digital signal representing a serial digital television signal. A select signal for the multiplexer is generated by a selection circuit that is enabled by a digital cursor ON command when the waveform monitor is in a cursor mode. The selection circuit at predetermined locations of the digital signal generates the select signal so that the appropriate cursor values are inserted into the digital signal at those locations.

Abstract: An integrated digital processing device and method for examining the operation thereof. An integrated multiple digital processing device has externally-accessible tag connections which provide signals representative of what circuit has access to external memory used by the processing device. The processing device includes a plurality of digital processor circuits, a DRAM refresh logic circuit, externally-accessible connections for receiving memory access signals from an external processor, and an arbitration circuit for determining which of the digital processor circuits, refresh logic circuit or external processor may have access to the external memory. The signals on the tag connections are provided by the arbitration circuit, and indicate which of the aforementioned circuits has access to the external memory at any moment.

Abstract: A system for automatic generation of vector reference graticules for a vectorscope display acquires the active video portion of a video signal that includes a color bar test signal. The values for each color difference component at each reference color plateau for the acquired color bar test signal are averaged to provide horizontal and vertical displacement values for each reference color, including black. Graticule boxes are electronically generated and positioned for each reference color on a display according to the respective horizontal and vertical displacement values.

Abstract: An RGB display of a transcoded serial digital video signal is produced by converting the serial digital video signal to a parallel digital video signal, separating the digital luminance component signal and the two digital difference component signals from the parallel digital video signal, converting the digital luminance and color difference component signals into analog encoded color component signals, transcoding the analog encoded color component signals into RGB component signals, and routing the RGB component signals to a waveform display device. The RGB component signals also are routed to a gamut detection circuit where each component is compared with nominal plus and minus limit levels to determine if there is a gamut error.

Abstract: A bright video line select display for a waveform monitor is achieved by storing a selected line from a video frame of a digital video input signal. The stored selected line is iteratively substituted for a plurality of video lines during the vertical interval of the digital video input signal. When line select mode is selected, those video lines during the vertical interval are displayed as a waveform, resulting in a brighter display of the selected video line.

Abstract: A method and apparatus for determining the internal state of a processor without disturbing the operational environment of the processor employs a two phase process. In the first phase, external signals produced by the processor in the execution of a known program are monitored and recorded for subsequent analysis. In the second phase, the recorded information is analyzed in the light of the known characteristic of the processor, the program it was executing, and the signals recorded during the first phase. The internal state of the processor is thereby determined after the execution of each instruction. In addition, provisions are made for the specification of breakpoints, and the examination of simulated status of the processor on the occurrence of the breakpoints.

Abstract: A system for providing input to a computer comprises a touchscreen apparatus for generating a grid of horizontal and vertical light beams and producing a set of output signals, each indicating whether a corresponding one of the light beams strikes an object. A scanning device repeatedly scans the states of the output signals, stores data representing the last scanned state of each output signal, and transmits a first interrupt signal to the computer whenever the state of any one of the output signals changes. In response to the interrupt signal, the computer reads the stored scan data, determines whether the data indicates that a horizontal and a vertical light beam is striking an object, and if so, sets parameter values to identify the horizontal and vertical light beams.

Abstract: An improved method and apparatus is disclosed for determining the internal state of a processor without disturbing the operational environment of the processor. A two phase process is employed. In the first phase, external signals produced by the processor in the execution of a known program are monitored and recorded for subsequent analysis. In the second phase, the recorded information is analyzed in the light of the known characteristic of the processor, the program it was executing, and the signals recorded during the first phase. The internal state of the processor is thereby determined after the execution of each instruction. In addition, provisions are made for the specification of breakpoints, and the examination of simulated status of the processor on the occurrence of the breakpoints.

Abstract: A method and apparatus is disclosed for the improved monitoring and detection of improper device operation. Operation of a prototype device is first modeled. In particular, a set of test vectors is selected to provide a desired degree of testing of the prototype unit. The expected response of the prototype to the selected set of test vectors is determined through the use of analytical prediction means, and stored for subsequent comparison with the operation of the prototype unit. Thereafter, the selected set of test vectors are applied to the prototype unit, and the response thereto compared in real time with the expected responses. Improper operation of the prototype device is thereby identified, and associate information recorded for subsequent analysis.

Abstract: For an oscilloscope capable of simultaneously displaying a plurality of waveforms on a screen and capable of performing operations with respect to a selected one of the displayed waveforms, a method and apparatus for permitting an operator to select a waveform. A touchscreen mechanism provides input signals to the oscilloscope indicating when and where an operator touches the surface of the screen and a microcomputer within the oscilloscope determines from data controlling the display of each waveform and from the data provided by the touchscreen whether the operator is touching any portion of a displayed waveform. If so, the microcomputer assumes that the operator has selected the waveform touched and reconfigures oscilloscope operation such that operations are performed with respect to the waveform touched by the operator.

Abstract: A memory preservation and verification system is provided in which memory contents are verified as being valid following an interruption and subsequent reapplication of operating power. A backup power supply is provided to maintain the status of the memory contents during the interruption or loss of a main power supply. First and second mathematically related numbers are generated and stored in memory locations. These numbers are subsequently retrieved and the mathematical relationship therebetween checked to provide the verification of the status of data in the memory.