Multi-standard video option for oscilloscope
First Claim
1. A multi-standard video option for an oscilloscope comprising:
- means for generating a ramp signal from a horizontal sync pulse of a composite sync signal derived from an input video signal;
means for reversing the slope of the ramp signal for a tri-level horizontal sync pulse when the horizontal sync pulse changes polarity;
means for rapidly discharging the ramp signal to zero for a bi-level horizontal sync pulse when the horizontal sync pulse changes polarity; and
means for determining from the ramp signal a digital trigger signal pulse having a width equal to the width of the horizontal sync pulse.
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Accused Products
Abstract
A multi-standard vide option for an oscilloscope detects whether an input video signal has a bi-level or a tri-level horizontal sync pulse from a composite sync signal derived from the input video signal. A ramp signal is generated from the horizontal sync pulse having a slope of one polarity that changes to a slope of the opposite polarity when the horizontal sync pulse is tri-level. For a bi-level horizontal sync pulse the ramp is limited in magnitude and rapidly discharged at the end of the horizontal sync pulse. A digital output signal is generated from the ramp signal and has a width equal to the width of the horizontal sync pulse regardless whether it is bi-level or tri-level. From the type of horizontal sync pulse and the width or the number of lines per frame, a video standard is determined and is subsequently used to determine field identification and to automatically set up the horizontal sweep of the oscilloscope according to a selected video setup.
13 Citations
17 Claims
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1. A multi-standard video option for an oscilloscope comprising:
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means for generating a ramp signal from a horizontal sync pulse of a composite sync signal derived from an input video signal; means for reversing the slope of the ramp signal for a tri-level horizontal sync pulse when the horizontal sync pulse changes polarity; means for rapidly discharging the ramp signal to zero for a bi-level horizontal sync pulse when the horizontal sync pulse changes polarity; and means for determining from the ramp signal a digital trigger signal pulse having a width equal to the width of the horizontal sync pulse. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A circuit for generating a field identification signal for an input video signal comprising:
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means for determining whether the input video signal is an interlaced or a non-interlaced signal to produce an interlaced indicator; means for determining whether the input video signal is a video signal having a video sync pulse that occurs at the beginning of a horizontal line of the input video signal for each field to produce a special indicator; and means for generating from the outputs of the two determining means the field identification signal. - View Dependent Claims (9, 10)
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11. A circuit for triggering an oscilloscope only during specified lines of a video signal comprising:
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means for generating a trigger signal in response to a horizontal clock signal derived from the video signal; means for arming the generating means in response to a trigger enable signal; and means for generating the trigger enable signal as a function of the horizontal clock signal, a field identification signal derived from the video signal, and a vertical sync signal derived from the video signal. - View Dependent Claims (12, 13)
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14. A method of automatically setting up an oscilloscope to display an input video signal comprising the steps of:
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automatically determining from the input video signal a television standard for the input video signal; determining a maximum and a minimun level for the input video signal; setting a volts/division value for the oscilloscope so that all levels of the input video signal are contained within the oscilloscope display area; setting up a counter to count the number of video lines per field of the input video signal; and setting up a seconds/division value for the oscilloscope so that at least one horizontal line of the input video signal is contained within the oscilloscope display area.
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15. A method of automatically selecting a format for displaying an input video signal on an oscilloscope display area comprising the steps of:
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determining from a composite sync signal derived from the input video signal the number of video lines per frame for the input video signal; accessing a lookup table based upon the number of video lines per frame to determine where line one of the input video signal occurs with respect to a vertical sync signal derived from the input video signal; and setting up a counter to count lines starting with line one of the input video signal based upon the output of the lookup table.
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16. A method of automatically presetting an oscilloscope display to display a selected format for an input video signal comprising the steps of:
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automatically determining from the input video signal a standard for the input video signal; setting a seconds/division value for the oscilloscope display as a function of the selected format and the standard; and setting up a region of the input video signal to be displayed determined by a start and a stop line for each field of the input video signal, the start and stop lines being programmable according to the selected format.
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17. A method of automatically determining a standard for an input video signal comprising the steps of:
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detecting whether the horizontal sync pulses of a composite sync signal for the input video signal are bi-level or tri-level to produce a digital output signal; generating from the composite sync signal and a horizontal clock signal phase locked to the composite sync signal a field identification signal; counting the number of horizontal lines in each field of the input video signal to determine a number of lines per frame for the video input signal; and determining from the width of the digital output signal, the field identification signal and the number of lines per frame the standard for the input video signal.
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Specification