Method of low cost self-test in a video display system system
First Claim
1. A display system with video analog self-test capability comprising:
- means, including a graphics processor, for generating digital video data;
the processor having means for generating a variable duty cycle squarewave and having a digital input port;
a digital to analog converter (DAC) for receiving the digital video data and converting the digital video data to an analog signal for input to a cathode ray tube monitor to display a graphics image;
an integrator circuit for integrating said variable duty cycle squarewave;
an analog comparator for comparing the analog signal to the integrated variable duty cycle squarewave; and
means for connecting the output of said analog comparator to the digital input port.
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Abstract
In a color graphics display system, video analog self-test hardware for testing the system elements between the frame buffer and the CRT display monitor is provided including a bi-directional data bus between the graphics processor and the color map, an analog comparator, an integrator, and an analog multiplexor. The self-test method includes calibrating the self-test circuitry with respect to a reference voltage. The method next includes testing the DACs by outputting predetermined bit patterns to each of the DACs via the frame buffer, measuring each DAC output level in response to each input bit pattern, comparing the DAC output levels to predetermined limits, and reporting the results. Provision is made also for testing the system clock.
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Citations
18 Claims
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1. A display system with video analog self-test capability comprising:
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means, including a graphics processor, for generating digital video data; the processor having means for generating a variable duty cycle squarewave and having a digital input port; a digital to analog converter (DAC) for receiving the digital video data and converting the digital video data to an analog signal for input to a cathode ray tube monitor to display a graphics image; an integrator circuit for integrating said variable duty cycle squarewave; an analog comparator for comparing the analog signal to the integrated variable duty cycle squarewave; and means for connecting the output of said analog comparator to the digital input port. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of self-testing in a video display system comprising:
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setting a DAC input; calibrating the self-test circuitry; converting the DAC input signal to an analog signal; measuring the analog signal at the DAC output; comparing the analog signal level to predetermined limits; and reporting the result of said comparison. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification